Excavating superior grain quality with aroma in doubled haploids derived from hybrid rice

Hybrid rice holds significant yield advantage over inbred lines, but its adoption rate is very slow in India. Development of cytoplasmic male sterile line (CMS) and fertility restorer line with superior grain quality is the prerequisite in three line hybrid rice breeding programme. Minimum of three to four years are required for development of useful R-line which severely delays the pace of hybrid breeding. Application of doubled haploid (DH) technology will be very useful to develop elite R-lines within short period of time. An elite inbred line LAXMI was crossed with the R-line RPR158 and anthers from the resulting F1 population was used for development of DH plants. Eight hormonal combinations and four different cold pre-treatment conditions were tried in tissue culture. Maximum callusing frequency was observed in N6 medium supplemented with 2.0 mg L−1 2, 4-diclorophenoxyacetic acid (2,4-D), 0.5 mg L−1 napthalene acetic acid (NAA), 0.5 mg L−1 benzyl amino purine(BAP) and 6% maltose with 3 days cold pre-treatment. Highest green plant regeneration frequency was found with Murashige and Skoog medium supplemented with 0.5 mg L−1 NAA, 0.5 mg L−1 kinetin, 2 mg L−1 BAP. A total of 280 DH plants were generated and evaluated under field conditions for agronomic characters and fertility restoration capacity in CMS system. Two distinct DH lines were identified as improved R-lines based on high restoration ability (94%), superior grain quality and medium slender grain type. This study successfully demonstrated that superior R-lines can be developed within two crop seasons through the application of DH technology.

The Philippines has recently been aiming to achieve self-sufficiency in rice. Recent programs and policies have been anchored on the development and adoption of high-yielding rice varieties in order to achieve this goal. Thus, this paper aims to identify the factors that significantly affect the farmers’ adoption of high-yielding varieties such as hybrid and certified inbred rice. Using a multinomial logistic model, these factors were estimated. Results show that the age, input assistance, and collective marketing significantly affect the adoption of certified inbred rice over farmers’ recycled seeds. On the other hand, irrigation, farm size, and trainings significantly affect the adoption of hybrid over farmer’s recycled seeds. In general, there was a low adoption rate of hybrid rice. Key informant interviews revealed that several issues arise in the process of seed growing, production, and marketing. Therefore, to increase the farmers’ incentive to adopt hybrid rice, a hybrid variety that produces superior grain quality and resistance to stresses must be developed and distributed at a reasonable price.

Increasing rice production in Iran, a country with limited land and water resources, is a challenging task, especially with consumer demand largely favoring varieties with superior grain quality. In 2000, Iran imported 1.2 million t of rice. But, in recent years, with increased adoption of improved varieties and with favorable climatic conditions, importation has been reduced to 0.98 million t (FAO 2006). However, with recent fluctuations in the availability of surplus rice from rice-exporting countries and the increasing rice demand in Asia alone, Iran has to initiate a well-drawn plan to attain self-sufficiency and sustain its rice production in the long term. Among the available approaches, the most viable is to pursue hybrid rice technology for Iran, on the basis of success achieved in India, Vietnam, and the Philippines. Hybrid rice technology could easily deliver hybrids with medium quality in the short term, with a 1.5−2.0 t ha–1 advantage over improved check varieties (such as Khazar), while superior quality with high yield can be combined in the hybrids, provided a systematic approach is followed. A comparative yield trial in 2002 involving four promising hybrids and their parents and inbred check variety Khazar revealed exceptional performance of the hybrid combination IR58025A/IR42686R. This hybrid gave the highest standard heterosis (57.9%), heterobeltiosis (53.3%), and commercial heterosis (45.2%) over improved check variety Khazar (Table 1). Furthermore, the number of days to 50% flowering of the parents differed by only 3, with the R line flowering earlier and having a relatively better quality than Khazar (data not shown). A pooled analysis of variance for the adaptive yield trial conducted over two different sites for 2003-04 showed significant yield differences among genotypes and in site-by-genotype-by-year interaction. IR58025A/IR42686R gave an average yield of 9.2 t ha–1 with a yield advantage of 28% over Khazar (Table 1). It was named IRH1. On-farm trials conducted in 2005 at four locations gave an impressive yield of 12 t ha–1, which was 85% higher than Khazar’s 6.5 t ha–1 (Table 2). The hybrids planning breeding programs to control genetic erosion and vulnerability, which is a great possibility because of the observed genetic uniformity. Reshuffling the genetic constituents is also necessary to increase yield potential. References Delannax X, Todgers DM, Palmer RG. 1983. Relative genetic contribution among ancestral lines to North American soybean cultivars. Crop Sci. 23:944-949. Dilday RH. 1990. Contribution of ancestral lines in the development of new cultivars of rice. Crop Sci. 30:905-911. Martin JM, Balke TK, Hockett EA. 1991. Diversity among North American spring barley cultivars based on coefficients of parentage. Crop Sci. 31:1131-1137. St. Martin SK. 1982. Effective population size for the soybean improvement program in maturity groups 00 to IV. Crop Sci. 22:151152.

