Functional Marker Assisted Improvement of Stable Cytoplasmic Male Sterile Lines of Rice for Bacterial Blight Resistance

Abstract

Bacterial blight (BB), caused by Xanthomonas oryzae pv.oryzae is one among the major diseases in rice, which in severe condition cause losses up to 60% in total yield. Marker assisted pyramiding of three broad spectrum BB resistance genes (xa5, xa13, and Xa21) in prominent rice varieties is the most economical and effective strategy for the management of the BB disease. We report here the pyramiding of three genes (xa5, xa13, and Xa21) in maintainer lines (CO 2B, CO 23B, and CO 24B) of three promising wild abortive cytoplasmic male sterile lines (CO 2A, CO 23A, and CO 24A) through functional markers assisted back cross breeding. IRBB60 with xa5, xa13, and Xa21 genes is used as a donor parent. BC2F1 and BC2F2 generations from a cross of CO 2B, CO 23B, and CO 24B with IRBB60 were evaluated for bacterial blight and non-fertility restoration. In BC2F1, plants with all three resistance genes (xa5, xa13, and Xa21) and high parent genome recovery was identified. In BC2F2, plants with all resistance genes and without fertility restorer (Rf3 and Rf4) were selected. Based on agronomic traits, BB resistance and maintenance of sterility, two plants each in CO 2B × IRBB60, CO 24B × IRBB60 and one plant in CO 23B × IRBB60 combinations were identified. The identified lines were crossed with respective male sterile lines for conversion of improved B line into CMS line through back-crossing, in addition to selfing. The plants with high recurrent genome and phenotypically similar to parental lines and sterile are being used for the hybrid rice development program. Currently, using these lines (improved CMS line), test crosses were made to develop new rice hybrids. Hybrids combinations viz., CO 23A × AD08009R and CO 24A × IET20898R were found to be stable at different locations with high yield. The R line used in this study has been introgressed with xa5, xa13, and Xa21 genes in a separate breeding program. These new hybrids with resistance against bacterial blight will increase the crop production at BB environment.

Pyramiding Bacterial Blight Resistance Genes in Tainung82 for Broad-Spectrum Resistance Using Marker-Assisted Selection

“…In addition, the results suggest that the gene combinations containing the Xa21 gene were most resistant, as evidenced by shorter lesions lengths, followed by Xa4 + Xa21, Xa7 + Xa21 and xa13 + Xa21, while lines with Xa4 + xa5, xa5 + xa13 and Xa7 + xa13 were less effective. These results are consistent with previous studies, which have shown the presence of Xa21 to be correlated with high levels of persistent resistance against BB disease in rice [6,14,15,17,25]. Xa21 is the cell surface receptor, kinase, which is able to provide resistance to Xoo infections; Xa21 not only suppresses Xoo growth, but also triggers broad perturbation in rice transcriptomes and mediated signaling pathways, preventing Xoo infections [14].…”

“…The utility of MAS in pyramiding several resistance genes to develop a variety possessing broad-spectrum durable resistance has been successfully demonstrated against numerous pathotypes [6,15,16]; Jalmagna, a high-yield, deep-water rice variety, was improved for BB resistance by pyramiding three resistance genes, xa5 + xa13 + Xa21 [6]; a Korean elite japonica variety, Mangeumbyeo, improved with the introgression of the Xa4 + xa5 + Xa21 genes, which were shown to possess a wide range of resistance to BB [16]. Recently, xa5, xa13 and Xa21 genes were introgressed into the hybrid rice maintainer lines CO2B, BO23B and CO24B through MAS, which can form the basis to develop new, widely adaptable heterotic hybrids possessing resistance against the destructive diseases to which rice is vulnerable [17]. In addition, there have been several examples of MAS being utilized to successfully incorporate different genes which provide higher resistance to various biotic and abiotic stresses (for example, the pyramiding of QTLs of submergence tolerance (Sub1A), leaf/neck blast (qBL1 and qBL11), brown planthopper (Bph3) and BB (xa5 and Xa21) in high-yielding and aromatic rice variety 'Pink3 [18]).…”

Marker-assisted selection and gene pyramiding for resistance to bacterial leaf blight disease of rice (Oryza sativaL.)

“…The reliability of a rice marker in predicting the phenotype would increase when flanking or intragenic markers are used. Although it may be difficult to obtain, some marker techniques require large quantity and high quality of DNA [54]. This increases the cost of the scheme.…”

“…It makes use of DNA-based markers that are tightly linked to the gene of interest to either assist or replace phenotypic evaluation. Identification of plants that carry specific genes or QTLs is based on their genotype and this is done by determining the allele of the molecular (DNA-based) marker [54]. Marker-assisted selection is very promising in the development of rice varieties resistant to BLB disease [5,97].…”

Expression Profile of Defense Genes in Rice Lines Pyramided with Resistance Genes Against Bacterial Blight, Fungal Blast and Insect Gall Midge

“…Sundaram et al ( 2008 ) introgressed three BB resistance gene in the background of an elite variety Samba Mahsuri which formed the basic material for pyramiding other genes used in this study. These genes were later introgressed in different combinations into other elite cultivars like Triguna (Sundaram et al 2009 ), parental lines of a hybrid Pusa RH10 (Basavaraj et al 2010 ), Lalat (Das and Rao 2015 ), MTU1010 (Arunakumari et al 2016 ), in both a maintainer line DRR17B, a restorer line RPHR-1005 (Balachiranjeevi et al 2015 ; Kumar et al 2017 ) and a set of three restorer and cytoplasmic male sterile lines (Ramalingam et al 2017 ). Several reports are also available from other countries (Ruengphayak et al 2015 ; Mi et al 2018 ).…”