Hybrid Seed Production of Tomato

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How to produce the hybrid seed in tomato

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Hybrid Seed Production of Tomato Hybrid Tomato M.K. Karnwal Asstt. Professor, Genetics & Plant Breeding College of Agriculture G.B.P.U.A.&T., Pantnagar

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Hybrid Seed Production of Tomato Hybridization : “ The mating or crossing of two plants or lines of dissimilar genotype is k/a Hybridization” Crossing : In plants crossing is done by placing pollen grains from one genotype (called the male plant) in to the stigma of flowers of the other genotype ( referred to as female plant)

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Hybrid Seed Production of Tomato Hybrid tomato varieties have many advantages compared to open-pollinated varieties. Hybrids usually produce higher yields. They generally mature earlier and more uniformly. Many hybrids have better fruit quality and disease resistance. The demand for hybrid tomato seeds can open a new market for growers interested in seed production. ... But hybrid tomato seed production is not easy. First, it requires much labor , especially during the time of making crosses. To be more specific, it requires 2-3 trained persons working for 5-6 weeks for every 0.1 ha of indeterminate female plants, or 4-6 trained persons working for 3 weeks on the same area of determinate female plants. Fortunately, the availability of labor is not a significant problem in developing countries. Second , it requires the mastery of special skills and a close attention to detail. This tutorial will teach these skills.

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Hybrid Seed Production of Tomato Corner Stone of Hybridization : Three corner stone S.N. Corner Stone Activity to Achieve the Corner Stone 1. Prevention of Self Pollination in the Flowers of Female Parent Emasculation of The Flower 2. Prevention of Pollination of Flowers of Female Parent by undefined Pollen Sources Bagging of The Female Flower 3. Ensuring Pollination by the selected Male Parent Hand Pollination

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Hybrid Seed Production of Tomato Procedure of Hybridization : Seven Steps are involved in the Hybridization programme Sl.N Steps Activity Remarks 1. Choice of Parent According to their per-se performance The selected parent must posses the good quality 2. Evaluation of Parent e.g. Disease resistance High yielder etc. ( Combining ability Tested i.e. GCA or SCA) GCA- Broad Genetic Base SCA – Narrow Genetic Base 3. Emasculation of The Female Flower Cold and Hot Treatment Hand Emasculation, Alcohol Treatment Method Suction Method, Genetic Emasculation( GMS, CMS, CGMS) Thermosensitive and Photosensitive male Sterility and Transgenic and Chemical Induced Male Sterility Removal of The male part of the flower 4. Bagging Butter paper and Vegetable Parchment bags are commonly used To avoid the Contamination 5. Tagging The Emasculated Flower/ bud immediately tagged( Date of Emasculation, Pollination, Name of Male and Female Parent) For easy identification 6. Pollination Mature, fertile and Viable pollens are dusted on the stigma of female Flower To ensure the hybridizatiuon 7. Harvesting of F1 Seed Harvested only the crossed fruit( the tagged/ marked fruits only)

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Crop Management Climate and Soils Ideal growing conditions are needed to produce high quality seed. Tomatoes grow best in the dry season under day temperatures of 21-25°C and night temperatures of 15-20°C . Vines will struggle to set fruit if temperatures exceed 30°C. Humidity is an important factor. Humidity levels higher than 60% at the time of fruit maturity will increase disease problems and reduce seed yields. it will leads to low yields and poor seed quality. Bacterial Spot ( common during the hot, rainy season )

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Avoid planting your tomato seed crop in a field previously planted with tomato, pepper, eggplant, or other Solanaceous crops. This will prevent the build-up of diseases and insects. Growing tomato after paddy rice reduces the incidence of diseases and nematodes. Crop Management Avoid planting a tomato seed crop following the planting of a Solanaceous crop Optimum soil pH for tomato is 6.0 to 7.0; disorders such as blossom end rot are common if soil pH is lower than 5.5. Blossom End Rot

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Selecting Parents and Sowing Crop Management F1 hybrid seed production involves the crossing of two different inbred lines . Either line can be the female or male parent, but normally the best seed yielder is selected as the female parent. Both parents should be pure, preferably being self-pollinated for more than 6 generations (this is called inbreeding). Parents are selected for their desirable traits (high yields, disease resistance, fruit quality, earliness, etc.). It is important to have plenty of pollen available for making hybrid crosses. Since tomato vines bloom profusely, a ratio of 1 male for every 4 female plants is recommended. Seeds of male plants are sown 3 weeks earlier to ensure that pollen is available from the beginning of breeding operations. Growing transplants

