Method of seed production

Method of seed production
    Stages of seed production
    • For seed multiplication and certification purposes following stages are recognized. BS FS I FS II CS I – CS II.
    • CS II: This is done in case of those varieties which have a low rate of multiplication and in years of shortage of seeds.
    Land requirements
    • A crop of seed potato shall not be eligible for certification if grown on land infested with wart and/or cyst forming nematodes; or brown rot or non cyst forming nematodes within the previous three years; and common scab. Preference should be given to two to three years crop rotation.
    Isolation requirements
    • A minimum isolation distance of 5 m for foundation and certified seed class should be provided all around a seed field to separate it from fields of other varieties, and fields of the same variety not conforming to varietal purity and health requirements for certification.
    Time of Sowing
    • The sowing should be done from 20th September (when rainfall is low) or 25th September up to 15th October. Delayed plantings will result in poor yields.
    Seed rate
    • Seed rate depends upon tuber size. Twenty five to 30 qtls of seed potato per hectare will be sufficient if the usual sized tubers (4 to 6 cm) are used.
    • All size of tubers like large, medium and small may be utilized as seed, but the medium size (25 – 55 mm or 25-75 g) often called as seed size performs better than other size grades as seed material.
    Fertilization
    • 125:80:100 kg NPK with 25t FYM/ha. Apply all phosphorus, potash and half of the nitrogen at the time of sowing. The remaining half of nitrogen should be applied about thirty five days after sowing, or when the plants are about to 30 cm height. For best results, the fertilizers should be placed either 5 cm below the tubers or on the sides.
    Method of sowing
    • Whole tubers should be used for planting. Tubers should be under sprouting (sprouts 0.5 to 1 cm long) for quick emergence. After 15th October when the temperature goes down, cut tubers can also be used for planting. Care must be taken that each piece to be used for planting has two or three emerging eyes and weighs at least 40 gm. By this practice the seed rate is reduced considerably. Plant the tubers 3 to 4 cm deep in the soil having adequate moisture. Row to row spacing at 60 cm and tuber to tuber spacing at 15 to 20 cm is recommended.
    Irrigation
    • Potato requires light and frequent irrigation. First irrigation should follow immediately after emergence. Subsequent irrigations should be given at proper intervals. Restrict the irrigation after the crop has tuber raised well. Withhold irrigation by the third week of December i.e., ten to fifteen days before cutting of haulms.
    Interculture
    • Keep the field free from weeds. At least one earthingup is a must. It should be done when plants attains the height of 15 cm.
    Haulm cutting
    • The practice of haulm cutting is adopted as a precautionary measure to avoid chances of viral disease transmission through the vectors like aphids. The haulms must be cut by the end of December, or at the latest by the first week of January before the aphid population reaches the critical stage (20 aphids per hundred compound leaves). No re-growth should be allowed.
    Roguing
    • Very careful roguing is required for producing a high quality crop of seed potato. The roguing is to be done at the following stages.
    First roguing
    • First roguing should be done 25 days after sowing to remove:
    • a) All virus affected plants and b) All plants apparently belonging to other varieties and which can be identified from foliage.
    Second roguing
    • It should be done when the crop is fully grown. This would be about 50 to 60 days after sowing. At this time tubers are formed and therefore, while roguing, not only the upper portion of plant, but all the tubers belonging to the plant should be removed carefully. Also at this stage the virus affected plant as well as off type, should be removed.
    Third roguing
    • This is the third and final roguing and should be done just before cutting the foliage. Foliage should not be cut unless this roguing has been completed. At this stage, all virus affected plant and off type plants, along with their tubers have to be very carefully removed.
    Harvesting
    a. The crop is ready for harvest ten to fifteen days after haulm cutting when the skin of tuber has hardened. Premature harvesting causes handling problems, as the soft skin gets easily peeled of and further such tubers cannot withstand long transportation and storage.
    b. At the time of potato digging, the moisture in soil should be optimum for obtaining clean tubers.
    c. The harvesting of seed potatoes can be done by any of the equipment available in the market for this purpose. Every effort should be made to avoid cuts, bruises, etc. After harvesting, tubers should not be left exposed to the hot sun for a prolonged period (not more than an hour). It should be immediately lifted and carried to an airy shed and kept in piles (height 1 m, width 3 m) for 7 to 10 days so that the superficial moisture evaporates and further hardening of skin is achieved. If sheds are not available, piles may be made in field and covered with dry haulms.
    Sorting and Grading
    • When the potatoes are properly cured, grading should be done. A single grade from 3.0 to 5.5 cm is being made at present for `Plain Seed' by hand grading. While grading, the shape, colour, depth of eyes, etc. of tubers should be critically examined and off types discarded. In addition to off types, the tubers with cuts, bruises, cracks or otherwise mechanically damaged or showing visible symptoms of late blight, dry rot, charcoal rot, wet rot, scab, black scruf, etc. should invariably be removed.
