Parental Lines Of Hybrid Rice Research Articles

Correction to: Identification of low phosphorus tolerant parental lines of hybrid rice based on stress indices and haplotype analysis using Pup1 linked markers

Correction to: Identification of low phosphorus tolerant parental lines of hybrid rice based on stress indices and haplotype analysis using Pup1 linked markers

Identification of low phosphorus tolerant parental lines of hybrid rice based on stress indices and haplotype analysis using Pup1 linked markers

Identification of low phosphorus tolerant parental lines of hybrid rice based on stress indices and haplotype analysis using Pup1 linked markers

Assessment of correlation and path analysis of hybrid rice parental lines in a multi-environment study (Oryza sativa L.)

Correlation and path analysis are useful selection aids for the plant breeder to understand the complex interactions among various factors that influence crop growth and yield. The data were collected from a diverse set of 150 genotypes, consisting of 129 restorers, 15 maintainers and 6 checks in three different environments (Kharif 2021@ICAR-IIRR, Hyderabad, Kharif, 2021@ Agricultural College, Tirupati and Rabi 21-22@ICAR-IIRR, Hyderabad) on 10 different component traits. The analysis included three data sets along with their pooled values. All of the component traits demonstrated a positive correlation with single plant yield, either significant or non-significantly in environment wise analysis as well as in the pooled analysis. The analysis revealed that certain traits, namely plant height, total number of tillers per plant, productive tillers per plant and spikelet fertility showed a significant positive correlation with single plant yield while the rest of the traits exhibited a positive non-significant correlation. Based on the results, plant height, biomass, and harvest index play a key role in determining final yield, as they have a strong positive correlation with single plant yield and exert positive direct effects on it. Therefore, prioritizing these traits during selection could be an effective approach for the indirect selection of increased grain yield.

B × R cross de rived parental line development using breeding value: A new model for hybrid rice parental line development

Three-line hybrid rice system is the most successful and widely practiced method around the world. Hybrid rice breeders have used B × B, A × R and R × R (R = Restorer line, B = Maintainer line, A = CMS line) scheme of parental line improvement frequently and avoided B × R and R × B scheme. As a result, female parents lack the genetic diversity carried by R lines. But B × R and R × B mating have great potential to produce high value parental lines of hybrid rice and overcome the limitation of the previous approach. We have demonstrated a new method for three-line hybrid system to minimize the barrier of crossing in parent selection for developing new elite maintainers and restorers. Parental combinations were selected based on breeding value of the genotypes. Breeding values were estimated based on ancestor, pedigree information and yield data of 74 test genotype to select parents for restorer and maintainer line improvement. This new protocol allows (B × R), (R × B) (R × Elite) and (B × Elite) improvement technique to bring out high yielding diverse B and R lines. This B line will be used for developing new A line in the genetic background of B line. Doubled haploid and RGA i.e. rapid generation advance tools of breeding will save the precious time and reduce breeding cycle length; and large population size will increase selection accuracy. We have predicted the genetic gain in parental line development for four parental cross using the studied 74 genotypes for doubled haploid and rapid generation advance methods. Our objectives were to demonstrate the new breeding approach plus breeding value and positive dominant gene effect-based parent selection strategy. We are hopeful about the new method that hybrid rice breeders across the world will extract benefit utilizing the new methodology of hybrid rice parental line development.

Improving hybrid rice parental lines for blast resistance by introgression of broad‐spectrum resistance genes Pi54 and Pi9 by marker‐assisted selection

AbstractHybrid rice technology offers a great promise to produce 15% to 20% more yield than pure line varieties. The success of hybrid rice hinges on developing superior parental lines. To improve the blast resistance of hybrid rice parental line RP5933‐1‐19‐2R, crosses were made with donors of two major blast resistance genes namely, Pi54 (Tetep) and Pi9 (IR71033–121‐15) and the resulting F1s were confirmed for their hybridity by using Pi54MAS and NMSMPi9‐1 genic markers. The confirmed F1s were intercrossed to obtain ICF1s and selected positive plants by markers were backcrossed to the recurrent parent, as well as selfed for advancing further to BC1F3 and ICF4 generations. The segregating plants were phenotyped for blast resistance at Uniform Blast Nursery. The identified complete restorers namely, RP 6619‐1, RP 6616‐26, RP 6619‐3 and RP 6619‐11 with Pi9 and Pi54 genes would serve as donors for broad spectrum blast resistance. This could ultimately lead to the development of new rice hybrids with improved resistance to blast disease, which is crucial for sustainable rice production and food security.

