Hybrid Rice Research: Current Status and Prospects

Heterosis is a solitary means of exploiting hybrid vigor in crop plants. Given its yield advantage and economic importance, several hybrids in rice have been commercialized in more than 40 countries, which has created a huge seed industry worldwide. India has made commendable progress and commercialized 117 three-line indica hybrids for different ecology and duration (115–150 days), which accounted for 6.8% of total rice area in the country. Besides, several indigenous CMS lines developed in diversified genetic and cytoplasmic backgrounds are being utilized in hybrid rice breeding. NRRI, which has been pioneering to start with the technology, has developed three popular rice hybrids, viz., Ajay, Rajalaxmi, and CR Dhan 701 for irrigated-shallow lowland ecosystem. Biotechnological intervention has supplemented immensely in excavating desirable genomic regions and their deployment for further genetic enhancement and sustainability in rice hybrids. Besides, hybrid seed production creates additional job opportunity (100–105 more-man days) and comparatively more net income (70% more than production cost) than HYVs. Hence, this technology has great scope for further enhancement in per se rice productivity and livelihood of the nation

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Not AvailableHeterosis is a solitary means of exploiting hybrid vigor in crop plants. Given its yield advantage and economic importance, several hybrids in rice have been commercialized in more than 40 countries, which has created a huge seed industry worldwide. India has made commendable progress and commercialized 117 three-line indica hybrids for different ecology and duration (115–150 days), which accounted for 6.8% of total rice area in the country. Besides, several indigenous CMS lines developed in diversified genetic and cytoplasmic backgrounds are being utilized in hybrid rice breeding. NRRI, which has been pioneering to start with the technology, has developed three popular rice hybrids, viz., Ajay, Rajalaxmi, and CR Dhan 701 for irrigated-shallow lowland ecosystem. Biotechnological intervention has supplemented immensely in excavating desirable genomic regions and their deployment for further genetic enhancement and sustainability in rice hybrids. Besides, hybrid seed production creates additional job opportunity (100–105 more-man days) and comparatively more net income (70% more than production cost) than HYVs. Hence, this technology has great scope for further enhancement in per se rice productivity and livelihood of the nation.ICAR-NRRI, Cuttac

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Pyramiding Submergence Tolerance and Three Bacterial Blight Resistance Genes in Popular Rice Variety Hasanta through Marker-Assisted Backcross Breeding

Flash flooding (FF) along with bacterial blight (BB) outbreak are very destructive for rice production in the rainfed shallow-lowland (RSL) ecosystem. The presence of dynamic Xoo races with varying levels of genetic diversity and virulence renders their management extremely challenging under RSL. In this context, the marker-assisted improvement of plant resistance/tolerance has been proven as one of the most promising strategies towards the development of sustainable cultivars. The present study demonstrates the marker-assisted introgression of the submergence tolerant (Sub1) and three bacterial blight resistant genes (Xa21 + xa13 + xa5) into the genetic background of Hasanta, a long duration popular rice variety in the eastern coastal region of India. The rice genotypes, Swarna Sub1 (carrying Sub1) and IRBB66 (carrying Xa21 + xa13 + Xa7 + xa5 + Xa4) had maximum genetic similarity (0.84 and 0.73, respectively) with Hasanta; recurrent parent (RP) was used as donor. The forward analysis of target genes in F1s, IC1F1s and backcross (BC) generations was performed by linked/genic markers (Sub1bc2; pTA248, xa13prom and RM122), whereas background recovery of RP in each BC and segregating generations was performed utilizing 108 hypervariable SSR markers. Intervened speed breeding (SB) strategy and intensive phenotyping could lead the development of near isogenic lines (NILs) as to the RP in all basic traits. The performance of the near isogenic lines (NILs, BC2F3 and BC2F4), HS 232-411-391-756-37, HS 232-411-391-809-8, HS 232-411-391-756-18, HS 110-224-197-10-36, HS 232-411-391-809-81, HS 110-224-197-10-41 and HS 232-411-391-809-63 establishes the utility of marker-assisted backcross-breeding (MAB) and SB in accelerated trait introgression. The introgressed lines carrying Sub1 + Xa21 + xa13 + xa5 showed 76% to 91% survival under 14 days of submergence and durable BB resistance (percent disease index-PDI of 2.68 ± 0.26 to 6.22 ± 1.08 and lesion length, LL of 1.29 ± 0.12 to 4.2 ± 0.64 cm). Physiological analysis revealed that improved NILs, carrying Sub1 gene conquered adaptive physiological modulations, had reduced the consumption of soluble sugar and the degradation of total chlorophyll contents (TCC), and an enhanced level of Alcohol Dehydrogenase activity (ADH) and proline accumulation in all submergence regimes. The pyramided lines attained complete product profile of RP, that will contribute to sustainable rice production under RSL, particularly in the coastal region that has substantial acreage under the variety Hasanta