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 AvailableAn immense increase in human population along with diminished lands necessitates the increase of rice production since, it serves the human population as a staple food. Though rice hybrids (RH) are showing considerable yield enhancement over inbreds in terms of both quality and quantity, farmers’ adoption of hybrid rice technology has been much slower than expected because of several constraints such as seed cost and quality. Doubled haploid (DH) technology was considered useful for the development of inbred lines from rice hybrids in a single generation. Androgenesis shows its significance in development of DHs in rice which requires an efficient method to establish the production of large population. To start the anther culture, anthers are the main component of androgenesis to be isolated from unopened spikes. However, the duration of spikes availability for anther culture coupled with the segregation of rice hybrids in the next generation requires the main crop be ratooned to reduce the cost of cultivation. Therefore, the efficiency of the androgenic method was tested in main crop using a quality indica rice hybrid, 27P63 and its ratooned ones. The effects of various factors such as cold temperature pre-treatment of boots, treatment duration, and different combination of plant growth regulators (PGR) on callus response along with shoot regeneration were tested for development of DHs from both ratooned and non-ratooned plants. The N6 medium supplemented with 2.0 mg/L 2,4-D (2,4-dichlrophenoxy acetic acid), 0.5 mg/L BAP (6-benzylamino purine), and 30 g/L maltose was found to be most effective for callusing as compared to MS (Murashige and Skoog) medium. The N6 media inducted calli showed maximum response rate for green shoot regeneration in MS media supplemented with 0.5 mg/L NAA (1-napthaleneacetic acid), 0.5 mg/L Kn (Kinetin; 6-furfurylaminopurine), 1.5 mg/L BAP and 30 g/L sucrose after 2 weeks of culture. The pre-treatment of spikes at 10 ◦C for 2 d followed by a 7th and 8th d were found to be most effective for callusing as well as for regeneration, producing a total of 343 green plants from ratooned and main rice hybrid, 27P63. Morpho-agronomic trait-based assessment of ploidy status revealed 94.46% diploids, 3.49% polyploids, 0.58% mixploids, and 1.45% haploids. Microsatellite markers could authenticate all 324 fertile diploids as true DHs. Though this study shows a reduction in generation of DHs from ratooned plants as compared to the main crop, manipulation of chemical factors could optimize the method to enhance the production of considerable number of DHs. Utilization of ratooned of hybrid rice in androgenesis would save time and cost of cultivation.ICAR-NRRI, Cuttac

Anther Culture Efficiency in Quality Hybrid Rice: A Comparison between Hybrid Rice and Its Ratooned Plants

An immense increase in human population along with diminished lands necessitates the increase of rice production since, it serves the human population as a staple food. Though rice hybrids (RH) are showing considerable yield enhancement over inbreds in terms of both quality and quantity, farmers’ adoption of hybrid rice technology has been much slower than expected because of several constraints such as seed cost and quality. Doubled haploid (DH) technology was considered useful for the development of inbred lines from rice hybrids in a single generation. Androgenesis shows its significance in development of DHs in rice which requires an efficient method to establish the production of large population. To start the anther culture, anthers are the main component of androgenesis to be isolated from unopened spikes. However, the duration of spikes availability for anther culture coupled with the segregation of rice hybrids in the next generation requires the main crop be ratooned to reduce the cost of cultivation. Therefore, the efficiency of the androgenic method was tested in main crop using a quality indica rice hybrid, 27P63 and its ratooned ones. The effects of various factors such as cold temperature pre-treatment of boots, treatment duration, and different combination of plant growth regulators (PGR) on callus response along with shoot regeneration were tested for development of DHs from both ratooned and non-ratooned plants. The N6 medium supplemented with 2.0 mg/L 2,4-D (2,4-dichlrophenoxy acetic acid), 0.5 mg/L BAP (6-benzylamino purine), and 30 g/L maltose was found to be most effective for callusing as compared to MS (Murashige and Skoog) medium. The N6 media inducted calli showed maximum response rate for green shoot regeneration in MS media supplemented with 0.5 mg/L NAA (1-napthaleneacetic acid), 0.5 mg/L Kn (Kinetin; 6-furfurylaminopurine), 1.5 mg/L BAP and 30 g/L sucrose after 2 weeks of culture. The pre-treatment of spikes at 10 °C for 2 d followed by a 7th and 8th d were found to be most effective for callusing as well as for regeneration, producing a total of 343 green plants from ratooned and main rice hybrid, 27P63. Morpho-agronomic trait-based assessment of ploidy status revealed 94.46% diploids, 3.49% polyploids, 0.58% mixploids, and 1.45% haploids. Microsatellite markers could authenticate all 324 fertile diploids as true DHs. Though this study shows a reduction in generation of DHs from ratooned plants as compared to the main crop, manipulation of chemical factors could optimize the method to enhance the production of considerable number of DHs. Utilization of ratooned of hybrid rice in androgenesis would save time and cost of cultivation

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Not AvailableThe rice (Oryza sativa L.) productivity is often adversely disturbed by several abiotic and biotic stresses such as drought, submergence, fungal, bacterial, and nematode oriented biotic diseases and pest like brown plant hopper (BPH) and stem borer (SB). The major biotic stresses such as bacterial leaf blight (BLB), sheath blight (ShB), blast, brown spot (BS), false smut (FS), brown plant hopper (BPH), yellow stem borer (YSB), and gall midge (GM) play crucial roles in decreasing the productivity and quality of rice grains. Among the several breeding procedures and various control measures available for mitigating the biotic stresses/factors, the host plant resistance is most effective, economic and eco-friendly which is basically developed by traditional breeding approaches. The related species of rice and wild sources are important for identification of many resistance genes/QTLs, which are successfully introgressed or deployed or pyramided in numerous breeding lines through resistance breeding program and various molecular approaches. In this chapter, an inclusive valuation of the conventional and molecular approaches for mitigating the biotic stresses in rice by imparting major resistance sources has been presented.Not Availabl

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Not AvailablePolicy-makers, research managers, and donors are interested in knowing the outputs, outcomes, and impacts of investment in agricultural research. Several institutions are engaged in rice research and impact assessment of rice research requires area coverage information for rice varieties. The area coverage information for individual varieties is not available at the national level in many developing countries as the conventional household survey method is expensive and time consuming. This article aims to find a cost-effective and quick method to estimate the area under popular rice varieties in India and their spread in different states. Secondary data collected from 27 states and 1 union territory of India were used to estimate the area. The results of the new method compared well with some of the studies conducted at the state level. The most important varieties identified using the new method were Swarna, Cottondora Sannalu, Samba Mahsuri, Vijetha, IR-64, and Ranjeet, which covered more than 1 million ha each in the country. On geographical coverage, IR-64 has spread to 17 states followed by Swarna, Cottondora Sannalu, Samba Mahsuri, Vijetha, IR-36, and Swarna Sub-1 which covered 14, 14, 12, 11, 11, and 10 states, respectively. The area information can be used to compute returns to rice research by different research institutions and study dynamics of varietal change over time. The popular varieties identified should be used in future breeding programs and biotechnological studies for the development of superior varieties.Not Availabl

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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

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