Identification of stable restorer lines developed through inter‐sub‐specific hybridization in rice (Oryza sativa) using multi‐trait stability index

AbstractInter‐sub‐specific hybridization between indica and tropical japonica rice germplasm is the most efficient approach for broadening the genetic base of hybrid rice parental lines and enhancing the heterotic potential of hybrids in a tropical country like India. In the present study, 106 indica/tropical–japonica derived lines were developed through inter‐sub‐specific hybridization and screened using functional markers with respect to the major fertility restorer genes, Rf3 and Rf4, and the wide compatibility gene, S5n. The fertility restoration ability of newly developed restorers was validated through test cross nursery performance. The functional markers were observed to accurately predict the trait of fertility restoration. From the present study, the decreasing order of efficiency of different gene combinations on fertility restoration ability are as follows: Rf4/S5n > Rf4/Rf3/S5n > Rf4 > Rf4/Rf3 > Rf3/S5n > Rf3. Based on multi‐trait stability index (MTSI) analysis, the four newly identified restorers, that is, RP6388‐90, RP6382‐49, RP6375‐81 and RP6368‐38, were selected as the top best performing genotypes with high stability for multiple traits, and these genotypes will be useful for the development of superior rice hybrids in India.

Improving blast resistance of maintainer line DRR 9B by transferring broad spectrum resistance gene Pi2 by marker assisted selection in rice.

Hybrid rice technology offers great promise to further enhance rice production and productivity for global food security. Improving hybrid rice parental lines is the first step in developing heterotic rice hybrids. To improve resistance against blast disease, a maintainer line DRR 9B was fortified with a major broad-spectrum blast resistance gene Pi2 through marker-assisted selection. The rice blast caused by Magnaporthe oryzae is a major disease and can cause severe yield losses upto 100%. The NILs of Samba Mahsuri namely BA-23-11-89-12-168 possessing Pi2 was utilized as a donor parent. The PCR-based molecular marker tightly linked to Pi2 gene was used for the foreground selection at BC1F1 generation. The molecular marker tightly linked to the major fertility restorer gene Rf4 was used for negative selection (i.e., selection of plants possessing non fertility restoring alleles) at BC1F1 generation to identify maintainer lines. The positive plants with Rf4 gene were added to the restorer pool for restorer line development. At each stage, MAS for Pi2 coupled with stringent phenotypic selection for agro-morphological and grain quality traits were exercised. At BC1F3 generation, one hundred families were screened against blast disease at uniform blast nursery (UBN) and selected resistant lines were advanced to next generations. In the BC1F5 generation plants were subjected to agro-morphological evaluation for yield and yield-contributing traits. The selected plants at BC1F5 generation were crossed with DRR 9A to assess the maintainer ability of blast resistance lines and for further CMS line conversion for hybrid rice breeding for developing blast resistance rice hybrids.

Evaluation of hybrid rice parental lines against bacterial blight disease and detection of resistant gene (s) by gene‐specific, linked markers

