Enhanced hybrid seed production in Tomato under cold and chilling stress

Transcription

1 Eco. Env. & Cons. 22 (2) : 216; pp. ( ) Copyright@ EM International ISSN X Enhanced hybrid seed production in Tomato under cold and chilling stress Sujatha Patta, Alice K. Vari, B.S. Tomar and Balraj Singh Division of Seed Science and Technology, Indian Agricultural Research Institute, New Delhi 11 12, India (Received 5 August, 215; accepted 15 October, 215) ABSTRACT The effective crossing period for tomato hybrid seed production of Pusa Hybrid-4 was doubled under protected condition of naturally ventilated green house compared to open field. Under protected condition, fruit set per cent was increased with the advance of crossing period and highest peak at February 2 nd week (89%), later it gradually decreased and number of seed per fruit gradually increased with the advance of crossing period. No seed set observed under open field when minimum temperatures are less than 1 o C and relative humidity less than 5 per cent. Seed produced from protected condition showed good seed quality with high germination (91) and seedling vigour index (1529 & 171). The highest percent of fresh and ungerminated seeds (7.) was observed in the protected condition from the early crossings. Better crop performace, the early flower initiation and extended flowering period was observed under protected condition. Key words : Tomato, Temperature, Relative humidity, Hybrid seed, Protected condition, Crossing period, Growing conditions, Seed quality Introduction Tomato is highly susceptible to chilling injury at temperatures between and 1 o C (32-5 o F). This may cause stunted growth, wilting, delayed growth and development, delayed flowering, slow to resume growth in severe cases it may lead to chlorosis leading to crop failure or reduction in some yield potential. In addition, low soil temperatures also stunted plant growth and prevent root development. In North India, under open field condition, with lower night temperatures, frost injury is common problem to most of solanaceous crops especially to tomato. This condition forces the seed grower to take up re-sowing when the temperature raises back. To avoid this type of damage to tomato and to protect seed crop during its initial stage, seed growers could grow the crop either in cloth mesh tunnels or in protected conditions. In addition, tomato hybrid seed production is mainly concentrated in southern and central western parts of India owing to favourable conditions like temperature and availability of skilled labours. This hybrid seed is supplied to Northern India for commercial cultivation. It enhances the cost of hybrid seed due to transportation and sometimes non-availability of quality seed at right time is also realized. Keeping less favourable North Indian climatic conditions in consideration, an experiment was conducted under protected condition and open field to enhance the feasibility of tomato hybrid seed production and seed availability with an objective of studying the effect of crossing period and growing conditions on seed set and seed quality. *Corresponding author s patta.sujatha@gmail.com