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Isolation Each tomato flower has both male and female parts. Male organs called stamens are illustrated in blue . The female organ, called the pistil , consists of a style and an ovary (shown in pink). Nearly all tomato lines, including today's modern varieties, are self-pollinating . In other words, the pollen from each flower's stamens fertilize only the ovary of the same flower. Isolation of these male and female parental lines is not necessary. Male plants can be planted as close as 2-m from female plants. Crop Management

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Isolation There are a few exceptions. Currant tomatoes ( Lycopersicon pimpinellifolium ) and potato-leaf types of L. esculentum generally have styles that protrude outside their blossom. These lines are more attractive to insects and thus, more likely to be cross-pollinated . Netting or caging to exclude pollinating insects is required if any of these types are used as female lines. Also, do not collect seeds of double fruits since double flowers are more prone to insect pollination. Crop Management Seed crop grown under netting (pepper crop shown)

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Crop Management Special Cultural Practices Healthy plants produce healthy seeds. Pests should be controlled . Nutrient and water management should be optimal to achieve good fruit and seed yield. Plant Location and Spacings Male lines are usually planted in a different location to facilitate operations and avoid shading from competing plants. Select a sunny spot to promote maximum production of flowers and pollen.

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Crop Management Special Cultural Practices Plant Location and Spacing Male and female lines are planted in double-row raised beds . The height of the bed during the dry season (recommended for seed production) is 20 cm, and the centers of beds are spaced 150 cm apart. For female lines , the plants are spaced 50 cm apart within the row. Plants are trellised along with plants from the adjoining bed so that work operations can be easily done on the raised bed rather than in the irrigation furrow. For male lines , the plants are spaced 40 cm apart within the row. Plant arrangements for female and male lines

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Crop Management Staking and Pruning The female parent is staked. Staking facilitates the handling of plants during emasculation and pollination. Staking also keeps the ripening fruits above the ground and prevents rotting. Among male lines, only indeterminate types need to be staked. Removing Off-Types The male and female lines must be 100% pure. Know the plant habit, leaf type, immature fruit characters (shape, size, green vs. uniform shoulder) of each parent. Regularly inspect the plants. Remove any off-type (usually inferior) or virus-infected plants before hybridization procedures begin. Symptoms of viruses that attack tomato include yellow mottling of leaves; severe curling, cupping or other distortion of foliage; and stunting of plants. Tomato Mosaic Virus Tomato Yellow Leaf Curl Virus Cucumber Mosaic Virus

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Hybridization Step #1. Emasculation Self-pollination cannot be allowed in hybrid seed production. The female flower must be pollinated by the pollen from the male line! To prevent self-pollination, remove the stamens from the flower buds of the female line before they shed their pollen. This process is called emasculation . Emasculation begins about 55-65 days after sowing. Flower buds from the second cluster which will open in 2-3 days are chosen for emasculation. The petals will be slightly out of the flower bud but not opened, and the corolla color is slightly yellow or even paler. Flowers from the first cluster are removed. Selecting bud for emasculation

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Hybridization Step #1. Emasculation Sterilize the forceps, scissors and hands by dipping them in 95% alcohol before emasculation is started. If gloves are used, these should also be dipped in 95% alcohol to prevent pollen contamination. Use sharp-pointed forceps to force open the selected buds. Then, split open the anther cone. Carefully remove the anther cone out of the bud, leaving the calyx, corolla and pistil. Sterilizing equipment Opening anther cone Removing anther cone

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Hybridization Step #1. Emasculation To help identify the hybrid fruits from selfed fruits at the time of harvest, cut a few of the sepals using a scissors. Cutting sepals and petals for identification

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Hybridization Step #2. Pollen Collection Collect flowers from the male parent to extract pollen. The best time for pollen collection is during the early morning before the pollen has been shed. Avoid pollen collection on rainy days Remove the anther cones from the flowers and put them in glassine envelopes . Dry the anther containers by placing them 30 cm below a 100-watt lamp for 24 hours . The lamp creates a drying temperature of about 30ºC . Pollen can also be sun-dried Collecting flowers for pollinating Putting anther cones in envelopes Drying anther cones

