Bactrocera dorsalis can be recognized by a predominantly black scutum with lateral yellow stripes; black oval to spherical large facial spots; 2 setae in the scutellum; black T-shaped mark on the abdomen and wings with a dark brown costal band and oval streak.
The damage to the fruit is caused by the abortive stinging and ovipo-sitional punctures by gravid female fruit flies. Passion fruits are attacked when raw, hard thickened areas develop around ovipositional punctures and such fruits become malformed and usually drop prematurely. Similarly coorg mandarins are stung by the female flies when still green, colouring later develops around the ovipositional punctures. Mango, papaya, banana and several other fruits become attractive to female fruit fly as they ripen. The fermenting organisms (bacteria and fungi) gain entry through these punctures and the fruits start rotting.
The hatching maggots feed on fruit pulp for 6-29 days and destroy it, converting it into a bad smelling, discoloured semi-liquid mass unfit for human consumption and marketing. The fruits develop brown rotten patches on them and fall to the ground. The ingestion of maggots by human beings could cause abdominal pain and even diarrhoea in some individuals
Saturday, August 30, 2008
MS (Murashige & Skoog) Media
Macronutrients
Ammonium nitrate (NH4NO3) 1,650 mg/l= 20.6 ml/L
Boric acid (H3BO3) 6.2 mg/l
Calcium chloride (CaCl2 • 2H2O) 440 mg/l
Cobalt chloride (CoCl2 • 6H2O) 0.025 mg/l
Magnesium sulfate (MgSO4 • 7H2O) 370 mg/l
Cupric sulfate (CuSO4 • 5H2O) 0.025 mg/l
Potassium phosphate (KH2PO4) 170 mg/l
Ferrous sulfate (FeSO4 • 7H2O) 27.8 mg/l
Potassium nitrate (KNO3) 1,900 mg/l
Manganese sulfate (MnSO4 • 4H2O) 22.3 mg/l
Potassium iodide (KI) 0.83 mg/l
Sodium molybdate (Na2MoO4 • 2H2O) 0.25 mg/l
Zinc sulfate (ZnSO4 • 7H2O) 8.6 mg/l
Na2EDTA • 2H2Oa 37.2 mg/lb
Common organic additives
i-Inositol 100 mg/l
Niacin 0.5 mg/l
Pyridoxine • HCl 0.5 mg/l
Thiamine • HCl 0.1 mg/l
IAA 1–30 mg/l
Kinetin 0.04–10 mg/l
Glycine (recrystallized) 2.0 g/l
Edamine 1.0 g/l
Sucrose 20 g/l
Agar 10 g/l
Ammonium nitrate (NH4NO3) 1,650 mg/l= 20.6 ml/L
Boric acid (H3BO3) 6.2 mg/l
Calcium chloride (CaCl2 • 2H2O) 440 mg/l
Cobalt chloride (CoCl2 • 6H2O) 0.025 mg/l
Magnesium sulfate (MgSO4 • 7H2O) 370 mg/l
Cupric sulfate (CuSO4 • 5H2O) 0.025 mg/l
Potassium phosphate (KH2PO4) 170 mg/l
Ferrous sulfate (FeSO4 • 7H2O) 27.8 mg/l
Potassium nitrate (KNO3) 1,900 mg/l
Manganese sulfate (MnSO4 • 4H2O) 22.3 mg/l
Potassium iodide (KI) 0.83 mg/l
Sodium molybdate (Na2MoO4 • 2H2O) 0.25 mg/l
Zinc sulfate (ZnSO4 • 7H2O) 8.6 mg/l
Na2EDTA • 2H2Oa 37.2 mg/lb
Common organic additives
i-Inositol 100 mg/l
Niacin 0.5 mg/l
Pyridoxine • HCl 0.5 mg/l
Thiamine • HCl 0.1 mg/l
IAA 1–30 mg/l
Kinetin 0.04–10 mg/l
Glycine (recrystallized) 2.0 g/l
Edamine 1.0 g/l
Sucrose 20 g/l
Agar 10 g/l
Tuesday, August 12, 2008
EARLY BLIGHT OF POTATO EPIDEMIOLOGY
Epidemiology
Alternaria solani overwinters primarily on infected crop debris. The dark pigmentation of the mycelium increases resistance to lysis which extends the survival time in the soil to several years. Thick-walled chlamydospores have been reported, but they are found infrequently. In mild climates the pathogen can survive from season to season on volunteer tomato and potato plants as well as other weedy Solanaceous hosts such as horsenettle and nightshade.
Warm, humid (24-29°C/ 75-84°F) environmental conditions are conducive to infection. In the presence of free moisture and at an optimum of 28-30°C (82-86°F), conidia will germinate in approximately 40 min. Desiccated germ tubes are able to renew growth when re-wetted, and, hence, infection can occur under conditions of alternating wet and dry periods. Germ tubes penetrate the leaf epidermis directly or enter through stomata. Infection of potato tubers usually occurs through wounds in the tuber skin. Wounds caused at harvest, that coincide with wet conditions favorable for spore germination, can lead to significant tuber infection. High soil moisture levels can cause swollen lenticels on tubers which are also easily invaded.
Time from initial infection to appearance of foliar symptoms is dependent on environmental conditions, leaf age, and cultivar susceptibility. Early blight is principally a disease of aging plant tissue. Lesions generally appear quickly under warm, moist conditions on older foliage and are usually visible within 5-7 days after infection.
A long wet period is required for sporulation, but it can also occur under conditions of alternating wet and dry periods. Conidiophores are produced during wet nights and the following day. Light and dryness induce them to produce spores, which emerge on the second wet night. Early blight is considered polycyclic with repeating cycles of new infection. Secondary spread of conidia is mainly by wind and occasionally by splashing water.
