No abstract

Rice blast, caused by fungus Magnaporthe grisea, is a serious disease causing considerable economic damage worldwide. Best way to overcome disease is to breed for disease-resistant cultivars/parental lines of hybrids. Pusa RH10, first aromatic, fine-grain rice hybrid released and cultivated extensively in India. Hybrid and its parental lines, Pusa 6A and PRR78, are highly susceptible to blast. CO39 pyramid carrying two dominant, broad-spectrum blast-resistance genes, viz. Pi-1 and Piz-5, used as a donor parent to introgress these genes into PRR78 using marker-assisted backcrossing (MABC). Microsatellite markers RM5926 and AP5659-5 tightly linked to Pi-1 and Piz-5 genes, respectively, were used for foreground selection to derive introgression lines. Further, these lines were evaluated for agronomic performance, disease reaction and cooking quality traits along with PRR78. Most of the improved lines were on par with PRR78 for all traits evaluated except gelatinization temperature. Recurrent parent genome percentage (RPG) study also revealed similarity of these lines with PRR78. Hybrids derived using improved PRR78 lines were superior over Pusa RH10 in terms of yield.

No abstract

Rice {Oryza sativa L.) is one of the important food crops drastically affected by drought. Considering the low heritability of grain yield under water stress, several secondary traits associated with drought tolerance have been used, but the success achieved in deriving cultivars with high yield potential under stress is less compared to irrigated conditions. Hence, objective of the experiment was to estimate heritability for grain yield under lowland stress and select for grain yield per se using wild species Oryza meridionalis Ng and also to identify physio-morphological traits responsible for withstanding water stress. A population derived from O. sativa cv. IR58025B X O. meridionalis (BC^Fg) was evaluated under control and stress conditions. Variability observed for yield and component traits indicated 0. meridionalis to be a good source of useful alíeles for drought tolerance. Broad-sense heritability {h^) of grain yield under stress, although only 33.1%, was comparable to control 59.4%, indicating direct selection for grain yield per se can be practiced. Twenty high-yielding selected lines and 40 random lines were evaluated under control and stress conditions to estimate selection response. Yield of selected lines outperformed random lines and checks under stress. Furthermore, 10 lines (5 high yielding and 5 low yielding) selected from the population were characterized for root morphological traits. Maximum root length (MRL) and root volume (RV) of selected high-yielding lines recorded maximum compared with checks and low-yielding lines indicating positive influence of drought avoidance root traits on grain yield under stress. Hence, O. meridionalis can be a good source of root traits contributing to stress tolerance and selection for grain yield under stress is an effective strategy in deriving drought tolerant lines in rice.