2 83 Eco. Env. & Cons. 22 (2) : 216 Materials and Methods The investigations were carried out on the standardization of optimum crossing periods and growing conditions on tomato hybrid seed production under protected condition and open field at Centre for Protected Cultivation and Technology, IARI and in the laboratory, Division of Seed Science and Technology, IARI, New Delhi with two parents of popular tomato hybrid, Pusa Hybrid-4 (Pusa-12 x Chikoo). The seedlings were raised in the multi celled plastic plug trays having cell volume of 2 cubic centimeters by using soil less media consisting of coco- peat, vermiculite and perlite in the ratio of 3:1:1 (on volume basis). Fertigation in the nursery was done once a day and the concentration of NPK plus micronutrients was kept from 2 ppm to 8 ppm depending upon the growing stage of the nursery and thirty days old tomato seedlings were transplanted in protected condition and open field at a planting distance of 5 x 6 cm and stacking was provided throughout the crop growth period. For emasculation, flowers at late bud stage were selected, the corolla is opened and the anthers are carefully removed with the help of forceps, in the afternoon, between 4 and 6 pm, one day before the anthers are expected to dehisce or mature and the stigma is likely to become fully receptive and bud is tagged. For pollination, fully opened flowers were plucked in the afternoon from pollen parent and anther cones were separated from sepals and spread over newspaper for drying in ambient temperature overnight. Then the pollen was collected by putting anthers in one steel cup covered with another cup of the same size and a muslin cloth kept between them. The cups were shaken rigorously by holding tightly by hand against each other to separate pollen from the anthers. The pollen was filtered through muslin cloth and thus pollen and anther tissue were collected in separate cups. This pollen was used for pollination in the next morning by dusting onto the stigma of emasculated flower bud. In order to compare the effect of temperature and relative humidity on hybrid seed production, crossings were done every day by considering seven day interval both in protected condition and open field throughout the crop growth period. Fourty flower buds which were likely to open next day were selected, emasculated and tagged under each replication. Pollination was done one day after emasculation and it was continued up to seven subsequent days (one crossing interval). After ten days from pollination, flower buds were examined and per cent fruit set was recorded. The temperature and relative humidity was recorded under both the conditions. Number of crosses turned into fruits in each treatment was counted to get fruit set percentage. Average fruit weight was expressed in grams. Seed number per fruit was counted and expressed in number per fruit. Germination studies were carried out as per ISTA Rules (1999). Vigour index I and II was calculated as suggested by Abdul-Baki and Anderson (1973). Results Effect of crossing period on hybrid seed set The protected condition maintained an average maximum temperature of 3.38 o C and minimum of o C and mean relative humidity of (7 hr) and (14 hr). In the same period, the mean temperature in the open field was o C (maximum) and o C (minimum) with RH of 89.3 (7 hrs) and 43.7 (14 hrs). The crossing period in the protected condition was ranged from last week of January to 1 st week of April with fruit set per cent from 15. to 7.33 with a mean of and seed number per fruit from 3.49 to 98. with a mean of Fruit set per cent was increased with the advance of crossing period and highest peak at February 2 nd week (89%), later it was gradually decreased (Table 1). Seed number per fruit was gradually increased with the advancement of crossing period and more number of seeds per fruit was recorded in the April 1 st week harvested fruits (98.), same trend was noticed under both conditions. The effective crossing period was doubled under protected condition (11 weeks) when compared to open field (5 weeks) making tomato hybrid seed production most economical for public and private seed industry under protected condition. The performance of protected condition grown plants were better compared to open field grown plants. More plant height ( cm), Early flower initiation (41 days) and extended flowering period (119 days) was observed under protected condition and these parameters differed significantly among growing conditions (Table 2). Under protected condition, seed set observed in the 1 st and 2 nd crossing periods (January 3 rd and 4 th week) was 3.49 and respectively when mini-

3 PATTA ET AL 831 Table 1. Effect of environmental factors on fruit set, fruit weight and seed per fruit in protected condition and open field Crossingperiod Protected condition Open field Temp. ( C) RH (%) Fruit Fruit Seed per Temp. ( C) RH (%) Fruit Fruit Seed per Max. Min. 7 hrs 14 hrs set weight fruit Max. Min. 7 hrs 14 hrs set weight fruit (%) (g) (no.) (%) (g) (no.) Jan Jan Feb Feb Feb Feb Mar Mar * * Mar * * Mar * * Mar.29-Apr * * Mean CD at 5% * Fruits were damaged due to insect attack mum temperatures are less than 13 o C and relative humidity less than 6 percent. While, there was no seed set observed under open field during the same crossing period when minimum temperatures are less than 1 o C and relative humidity less than 5 percent. This observation gives good information that the tomato hybrid seed production will be economical when the temperatures are above 13 C and relative humidity above 6 per cent. Under protected condition, seed set was increased (62 seed per fruit) from February first week crossings onwards when minimum temperatures were raised to o C and RH to per cent. During the same crossing period when the temperature 9.65 o C and RH per cent seed set obtained under open field was seed per fruit. Highest seed number per fruit (98) was observed in March last week-april first week crossings when temperature was o C and RH as per cent. During same crossing period seed recovery was nil under open field because of severe infestation of fruit borers making fruit and seed recovery practically impossible. Effect of crossing period on seed quality The initial seed quality is an indicator of good planting value and stand establishment. The results of the effect of crossing period and growing condition on the initial seed quality are presented in the Tables 3. Seed produced from protected condition showed good seed quality with high germination (91) and seedling vigour index (1529 & 171). Among the crossing periods, no significant variation was observed in germination. The seed produced from first few crossings showed less mean germination (85 % and 8%, protected condition and open field, respectively) due to presence of more fresh and ungerminated seeds. The presence of low air temperatures during January last week to February last week could have induced dormancy in the seeds under both the growing conditions (Sujatha et al., 215). The seedling characters like shoot length, root length and seedling dry weight showed differences with respect to crossing period and growing conditions. Seedling vigour index I and II showed variation with respect to crossing period and growing conditions. The seed of early crossings under both the conditions showed lesser EC values (7.2 µmhos/ cm/5 seeds) as compared to the seeds of late crossings (11.5 µmhos/cm/5 seeds). The EC value also differed significantly with respect to crossing period