    Seed standards
    • Size of seed tuber: 4 6cm x 2.5 to 3.5cm in diameter; weight: 20 40g
    Packing
    • After sorting and grading the seed potatoes should be put in clean jute hessian bags (50 kg size) and the bags appropriately labeled.
    Storage
    • Soon after packing, the seed potatoes should be moved to the end use areas for cold storage. If the ambient temperatures are above 32°C, the seed potato should first be kept in pre-cooling chambers, or in a cool place for preconditioning, and then stored in cold storage at temperatures from 2.2 to 3.3° C and 75 to 80 % relative humidity. Periodic inspection of seed stocks in cold storage is necessary, to ensure that stocks are keeping good. Turning of bags during rainy season helps in improving aeration.
    • Potato is traditionally grown vegetatively through seed tubers. This results in continuous accumulation and increase of various tuber borne diseases in seed tubers and consequent reduction in crop yields. To overcome these problems a new potato production technology making use of True Potato Seed (TPS) as planting material for raising the crop has been developed. TPS can serve as a cheap and highly productive planting material for raising commercial potato crop, especially in areas where good quality seed tubers at reasonable prices and in adequate quantities are not available.
    The major advantages of this technology over the traditional seed tuber technology are as follows:
    1. Unlike the seed potato production which is confined to northern India only, the TPS can be produced in all potato growing regions.
    2. The crop raised through TPS is almost disease free as most of the diseases get filtered out during TPS production.
    3. The TPS being very small, can be stored and transported easily, whereas the seed tubers are bulky hence the storage and transport are expensive.
    4. TPS provides a low cost potato production technology where only about 50 g TPS is required for sowing in about 375 m2 area for producing seedling tubers enough for planting one hectare next year. About 150 g TPS/ha is required if the commercial crop is to be raised in the first year itself by transplanting seedlings in field.
    The TPS technology involves two major steps viz.,
    1. (a) Production of hybrid seeds and
    2. (b) Its used as planting material for raising the commercial crop.
    • Two high yielding TPS hybrids viz., TPS C 3 and HPS 1/13 have been recommended for commercial use.
    Hybrids and their parents
    TPS C‑3 : JTH/C.107 X JEX/A 680‑16
    (Female x Male)
    HPS 1/13 : MF.1 x TPS‑13
    (Female x Male)

    Production of Hybrid TPS
    • The hybrid TPS can be produced both in the hills, where the crop is grown during long summer days and also in the plains where the crop is grown in winters. Whereas, in the hills the crop flowers natural and hybridization for seed production can be done easily; in the plains, however, additional light has to be provided to induce flowering in the crop. In northern plains, where the winters are severe, the parental lines need to be planted either about 15 20 days before optimum time of the planting of the crop, or the planting is delayed till the second week of November so that the flowering time does not coincide with the severe winter period. Delayed planting of parental lines should not be done in frost prone areas.
    Following steps are involved in the production of hybrid True Potato Seed (TPS)
    1. If the TPS parents are planted in the plains, there is generally need to provide extra light for about 5 hours at the end of the day to prolong the day length and get proper flowering. Arrangements can be made for providing light from 150 W sodium vapour lamp (one for about every 100 sq.m). Light arrangement is not required if the parents are planted (in April/May) in the northern hills during summer crop season.
    2. Plant male and female parental lines (TPS 13 as male and MF 1 as female for producing hybrid TIPS HIPS V13, and JEX/A 680 16 as male and JTH/C 107 as female for producing hybrid TPS of C 2) in two separate but adjacent blocks. The area required for planting male block is generally kept at about 1/4 to 1/6 of the female block, depending on pollen producing ability of the male parent.
    3. Plant the male block about a week before planting female block during the main crop season in the plains. Follow the spacing of 60 x 20.cm.
    4. In the female block, prepare beds of three rows each. For this, draw 3 rows at 50 cm inter row distance leaving 80 cm walking space between two adjacent beds. Plant tubers at 15 cm intra row distance.
    5. Use about 30 g size seed tubers or the seed pieces for planting female block. After germination, trim the plants in female block to retain a single stem per plant.
    6. Follow all other cultural and plant protection practices for potato crop.
    7. In the plains, after the germination is complete, switch on the light in hybridization block in the evening before sunset for a period of 5 hours every day. This will facilitate rapid plant growth and flowering in the parental material.
    Hybridization
    • When the parental material comes to flowering, follow the steps given below to produce hybrid TPS
    1. Trim the flower bunches in the female plants to retain only 6 8 large size buds per bunch. Very small buds, old flowers and berries if any, should be removed from the bunches and prepared for pollination next day.
