Development of Early Maturing Rice Lines with Genes Conferring Resistance to Bacterial Blight and Rice Stripe Virus for Enhancing the Adaptability in Plain Area

Abstract

This study was conducted to develop the early maturing rice lines with genes conferring resistance to bacterial blight and rice stripe virus to enhance the adaptability in plain area. Unkwang carrying Xa3 was used as a recurrent parent and SR30075 carrying Xa4+xa5+Xa21+Stvb-i was used as a donor parent. RL1(Resistant Line, BC1F7), RL2, RL3, RL4, and RL5(BC2F6) were bred through bio-assay of K3a race inoculation and phenotypic selection of agronomic traits. The presence of introduced genes was confirmed by testing the resistance levels against bacterial blight and rice stripe virus and then double-checked by using DNA marker. RL1 has all target genes, Xa3+xa5+Xa21+Stvb-i. RL2, RL3, and RL5 have Xa3+Xa21+Stvb-i whereas RL4 has only Xa21. Rice lines carrying Stvb-i showed resistance reaction to rice stripe virus. The combinations of bacterial blight resistant genes(Xa3+xa5+Xa21 and Xa3+Xa21) were found to be promising, as the rice lines carrying these genes enhanced a strong resistant reaction against 16 bacterial blight isolates. Also, the inoculation of K3a race did not alter the brown rice yield, ripened grain ratio and kernel quality of brown rice compared to control. Although RL1 containing all the target resistance genes showed excellent resistance performance, it is not suitable to cultivate in plain area due to instability to lodging, 80% yield level than Unkwang, and low grain quality. RL5 backcrossed twice with Unkwang was found to be a promising line due to its effective resistance gene combination, Xa3+Xa21+Stvb-i and good agronomic traits such as stability to lodging, higher yield and quality compared to Unkwang.

Hd1 Allele Types and Their Associations with Major Agronomic Traits in Korean Rice Cultivars

“…Developing early heading rice cultivars is especially important in high latitude and mountainous areas where early heading characteristics are required for rice plants to complete grain filling before the risk of cold winter [3]. Early heading rice cultivars are also useful for avoiding extreme whether events due to climate change and mitigating methane emissions from rice paddies by minimizing the duration of rice cultivation [25,26]. To exploit such advantages, tremendous efforts have been made in Korean rice breeding programs to develop a number of early heading rice cultivars [19,20].…”

Characterization of QTLs and Candidate Genes for Days to Heading in Rice Recombinant Inbred Lines

“…The utilization of early heading rice cultivars can be also useful for reducing cropping duration in order to minimize damages from erratic weather events. Although over 80 rice cultivars classified as the early heading group have been released in Korea, they occupy less than 10% of the rice cultivation area in Korea as many rice growers generally prefer mid-late heading cultivars because of their higher yield and grain quality compared to the early heading cultivars [ 13 ].…”