AbstractBacterial blight (BB) disease, caused by Xanthomonas oryzae pv. oryzae (Xoo), is one of the major bottlenecks of rice (Oryza sativa) production. The present study was undertaken to identify BB‐resistant parental lines of hybrid rice based on pathogenicity tests and molecular screening. Three virulent races of Xoo, i.e. BXo93, BXo822 and BXo887 were used to evaluate the 66 maintainers and 200 elite restorer lines against BB. Based on the pathogenicity test, none of the maintainer lines was found resistant, whereas 16 restorers were resistant against the three races and 15 restorers were resistant to a single race (Bxo93). These 31 restorer lines were selected to detect the presence of major bacterial blight resistance genes, i.e. Xa4, xa5, Xa7, xa13, Xa21 and Xa23 using molecular markers. Thirteen restorer lines carried the Xa4 gene but were not resistant to all three races of BB. Fourteen restorers and one restorer had two (Xa4 + xa5; Xa4 + Xa7; Xa4 + Xa21 and Xa7 + Xa21) and three (Xa4 + xa5 + Xa7) BB resistance genes, respectively. Genotypes having Xa21, Xa7 + Xa21 or Xa4 + Xa21 had reduced lesion lengths that ranged from 1.4 cm (against BXo93)–3.0 cm (against BXo887), 1.6 cm (against BXo93)–2.0 cm (against BXo822 and BXo887) and 2.5 cm (against BXo887)–3 cm (against BXo822), respectively, and were found to be the most effective resistance genes against bacterial blight. The restorer lines having the Xa21, Xa7 + Xa21 or Xa4 + Xa21 could be used as parental lines for the development of bacterial blight‐resistant hybrid varieties.

Assessment of Genetic Parameters and Gene Action Associated with Heterosis for Enhancing Yield Characters in Novel Hybrid Rice Parental Lines.

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.

Development and Application of Identification Markers for Main Parental Lines of Hybrid Rice

As the development of the modern hybrid rice breeding, many disadvantages behaved in variety identification, variety authenticity identification and seed genetic purity test based on phenotype, which was not suitable for the modern breeding. Insertion-Deletion (ID) loci in rice genome sequence were used to develop 9 ID markers to identify 29 hybrid rice backbone parental lines which were widely used in rice production. Cluster analysis of 29 parental lines were conducted using electrophoresis of those ID markers, and they were clustered into five groups with similarity coefficients of about 0.55. In addition, according to relatedness and original region these lines were clustered into nine subgroups. Genetic purity was conducted for a hybrid rice Guangliangyou476 using ID marker and growth-out test methods, and similar results were generated. So molecular marker could be used into each stage of the modern breeding to accelerate breeding new variety. This research will be helpful for rice breeding, new cultivar registration and seed production.

Combining ability, floral biology, and seed producibility of promising cytoplasmic male-sterile (CMS) lines for hybrid rice development

BackgroundA combining ability analysis is a useful tool of plant breeders in screening and identifying promising parental lines with high potential for developing competitive rice hybrids. Also, one important factor that strongly determines the suitability of commercial utilization of hybrid rice parental lines is their extent of seed producibility.MethodsIn this study, the combining ability, floral biology and seed producibility of cytoplasmic male sterile (CMS) lines were investigated to identify good combiners with good seed production potential. The Line × Tester analysis was used to determine the general combining abilities (GCA) of hybrid rice parental lines, and Specific Combining Abilities (SCA) of the different hybrid combinations. A correlation analysis was also done to determine floral traits that influence the outcrossing rate of the CMS lines. There were 4 CMS lines, 6 restorer lines, 24 hybrid combinations and 1 check variety in a randomized complete block Design (RCBD) with 3 replicates.ResultsResults indicated that CMS lines IR79128B and IR102758B were good combiners and the most promising restorer lines were D2031-7-1-2R, Hanareumbyeo 2, and XTR036-54-10R. Based on specific combining ability test, the most promising combination was entry 10 (IR58025A/D2013-7-1-2R). It has the highest yield of 7496 kg ha−1, a high positive SCA score of 570.54, and highest standard heterosis of 12.9%. Based on floral traits, IR79128B was the most promising with a high positive GCA score of 186.93, panicle exertion rate of 74.8%, and a high outcrossing rate of 51%. There was a significant positive association between outcrossing rate, duration of floral opening, panicle exertion rate, and general combining ability.ConclusionThe floral traits found to be significantly associated with outcrossing rate are useful selection criteria not only for identifying economically usable CMS lines but also for developing new and promising parental lines and hybrids. These CMS lines do not only give heterotic combinations but are also commercially producible, the two most important factors to the success of any hybrid rice breeding program.