Symptoms of early blight
occur on fruit, stem and foliage of tomatoes and stem, foliage and tubers of potatoes. Initial symptoms on leaves appear as small 1-2 mm black or brown lesions. Under conducive environmental conditions, the lesions enlarge and are often surrounded by a yellow halo (Figures 2 and 3). Lesions greater than 10 mm in diameter often have dark pigmented concentric rings. This so-called "bullseye" type lesion is highly characteristic of early blight (Figure 4). As lesions expand and new lesions develop, entire leaves may turn chlorotic and dehisce, leading to significant defoliation. Lesions on stems are often sunken and lens-shaped with a light center and have the typical concentric rings (Figure 5). On young tomato seedlings, lesions may completely girdle the stem, a phase of the disease known as "collar rot," which may lead to reduced plant vigor or death.
Infection of both green and ripe tomato fruit normally occurs through the calyx with lesions sometimes reaching a considerable size (Figure 6). The lesions appear leathery and may have the characteristic concentric rings. Infected fruit will frequently drop prematurely. Symptoms on potato tubers are characterized by sunken, irregular lesions (Figure 7), which are often surrounded by a raised purple border. Beneath the lesion surface, the tuber tissue is leathery or corky with a brown discoloration. Early blight lesions on tubers tend to be dry and are less prone to invasion by secondary organisms compared to lesions of other tuber rots. After prolonged storage, severely diseased tubers may become shriveled.
Alternaria solani overwinters primarily on infected crop debris. The dark pigmentation of the mycelium increases resistance to lysis which extends the survival time in the soil to several years. Thick-walled chlamydospores have been reported, but they are found infrequently. In mild climates the pathogen can survive from season to season on volunteer tomato and potato plants as well as other weedy Solanaceous hosts such as horsenettle and nightshade.
Warm, humid (24-29°C/ 75-84°F) environmental conditions are conducive to infection. In the presence of free moisture and at an optimum of 28-30°C (82-86°F), conidia will germinate in approximately 40 min. Desiccated germ tubes are able to renew growth when re-wetted, and, hence, infection can occur under conditions of alternating wet and dry periods. Germ tubes penetrate the leaf epidermis directly or enter through stomata. Infection of potato tubers usually occurs through wounds in the tuber skin. Wounds caused at harvest, that coincide with wet conditions favorable for spore germination, can lead to significant tuber infection. High soil moisture levels can cause swollen lenticels on tubers which are also easily invaded.
Time from initial infection to appearance of foliar symptoms is dependent on environmental conditions, leaf age, and cultivar susceptibility. Early blight is principally a disease of aging plant tissue. Lesions generally appear quickly under warm, moist conditions on older foliage and are usually visible within 5-7 days after infection.
A long wet period is required for sporulation, but it can also occur under conditions of alternating wet and dry periods. Conidiophores are produced during wet nights and the following day. Light and dryness induce them to produce spores, which emerge on the second wet night. Early blight is considered polycyclic with repeating cycles of new infection. Secondary spread of conidia is mainly by wind and occasionally by splashing water.
Symptoms of early blight
occur on fruit, stem and foliage of tomatoes and stem, foliage and tubers of potatoes. Initial symptoms on leaves appear as small 1-2 mm black or brown lesions. Under conducive environmental conditions, the lesions enlarge and are often surrounded by a yellow halo (Figures 2 and 3). Lesions greater than 10 mm in diameter often have dark pigmented concentric rings. This so-called "bullseye" type lesion is highly characteristic of early blight (Figure 4). As lesions expand and new lesions develop, entire leaves may turn chlorotic and dehisce, leading to significant defoliation. Lesions on stems are often sunken and lens-shaped with a light center and have the typical concentric rings (Figure 5). On young tomato seedlings, lesions may completely girdle the stem, a phase of the disease known as "collar rot," which may lead to reduced plant vigor or death.
Infection of both green and ripe tomato fruit normally occurs through the calyx with lesions sometimes reaching a considerable size (Figure 6). The lesions appear leathery and may have the characteristic concentric rings. Infected fruit will frequently drop prematurely. Symptoms on potato tubers are characterized by sunken, irregular lesions (Figure 7), which are often surrounded by a raised purple border. Beneath the lesion surface, the tuber tissue is leathery or corky with a brown discoloration. Early blight lesions on tubers tend to be dry and are less prone to invasion by secondary organisms compared to lesions of other tuber rots. After prolonged storage, severely diseased tubers may become shriveled.
YMV OF OKRA AND CONTROL
Yellow vein mosaic disease of bhendi
THE YELLOW vein mosaic disease of bhendi is a virus disease which causes heavy crop loss especially if the disease occurs in the early stages of crop growth.
The virus is transmitted by the white fly (Bemisia tebaci). The population of vector being high during hot summer months, the crop is often seriously affected then.
Vein clearing and veinal chlorosis of the leaves are the early symptoms.
As the disease progresses the yellow network of veins become very conspicuous and veins and vein-lets get thickened.
Distortion of leaf stalks and stems occurs at the advanced stage of infection.
Fruits become small and yellowish green.
The following measures are important in the management of the disease.
— Cultivate resistant varieties such as Arka Anamika (from IIHR banglore), Arka Abhay, parbhani kranti , surkh bhindi , safal , pahuja, subz pari ,selection-2 from NBPGR ,Hy. Co-3 and Punjab Padmini.
— In private sector –Hy. No 1 & 2 from sungro seeds and parbhawa from Nuziveedu seeds
— Use seeds collected from disease-free plants.