4 832 Eco. Env. & Cons. 22 (2) : 216 and growing conditions and the seed of early crossings had less EC value both in open field and protected condition. Discussion Effect of crossing period on hybrid seed set Max. Tem., Min. Tem., RH (7rhs), RH (14 hrs) Max. temp Min. temp RH 7hrs RH 14 hrs Fruit set (%) Average fruit weight (g) Seed number per fruit Crossing period Fruit set (%), Average fruit wt. (gm) and Seed No./futi Fig. 1. Effect of environmental factors on fruit set (%), fruit weight (g) and seed number per fruit in protected condition Jan Jan Feb. 1-7 Feb Feb Feb Mar. 1-7 Mar Mar Ma Mar. Apr Max. Tem., Min. Tem., RH (7rhs), RH (14 hrs) Max. temp Min. temp RH 7hrs RH 14 hrs Fruit set (%) Average fruit weight (g) Seed number per fruit Crossing period Crosses were done at different intervals during the entire cropping season and correlated with the prevailing temperature and relative humidity to find the effect of environmental factors on fruit and seed set in tomato (Fig. 1 and Fig. 2). It was observed that the fruit set, fruit size and seed number per fruit varied significantly for the crossing period and growing conditions. Both temperature and relative humidity played a significant role and more uniform fruit set and seed set was observed when the mean temperature was optimum (2 o C) and relative humidity remained above 5 per cent (14 hours). Fruit set and seed set was lowest when the night temperature fell below 13 o C in the first three crossing periods in all the environments (Sujatha et al., 213). This observation is supported by Rylski and Aloni (1994) who observed that temperature and irradiation condition at the early stages of flower development are important factors which determine yield and fruit quality. Towards the end of cropping season (last week of March and first week of April) the fruit set was slightly reduced. This reduction could be attributed mainly to the reduction in pollen viability and also drying of stigmatic surface due to increased temperature and lower relative humidity during this period. Tiwari and Choudhary (1996) studied the effect of temperature on the fruit set in tomato and he stated that the fruit set was mainly dependent upon the night temperature with an optimum range between 13 to 2 o C and it is greatly hampered when the temperatures are either high or low. Araki et al. (2) findings also supported the increased seed set and fruit development at raised temperatures in the protected condition. Raised temperatures in the day time in winter months activated the leaf temperature, fruit respiration and phloem and xylem sap fluxes in tomato plants, which results in the increase in fruit growth and photo-assimilate accumulation in the fruit and helped in retention of crossed fruit. Ercan and Vural (1994) also observed that the low temperatures reduce pollen count and viability and Jan Jan Feb. 1-7 Feb Feb Feb Mar. 1-7 Mar Mar Ma Mar. Apr Fig. 2. Effect of environmental factors on fruit set (%), fruit weight (g) and seed number per fruit in open field condition Fruit set (%), Average fruit wt. (gm) and Seed No./futi Table 2. Comparision of phenotypic characters h in female parent (Pusa-12) in greenhouse and open field Plant Parameters Greenhouse Open field Mean CD at 5% Plant height (cm) No. of main branches No. of truss/branch No. of flowers/truss NS No. days taken for 1 st truss formation (DAT) Duration of flowering (days) Mean fruits / truss