Profiling of monosporidial populations of Tilletia barclayana causing kernel smut of rice

Kernel smut of rice caused by Tilletia barclayana has become a notable constraint in hybrid seed production of rice in many rice producing countries worldwide. The disease is reported to cause 20–50 per cent yield and quality losses in parental lines of hybrid rice. No commercial cultivar has been reported to possess complete resistance against the pathogen. Teliospore germination studies in laboratory and pathogenic variability studies in field indicated that the virulence of different isolates of T. barclayana are correlated with the sporidial production index of various isolates. On the basis of pathogenicity data of 14 different isolates of T. barclayana, the isolates were grouped into 2 major clusters at 40% level of similarity index. Tb-24 was the most virulent isolate which emerged as a separate lineage from all the other isolates. A total of 10 URPs were used to study the variability among T. barclyana isolates at genetic level. High range of variability (95.6% polymorphism) was obtained with all the primers used for amplification of fourteen monosporidial isolates. Isolate Tb-24 had a distinctive banding pattern with unique bands of approximately 3 kb and 500 bp indicating its genetic difference from all other isolates of T. barclayana.

The resistance of restorer lines and F1 hybrids to bacterial leaf blight disease

Bacterial leaf blights (BLB) is one of a major problem in hybrid rice cultivation cause yield losses from 15 to 80%. The disease is caused by the bacterium of Xanthomonas oryzae pv. oryzae (Xoo). To overcome this problem, improvement of hybrid rice parental lines have been conducted since 2010 in the Indonesian Center for Rice Research. There were two activities conducted in the research i.e. evaluation of some improved parental lines resistance to BLB and evaluation of their F1 hybrid for yield and agronomic traits during the dry season of 2015 in a field station. Results showed that several Restorer lines were resistant to BLB. The restorer lines CRS850, CRS851, CRS882, 890, and CRS982 have been identified as resistant lines in early tillering and booting stages to both Xoo IV and VIII races. Those Restorer lines are the potential to use as parental lines to develop new hybrid varieties possessing resistance to BLB. The best F1 hybrids with resistance to BLB was GMJ7/CRS850 that showed resistance in early tillering and booting stages to both Xoo IV and VIII races. GMJ12/CRS890 hybrid showed the best performance and yielded higher than that of the check variety.

Flowering Synchronization in Hybrid Rice Parental Lines at Different Sowing Dates

Hybrid seed set on the female line depends primarily on its flowering synchronization with the restorer line (R), therefore, the sowing of male and female lines must be planned properly to achieve this. Field experiments on different sowing dates (May 1st, May 15th, and May 30th) of R lines (Giza 178R, Giza 179R, and Giza 181R) and cytoplasmic male sterile (CMS) lines (IR69625A, IR70368A, IR58025A, K17A, and G46A) were carried out at the farm of Sakha Agricultural Research Station, Kafr El-Sheikh, Egypt during 2019 and 2020 to study the effect of sowing dates on flowering synchronization in hybrid rice. The results indicated that the synchronization of flowering between CMS lines and R lines has highly significant effects on the days to 50% heading, number of leaves, effective accumulated temperature (EAT), plant height, panicle exertion percentage, panicle length, number of fertile panicles, panicle weight, seed set percentage, harvest index and seed yield of hybrid rice. The highest seed yield (1.72 and 1.41 t ha−1, respectively in 2019 and 2020) was recorded from the sowing date May 1st and the hybrid combination of Giza 178R × IR58025A (2.06 and 2.12 t ha−1 in 2019 and 2020, respectively). The grain yield had a significant and highly significant positive correlation with the plant height (cm), panicle exertion percentage, panicle length, number of panicles plant−1, panicle weight, seed set percentage, and harvest index. In Egypt, May 1st is the best time for the synchronization of hybrid rice lines and a combination of Giza 178R × IR58025A may be recommended for better performance.