— Remove and destroy disease-affected plants from crop fields to avoid secondary spread.
— Destroy host weeds, such as Croton sparsiflora and Ageralium spp.
— Follow crop rotation.
— Control the insect vector by spraying dimethoate 0.03 per cent or monocrotophos 0. 05 per cent.
Biocontrol- leaf extract of Bougainvillea spectabilis & Prosopis chilensis was effective against white fly
Growing maize, sunflower or pearl millet as guard crop reported a markedly decrease in nos. of white flies per okra.
The disease is characterized by a homogenous interwoven net work of yellow veins enclosing islands of green tissue within. In extreme cases, the infected leaves become totally yellow or cream colour. Infected plants remain stunted and bear very few deformed and small fruits. The disease causes heavy loss in yield if the plants get infected within 20 days after germination.
2. One soil application of Furadon @ 1.5 kg a.i./ha at the time of sowing seeds is also recommended. 3. Infected plants must be removed from the field
THE YELLOW vein mosaic disease of bhendi is a virus disease which causes heavy crop loss especially if the disease occurs in the early stages of crop growth.
The virus is transmitted by the white fly (Bemisia tebaci). The population of vector being high during hot summer months, the crop is often seriously affected then.
Vein clearing and veinal chlorosis of the leaves are the early symptoms.
As the disease progresses the yellow network of veins become very conspicuous and veins and vein-lets get thickened.
Distortion of leaf stalks and stems occurs at the advanced stage of infection.
Fruits become small and yellowish green.
The following measures are important in the management of the disease.
— Cultivate resistant varieties such as Arka Anamika (from IIHR banglore), Arka Abhay, parbhani kranti , surkh bhindi , safal , pahuja, subz pari ,selection-2 from NBPGR ,Hy. Co-3 and Punjab Padmini.
— In private sector –Hy. No 1 & 2 from sungro seeds and parbhawa from Nuziveedu seeds
— Use seeds collected from disease-free plants.
— Remove and destroy disease-affected plants from crop fields to avoid secondary spread.
— Destroy host weeds, such as Croton sparsiflora and Ageralium spp.
— Follow crop rotation.
— Control the insect vector by spraying dimethoate 0.03 per cent or monocrotophos 0. 05 per cent.
Biocontrol- leaf extract of Bougainvillea spectabilis & Prosopis chilensis was effective against white fly
Growing maize, sunflower or pearl millet as guard crop reported a markedly decrease in nos. of white flies per okra.
The disease is characterized by a homogenous interwoven net work of yellow veins enclosing islands of green tissue within. In extreme cases, the infected leaves become totally yellow or cream colour. Infected plants remain stunted and bear very few deformed and small fruits. The disease causes heavy loss in yield if the plants get infected within 20 days after germination.
2. One soil application of Furadon @ 1.5 kg a.i./ha at the time of sowing seeds is also recommended. 3. Infected plants must be removed from the field
PGR'S AND THEIR USE IN PLANT TISSUE CULTURE
Introduction:-
Plant hormones (also known as plant growth regulators (PGRs) and phytohormones) are chemicals that regulate plant growth. Plant hormones are signal molecules produced at specific locations in the plant, and occur in extremely low concentrations. The hormones cause altered processes in target cells locally and at other locations. Plants, unlike animals, lack glands that produce and secrete hormones. Plant hormones shape the plant, affecting seed growth, time of flowering, the sex of flowers, senescence of leaves and fruits. They affect which tissues grow upward and which grow downward, leaf formation and stem growth, fruit development and ripening, plant longevity and even plant death.
Auxin
They stimulate cambium cells to divide and in stems cause secondary xylem to differentiate. Auxins act to inhibit the growth of buds lower down the stems, affecting a process called apical dominance, and also promote lateral and adventitious root development and growth. Auxins promote flower initiation, converting stems into flowers
Auxins are toxic to plants in large concentrations; they are most toxic to dicots and less so to monocots. Because of this property, synthetic auxin herbicides including 2, 4-D and 2, 4, 5-T have been developed and used for weed control. Auxins, especially 1-Naphthaleneacetic acid (NAA) and Indole-3-butyric acid (IBA), are also commonly applied to stimulate root growth when taking cuttings of plants. The most common auxin found in plants is indole-acetic acid or IAA.
• Stimulates cell elongation
• Stimulates cell division in the cambium and cell swelling, in tissue culture
• Stimulates differentiation of phloem and xylem
• Stimulates root initiation on stem cuttings and lateral (adventious) root development in tissue culture
• Mediates the tropistic response of bending in response to gravity and light
• The auxin supply from the apical bud suppresses growth of lateral buds
• Induces cell division and callus formation
• Involved in assimilate movement toward auxin possibly by an effect on phloem transport
• Stimulates the production of ethylene at high concentrations
• It inhibits adventious and axillary shoot formation
Plant Cell Culture Tested Auxins are generally used in plant cell culture at a concentration range of 0.01-10.0 mg/L. When added in appropriate concentrations, they may regulate cell elongation, tissue swelling, cell division, formation of adventitious roots, and inhibition of adventitious and axillary shoot formation, callus initiation and growth, and induction of embryogenesis..
Indole-3-butyric acid (1H-Indole-3-butanoic acid, IBA) is a white to light-yellow crystalline solid, with the molecular formula : C12H13NO2
As a Plant Hormone
IBA is a plant hormone in the auxin family and is an ingredient in many commercial plant rooting horticultural products.
For use as such, it should be dissolved in about 75% (or purer) alcohol (as IBA does not dissolve in water), until a concentration from between 10,000 ppm to 50,000 ppm is achieved - this solution should then be diluted to the required concentration using distilled water. The solution should be kept in a cool, dark place for best results. This compound had been thought to be strictly synthetic; however, it was reported that the compound was isolated from leaves and seeds of maize and other species.
