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Effect of harvest date on seed viability of different sunflower genotypes

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Effect of harvest date on seed viability of different sunflower genotypes
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   HELIA , 29 , Nr. 44, p.p. 127-134, (2006) UDC 633.854.78:631.527.53 EFFECT OF HARVEST DATE ON SEED VIABILITY OF DIFFERENT SUNFLOWER GENOTYPES Mikli č , V., 1*  Crnobarac, J., 2  Joksimovi ć , J., 1  Dušani ć , N., 1  Vasi ć , D., 1  Joci ć , S. 1 1  Institute of Field and Vegetable Crops, M. Gorkog 30. Novi Sad, Serbia 2  Faculty of Agriculture, Novi Sad, Serbia Received: September 10, 2005 Accepted: March 25, 2006 SUMMARY Effect of harvest date on seed viability has been examined in 3 different sunflower genotypes. Harvesting started 7 days after fertilization. It was done10 times, at 3-4-day intervals. Seed moisture was determined before each har- vest. Trials were conducted in India and Serbia. Seed viability was determined3 months after the harvest. Genotype ranking regarding seed viability, was not the same in the two locations; higher average seed germination was registeredin Serbia. There were no significant increases in seed viability once the averageseed moisture at the time of harvest reached 41% (India) and 48% (Serbia).Differences existed between the locations in minimum and maximum daily temperatures. Regression analysis showed that highest seed germination rates were reached when seed moisture content at harvest went below 32%, in most cases when seed moisture reached 22-23%. Key words:sunflower, seed germination, seed moisture content, air temperature INTRODUCTION The process of seed forming and filling, which starts right after pollination, isactually a set of physiological processes aimed at enabling the seed to germinateafter a rest period. Many authors have studied sunflower seed viability and dor-mancy period, i.e., the number of days after flowering (DAF). Jan č i ć  and Pap (1983)found that highest increase in viability occurred in the period 20-40 DAF; Maeda et al. (1987) found that highest viability was achieved when performing harvest at 30DAF. Šepetina and Rogoževa (1971) had reported similar results. They alsoclaimed that viability starts to go down 30-35 DAF, mainly because of the occur-rence of diseases. *Corresponding author, Phone: +381 21 4898 414, Fax: +381 21 413 833, e-mail: miklicv@ifvcns.ns.ac.yu  128  HELIA , 29 , Nr. 44, p.p. 127-134, (2006)Since differences in the environment and genotypes used make the seed viabil-ity results unsuitable for comparison, researchers prefer moisture content in seedover DAF as a more reliable indicator. So, Ra  đ enovi ć  (1989) asserted that maxi-mum viability is achieved 30-35 DAF, at seed moisture of 22-36%, but he addedthat there is no significant increase in viability after the seed reaches the moistureof 49-53%. Crnobarac (1987) found high viability already at moisture level of 57%.Regarding the effect of air temperature on the process of maturation, opinionsare split between those authors who argue that low temperatures in the period of maturation tend to improve viability (Bewley, 1979) and those who claim that seedproduced under warm conditions is superior in viability, especially if harvestedearly, 28-31 DAF (Crnobarac, 1987).Early harvest dates increase seed dormancy (Crnobarac, 1987), and such seedloses viability faster (Gypta and Kole, 1982). Viability of the seed harvested up to 19DAF starts to decrease after 6 months, if it was harvested 22 DAF after 18 months,and if it was harvested 34 DAF after 36 months (Crnobarac and Marinkovi ć , 1994).The aim of this study was to determine the behavior of three sunflower geno-types grown under different conditions regarding the influence of early harvest dateon seed viability. MATERIALS AND METHODS Experiments were established in two locations: in Hyderabad (India) and at Rimski Šan č evi (S&M). Three genotypes - female lines of sunflower hybrids - weretested: Ha-26, OCMS-98 and OCMS-74. The trials set up in random block design were replicated three times. Conventional cultivation practices were applied. The first harvest was performed 7 days after the end of flowering. Subsequent harvests took place at 3-4-day intervals till full maturity. A total of 10 harvests wereperformed. Immediately after harvest, seed moisture was determined by themethod of drying at 105 o C till constant weight. Seed viability was determined by themethod of filter paper, 3 months after harvest. Meteorological data were received from local meteorological stations. Experi-mental data were statistically processed by the analysis of variance of two-factorialtrial and by regression analysis. RESULTS AND DISCUSSION In India, the line Ha-26 achieved the highest average seed viability (Table 1).This value was not significantly different from that achieved with the line OCMS-98,however, both of these lines