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Hybridization Step #2. Pollen Collection Put the dried anther cones in a plastic pan or cup. Cover the cup with a fine mesh screen (200-300 mesh) and then seal it with a similar tight-fitting cup, serving as a lid. Shake the cup about 10-20 times so that the pollen is collected in the “lid” cup. Transfer the pollen into a small convenient-to-handle container for pollination. Fresh pollen is best for good fruit-set . It can be kept for one day at moderate room temperature. Prepare for shaking Collecting pollen from anther cones Transferring pollen

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Step #2. Pollen Collection When weather conditions are not suitable for pollination, dried or dehydrated pollen can be stored in a sealed container (capsule or vial) and kept in the freezer for about a month. Without freezing, the pollen can be kept in an ordinary refrigerator for 2-3 days without any significant loss in viability. The pollen should be taken from the freezer and kept closed until the container warms to room temperature. This will prevent the pollen from getting wet due to condensation. Hybridization

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Hybridization Step #2. Pollination Emasculated flowers are generally pollinated two days later . Try to avoid pollination on rainy days. The corolla of the emasculated flower turns bright yellow , signalling that the stigma is ready for pollination. Expose the stigma to facilitate pollination Dip the stigma into the pool of pollen in the pollen container or ... .. pollinate by touching the stigma with the tip of the index finger dipped in the pollen pool. Exposing the stigma (tip of style) Dipping stigma into pollen Pollinating by using finger

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Hybridization Step #2. Pollination Pollination is usually done 3 times weekly over a 3-5 week period . Successful pollinations are easily seen within one week by the enlargement of the fruit. After breeding operations are completed, any non-crossed flowers on the female plants are removed to lessen the chance of contamination from selfed seeds before harvest .

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Fruit Production Fruit Production The number of hybrid fruits produced per plant depends on the fruit size of the maternal parent. As a rule of thumb , maintain the following: 30 fruits for large-fruited parent; 40 fruits for medium-fruited parent; and 50 or more fruits for small-fruited parent. Hybrid fruits are easily recognized by their cut sepals. Remove the naturally-pollinated (non-hybrid) fruits from the female plants. This removal will prevent the accidental mixture of non-hybrid with hybrid fruits. Furthermore, non-hybrid fruits will steal nutrition away from the ripening hybrid fruits. Fruits with hybrid seeds (observe the cut sepals)

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Fruit Production and Harvesting Harvesting Tomato fruits ripen about 50-60 days after pollination , but may take longer if temperatures are cool. Keep the fruits on the vine until they are fully mature , preferably to the pink or red ripe stage. This enables the seed to develop normally and fully. If fruits are harvested at an earlier stage, place them in a covered, cool dry place for 3 or 4 days until they become red ripe. Be sure to check for the clipped sepal before harvesting fruit. Collect fruits in nonmetallic containers , such as nylon net bags, plastic buckets, or crates. Metal containers may react with acids in the tomato juice and affect seed viability. Hence, they should not be used. Harvesting fruits

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Seed Processing Manual Seed Extraction Extraction may be done either manually or mechanically. To extract manually, it's best to harvest the fruit in nylon bags. Crush the fruits by trampling with feet Put the bags of crushed fruits into big plastic containers and ferment to separate the gel mass embedding the seeds . To hasten the fermentation process, put weights over the bags or keep the fruits submerged in the liquid fruit mass. Nylon bags filled with fruit Crushing fruit Fermenting seeds

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Seed Processing Manual Seed Extraction The time of fermentation depends upon the ambient room temperature. If temperature is above 25ºC, one day of fermentation may be sufficient . If below, 2 days of fermentation may be needed. Fermentation for more than 3 days may spoil the seeds quality . Put the seeds in an open plastic container. Then, fill up the container with water and stir the seeds to allow the pieces of flesh and skin sticking on the seeds to float. Incline the container and gently remove the floating refuse, making sure that the seeds remain at the bottom . Repeat the washing several times , adding fresh water to the container every time until all the flesh and gel are completely removed, leaving clean seeds at the bottom. Removing debris Cleaning seed Cleaning seed

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Seed Processing Mechanical Seed Extraction Mechanical seed extraction is used by large-scale operations . Put the ripe fruits into the mechanical seed extractor for crushing and separation of the seeds and gel from the pulp Gather the seeds and gel mass in a suitable container such as plastic tub or bucket. Instead of fermentation , treat the seed-gel mass with 0.7% hydrochloric acid (HCl) at a rate of seven milliliters of HCl per kilogram of seed-gel mass (Figure 27). Stir the seed-gel mass while the acid is being added. Continue stirring for 40 minutes until the gel is visibly softened or dissolved. Caution: Higher concentration of acid or longer treatment will injure the seeds. Placing fruit into mechanical seed extractor Extracted seed and gel mass Treating with hydrochloric acid to remove gel that surrounds seed