Abscisic acid
Abscisic acid also called ABA, was discovered and researched under two different names before its chemical properties were fully known, it was called dormin and abscicin II. Once it was determined that the two latter named compounds were the same, it was named abscisic acid. The name "abscisic acid" was given because it was found in high concentrations in newly-abscissed or freshly-fallen leaves.
This class of PGR is composed of one chemical compound normally produced in the leaves of plants, originating from chloroplasts, especially when plants are under stress. In general, it acts as an inhibitory chemical compound that effects bud growth, seed and bud dormancy
• Inhibits shoot growth but will not have as much affect on roots or may even promote growth of roots.
• Inhibits the affect of gibberellins on stimulating de novo synthesis of a-amylase.
• Induces gene transcription especially for proteinase inhibitors in response to wounding which may explain an apparent role in pathogen defense.
• Induction of embryogenesis.
Cytokinins
Cytokinins are a group of chemicals that influence cell division and shoot formation.
They help delay senescence or the aging of tissues, are responsible for mediating auxin transport throughout the plant, and affect internodal length and leaf growth.
Cytokinins counter the apical dominance induced by auxins; they in conjunction with ethylene promote abscission of leaves, flower parts and fruits.
• Stimulates cell division.
• Stimulates morphogenesis (shoot initiation/bud formation) in tissue culture.
• Stimulates the growth of lateral buds-release of apical dominance.
• Stimulates leaf expansion resulting from cell enlargement.
• Promotes the conversion of etioplasts into chloroplasts via stimulation of chlorophyll synthesis.
Plant Cell Culture Tested Cytokinins are generally used in plant cell culture at a concentration range of 0.1-10.0 mg/L. When added in appropriate concentrations, they may regulate cell division, stimulate axillary and adventitious shoot proliferation, regulate differentiation, inhibit root formation, activate RNA synthesis and stimulate protein and enzyme activity.
Stock solutions of IAA and kinetin are stored in amber bottles covered with a black paper and kept in dark since they are unstable in light
Ethylene
Ethylene is a gas that forms from the breakdown of methionine, which is in all cells. Ethylene has very limited solubility in water and does not accumulate within the cell but diffuses out of the cell and escapes out of the plant. Its effectiveness as a plant hormone is dependent on its rate of production versus its rate of escaping into the atmosphere
Ethylene affects cell growth and cell shape; when a growing shoot hits an obstacle while underground, ethylene production greatly increases, preventing cell elongation and causing the stem to swell. Ethylene affects fruit-ripening: Normally, when the seeds are mature, ethylene production increases and builds-up within the fruit, resulting in a climacteric event just before seed dispersal. But, in tissue culture its function is unknown.
• Stimulates the release of dormancy.
• Stimulates shoot and root growth and differentiation (triple response)
• Have a role in adventitious root formation.
• Stimulates leaf and fruit abscission.
Giberallins
Gibberellins or GAs include a large range of chemicals that are produced naturally within plants and by fungi. They were first discovered when Japanese researchers noticed a chemical produced by a fungus called Gibberella fujikuroi that produced abnormal growth in rice plants. Gibberellins play a major role in seed germination, affecting enzyme production that mobilizes food production that new cells need for growth.
During seed germination, the seedling produces GA that is transported to the aleurone layer, which responds by producing enzymes that break down stored food reserves within the endosperm, which are utilized by the growing seedling. GAs increase internodal length. They promote flowering, cellular division, and in seeds growth after germination. Gibberellins also reverse the inhibition of shoot growth and dormancy induced by ABA. In tissue culture they are mainly used for plant regeneration. They are very essential for meristem culture.
• Stimulate stem elongation by stimulating cell division and elongation and growth of meristems or buds in vitro
• Stimulates bolting/flowering in response to long days.
• Breaks seed dormancy in some plants which require stratification or light to induce germination.
• Stimulates enzyme production (a-amylase) in germinating cereal grains for mobilization of seed reserves
Plant hormones (also known as plant growth regulators (PGRs) and phytohormones) are chemicals that regulate plant growth. Plant hormones are signal molecules produced at specific locations in the plant, and occur in extremely low concentrations. The hormones cause altered processes in target cells locally and at other locations. Plants, unlike animals, lack glands that produce and secrete hormones. Plant hormones shape the plant, affecting seed growth, time of flowering, the sex of flowers, senescence of leaves and fruits. They affect which tissues grow upward and which grow downward, leaf formation and stem growth, fruit development and ripening, plant longevity and even plant death.
Auxin
They stimulate cambium cells to divide and in stems cause secondary xylem to differentiate. Auxins act to inhibit the growth of buds lower down the stems, affecting a process called apical dominance, and also promote lateral and adventitious root development and growth. Auxins promote flower initiation, converting stems into flowers
Auxins are toxic to plants in large concentrations; they are most toxic to dicots and less so to monocots. Because of this property, synthetic auxin herbicides including 2, 4-D and 2, 4, 5-T have been developed and used for weed control. Auxins, especially 1-Naphthaleneacetic acid (NAA) and Indole-3-butyric acid (IBA), are also commonly applied to stimulate root growth when taking cuttings of plants. The most common auxin found in plants is indole-acetic acid or IAA.
