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

Identification and characterization of polymorphic genic SSR markers between cultivated (Oryza sativa) and Indian wild rice (Oryza nivara)

299-310In the present study, we developed a set of 100 BC2F4 mapping lines derived from the cross between the Oryza nivara (AC100476) and high yielding indica rice, Lalat. Out of 410 RM markers used for polymorphism survey between the parental lines, we identified around 113 (28.9%) polymorphic rice microsatellite (RM) markers between the parental lines that were uniformly distributed among the 12 chromosomes except for few gaps on chromosome 1, 7 and 10. On the basis of motif length, the trinucleotide repeats-motif, (TTA)n was the longest with a maximum motif length of 177 nucleotides. Among the repeat motifs, di-nucleotide repeat-motifs was the most abundant (68.14%) with the motifs (AC/GT)n were the most abundant accounting 56.32% of the total dinucleotide repeat-motifs. Out of the 113 polymorphic RM markers, 56 (49.55%) were found to be genic markers and broadly distributed into three groups such as molecular, biological and cellular categories with 38%, 32% and 30% frequencies, respectively. The present finding would be useful for the identification and mapping of drought related traits and development of drought tolerant rice cultivars in rice breeding program

Prevalence of cry2-type genes in Bacillus thuringiensis isolates recovered from diverse habitats in India and isolation of a novel cry2Af2 gene toxic to Helicoverpa armigera (cotton boll worm)

Deployment of cry1A-type genes from Bacillus thuringiensis (Bt) in first generation transgenic crops has led to development of resistance in lepidopteran insects. Novel cry2-type genes are required for gene pyramiding to delay evolution of resistance. Two PCR-based techniques were employed for screening of cry2-type genes in 129 Bt isolates from diverse habitats in India and 27 known Bt strains. The cry2Ab-type genes were more prevalent than cry2Aa- and cry2Ac-type genes. Correlation between source of isolates and abundance of cry2-type genes was not observed. Full length cry2A-type genes were amplified from nine Bt isolates and four Bt strains using specially designed primers. The genes from Bt isolates SK-758 from Sorghum grain dust and SK-793 from Chilli seeds warehouse, Andhra Pradesh, were cloned and sequenced. The gene from SK-758 (NCBI GenBank accession GQ866915) was novel while that from SK-793 (NCBI GenBank accession GQ866914) was identical to cry2Ab1 gene. Bacillus thuringiensis Nomenclature Committee (http://www.biols.susx.ac.uk/Home/Neil_Crickmore/BT/) named these genes as cry2Af2 and cry2Ab16 respectively. The cry2Af2 gene was expressed in Escherichia coli and found to be toxic towards Helicoverpa armigera. The cry2Af2 gene will be useful for pyramiding in transgenic crops.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

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Not AvailableRice is one of the important food crops, feeding more than 50% of the global population. The climate change is adversely affecting the rice production across the rice growing regions. The major challenges posing threat to the world rice production are various biotic and abiotic stresses. Rice is grown and consumed largely by the developing countries, and most part of the population in these regions are undernourished with unbalanced and comparatively low nutritional food. Therefore, it is of utmost importance to develop rice varieties for higher nutritional value with attributes for better adaptability to various stresses. In the present review, we have discussed about the different CRISPR/Cas genome editing tools, and their applications for biotic and abiotic stress tolerance, yield and also for grain and nutritional quality improvement in rice.Not Availabl

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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 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

Effect of multiple allelic combinations of genes on regulating grain size in rice

<div><p>The grain size is one of the complex trait of rice yield controlled by a plethora of interaction of several genes in different pathways. The present study was undertaken to investigate the influence of seven known grain size regulating genes: <i>DEP1</i>, <i>GS7</i>, <i>GS3</i>, <i>GW8</i>, <i>GL7</i>, <i>GS5</i> and <i>GW2</i>. A wide phenotypic variation for grain length, grain width and grain length-width ratio were observed in 89 germplasm. The correlation analysis showed a strong association among these three grain traits viz. GL, GW, GLWR and TGW which play important roles in determining the final rice grain size. Except for <i>GW2</i>, all six genes showed strong association with grain size traits. A total of 21 alleles were identified with an average of 2.1 allele/locus in 89 germplasm of which seven alleles were found to be favourable alleles for improving the grain size with the frequency range of 24 (26.97%) to 82 (92.13%); the largest was found in <i>GS5</i> followed by <i>GW8</i>, <i>GL7</i>, <i>DEP1</i>, <i>GS3</i> and <i>GS7</i> genes. Through ANOVA, four markers (GS3-<i>Pst</i>I, S9, GID76 and GID711) of three genes (<i>GS3</i>, <i>DEP1</i> and <i>GL7</i>) were found significantly associated with all the three traits (GL, GLWR and TGW). Concurrent results of significant associations of grain size traits with other markers were observed in both analysis of variance and genetic association through the general linear model. Besides, the population structure analysis, cluster analysis and PCoA divided the entire germplasm into three sub-groups with the clear-cut demarcation of long and medium grain types. The present results would help in formulating strategies by selecting suitable candidate markers/genes for obtaining preferred grain shape/size and improving grain yield through marker-assisted breeding.</p></div

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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