Rice (Oryza sativa L.) is a staple food that is consumed worldwide, and hybrid rice has been widely employed in many countries to greatly increase yield. However, the frequency of extreme temperature events is increasing, presenting a serious challenge to rice grain quality. Improving hybrid rice grain quality has become crucial for ensuring consumer acceptance. This study compared the differences in milling quality, appearance quality, and physical and chemical starch properties of rice grains of five restorer lines (the male parent of hybrid rice) when they encountered naturally unfavorable temperatures during the filling period under field conditions. High temperatures (HTs) and low temperatures (LTs) had opposite effects on grain quality, and the effect was correlated with rice variety. Notably, R751, R313, and Yuewangsimiao (YWSM) were shown to be superior restorer lines with good resistance to both HT and LT according to traits such as head rice rate, chalkiness degree, chalky rice rate, amylose content, alkali spreading value, and pasting properties. However, Huazhan and 8XR274 were susceptible to sub-optimal temperatures at the grain-filling stage. Breeding hybrid rice with adverse-temperature-tolerant restorer lines can not only ensure high yield via heterosis but also produce superior grain quality. This could ensure the quantity and taste of rice as a staple food in the future, when extreme temperatures will occur increasingly frequently.

A field in the kharif season of 2021, a field experiment was conducted at Sam higginbottom University of Agricultural Technology And Sciences, Prayagraj, with the purpose of evaluating ten rice hybrids (UR-26, UR-27, UR-28, UR-29, UR-30, UR-31, UR-32, UR-33, UR-34, and UR-35) under Uttar Pradesh's agro-climatic conditions. The study aimed to assess their growth, productivity, and grain quality attributes. The experiment addressed a gap in knowledge regarding which rice hybrids perform best in the specific agro-climatic conditions. By comparing these hybrids, the study sought to provide insights into selecting the most suitable varieties for maximizing agricultural productivity in the region. Among the hybrids evaluated, UR-32 demonstrated exceptional performance and exhibited superior grain quality characteristics including better hulling, milling, and head rice recovery rates. These results highlight UR-32 as a promising choice for farmers in Uttar Pradesh seeking to optimize both yield and grain quality during the kharif season. In conclusion, the study not only filled a research gap by identifying the top-performing rice hybrid under Uttar Pradesh's agro-climatic conditions but also provided valuable data for enhancing agricultural practices and crop selection strategies in the region