• Stimulates cell elongation
• Stimulates cell division in the cambium and cell swelling, in tissue culture
• Stimulates differentiation of phloem and xylem
• Stimulates root initiation on stem cuttings and lateral (adventious) root development in tissue culture
• Mediates the tropistic response of bending in response to gravity and light
• The auxin supply from the apical bud suppresses growth of lateral buds
• Induces cell division and callus formation
• Involved in assimilate movement toward auxin possibly by an effect on phloem transport
• Stimulates the production of ethylene at high concentrations
• It inhibits adventious and axillary shoot formation
Plant Cell Culture Tested Auxins are generally used in plant cell culture at a concentration range of 0.01-10.0 mg/L. When added in appropriate concentrations, they may regulate cell elongation, tissue swelling, cell division, formation of adventitious roots, and inhibition of adventitious and axillary shoot formation, callus initiation and growth, and induction of embryogenesis..
Indole-3-butyric acid (1H-Indole-3-butanoic acid, IBA) is a white to light-yellow crystalline solid, with the molecular formula : C12H13NO2
As a Plant Hormone
IBA is a plant hormone in the auxin family and is an ingredient in many commercial plant rooting horticultural products.
For use as such, it should be dissolved in about 75% (or purer) alcohol (as IBA does not dissolve in water), until a concentration from between 10,000 ppm to 50,000 ppm is achieved - this solution should then be diluted to the required concentration using distilled water. The solution should be kept in a cool, dark place for best results. This compound had been thought to be strictly synthetic; however, it was reported that the compound was isolated from leaves and seeds of maize and other species.
Abscisic acid
Abscisic acid also called ABA, was discovered and researched under two different names before its chemical properties were fully known, it was called dormin and abscicin II. Once it was determined that the two latter named compounds were the same, it was named abscisic acid. The name "abscisic acid" was given because it was found in high concentrations in newly-abscissed or freshly-fallen leaves.
This class of PGR is composed of one chemical compound normally produced in the leaves of plants, originating from chloroplasts, especially when plants are under stress. In general, it acts as an inhibitory chemical compound that effects bud growth, seed and bud dormancy
• Inhibits shoot growth but will not have as much affect on roots or may even promote growth of roots.
• Inhibits the affect of gibberellins on stimulating de novo synthesis of a-amylase.
• Induces gene transcription especially for proteinase inhibitors in response to wounding which may explain an apparent role in pathogen defense.
• Induction of embryogenesis.
Cytokinins
Cytokinins are a group of chemicals that influence cell division and shoot formation.
They help delay senescence or the aging of tissues, are responsible for mediating auxin transport throughout the plant, and affect internodal length and leaf growth.
Cytokinins counter the apical dominance induced by auxins; they in conjunction with ethylene promote abscission of leaves, flower parts and fruits.
• Stimulates cell division.
• Stimulates morphogenesis (shoot initiation/bud formation) in tissue culture.
• Stimulates the growth of lateral buds-release of apical dominance.
• Stimulates leaf expansion resulting from cell enlargement.
• Promotes the conversion of etioplasts into chloroplasts via stimulation of chlorophyll synthesis.
Plant Cell Culture Tested Cytokinins are generally used in plant cell culture at a concentration range of 0.1-10.0 mg/L. When added in appropriate concentrations, they may regulate cell division, stimulate axillary and adventitious shoot proliferation, regulate differentiation, inhibit root formation, activate RNA synthesis and stimulate protein and enzyme activity.
Stock solutions of IAA and kinetin are stored in amber bottles covered with a black paper and kept in dark since they are unstable in light
Ethylene
Ethylene is a gas that forms from the breakdown of methionine, which is in all cells. Ethylene has very limited solubility in water and does not accumulate within the cell but diffuses out of the cell and escapes out of the plant. Its effectiveness as a plant hormone is dependent on its rate of production versus its rate of escaping into the atmosphere
Ethylene affects cell growth and cell shape; when a growing shoot hits an obstacle while underground, ethylene production greatly increases, preventing cell elongation and causing the stem to swell. Ethylene affects fruit-ripening: Normally, when the seeds are mature, ethylene production increases and builds-up within the fruit, resulting in a climacteric event just before seed dispersal. But, in tissue culture its function is unknown.
• Stimulates the release of dormancy.
• Stimulates shoot and root growth and differentiation (triple response)
• Have a role in adventitious root formation.
• Stimulates leaf and fruit abscission.
Giberallins
Gibberellins or GAs include a large range of chemicals that are produced naturally within plants and by fungi. They were first discovered when Japanese researchers noticed a chemical produced by a fungus called Gibberella fujikuroi that produced abnormal growth in rice plants. Gibberellins play a major role in seed germination, affecting enzyme production that mobilizes food production that new cells need for growth.
During seed germination, the seedling produces GA that is transported to the aleurone layer, which responds by producing enzymes that break down stored food reserves within the endosperm, which are utilized by the growing seedling. GAs increase internodal length. They promote flowering, cellular division, and in seeds growth after germination. Gibberellins also reverse the inhibition of shoot growth and dormancy induced by ABA. In tissue culture they are mainly used for plant regeneration. They are very essential for meristem culture.
• Stimulate stem elongation by stimulating cell division and elongation and growth of meristems or buds in vitro
• Stimulates bolting/flowering in response to long days.
• Breaks seed dormancy in some plants which require stratification or light to induce germination.
• Stimulates enzyme production (a-amylase) in germinating cereal grains for mobilization of seed reserves
SEED MOISTURE AND ITS DETERMINATION
Moisture content of seeds is one of the most important factors in the maintenance of seed quality. From the time of harvest to time of planting, seed moisture varies and if it rises above certain critical levels for any appreciable time period at any stage there is danger of undesirable stimulation of physiological processes within the seed with consequent weakening and loss of seed viability. Knowledge of moisture content therefore is needed to decide whether seeds should be dried down before storage or shipment and to determine proper conditions of storage.