Combining Ability and Gene Action for Yield Characteristics in Novel Aromatic Cytoplasmic Male Sterile Hybrid Rice under Water-Stress Conditions

Hybrid rice parental lines with better combining abilities provide an efficient tool to increase rice production. In the current study, twenty hybrid combinations were generated from five aromatic cytoplasmic male sterile (CMS) lines and four restorer lines (three of them aromatic) using a line × tester mating design. The hybrids and their parental lines were evaluated under two water regimes: normal irrigation and water-stress. Ten yield-component traits were studied over a period of 2 years, and the significant differences between the parents and hybrids are reported in this investigation. Overall, all yield component traits were significantly affected by the water deficit and were governed by both additive and non-additive gene actions. More specifically, the grain yield (GY) was mainly controlled by non-additive gene action under both normal and water-stress conditions. The contribution of the additive variance (σ2 A) was more prominent in the genetic components of traits as compared to the dominance variance (σ2 D). The aromatic parental line CMS IR58025A and the restorer line PR2 were recorded as the best combiners for the GY and good combiners for many other characteristics under both growth conditions. The cross combinations Pusa12A/IR25571-31R and Pusa12A/Giza-Basmati-201 revealed significantly positive specific combining ability (SCA) effects for the GY under both normal and water-stress conditions. The inconsistent correlation between the general combining ability (GCA) and SCA manifested complex interactions among the positive and negative alleles of the genes controlling the yield traits. Generally, the findings of this investigation demonstrated the importance of the GCA and SCA for understanding the genetic components and gene actions of the yield characteristics in new aromatic hybrid rice parental lines. Therefore, we recommend considering these findings in the selection of elite parents for developing superior aromatic hybrid rice varieties under water-stress conditions.

Genetic Diversity Analysis of Hybrid Rice Parental Lines and Genetic Purity Assessment of Hybrid Seeds of China

Thirty-five pairs of SSR primers were used for genetic diversity analysis and DNA fingerprinting of 31 hybrid rice core parental lines developed in central- and southern-China using one japonica rice line and three inbred rice lines as the check varieties. The average number of alleles (Na) per SSR locus was 4.02, with a range of two to eight, the effective number of alleles (Ne) was 83.16 with a mean of 2.38, ranging from 1.19 to 4.66. The polymorphic information content (PIC) ranged from 0.16 to 0.79, with an average number of 0.52. The results of the cluster analysis indicated that the check varieties viz., one japonica rice and three inbred rice, were clustered into two groups with similarity coefficients of 0.62 and 0.71 respectively indicating their relatedness. Thirty-one hybrid rice parental lines were clustered into 6 groups according to their different types, pedigrees and regions of development with similarity coefficients of approximately 0.76. The highest genetic similarity coefficient (0.94) was observed between Y58S and C815S, and the lowest (0.63) was observed between Quan9311A and Peiai64S. The purity of one hybrid rice cultivar was tested using characteristic marker and the field test, and it was demonstrated that the purities obtained using the two methods were similar. This research will be helpful for rice breeding, new cultivar registration and seed production.

Divergence in hybrid rice parental lines detected by RAPD and ISSR markers

Genetic distance between parental lines used in hybrid rice breeding program was estimated based on information from molecular markers data. Sixteen parents (5 CMS, 5 maintainers and 6 restorers) were analyzed with 15 random amplification polymorphic DNA (RAPD) and 20 inter simple sequence repeat (ISSR) marker. Out of 15 RAPD markers, 9 were polymorphic and 79 bands were generated, of which 28 bands were polymorphic (35 %). By using 10 out of 20 ISSR markers 86 bands were detected, of which 35 bands were polymorphic (41 %). Marker index (RAPD = 1.68; ISSR = 1.88) and percent of polymorphic bands indicated that ISSR markers were relatively more efficient in polymorphism detection. Cluster analysis of the parents based on Jaccard’s genetic similarity and UPGMA method were revealed 3 groups. Restorer lines IR68061 and IR5931 with origin of the Philippines were found in distinct group. Results suggesting the cross between CMS lines Neda and Nemat with restorer lines IR68061 and IR5931, can be used as the best heterotic groups for exploration of heterosis.