5 PATTA ET AL 833 Table 3. Effect of crossing period and growing condition on tomato hybrid seed quality under North Indian condition Crossingperiod Green house Open field Germination Seedling Seedling SVI-I SVI-II EC Germination Seedling Seedling SVI-I SVI-II EC (%) length dry wt. (µmhos/ (%) length dry wt. (µmhos/ (cm) (mg) cm/5 (cm) (mg) cm/5 seeds) seeds) Jan (7) Jan (71) Feb (71) (67) Feb (72) (8) Feb (75) (84) Feb (81) (73) Mar (79) (71) Mar (85) Mar (72) Mar (84) Mar.29-Apr.4 97 (74) Mean 91.9 (76) (74) CD at 5% thus negatively affecting the fruit set and yield of tomato and could be suggested as the possible reason for the lower fruit set per cent in the first two to three crossing periods observed in the present study. Effect of crossing period on seed quality Favourable weather conditions for better fruit and seed production will positively affect the quality of the seed produced in the various crossing periods. Therefore, the seed quality was compared for the crossing period. Among the crossing periods the seed produced during the first two crossing periods gave less mean germination under both the growing conditions in both the cropping seasons. This is mainly due to presence of fresh ungerminated seed. The highest percent of fresh ungerminated seed was observed in the protected condition. The presence of low air temperatures during January last week to February last week could have induced dormancy in the seeds under both the growing conditions and it was slightly more in the seed that was produced under open field conditions. This finding was confirmed by the findings of de Castro et al., (21) who reported primary and secondary dormancy in tomato during seed development. Kaur and Kanwar (26) also reported that the highest fruit yield, 1-seed weight and seed vigour index in the November 2 planted tomato crop when the environmental conditions are better for fruit and seed development. Thus, the findings of this research greatly helps Indian seed industry to make effective and efficient planning of tomato hybrid seed production under North Indian conditions during Rabi season to meet seed demand of the Northern states of India. References Abdul-Baki, A.A. and Anderson, J.D Vigour determination in soybean seed by multiple criteria. Crop Science. 13 : Araki, T., Kitano, M. and Eguchi, H. 2. Dynamics of fruit growth and photoassimilate translocation in tomato plant (Lycopersicon esculentum Mill.) under controlled environment. Proc. Int. Conf. and British- Israeli Workshop on Greenhouse Tech. towards 3 rd Mill de Castro, R.D., Bino, R.J., Jing, H., Kieft, H. and Hilhorst, H.W.M. 21. Depth of dormancy in tomato (Lycopersicon esculentum Mill.) seeds is related to the progression of the cell cycle prior to the induction of

6 834 Eco. Env. & Cons. 22 (2) : 216 dormancy. Seed Science Research. 11 : Ercan, N. and Vural, H The effect of low temperatures on fruit set of tomatoes. Acta Horticulturae., 366 International Seed Testing Association International rules for seed testing. Seed Science and Technology., V. 27, p , Supplement. Kaur, M. and Kanwar, J.S. 26. Response of genotypes and planting schedule in relation to seed quality in tomato. Seed Res. 34 (1) : Sujatha, P., Alice, K. Vari, Tomar, B. S. and Balraj Singh Low cost standard technology for tomato hybrid seed crop productivity enhancement (ICBSM2539). Abstr 2nd International Conference on Bio-Resource and Stress Management, Hyderabad, 7-1 January Sujatha, P., Alice, K. Vari, Tomar, B.S. and Balraj Singh Effect of crossing period and growing conditions on tomato hybrid seed production. XIII ISST National Seed Seminar. June 8-1, Bengaluru. Abstracts. PS-I-14 pp12. Tewari, R.N. and Choudhary, H Solanaceous crop. In: Vegetable Crops in India (Ed.) Bose, T.K., Som, M.G. Published by Naya Prakashan, Calcutta (India).