Definition of Seed Moisture:-The moisture content a seed sample is the loss in weight when it is dried. It is expressed as a percentage of the weight of the original sample.
Determination of Seed Moisture: - Methods for measuring moisture content are generally classified as reference methods, routine methods and practical methods.
REFERENCE METHODS
Phosphorous pentoxide method-This method was described by leendertz (1948).In this method seeds are dried to a constant weight at 800C in a vacuum. The moisture is absorbed on phosphorous pentoxide placed in the same tube with the sample. This method is considered to be very accurate and is relatively free of the errors, namely the influence of the humidity of the air upon the sample, incomplete determination of moisture and decomposition of the sample from high temperature.
The ISTA recommends the vacuum phosphorous pentoxide method as a control in calibrating other methods suitable for routine work. The use of lower temperature and pressure, however, may not eliminate the possibility of losing non aqueous volatile matter.
Karl Fischer Method-This method was originated by Karl Fischer. It is considered to be most accurate method available for moisture determination. Determination of moisture content of seeds in this method is based upon the chemical reaction of water with Karl Fischer reagent (reaction of iodine with water in presence of SO2 and pyridine to form hydriodic acid and sulphuric acid).The water is extracted from the seed with a water solvent, methanol and titrated with the reagent. A modified stein mill is used for simultaneous grinding and extracting the grain sample. The water is extracted from the grain sample in 5 minutes at a temperature of 64.50C.Because the grain is ground and extracted quickly there is little chance of moisture loss. Because the Karl Fischer reaction is specific for the determination of water, other volatile constituents, which might be driven off by prolonged heating at high temperatures in the oven methods, are not calculated as water. The water is completely extracted because amount of water in the solvent. The only disadvantage of the method is that it requires a more skilled technician than the oven method and takes more time.
Advantage of analysis
The popularity of the Karl Fischer titration is due in large part to several practical advantages that it holds over other methods of moisture determination, including:
• High accuracy and precision
• Selectivity for water
• Small sample quantities required
• Easy sample preparation
• Short analysis duration
• Nearly unlimited measuring range (1ppm to 100%)
• Suitability for analyzing:
o Solids
o Liquids
o Gases
• Independence of presence of other volatiles
• Suitability for automation
The most important advantage of Karl Fischer titration method over conventional loss on drying (LOD) thermal methods of moisture determination is its specificity for water. Loss on drying will detect the loss of any volatile substance.
Definition of Seed Moisture:-The moisture content a seed sample is the loss in weight when it is dried. It is expressed as a percentage of the weight of the original sample.
Determination of Seed Moisture: - Methods for measuring moisture content are generally classified as reference methods, routine methods and practical methods.
REFERENCE METHODS
Phosphorous pentoxide method-This method was described by leendertz (1948).In this method seeds are dried to a constant weight at 800C in a vacuum. The moisture is absorbed on phosphorous pentoxide placed in the same tube with the sample. This method is considered to be very accurate and is relatively free of the errors, namely the influence of the humidity of the air upon the sample, incomplete determination of moisture and decomposition of the sample from high temperature.
The ISTA recommends the vacuum phosphorous pentoxide method as a control in calibrating other methods suitable for routine work. The use of lower temperature and pressure, however, may not eliminate the possibility of losing non aqueous volatile matter.
Karl Fischer Method-This method was originated by Karl Fischer. It is considered to be most accurate method available for moisture determination. Determination of moisture content of seeds in this method is based upon the chemical reaction of water with Karl Fischer reagent (reaction of iodine with water in presence of SO2 and pyridine to form hydriodic acid and sulphuric acid).The water is extracted from the seed with a water solvent, methanol and titrated with the reagent. A modified stein mill is used for simultaneous grinding and extracting the grain sample. The water is extracted from the grain sample in 5 minutes at a temperature of 64.50C.Because the grain is ground and extracted quickly there is little chance of moisture loss. Because the Karl Fischer reaction is specific for the determination of water, other volatile constituents, which might be driven off by prolonged heating at high temperatures in the oven methods, are not calculated as water. The water is completely extracted because amount of water in the solvent. The only disadvantage of the method is that it requires a more skilled technician than the oven method and takes more time.
Advantage of analysis
The popularity of the Karl Fischer titration is due in large part to several practical advantages that it holds over other methods of moisture determination, including:
• High accuracy and precision
• Selectivity for water
• Small sample quantities required
• Easy sample preparation
• Short analysis duration
• Nearly unlimited measuring range (1ppm to 100%)
• Suitability for analyzing:
o Solids
o Liquids
o Gases
• Independence of presence of other volatiles
• Suitability for automation
The most important advantage of Karl Fischer titration method over conventional loss on drying (LOD) thermal methods of moisture determination is its specificity for water. Loss on drying will detect the loss of any volatile substance.
SIGNIFICANCE OF CHELATION
THE SIGNIFICANCE OF CHELATION PROCESS IN SOIL ARE:
1. Increase the availability of nutrients.
Chelating agents will bind the relatively insoluble iron in high pH soil and make it available to plants.
2. Prevent mineral nutrients from forming insoluble precipitates.
The chelating agents of the metal ions will protect the chelated ions from unfavorable chemical reactions and hence increase the availability of these ions to plants. One example is iron in high pH soil. In high pH soil, iron will react with hydroxyl group (OH-) to form insoluble ferric hydroxide (Fe (OH) 3) which is not available to plants.
Fe+3 + 3 OH- --------> Fe (OH)3
Soluble Insoluble
Chelation will prevent this reaction from happening and hence render iron available to plants.
