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Articles by N. Nadarajan
Total Records ( 3 ) for N. Nadarajan
  A. Manickavelu , N. Nadarajan , S.K. Ganesh and R.P. Gnanamalar
  The experiment was conducted to develop and evaluate the biparental progenies for drought tolerance breeding in rice. Genetic analysis of biparental progenies resulted that, the traits viz., days to 70% RWC, leaf rolling, leaf drying and plant height were governed by additive gene action and for improvement of these traits, pureline selection, mass selection and/or progeny selection and pedigree breeding method may be followed. Preponderance of non-additive gene action was observed in drought recovery rate, days to flowering, productive tillers per plant, grains per panicle, spikelet fertility, hundred grain weight, biomass yield, root length, dry root weight, root/shoot ratio, harvest index and grain yield. Hence, improvement of these characters could be possible through heterosis breeding or selection of single plants at later generations after hybridization or intermating of selected segregants through recurrent selection techniques.
  A. Manickavelu , R.P. Gnanamalar , N. Nadarajan and S.K. Ganesh
  Rice is the principle food crop and is drastically affected by drought. Breeding for drought tolerance is a challenging task because of the complexity of the component traits, screening technique, environmental factors and their interaction. The major set back in drought tolerance breeding is the poor understanding of genetics and inheritance of drought tolerance traits and complete ignorance about the relationship between traits of physiological drought tolerance and plant productivity under stress. Present study consisted of BIPs, F3 and RIL population screnned under drought condition to know the association nature. Association analysis in BIPs revealed that, if selection pressure is given on the positive side for days to 70% RWC, dry root weight, harvest index, root/shoot ratio and biomass yield and negative side for leaf rolling and leaf drying, it will result in high grain yield under drought situations. From F3 studies it is concluded that selection pressure should be given on harvest index and productive tillers per plant in positive direction and plant height and leaf drying in negative direction for yield improvement in drought resistance breeding programme. The association analysis of RILs showed that, to harness high yield combined with drought tolerance, breeders should give selection pressure on days to 70% RWC, panicle length, grains per panicle, harvest index, biomass yield, root/shoot ratio and root length in positive direction and leaf rolling, leaf drying and drought recovery rate in negative direction. Association studies in three breeding materials combinedly pointed out that there is much scope for selecting high yielding genotypes with drought tolerance in rice, if selection pressure is exerted on days to 70% RWC, root/shoot ratio, biomass yield and harvest index and low scores of leaf rolling and leaf drying.
  A. Manickavelu , R.P. Gnanamalar , N. Nadarajan and S.K. Ganesh
  Drought is a major natural disaster that has been striking one or other regions of the world with a canny regularity. To develop high yielding genotypes coupled with drought tolerance, populations with high variability serves always as prime source for effective selection. Present variability studies of different breeding populations showed high phenotypic and high and moderate genotypic coefficients of variation for most of the traits studied. The traits viz., days to 70% RWC, leaf rolling, leaf drying, harvest index, biomass yield and grain yield expressed high or moderate heritability along with high genetic advance. Hence, these characters offer much scope for improvement by way of simple selection techniques. The three traits, days to flowering, panicle length and plant height showed low heritability with low genetic advance offers little scope for improvement by way of selection. Biparental mating and F3 showed the similar trend of variability, heritability and genetic advance implied that single cycle of intermating of segregants in F2 is not sufficient to release variability. Hence more cycles of intermating of selected segregants is suggested.
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