IntroductionOver the past three decades, Guangdong Province has released numerous rice varieties, but comprehensive analyses of their yield and quality characteristics remain limited.MethodsThis study systematically evaluated a total of 982 rice varieties released in Guangdong Province from 1990 to 2020, focusing on grain yield, yield components, and quality parameters.Results and discussionThe results revealed that the number of inbred rice varieties was significantly lower than that of hybrid rice varieties, while the number of high-quality late rice varieties was greater than that of high-quality early rice varieties. Temporal analysis showed significant increases in the release of inbred rice, hybrid rice, and high-quality hybrid late rice varieties. Hybrid rice demonstrated superior grain yield (6.98 t hm−2) compared to inbred rice (6.50 t hm−2), which was primarily attributable to enhanced spikelet per panicle and grain weight. Both inbred and hybrid rice exhibited significant yield improvements over time, driven by increases in spikelet per panicle, filled grain percentage, or grain weight. Notably, the panicle number of both inbred and hybrid rice displayed a significant declining trend. Quality analysis indicated that inbred rice surpassed hybrid rice in head rice rate and chalkiness, while late rice outperformed early rice in these parameters. Early rice exhibited higher gel consistency but lower amylose content compared to late rice. However, both inbred and hybrid rice showed declining trends in head rice rate, chalkiness, and amylose content over the study period. In the future, rice breeding strategies in Guangdong should focus on improving spikelet per panicle and grain weight in inbred rice, and enhancing panicle number in both inbred and hybrid rice varieties to achieve further yield improvement. Furthermore, the development of new varieties should prioritize higher head rice rate, particularly for early rice. These findings provide crucial insights into the evolving patterns of grain yield and quality in Guangdong Province, offering valuable guidance for future breeding strategies and cultivation practices.

In the present study, 88 hybrids were evaluated under aerobic and flooded conditions, out of which 35 hybrids were identified for grain quality analysis based on single plant yield, grain type, and parental line flowering synchronization.The grains of 35 high yielding hybrids and their respective parents were subjected to grain quality analysis as per the procedures given in the standard evaluation system.The released rice hybrids ADTRH 1 and CORH 2 and the popular fine grain varieties ADT 43 and BPT 5204 were used as standard checks for effective comparison.Data were recorded for the following quality characters like milling quality traits, physical grain quality traits and cooking quality traits.The hybrid COMS 14A × IR 62161-184-3-1-3-2 was identified as the best hybrid since it recorded the highest total score followed by IR 68888A × IR 69715-72-1-3, IR 68888A × WGL 32100, IR 68897A × IR 72875-94-3-3-2, COMS 14A × IR 69715-72-1-3 and COMS 14A × WGL 14, COMS 14 A × IR55838-B2-2-3-2-3 and IR 68897 A × IR 71604-4-1-4-7-10-2-1-3.These hybrids had good scores for more number of quality traits such as milling per cent, head rice recovery, chalkiness, volume expansion, intermediate GT, soft gel consistency and amylose content.The parents of these hybrids also had higher total score for most of the quality traits.These hybrids with higher yield and good grain quality, can be exploited commercially for grain yield and quality improvement.The male parents viz., WGL 14, IR 71604-4-7-10-2-1-3, IR 62161-184-3-1-3-2, IR55838-B2-2-3-2-3, IR 62030-54-1-2-2, PSBRC 82, IR 36,and female parents viz., IR 68888A, IR 68897A and COMS 14A, with desirable grain quality had produced hybrids with superior grain quality.These parents could also be exploited further for developing heterotic rice hybrids with improved grain quality.

China is the first country to use heterosis successfully for commercial rice production. This study compared the main quality characteristics (head rice rate, chalky rice rate, chalkiness degree, gel consistency, amylose content, and length-to-width ratio) of 635 rice varieties (not including upland and glutinous rice) released from 2000 to 2014 to establish the quality status and offer suggestions for future rice breeding for grain quality in China. In the past 15 years, grain quality in japonica rice and indica hybrid rice has improved. In japonica rice, inbred varieties have increased head rice rates and decreased chalkiness degree over time, while hybrid rice varieties have decreased chalky rice rates and chalkiness degree. In indica hybrid rice, the chalkiness degree and amylose contents have decreased and gel consistency has increased. Improvements in grain quality in indica inbred rice have been limited, with some increases in head rice rate and decreases in chalky rice rate and amylose content. From 2010 to 2014, the percentage of indica varieties meeting the Grade III national standard of rice quality for different quality traits was low, especially for chalky rice rate and chalkiness degree. Japonica varieties have more superior grain quality than indica rice in terms of higher head rice rates and gel consistency, lower chalky rice rates and chalkiness degree, and lower amylose contents, which may explain why the Chinese prefer japonica rice. The japonica rice varieties, both hybrid and inbred, had similar grain qualities, but this varied in indica rice with the hybrid varieties having higher grain quality than inbred varieties due to significantly better head rice rates and lower chalkiness degree. For better quality rice in future, the chalky rice rate and chalkiness degree should be improved in japonica rice along with most of the quality traits in indica rice.

