Genetic analysis in F2 And F3 progenies of selected crosses of rice varieties of diverse origin

Abstract

The research project 'Genetic Analysis in F2 and F3 Progenies of Selected Crosses of Rice Varieties of Diverse Origin' was carried out in the College of Horticulture, Kerala Agricultural University, Vellanikkara, Thrissur durinq the period January to December, 1998. The major objectives of the study were to understand the various genetic parameters of characters under study, identification of yi&ld components and formulation of selection model so as to isolate promising lines having desirable ideotypic features • from the segregating generations. The high yielding varieties developed from such lines will have a broad genetic base as the parents of selected crosses are of diverse origin. Components of heritable variation revealed that the characters showed decreased trend of variability from F2 to F3. PCV was higher than GCV in both generations for all the characters studied. Low PCV and GCV were observed for grain length, panicle length and duration to 50% flowering in both generations, while grain density showed low PCV and GCV in F3 only. In general, broad sense heritability estimates were observed to be higher in F2 than F3. The characters, plant height at harvest, total tillers plant", LIB ratio, 1000 grain weight, secondary branches panicle' and tertiary branches panicle:' provided great help in direct selection from phenotypic performance, as they exhibited higher values of genotypic coefficient of variation, heritability and expected genetic advance. The

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character, grain length showed little scope of improvement through selection due to low GCV and GA . • Correlation studies in F2 and F3 revealed that positive correlation existed between yield and component characters, namely, total tillers, panicle bearing tillers and tertiary branches panicle". Negative correlation was observed for 1000 grain weight with yield in both the generations. Panicle length and duration to 50% flowering exhibited absence of association with yield in F2 and F3, which indicate that these traits can be recombined as desired. In F3, LIB ratio and grain length exhibited positive correlation and grain breadth exhibited negative correlation, with yield, while these characters showed absence of association with yield in F2• Plant height and number of grains panicle:' exhibited negative association with yield in F2 where as number of grains panic!e' exerted positive association with yield in F3 and plant height showed absence of association with yield in F3. Genotypic correlation among di~ferent yield components in F2 and F3 revealed that semidwarf plants with higher number of productive tillers produced grains with higher LIB ratio and lesser grain weight, which in turn increased the yield. The study also showed that, when number of grains and compactness of• panicles increase, grains become more slender with reduced grain weight. Study of path coefficient analysis revealed that all the characters influenced the yield directly or indirectlv through some other traits. The correlation and path analysis study suggested that during selection, breeder

should give emphasis on" semidwarf olant stature, higher number of productive tillers, compact panicles, reduced number of secondary branches, high LIB ratio of grains with reduced density and weight. A selection model was formulated consisting of the characters, , namely, yield ha:'. total tillers plant". LIB ratio, grain breadth and grain density. Using this model, ranking of 105 genotypes in F3 was done and identified that the accessions, V 82 and V 89' belonging to lA 36 x Mattathriveni, were the best genotypes. Study revealed that all the four crosses namely, Vytilla 3 x Mattathriveni, Vytilla 3 x Kaohsiung Sen Vu 338, Mattathriveni x Mahsuri and lA 36 x Mattathriveni, were promising enough to derive superior segregants, the best among them being IR 36 x Mattathriveni. The plants with red kernel, identified in F3 of the cross IR 36 x Mattathriveni, can be used for the development of high yielding varieties with red kernel and preferable cooking qualities suited to Keralites, as well as resistance to biotic and abiotic stresses. This investigation also suggested that crosses from parents of diverse origin will broaden the genetic base of the varieties to be developed in future and will help to break the yield plateau in rice.