3. Reduce toxicity of some metal ions to plants.
Chelation in the soil may reduce the concentration of some metal ions to a non-toxic level. This process is usually accomplished by humic acid and high-molecular-weight components of organic matter.
4. Prevent nutrients from leaching.
Metal ions forming chelates are more stable than the free ions. Chelation process reduces the loss of nutrients through leaching.
5. Increase the mobility of plant nutrients.
Chelation increases the mobility of nutrients in soil. This increased mobility enhances the uptake of these nutrients by plants.
6. Suppress the growth of plant pathogens.
Some chelating agents may suppress the growth of plant pathogens by depriving iron and hence favor plant growth.
1. Increase the availability of nutrients.
Chelating agents will bind the relatively insoluble iron in high pH soil and make it available to plants.
2. Prevent mineral nutrients from forming insoluble precipitates.
The chelating agents of the metal ions will protect the chelated ions from unfavorable chemical reactions and hence increase the availability of these ions to plants. One example is iron in high pH soil. In high pH soil, iron will react with hydroxyl group (OH-) to form insoluble ferric hydroxide (Fe (OH) 3) which is not available to plants.
Fe+3 + 3 OH- --------> Fe (OH)3
Soluble Insoluble
Chelation will prevent this reaction from happening and hence render iron available to plants.
3. Reduce toxicity of some metal ions to plants.
Chelation in the soil may reduce the concentration of some metal ions to a non-toxic level. This process is usually accomplished by humic acid and high-molecular-weight components of organic matter.
4. Prevent nutrients from leaching.
Metal ions forming chelates are more stable than the free ions. Chelation process reduces the loss of nutrients through leaching.
5. Increase the mobility of plant nutrients.
Chelation increases the mobility of nutrients in soil. This increased mobility enhances the uptake of these nutrients by plants.
6. Suppress the growth of plant pathogens.
Some chelating agents may suppress the growth of plant pathogens by depriving iron and hence favor plant growth.
Chelation and Mineral Nutrition
CHELATION is a natural process. In order to prevent absorbed nutrients from precipitation resulting from the interaction of nutrients, such as iron forming precipitation with phosphorus, upon entering plant cells cationic nutrients will immediately form chelates with ORGANIC ACIDS such as citric acids, malonic cid, and some amino acids. This chelation process will then enable the nutrients to move freely inside the plants.
CHELATION in soil increases nutrient availability to plants. Organic substances in the soil either applied or produced by plants or microorganisms are the natural chelating agents. The most important substances having this nature are Hydroxamate Siderophores, Organic Acids and Amino Acids.
Hydroxamate Siderophores are naturally produced by soil microorganisms and are essential in natural ecosystems to solubilize and transport nutrients, especially iron to plant roots. Under Iron deficient I conditions, microorganisms will produce siderophores to overcome the iron starvation. Neilands and co-workers at the University of California found that Rhizobium meloti was able to correct the iron starvation using this mechanism. Neilands, Cline and co-workers of Colorado State University reported the abilities and mechanisms by which sunflower and sorghum acquire iron supplied as a ferrated hydroxamate siderophore. Research on oats by Read and co-workers of Colorado State and the University of Texas found that the absorption of iron from ferrichrome was nearly two orders of magnitude greater than that from the EDDHA treatment when there was excess supply of the ligand. Their results indicated that iron uptake by monocots may be more efficient from naturally occurring chelates than from synthetic chelates.
Organic acids and amino acids such as citric acid and glycine are also naturally occurring chelating agents. Glycine is the simplest amino acid with a molecular weight of 75. Chelates of glycine with cations such as iron, zinc, and copper have been fully studied
CHELATION is a natural process. In order to prevent absorbed nutrients from precipitation resulting from the interaction of nutrients, such as iron forming precipitation with phosphorus, upon entering plant cells cationic nutrients will immediately form chelates with ORGANIC ACIDS such as citric acids, malonic cid, and some amino acids. This chelation process will then enable the nutrients to move freely inside the plants.
CHELATION in soil increases nutrient availability to plants. Organic substances in the soil either applied or produced by plants or microorganisms are the natural chelating agents. The most important substances having this nature are Hydroxamate Siderophores, Organic Acids and Amino Acids.
Hydroxamate Siderophores are naturally produced by soil microorganisms and are essential in natural ecosystems to solubilize and transport nutrients, especially iron to plant roots. Under Iron deficient I conditions, microorganisms will produce siderophores to overcome the iron starvation. Neilands and co-workers at the University of California found that Rhizobium meloti was able to correct the iron starvation using this mechanism. Neilands, Cline and co-workers of Colorado State University reported the abilities and mechanisms by which sunflower and sorghum acquire iron supplied as a ferrated hydroxamate siderophore. Research on oats by Read and co-workers of Colorado State and the University of Texas found that the absorption of iron from ferrichrome was nearly two orders of magnitude greater than that from the EDDHA treatment when there was excess supply of the ligand. Their results indicated that iron uptake by monocots may be more efficient from naturally occurring chelates than from synthetic chelates.
Organic acids and amino acids such as citric acid and glycine are also naturally occurring chelating agents. Glycine is the simplest amino acid with a molecular weight of 75. Chelates of glycine with cations such as iron, zinc, and copper have been fully studied
MOST COMMON DISEASES OF MANGO AND THEIR CONTROL
Black-tip
The first symptom of the disease is the development of a small aetiolater area at the distal-end of fruits which show an intensification of the normal green colour against the general green colour of the skin. Later affected area spreads, turns nearly black and covers the tip completely, The infected fruits do not ripe properly.
Control: The incidence of black tip can be minimized by spraying of borax (1%). The first spray should be done positively at pea-sized stage, followed by 2 more sprays at 15 days interval. Planting of mango orchard in north-south direction and 5-6 km away from the brick kilns reduces the incidence of black tip to a greater extent.
