Role of secondary and putative traits for improvement of upland rice

Even though yield under stress is the primary trait for selection in breeding programmes for drought prone environments,low heritability of yield necessitates an alternative approach such as selection for secondary and putative traits. For asecondary or putative trait to be useful in a breeding programme, it must be genetically correlated with grain yield understress condition. In the present investigation, single plant yield exhibited positive and significant association with spikeletfertility, panicle harvest index, days to attain 70 % RWC, root length, dry root weight and root: shoot ratio. Hence, thesetraits are to be given importance while selection. Since the traits spikelet fertility and panicle harvest index expressed exactcorrelation with each other, any one of these two traits may be considered during the selection process. The trait days toattain 70 % RWC positively correlated with root traits such as root length, dry root weight and root : shoot ratio suggestingthat selection based on days to attain 70 % RWC is highly fruitful in developing drought tolerant genotypes as it will bringsimultaneous improvement of these traits. Apportioning the correlation coefficients into direct and indirect effects revealedthat the traits spikelet fertility, leaf drying and dry root weight had high direct effect with grain yield. The traits days to attain70 % RWC, leaf drying, canopy temperature, drought recovery percentage, dry root weight and root: shoot ratio also showedlow to high indirect effect via spikelet fertility. Likewise all traits except days to 50% flowering expressed moderate to highindirect effects via leaf drying and dry root weight. The study indicates that the traits spikelet fertility, leaf drying and dryroot weight greatly influenced the grain yield both directly and indirectly and hence these three traits should be givenmore importance for enhancing grain yield under the drought stress situation.