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

Abstract

Tainung82 (TNG82) is one of the most popular japonica varieties in Taiwan due to its relatively high yield and grain quality, however, TNG82 is susceptible to bacterial blight (BB) disease. The most economical and eco-friendly way to control BB disease in japonica is through the utilization of varieties that are resistant to the disease. In order to improve TNG82’s resistance to BB disease, five bacterial blight resistance genes (Xa4, xa5, Xa7, xa13 and Xa21) were derived from a donor parent, IRBB66 and transferred into TNG82 via marker-assisted backcrossing breeding. Five BB-resistant gene-linked markers were integrated into the backcross breeding program in order to identify individuals possessing the five identified BB-resistant genes (Xa4, xa5, Xa7, xa13 and Xa21). The polymorphic markers between the donor and recurrent parent were used for background selection. Plants having maximum contribution from the recurrent parent genome were selected in each generation and crossed with the recipient parent. Selected BC3F1 plants were selfed in order to generate homozygous BC3F2 plants. Nine pyramided plants, possessing all five BB-resistant genes, were obtained. These individuals displayed a high level of resistance against the BB strain, XF89-b. Different BB gene pyramiding lines were also inoculated against the BB pathogen, resulting in more than three gene pyramided lines that exhibited high levels of resistance. The five identified BB gene pyramided lines exhibited yield levels and other desirable agronomic traits, including grain quality and palatability, consistent with TNG82. Bacterial blight-resistant lines possessing the five identified BB genes exhibited not only higher levels of resistance to the disease, but also greater yield levels and grain quality. Pyramiding multiple genes with potential characteristics into a single genotype through marker-assisted selection can improve the efficiency of generating new crop varieties exhibiting disease resistance, as well as other desirable traits.

Gene Pyramiding for Achieving Enhanced Resistance to Bacterial Blight, Blast, and Sheath Blight Diseases in Rice

“…This is due to the similar morphological characters of pyramided lines with their recurrent parent's. Similar results were also obtained by Pradhan et al (2015) and Hsu et al (2020), while introgressing BB resistance genes, which supports the present study results.…”

“…In addition, the present study results also reveal that the gene combination with Xa21 component expressed a shorter lesion length than the remaining gene combinations. These results were consistent with the results of previous studies (Peng et al, 2015;Pradhan et al, 2015;Ramalingam et al, 2017;Yugander et al, 2018;Hsu et al, 2020). The improved pyramided lines harboring the Pi54 gene and ShB-resistant QTLs have expressed a similar disease reaction as donor parent, Tetep.…”

“…Till date, 46 resistance genes have been identified from the different sources of rice (Chen et al, 2020). Of these, the Xa4, xa5, Xa7, xa13, Xa21, Xa33, and Xa38 genes are most frequently utilized in hybridization programs for developing BB-resistant cultivars (Hsu et al, 2020). Natural allelic variations in Xoo challenges the resistance levels conferred by a single gene; hence, pyramiding of two or more effective resistance genes is highly essential for broad-spectrum and durable resistance to Xoo at field conditions.…”

Molecular and Phenotypic Assay of Improved Lines Harboring Bacterial Blight Resistance

“…The morphological characters of the most of the improved lines were in similar with recurrent parent, due to the transfer of all the recurrent parent alleles for superior morphological characters as recurrent parents. The similar results were also obtained by (Hsu, Chiu, Yap, Tseng, & Wu, 2020), while introgressingXa4, xa5, Xa7, xa13 and Xa21 in to the TNG82 cultivar through markerassisted backcross breeding (MABB). Further, the improved lines with superior morphological characters and having physical resistance to BB were tested in multilocational trails to be release as new improved variety for BB prone rice cultivating areas or can be used as a potential donor in breeding programmes.…”

Recent Advances in Molecular Research in Rice: Agronomically Important Traits

“…Hsu et al developed a rice line, pyramiding five bacterial blight resistance genes: Xa4 , xa5 , Xa7 , xa13 , and Xa21 . The pyramiding line showed not only high levels of resistance to bacterial blight disease, but also increased grain yield and grain quality [ 20 ].…”