Anthracnose
Caused by Colletotrichum gleosporioides, it affects leaves, petioles, twigs, blossoms and fruits. The symtoms appear as oval or irregular vinaceous brown to deep brown spots of various sizes scattered all over the leaf sufraces. Under damp conditions, the fungus grows rapidly forming elongated, brown, necrotic areas measuring 20-25 mm in diameter. Petioles, when affected, turn grey or black. The leaves droop down, slowly dry up and ultimately fall-off, leaving a black scar on twigs. Disease produces elongated black necrotic areas on twigs. The tip of very young branches start drying from tip downwards showing characteristic symptoms of wither tip. Young leaves are more prone to attack than the older ones. The earliest symptoms of the disease are the production of blackish-brown specks on peduncle and flowers. Small, black spots appear on panicles and open flowers, which gradually enlarge and coalesce to cause drying of flowers.
Initially the sopts are round but later coalesce to form large irregular botches. The spots have large, deep cracks and the fungus penetrates deep into the fruit causing extensive rotting.
Control: Diseased leaves, twigs and fruits, lying on the floor of the orchard, shoud be collected and burnt. All infected twigs from the tree should be pruned and burnt.
Blossom/foliar infection can be controlled effectively by spraying of Carbendazim (0.1%) or copper oxychloride (0.3%) twice at 15 days interval. Hot-water treatment at 52°C for 30 minutes gives good control to anthracnose. However, its duration can be reduced to 15 minutes by supplementing with Carbendazim or thiophanate methyle (0.1%).
Malformation
It is caused by Fusarium subglutinans. Vegetative malformation is pronounced in young seedlings. The affected seedlings develop excessive vegetative growth. The internodes are of limited growth and short. These form buches of various sizes which are often produced on the top of the seedlings giving bunchy-top appearance.
The characteristic symptom of floral malformation is reduction in length of the primary axis and the secondary branches of the panicle which make the flowers appear in clusters. The flower buds are transformed into vegetative buds. A large number of small leaves and stems, characterized by appreciable reduced internodes, give an appearance of withers broom like appearance.
Control : Application of NAA (200ppm) in the first week of October followed by deblossoming in late-December or January reduces its incidence. The floral malformed panicles/ vegetative malformed shoots should be pruned regularly and burnt.
Black-tip
The first symptom of the disease is the development of a small aetiolater area at the distal-end of fruits which show an intensification of the normal green colour against the general green colour of the skin. Later affected area spreads, turns nearly black and covers the tip completely, The infected fruits do not ripe properly.
Control: The incidence of black tip can be minimized by spraying of borax (1%). The first spray should be done positively at pea-sized stage, followed by 2 more sprays at 15 days interval. Planting of mango orchard in north-south direction and 5-6 km away from the brick kilns reduces the incidence of black tip to a greater extent.
Anthracnose
Caused by Colletotrichum gleosporioides, it affects leaves, petioles, twigs, blossoms and fruits. The symtoms appear as oval or irregular vinaceous brown to deep brown spots of various sizes scattered all over the leaf sufraces. Under damp conditions, the fungus grows rapidly forming elongated, brown, necrotic areas measuring 20-25 mm in diameter. Petioles, when affected, turn grey or black. The leaves droop down, slowly dry up and ultimately fall-off, leaving a black scar on twigs. Disease produces elongated black necrotic areas on twigs. The tip of very young branches start drying from tip downwards showing characteristic symptoms of wither tip. Young leaves are more prone to attack than the older ones. The earliest symptoms of the disease are the production of blackish-brown specks on peduncle and flowers. Small, black spots appear on panicles and open flowers, which gradually enlarge and coalesce to cause drying of flowers.
Initially the sopts are round but later coalesce to form large irregular botches. The spots have large, deep cracks and the fungus penetrates deep into the fruit causing extensive rotting.
Control: Diseased leaves, twigs and fruits, lying on the floor of the orchard, shoud be collected and burnt. All infected twigs from the tree should be pruned and burnt.
Blossom/foliar infection can be controlled effectively by spraying of Carbendazim (0.1%) or copper oxychloride (0.3%) twice at 15 days interval. Hot-water treatment at 52°C for 30 minutes gives good control to anthracnose. However, its duration can be reduced to 15 minutes by supplementing with Carbendazim or thiophanate methyle (0.1%).
Malformation
It is caused by Fusarium subglutinans. Vegetative malformation is pronounced in young seedlings. The affected seedlings develop excessive vegetative growth. The internodes are of limited growth and short. These form buches of various sizes which are often produced on the top of the seedlings giving bunchy-top appearance.
The characteristic symptom of floral malformation is reduction in length of the primary axis and the secondary branches of the panicle which make the flowers appear in clusters. The flower buds are transformed into vegetative buds. A large number of small leaves and stems, characterized by appreciable reduced internodes, give an appearance of withers broom like appearance.
Control : Application of NAA (200ppm) in the first week of October followed by deblossoming in late-December or January reduces its incidence. The floral malformed panicles/ vegetative malformed shoots should be pruned regularly and burnt.
Thursday, July 10, 2008
Stem Gall of Coriander
PD1 variety-resistant to stem gall
Management-it has been possible to obtain at least a partial field control of this disease, through seed treatment with thiram at the dose of 0.25 kg per 100 kg of seed.
Spray 0.1% solution of Bavistin when the symptoms start appearing and repeat the spraying at an interval of 20 days till the disease is completely controlled.
Characterstic Symptom-Galls glossy when new and become rough later they are 15mm long and 4mm broad.
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