AUTHOR=Wang Shiguang , Liu Wei , Lu Dongbai , Lu Zhanhua , Wang Xiaofei , Xue Jiao , He Xiuying 

TITLE=Distribution of Bacterial Blight Resistance Genes in the Main Cultivars and Application of Xa23 in Rice Breeding

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 11 - 2020

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.555228

DOI=10.3389/fpls.2020.555228

ISSN=1664-462X

ABSTRACT=<p>Bacterial blight (BB) is an important constraint on achieving a high and stable rice grain yield. An increasing number of BB resistance (<italic>R</italic>) genes have been identified and cloned to increase the available options for rice disease resistance breeding. However, it is necessary to understand the distribution of <italic>R</italic> genes in rice varieties for rational distribution and breeding. Here, we genotyped five <italic>R</italic> genes, <italic>i.e. Xa4</italic>, <italic>Xa7</italic>, <italic>Xa21</italic>, <italic>Xa23</italic>, and <italic>Xa27</italic>, in seventy main cultivars from Guangdong Province, South China using the corresponding specific markers. Our results showed that 61 varieties carried <italic>Xa4</italic>, only three varieties carried <italic>Xa27</italic>, and <italic>Xa7</italic>, <italic>Xa21</italic>, or <italic>Xa23</italic> was not detected in all tested varieties. Notably, only 33 varieties exhibited resistance to pathotype IV <italic>Xoo</italic> strains. These results indicate that <italic>Xa4</italic> is no longer suitable for widespread use in rice breeding, although <italic>Xa4</italic> is widely present in tested varieties. Remarkably, the strongly virulent BB strains of pathotype IX evolved quickly in southern China, and <italic>Xa23</italic> was found to effectively confer resistance against the pathotype IX strains. Subsequently, we successfully bred two novel inbred rice varieties as also being restorer lines and two photoperiod- and thermo-sensitive genic male sterility (P/TGMS) lines using the broad-spectrum resistance gene <italic>Xa23</italic> through marker-assisted selection (MAS) combined with phenotypic selection. All of the developed lines and derived hybrids exhibited enhanced resistance to BB with excellent yield performance. Our research may potentially facilitate both of the inbred and hybrid rice disease resistance breeding.</p>