Search

Being a model crop as well as a staple food crop, rice possesses a conspicuous position in plant sciences. Doubled haploid (DH) breeding in rice offers multiple advantages over conventional methods via accelerating the process of pure lines development. For ages, several methods have been devised for haploid production in rice. In vitro‐based methods have demonstrated their potential in DH production, but these methods are further impeded by stringent requirements and restricted to few species. Further, unlike maize, the in vivo DH breeding technology is still impractical in rice. Recent findings of the key molecular players behind the haploid induction (HI) trait in maize and rice have shown their potential in rice improvement programmes. In this review, we have discussed different strategies of HI in rice particularly focusing on recent progress made for developing haploid inducer stock (HIS) by employing both conventional and modern approaches. It also focuses on future implications of HIS so that it can be incorporated in the pipeline of modernized rice breeding. [ABSTRACT FROM AUTHOR]

Key message: A BPH-resistant locus designated as Bph34 identified in Oryza nivara acc. IRGC104646 on long arm of chromosome 4 using high-resolution mapping with 50 K SNP chip. BPH resistance contributed by locus showed dominant inheritance in F2 and F3. The Bph34 locus is 91 kb in size and contains 11 candidate genes. In addition to SNP markers, SSR markers, RM16994 and RM17007 co-segregated with the BPH resistance. These two SSR markers can facilitate marker-assisted transfer of the Bph34 locus into elite rice cultivars in all labs.Abstract: Brown planthopper (BPH, Nilaparvata lugen Stål) is one of the most destructive insects of rice (Oryza sativa L.) causing significant yield losses annually. Exploiting host plant resistance to BPH and incorporating resistant genes in susceptible commercial cultivars is economical and environmentally friendly approach to manage this pest. Here, we report high-resolution mapping of a novel genetic locus for resistance to BPH, designated as Bph34 on long arm of rice chromosome 4. The locus was mapped using an interspecific F2 population derived from a cross between susceptible indica cultivar PR122 and BPH-resistant wild species, O. nivara acc. IRGC104646. Inheritance studies performed using F2 and F2:3 populations revealed the presence of single dominant gene. Construction of high-density linkage map using 50 K SNP chip (OsSNPnks) followed by QTL mapping identified single major locus at 28.8 LOD score between SNP markers, AX-95952039 and AX-95921548. The major locus contributing resistance to BPH designated as Bph34 and explained 68.3% of total phenotypic variance. The Bph34 locus is 91 Kb in size on Nipponbare reference genome-IRGSP-1.0 and contains 11 candidate genes. In addition to associated SNP markers, two SSR markers, RM16994 and RM17007, also co-segregated with the Bph34 which can be used efficiently for markers assisted transfer into elite rice cultivars across the labs. [ABSTRACT FROM AUTHOR]

Considering the potentials of wild rice (Oryza spp.), as well as the need to enhance the yield potential of rice and to increase rice production to meet increasing demands, 1780 backcross inbred lines (BILs) were generated by crossing 70 accessions of six "AA" genome species: Oryza glaberrima Steud., Oryza barthii A. Chev., Oryza nivara Sharma & Shastry, Oryza rufpogon Griff., Oryza longistaminata A. Chev. & Roehr., and Oryza glumaepatula Steud. with two elite cultivars of Oryza sativa L. The wild species accessions were selected based on variation at the DNA markers and agromorphological traits. The BILs were generated by backcrossing F1s twice (thrice in some cases) to recipient parents, followed by continuous selfing and selection for the yield and yield component traits. The set of 1780 BC2F5 to BC2F10 BILs were evaluated in an augmented design over 3 yr. Based on ANOVA in augmented design, 108 agronomically superior BILs were selected and evaluated in randomized complete block design. Of the 108 BILs evaluated, 15 BILs showed >10% yield superiority over the recurrent parent, with spikelet per panicle and thousand-grain weight as most significant traits contributing to yield increase. Based on the contribution of donor accessions for the improvement of yield component traits, six accessions of O. glaberrima, one of O. barthii, two of O. nivara, two of O. rufpogon, and one each of O. longistaminata and O. glumaepatula were identified as potential donors that could be used more rigorously in transferring genes to cultivated rice. The BILs generated in the present study represents a reservoir of novel genetic variation. [ABSTRACT FROM AUTHOR]

Utilization of “hidden genes” from wild species has emerged as a novel option for enrichment of genetic diversity for productivity traits. In rice we have generated more than 2000 lines having introgression from ‘A’ genome-donor wild species of rice in the genetic background of popular varieties PR114 and Pusa44 were developed. Out of these, based on agronomic acceptability, 318 lines were used for developing rice hybrids to assess the effect of introgressions in heterozygous state. These introgression lines and their recurrent parents, possessing fertility restoration ability for wild abortive (WA) cytoplasm, were crossed with cytoplasmic male sterile (CMS) line PMS17A to develop hybrids. Hybrids developed from recurrent parents were used as checks to compare the performance of 318 hybrids developed by hybridizing alien introgression lines with PMS17A. Seventeen hybrids expressed a significant increase in yield and its component traits over check hybrids. These 17 hybrids were re-evaluated in large-size replicated plots. Of these, four hybrids, viz., ILH299, ILH326, ILH867 and ILH901, having introgressions from O. rufipogon and two hybrids (ILH921 and ILH951) having introgressions from O. nivara showed significant heterosis over parental introgression line, recurrent parents and check hybrids for grain yield-related traits. Alien introgressions were detected in the lines taken as male parents for developing six superior hybrids, using a set of 100 polymorphic simple sequence repeat (SSR) markers. Percent introgression showed a range of 2.24 from in O. nivara to 7.66 from O. rufipogon. The introgressed regions and their putative association with yield components in hybrids is reported and discussed. [ABSTRACT FROM AUTHOR]