    2. Collect flowers from the male parent in the evening preceding the day of pollination. Only just opened flowers with anthers that are about to shed pollen or the large size buds, which would open next day, should be collected.
    3. Spread flowers of the male parent on a sheet of paper placed on the table at room temperature and use them for extracting pollen next morning.
    4. Extract the pollen in a small dish by shaking anthers using electric buzzer or manually.
    5. Pollinate the flowers of the female parent by dipping the stigma in pollen or applying pollen to the stigma using a brush. Do the first pollination between 8 10 AM and re-pollinate the flowers at the same time next day. Continue the process of pollination till the flowering period of the crop is over. Usually there are two flushes of flowers during the crop period.
    6. Store the left over pollen in small vials, keep the vials in desiccators and place the desiccators in refrigerator at 6 10° C for the use of next day, if necessary. It is advisable to use fresh pollen for pollination every day.
    7. Provide support (use sticks) to the stems of female plants.
    8. After berries are formed, the berry bunches should be covered with thin muslin cloth bags of about 8 x 12 cm size.
    Seed extraction and storage
    1. Collect well developed berries about 50 55 days after pollination, keep them in trays and allow them to ripen at room temperature for a period of about 2 weeks.
    2. Mash the soft ripe berries.
    3. After mashing the berries, separate out the TPS with a high pressure water source. Treat the seed and pulp mass with 10% hydrochloric acid (HCI) with continuous stirring for 20 minutes. Wash the seeds with water at least 3 4 times to ensure complete removal of HCl.
    4. Immediately after washing, surface disinfect the seeds by soaking in 0.05% solution of Sodium hypochlorite for 10 minutes and again wash with clean water to ensure that there is no sodium hypochlorite solution on seed.
    5. Spread the seed in a thin layer on muslin cloth stretched over a wooden frame and keep the frames in a well ventilated room preferably under fan for 24 hrs, in shade. TPS can be safely dried in any type of low moisture environment i.e. forced air oven, fan etc. Temperatures above 300C should be avoided during the initial seed drying period. Thereafter, seeds can be safely dried under temperatures not exceeding 400C + 50C.
    6. Expose the shade dried seeds to warm sun for about ½ hr to reduce the moisture content.
    7. Keep the seeds in a moisture proof container along with silica gel bags and store them at low temperatures. The seeds may be kept in polythene lined aluminum foil covers or double polythene bags or tin cans, sealed and stored in desiccators kept in refrigerator at 6 100C or even at room temperature during the winters.
    Plant protection
    Pests
    Nematodes
    • Growing potato year after year in the same field should be avoided. Crop rotation with vegetables and green manure may be followed. Application of carbofuran 3 G (1.0 kg a.i.) 33 kg/ha in furrows while seeding has to be done. For cyst nematode resistant variety Kufri Swarna, application of half dose of the above nematicide is enough.
    Biological control of nematodes
    • Applicaton of Pseudomonas fluorescens at 10 kg/ha.
    Aphids
    • Spray of methyl demeton 25 EC or dimethoate 30 EC 2 ml/lit.
    Cut worms
    1. Installation of light trap during summer to attract adult moths.
    2. Soil drenching at collar region of the plants in evening hours with chlorpyriphos or endosulfan 2ml/lit a day after planting.
    White grub
    1. Summer ploughing to expose the pupae and adults.
    2. Quinalphos 5 D at 25 kg/ha 10 days after first summer rains.
    3. In endemic areas application of phorate 10 G at 25 kg/ha during autumn season (August - October) is recommended.
    Potato tuber moth
    1. Installation of pheromone traps at 20 No/ha.
    2. Earth up at 60 days after planting to avoid potato tuber moth egg laying in the exposed tubers.
    3. Foliar spraying of NSKE 5 % or quinalphos 20 EC 2 ml/lit (ETL 5 % leaf damage).
    4. Seed tubers treated with quinalphos @ 1 kg/100 kg of tubers.
    Diseases
    Late blight
    • Spraying of Mancozeb 2 g/lit or Chlorothalonil 2 g/lit on 45, 60 and 75 days after planting.
    • Growing of late blight resistant varieties like Kufri Jyothi, Kufri Malar and Kufri Thangam.
    Brown rot
    • Proper drainage facilities are important. Affected plants are removed and destroyed.
    Early blight
    • Spraying of Mancozeb 2 g/lit or Chlorothalonil 2 g/lit at 45, 60 and 75 days after planting.
    Virus diseases
    • Virus free potato seeds should be used. Virus affected plants are rogued regularly.
    • The aphid vectors are controlled by spraying of Dimethoate or Methyl demeton 2 ml/ha.

Last modified: Monday, 25 June 2012, 4:28 AM