Synthetic apomixis with normal hybrid rice seed production

The technology of hybrid rice utilizing heterosis is an essential requirement for achieving food security. The current study was aimed at assessing the genetic parameters and the gene actions of 15 yield-component traits associated with heterosis, in 9 new parental lines of hybrid rice and their generated hybrids. Five cytoplasmic male sterile (CMS) lines were crossed with four restorer (R) lines using twenty generated line × tester designation hybrid combinations. The results revealed that all the traits were controlled by additive and non-additive gene actions. However, the additive variance was the main component of the total genotypic variance. Assessment of the general combining ability (GCA) detected the best combiners among the genotypes. The hybrid combinations that expressed the highest-positive specific combining ability (SCA) for grain-yield were detected. The correlation between the GCA and SCA was evaluated. The hybrid crosses with high-positive heterosis, due to having a better parent for grain yield, were detected. The principal component analysis (PCA) recorded the first four principal axis displayed Eigenvalues >1 and existing variation cumulative of 83.92% in the genotypes for yield component characteristics. Three-dimensional plots corresponding to the studied traits illustrated that the genotypes Guang8A × Giza181, Quan-9311A × Giza179, II-32A × Giza181, and II-32A × Giza179 are classified as possessing superior grain yield.

The most important concerns of hybrid rice breeders are selection of donors to improve parental lines and prediction of hybrid performance. In this study, SSR molecular marker technology and a half-diallel method were used to address these related hybrid production issues. The results show that genetic diversity among the parental lines is certainly related to heterosis. The heterozygosity of each parental pair is significantly associated with the general combining ability, not with the specific combining ability. However, neither genetic diversity nor heterozygosity is a good indicator for predicting heterosis. From these results, it is suggested that donors for improving parents of hybrids be selected from the improved inbred lines by conventional breeding programs. In this investigation, we also discovered that four favorable alleles and six favorable heterogenic patterns on the parental lines significantly contribute to the heterosis of their hybrids in grain yield, whereas six unfavorable alleles and six unfavorable heterogenic patterns significantly reduce heterosis. These noticeable findings could be, in practice, useful for hybrid rice breeding programs with SSR marker-assisted selection. It is suggested that the optimal combinations with the superior grain yield could be bred out by assembling those favorable alleles into their parental lines and by removing the unfavorable alleles from the parental lines. This study also indicates that there is still a great heterosis potential to be exploited in indica/indica hybrids by the same strategy. In indica/japonica hybrid breeding programs, it may also be important to remove unfavorable alleles rather than broaden genetic diversity or heterozygosity of the parents.

Superior grain quality is the main goal of rice breeders because of its high commercial value. Progress in selection for grain quality with yield in harsh environments is markedly affected by environmental variation. The genotype by environmental (G × E) interaction influence on grain quality was analyzed in this study, comprised of 17 rice hybrids grown in six location- year environments. The objective of this study was to examine the influence of G × E interaction for grain quality in hybrid rice by using AMMI model. Results of the trial revealed that grain quality was highly influenced by environmental factors and brings out the suitability of specific genotype to specific location/season through the biplot. On the other hand, external environmental variables can be regressed on the environmental scores to lead to a useful biological interpretation of the interaction effects, which is not possible in additive effect models. The implications of these results for rice hybrids on grain quality in varied environmental location are discussed.

Indica–japonica hybrid rice (I–JR) typically has greater grain yield than that of Indica hybrid rice (IR) under prolific shading, but it is not known how shading impacts on physiological characteristics underpinning grain quality. Here, we conducted a two-year field experiment in the mid-reaches of the Yangtze River region using I–JR (genotypes Yongyou 1540 and Yongyou 538) and IR (genotypes Y-liangyou 900 and Quanyouhuazhan). We found that shading reduced grain appearance and quality, particularly milling and heading rates, and chalkiness. Shading disrupted carbon and nitrogen metabolism, impacting traits influencing the human perception of the taste of the grain, such that amylose decreased by 5.9% (I–JR) and 12.9% (IR); grain protein significantly increased, with lesser effects in I–JR than IR under shading. Shading also reduced peak, hot, and final viscosities, and breakdown value. I–JR had improved rice quality compared with that of IR due to the greater propensity of the former to photosynthesize under shading, leading to the improved functioning of carbon and nitrogen metabolism.

