GENETICS OF PREHARVEST SPROUTING TOLERANCE AND OTHER QUANTITATIVE CHARACTERS IN RICE GENOTYPES (Oryza sativa L.)

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Date
2018
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PROFESSOR JAYASHANKAR TELANGANA STATE AGRICULTURAL UNIVERSITY
Abstract
The present investigation on “Genetics of preharvest sprouting tolerance and other quantitative characters in rice genotypes (Oryza sativa L.)” was conducted to identify the tolerant and susceptible genotypes for preharvest sprouting along with yield and yield component characters. This study encompassed genetic diversity studies for identification of suitable parents and develop hybrids with high combining ability and study the gene action, heterosis and stability across three environments for preharvest sprouting tolerance, grain yield and yield contributing characters. Correlation and path analysis were assessed for grain yield and yield component characters over environments. The research work was conducted with seventy four rice genotypes in a randomized block design with three replications at ICAR-Indian Institute of Rice Research Farm, RC Puram, ICRISAT Campus, Patancheru, Hyderabad with objectives of screening for preharvest sprouting tolerance and genetic divergence studies during kharif 2013. Screening for preharvest tolerance was estimated as days taken to 80 % germination of seeds done by 3 methods viz., panicle method, petriplate method and petriplate method after threshing and drying seeds.The genotypes were classified as susceptible (if 80% germination occurred in less than 14 days) and tolerant (if 80% germination occurred for more than 21 days). Nine genotypes with less than 7 days, 19 with 7-14 days, 29 with 14-21 days,7 with 21-28 days, 3 with 28-35 days and one genotype more than 35 days recorded 80 % germination of seeds. Divergence studies through D2 statistic indicated high genetic divergence and the 74 genotypes of rice were grouped into 9 divergent clusters. The panicle length, preharvest sprouting tolerance, 1000 grain weight, number of filled grains per panicle and grain yield per plant together contributed 97.17 % towards total divergence. Based on screening and genetic diversity studies, 8 tolerant lines [MTU 1010 (L1) , MTU 1001(L2), MTU 1064 (L3), MTU 7029 (L4), MTU 5249 (L5), MTU 1061(L6), IC-67729 (L7), IC-85740 (L8)] were used as male parents and 6 susceptible testers [BPT 5204 (T1), PLA 1100(T2), MTU 1075 (T3), SAMPADA(T4), IR 64 (T5), MTU 2716 (T6)] were used as females and crossed in Line × Tester mating design during rabi 2013-14 at Indian Institute of Rice Research, Rajendranagar, Hyderabad. The resultant 48 crosses along with their parents and 2 checks (MTU 1010, MTU 1001) were evaluated for combining ability, heterosis and stability at three representative locations of Telangana State viz., Hyderabad (RC Puram), Jagtial and Kampasagar during kharif 2014 with data were recorded for 12 characters. viz., days to 50 per cent flowering, plant height, panicle length, number of tillers per plant, number of productive tillers per plant, days to maturity, number of filled grains per panicle, number of unfilled grains per panicle, spikelet fertility percentage, 1000 grain weight, grain yield per plant and preharvest sprouting tolerance. The analysis of variance revealed the presence of significant differences among the lines, testers and their F1 hybrids for all the quantitative traits under consideration. The pooled analysis of variance for combining ability revealed significant differences due to environments, parents and hybrids indicating the existence of sufficient variation in the material studied. The ratio of gca to sca variances revealed that non-additive gene action was predominant for all the 12 characters under study. Based on per se performance, sca effects, the corresponding gca status of parents and standard heterosis, the top five crosses for both preharvest sprouting tolerance, grain yield per plant and yield component characters were IC-85740 × IR 64, MTU 7029 × BPT 5204, MTU 1010 × BPT 5204, MTU 1001 × BPT 5204 and MTU 1001 × PLA 1100 were identified as best specific cross combinations. This also indicated that these yield attributes played greater role in expression of high heterosis for grain yield per plant ultimately. These hybrids recorded significant positive standard heterosis over the check MTU 1010 for preharvest sprouting tolerance and significant positive standard heterosis over both the checks MTU 1010 and MTU 1001 for grain yield per plant. Pooled analysis of variance for stability revealed that genotype x environment interaction was significant for all the characters studied implying the differential behaviour of genotypes in changing environments. Significance of both linear and non-linear component for all the characters indicated that only part of performance of genotypes could be predicted for these characters. Based on stability parameters viz., mean (µ), regression coefficient (bi) and deviation from regression (S2di) the hybrids, IC-85740 × IR 64, MTU 1010 × BPT 5204, MTU 1001 × BPT 5204, MTU 1001 × PLA 1100, MTU 1001 × SAMPADA and MTU 7029 × BPT 5204 were identified as stable genotypes for preharvest sprouting tolerance, grain yield per plant and its component traits. A critical analysis of both character association and path analysis indicated that among the yield components investigated, number of tillers per plant, spikelet fertility percentage, 1000 grain weight, panicle length, number of filled grains per panicle and number of productive tillers per plant were determined as most critical ones as both the correlation coefficients as well the direct effects were high with grain yield per plant. It was concluded from the study that the hybrids, IC-85740 × IR 64, MTU 1010 × BPT 5204, MTU 1001 × BPT 5204, MTU 1001 × PLA 1100, MTU 1001 × SAMPADA and MTU 7029 × BPT 5204 were stable with desirable sca effects, heterosis and per se performance for preharvest sprouting tolerance, grain yield and its components. Hence, these hybrids should be advanced to F2 generation for selection of new genotypes with preharvest sprouting tolerance and high grain yield.
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