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Seed Processing Mechanical Seed Extraction When the seed is separated from the gel, pour the acid-treated seeds into a clean fine-mesh bag. Wash the bag with tap water thoroughly so that no acid is left on the seeds’ surface. While washing, step on the bag to squeeze out the remaining gel. Place the seeds into a plastic container, filling it to one-third capacity . Then, fill up the container with tap water. Stir the seeds to enable the small pieces of flesh and skin to float. Incline the container and remove the floating debris. Make sure the seeds remain at the bottom of the container. Repeat the washing procedure several times until all the debris is gone and the seeds are clean. Washing acid from seed Cleaning seed

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Seed Processing Seed Drying Placed the washed seeds in fine-mesh bags. Excess water can be removed by hanging the seeds in the shade for a day. An even quicker way to remove excess water from seeds is to spin them in a washing machine . Use the spin-cycle of a clothes washing machine (don't wash the seeds, only spin dry them). After the excess water is removed, uniformly spread the partially dried seeds in a flat plastic container or aluminum pan. Loosen any clumps of seeds . Enclose this container with its seeds into a net nylon bag. Spin-drying seeds Loosening clumps of seeds

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Seed Processing Seed Drying Place the container in a seed dryer . Drying continues for 3-4 days , maintaining a temperature of 28-30ºC . Higher temperatures at the time of drying may cause seeds to germinate. Stir the seeds 2-3 times daily so that seeds dry uniformly. Loosen any seeds that clump together. These procedures will get the seeds to the desired 6-8% moisture content . Placing seeds in seed dryer

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Seed Processing Seed Packaging and Storage Pack and deliver the dried seeds according to specifications of the seed company or contract agency. If necessary, tomato seeds can be safely stored for at least 3-5 years. Place seeds in manila envelopes, cloth or mesh bags, plastic containers, or foil envelopes. The best containers are airtight, such as a sealed glass jar, metal can or foil envelope. Label each container carefully. Note the names of the hybrid and parents, the year, and any other information you feel is valuable.

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Seed Processing Seed Packaging and Storage Store seeds in a cool, dry place. Small quantities can be kept in an air-tight container inside a refrigerator. For larger quantities, a special room with controlled humidity and temperature should be used. The temperatures should not exceed 20°C and relative humidity (RH) in the storage area should not exceed 30%. Seed storage room

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Hybrid of Tomato Hybrids of Tomato So many hybrid varieties of Tomato have been developed by the public and private sectors Public sector Hybrid Private Sector Hybrid Pant Hybrid 2, Pant Hybrid 10, Kt-4, Pusa Hybrid 1, Pusa Hybrid 2, Pusa Hybrid 3, Pusa Hybrid 4, Arka Shreshta, Arka Vardan, Arka Abhijit etc. Sheetal , Rupali , Mangla , Naveen, MTH-2, MTH-6, MTH-15, MTH-16, Priti , Ratna , Sadabahar , Lerica , Vijay, Vipul , Sc-9, GS-12, SH-18, Sutton Gram Wonders, Masuraj , Arth-3, Arth-4, ATH-1, NARF-101, Avinash-2, BSS-172, BSS-175, Madhuri , Meenakshi ( BSS-20), Manisha (BSS-99), Meghna ( BSS-98), Rashmi , Karnataka Vaishali etc.

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Thanks

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Hybrid Seed of Tomato Quiz 1. Hybrid varieties are generally superior to open-pollinated types because: a. They produce higher yields b. They mature earlier and more uniformly c. They resist more diseases 2. Ideal growing conditions are required for the production of high quality seed. ……..Off-season production should be avoided. 3. How does the breeder select which line is the female line? ……….. The line that produces most seeds 4. To ensure enough pollen, grow 4 plants of the male line for each 1 plant of the female line. ………False, grow 1 male for 4 female plants

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Hybrid Seed of Tomato Quiz 5. To prevent self-pollination, which of these flower parts must be removed before it sheds its pollen? ……………….. Stamens 6. Why are female lines staked and pruned? …………..Easier to pollinate flowers …………… Less rotting of fruits 7. When is the best time to harvest pollen for making crosses? Early morning …………before pollen is shed 8. What technique is used to identify fruits containing hybrid seeds? ……………. Flower sepals are clipped