Study on floral traits and seed setting in parental lines of hybrid rice during early ahu and kharif seasons

Two CMS lines, IR 58025A and IR 68888A along with their maintainers and two fertility restorers, LuitR and IR 36R, were evaluated for flower and plant characters during early ahu (February-June) and kharif (July-November) seasons. IR 58025A showed longer stigmata and styles, and higher spikelet Length/Breadth (L/B) ratio while IR 68888A showed broader stigmata and wider glume opening angle in both the seasons. IR 68888A also exhibited higher pollen sterility during early ahu. IR 36R was characterized with broad anthers. LuitR showed longer and broader anthers with more pollen than others. Plant height, flag leaf length, flag leaf width and area were higher in IR 36R. Panicle exsertion was complete in pollen parents whereas it was 78-80% in CMS lines. The widest flag leaf angle was found in IR 58025B during early Ahu and in IR 36R during kharif. Kharif season was more favourable for growth of the plants with higher seed set percentage while floral traits of the CMS lines were better expressed in early Ahu. Manipulation of the seeding sequence of the parental lines in early Ahu is warranted for better seed set provided the seed crop escapes heavy premonsoon showers during reproductive stage. IR 68888A/LuitR was a good combination for pollen dispersal and seed setting.

Multi-trait improvement in rice through marker-assisted breeding

Biotechnological tools like molecular markers can add precision to breeding and accelerate breeding efforts. Towards this objective, our research team at ICAR-IIRR has applied marker-assisted breeding (MAB) for improvement of multiple traits like resistance against bacterial blight, blast, gall midge and BPH, heterosis related traits, improvement of low soil P tolerance, grain quality and yield. Through marker-assisted backcross breeding (MABB), a high-yielding, bacterial blight resistant rice variety possessing fine-grain type and low glycemic index (GI), named Improved Samba Mahsuri (ISM) has been developed and released for cultivation by farmers. MABB has also been applied for improving bacterial blight resistance of a few important traditional and evolved Basmati rice varieties and hybrid rice parental lines. A novel bacterial blight resistance gene, Xa33 has been identified from an accession of the wild rice, O. nivara, fine-mapped and transferred into several elite genetic backgrounds. Novel sources of resistance against bacterial blight and blast diseases have been identified and characterized and major blast resistance have been transferred to several elite genetic backgrounds and a major QTL associated with neck blast resistance has been identified from wild rice. Additionally, genepyramid lines possessing resistance against gall midge have also been developed and a novel and highly effective BPH resistance gene has also been identified and mapped with molecular marker and few promising donors possessing resistance against sheath blight have been identified. A molecular marker-based assay has been designed for rapid and accurate determination of impurities in seed-lots of rice hybrids and their parental lines and functional markers have been developed for the traits relevant to hybrid rice, viz., wide-compatibility, wild-abortive cytoplasmic male sterility and fertility restoration. Functional markers have also been developed for major grain quality determining genes, fgr and GS3 and a major QTL controlling gelatinization temperature has been identified through molecular mapping. The major QTL responsible for low soil phosphorus (P tolerance, viz., Pup1 has been transferred to Improved Samba Mahsuri, MTU1010 and IR64 and novel, non-Pup1 type donors have been identified for the trait. Four major yield enhancing genes, viz., Gn1a, SCM2, OsSPL14 and GW5 have been transferred to elite rice cultivars, viz., Improved Samba Mahsuri, Swarna, MTU1010 and NDR359.

Breeding strategies for hybrid rice parental line improvement

In our country, significant progress has been made in the development of hybrid rice parental lines both female and male parents with good floral traits. An array of hybrids with good grain quality (both unique Basmati type and medium slender (MS) grain type) is developed. Efforts are focussed on the development of restorer lines through exploitation of inter sub-specific hybridization, recurrent selection and population improvement that will help in the development of highly heterotic rice hybrids. The female parental lines are being improved for traits like stigma exsertion and high outcrossing that helps in higher seed yields, thereby reducing the hybrid seed cost. Efforts are on to develop appropriate parental lines that can help in the development of suitable hybrids in late duration group and also for unfavourable ecologies. Many newly developed parental lines are being fortified with resistance genes for major diseases such as BB, blast and insect pests such as BPH that will help in the development of hybrids having resistance to major pests and diseases.