This research was carried out at the Experimental Farm of Sakha Agricultural Research Station, Sakha, Kafr El-Sheikh, Egypt, during the 2018–2020 rice-growing seasons to develop and evaluate four iso-cytoplasmic rice-restorer lines: NRL79, NRL80, NRL81, and NRL82, as well as Giza 178, with ten new hybrids in order to estimate genotypic coefficient, phenotypic coefficient, heritability in a broad sense, and advantage over Giza 178 as a check variety (control) of new restorer lines. This study also estimated combining ability, gene action, better-parent heterosis (BP), mid-parents heterosis (MP), and standard heterosis (SH) over Egyptian Hybrid one (IR69A × Giza 178) as a check hybrid (control) for grain yield, agronomic traits, and some grain quality characters in restorer lines and hybrids. The percentage of advantage over commercial-variety Giza 178 (check) was significant, and highly significant among the newly developed restorer fertility lines for all the studied traits. This indicates that the selection is a highly effective factor in improving these traits. New restorer fertility lines showed highly significant positive values over commercial restorer for grain yield; the values ranged from 51% for NRL80 to 100.4% for NRL82, respectively. Meanwhile, in regard to the grain shape of paddy rice, three lines of the promising lines showed highly significant negative desirable values compared with Giza 178; the values ranged from −7.7% for the NRL80 to −15.2% for NRL79, respectively. Based on the superiority of the new lines, the new lines can be used as new restorer fertility lines to breed promising new hybrids and new inbred rice lines or varieties. From the results of the testcross experiment, the four promising lines were identified as effective restorer fertility lines for two cytoplasmic male sterile (CMS) lines. Moreover, the six rice hybrids showed values for SH heterosis of grain yield/plant of more than 15% over the check hybrid variety, with high values of 1000-grain weight and desirable grain shape; these hybrids were G46A × NRL81 (125.1%), G46A × NRL80 (66.9%), IR69A × NRL79 (47.2%), G46A × NRL79 (24.6%), IR69A × NRL81 (23.4%), and IR69A × NRL82 (16.2%).

To evaluate the grain-filling pattern, Chinese first super hybrid rice, Liangyoupeijiu was grown under tillage and establishment methods at a spacing of 20 cm × 20 cm with one seedling hill-1 and at a seeding rate of 22.5 kg ha-1 in Changsha, Hunan Province, China in 2012. Our results showed that, superior grain weight in TP had always higher than DS up to 24 DAH but at 36 DAH, grain weight had similar in both TP and DS. Middle grain weight was higher in TP than DS up to 18DAH but it was higher in DS than TP at 24 – 36 DAH and at 36 DAH, grain weight of DS had significantly higher than TP. Inferior grain weight was higher in TP than DS up to 12 DAH but it was higher in DS than TP at 24 -36 DAH and at 36 DAH, grain weight of DS had significantly higher than TP. Grain-filling rate of superior grain had higher in TP than DS up to 18 DAH but it was higher in DS than TP at 30 DAH. In middle grain, it was higher in TP at 6DAH but in DS, it was higher at 30 DAH. In inferior grain, it was higher in TP at 36 DAH but in DS, it was higher at 30 DAH. The heavier grain was found in TP only in superior grain but DS had heavier grain both in middle and inferior grain. Grain-filling rate of superior grain was higher in TP than DS and it was similar in both TP and DS in middle grain. But in inferior grain, it was significantly higher in DS than TP. Transplanting method produced slightly higher grain yield due to higher sink size (more number of spikelet’s caused by longer panicle and more number of spikelet per cm of panicle) but it was statistically similar with DS. DOI: http://dx.doi.org/10.3329/ijarit.v4i1.20972 Int. J. Agril. Res. Innov. & Tech. 4 (1): 11-15, June, 2014