had significantly higher seed viability than the lineOCMS-74. Highest average seed viability was realized in the 10 th  harvest date, at theaverage seed moisture of 10.8%. From the 7 th  date on, when the average seed mois-   HELIA , 29 , Nr. 44, p.p. 127-134, (2006) 129 ture reached 40.63%, there were no significant increases in seed viability. In thecase of the line Ha-26, the plateau was achieved in the 5 th  date, at the average seedmoisture of 46.28%. In the case of the lines OCMS-98 and OCMS-74, the plateau was achieved in the 5 th  and 7 th  dates, at the average seed moistures of 48.18% and41.00%, respectively.In Serbia, the line OCMS-98 achieved the highest average seed viability (Table2). This value was not significantly different from that achieved with the line Ha-26,however, both of these lines had significantly higher seed viability than the lineOCMS-74. Highest average seed viability was realized in the 9 th  harvest date, at theaverage seed moisture of 19.2%. From the 5 th  date on, when the average seed mois-ture reached 47.90%, there were no significant increases in seed viability. In thecase of the line Ha-26, the plateau was achieved in the 4 th  date, at the average seedmoisture of 50.14%. In the case of the lines OCMS-98 and OCMS-74, the plateau was achieved in the 3 rd  and 5 th  dates, at the average seed moistures of 66.25% and43.22%, respectively.The regression analysis showed that the theoretical maximum of viability in theline Ha-26 was achieved at seed moistures of 23.03% and 21.66% in India and Ser- bia, respectively (Figure 1). Coefficients of determination were high in both loca-tions. The theoretical maximum of viability in the line OCMS-98 was achieved at seed moistures of 11.70% (along with a somewhat lower coefficient of determina- Table 1: Seed viability (%) of different genotypes at different harvest dates in India  GenotypeHarvest date Average1 2 3 4 5 6 7 8 9 10Ha-26 0.0 7.7 44.3 65.7 95.0 97.7 97.0 95.7 97.7 99.3 70.0Ocms-98 0.0 1.0 11.7 76.7 94.0 94.7 99.3 98.3 99.9 99.7 67.5Ocms-74 0.0 0.0 0 50.3 40.7 60.0 94.0 98.7 99.7 99.7 54.3 Average 0.0 2.9 18.7 64.2 76.6 84.1 96.8 97.6 99.1 99.6 63.9LSD Genotype Harvest date Genotype × date5% 4.38 8.00 13.851% 5.83 10.64 18.43 Table 2: Seed viability (%) of different genotypes at different harvest dates in Serbia  GenotypeHarvest date Average1 2 3 4 5 6 7 8 9 10Ha-26 79.0 76.0 85.7 96.7 96.3 98.7 96.3 97.3 99.7 99.0 92.5Ocms-98 77.3 84.0 94.0 90.7 99.7 98.7 99.3 99.9 99.3 98.7 94.2Ocms-74 55.7 67.0 80.3 80.7 963 98.7 99.7 99.7 99.9 99.7 87.8 Average 70.7 75.7 86.7 89.3 97.4 98.7 98.5 99.0 99.7 99.1 91.5LSD Genotype Harvest date Genotype × term5% 3.64 6.65 11.521% 4.85 8.85 15.32  130  HELIA , 29 , Nr. 44, p.p. 127-134, (2006)  Figure 1:Effect of seed moisture at the moment of harvest on seed viability   HELIA , 29 , Nr. 44, p.p. 127-134, (2006) 131 tion) and 31.6% in Indiji and Serbia, respectively. The theoretical maximum of via- bility in the line OCMS-74 was achieved at seed moistures of 22.82% and 22.77% inIndia and Serbia, respectively. Positions of the curves indicated that, in Serbia, highseed viability was achieved early during the period of maturation. In India, differences between minimum and maximum air temperatures during the period of maturation were higher than in Serbia (Figure 2). The maximum tem-peratures were more or less steady but the minimum ones kept increasing. In Ser- bia, air temperatures were higher than those in India at the initial stages of maturation but after a fortnight they began to go down. There was no heavy rainfallin either location. Daylength was significantly longer in Serbia than in India.High seed viability was achieved early, at high values of seed moisture, which isin agreement with the results of Crnobarac (1987) and Ra  đ enovi ć  (1989). The ear-lier attainment of high viability in Serbia may be due to the high air temperatures inthe first two weeks after pollination, which evidently accelerated plant metabolicprocesses over the rates that took place in India. Differences among the genotypesin the date of attainment of high viability at maturity persisted in both locations,indicating that the characteristic is under genetic control and that it came to expres-sion despite the different environmental conditions. The observed differencesshould be taken into account in breeding and seed processing. The early attainment of high viability is important in breeding, to accelerate the production of new gener-ations; however, it may pose problems with prolonged dormancy (Crnobarac,1987). In seed production, care should be exercised with early harvest because, inaddition to prolonged dormancy, early harvest may accelerate the loss of viability during storage compared with conventional harvest dates (Gupta and Kole, 1982;Crnobarac and Marinkovi ć , 1994).  Figure 2:Minimum and maximum daily temperatures at the time of full maturity
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