Search

Summary: Rice blast and bacterial blight represent two of major diseases having devastating impact on the yield of rice in most rice‐growing countries. Developments of resistant cultivars are the most economic and effective strategy to control these diseases. Here, we used CRISPR/Cas9‐mediated gene editing to rapidly install mutations in three known broad‐spectrum blast‐resistant genes, Bsr‐d1, Pi21 and ERF922, in an indica thermosensitive genic male sterile (TGMS) rice line Longke638S (LK638S). We obtained transgene‐free homozygous single or triple mutants in T1 generations. While all single and triple mutants showed increased resistance to rice blast compared with wild type, the erf922 mutants displayed the strongest blast resistance similar with triple mutants. Surprisingly, we found that Pi21 or ERF922 single mutants conferred enhanced resistance to most of tested bacterial blight. Both resistances in mutants were attribute to the up‐regulation of SA‐ and JA‐pathway associated genes. Moreover, phenotypic analysis of these single mutants in paddy fields revealed that there were no trade‐offs between resistances and main agricultural traits. Together, our study provides a rapid and effective way to generate rice varieties with resistance to both rice blast and bacterial blight. [ABSTRACT FROM AUTHOR]

Hybrid rice, as one of the most successful crops exploiting heterosis, has greatly contributed to global food security. Due to its high‐yield potential, approximately half of the rice‐growing area in China is planted with hybrid rice varieties. However, the extreme vulnerability of hybrid rice to various diseases and poor grain quality pose great challenges to rice breeders. Here, we report the development of five new restorer lines pyramiding the broad‐spectrum blast resistance gene Pigm and low/intermediate amylose content‐associated gene Wxb by marker‐assisted and phenotypic selection. All these new restorer lines showed enhanced blast resistance in the disease nursery compared with the original restorer lines and had low‐to‐intermediate apparent amylose contents, ranging from 11.3% to 14.2%. Genetic background analysis based on next‐generation sequencing indicated that the proportion of Gumei 4 (donor of Pigm) genome in the five new restorer lines ranged from 9.89% to 21.69%. Eight of their derived hybrid combinations, which exhibited better grain quality and higher levels of blast resistance, have been certificated for commercial release in different ecological regions of China. Among them, Jing‐Liang‐You 3189, Yue‐Liang‐You 3189, Jing‐Liang‐You 1074 and Long‐Liang‐You 3188 meet the national standards for superior‐quality rice in China. These results confirmed the success of developing elite restorer lines through marker‐assisted and phenotypic selection, and these new restorer lines have great potential in developing more elite hybrid rice combinations. [ABSTRACT FROM AUTHOR]

Rice blast, caused by the fungal pathogen Magnaporthe oryzae (M. oryzae), is one of the most destructive and widespread plant diseases in the world. Utilization of resistance genes in rice breeding is considered to be an effective and economical method to control this disease. To identify new sources of blast resistance, a set of 1160 introgression lines (ILs) containing chromosome segments of Chaling common wild rice (Oryza rufipogon Griff.) in the genetic background of an elite indica rice variety 93‐11 were developed and phenotyped in the blast nursery. Thirty‐three ILs displaying stable blast resistance in three consecutive years were obtained. Among them, one line, IL1043, was subsequently found to be resistant to all of the 28 M. oryzae isolates from different regions through artificial inoculation in greenhouse. By combining bulk segregant analysis coupled with next‐generation sequencing (BSA‐seq) and recessive class analysis (RCA), a major blast resistance gene in IL1043, designated Picl(t), was mapped on rice chromosome 6 flanked by the markers RM527 and Indel6 with an interval of approximately 925 kb, which covers the Pi2/9 locus. These results will facilitate fine mapping and cloning of Picl(t), and the linked markers will further provide a useful tool for rice blast resistance breeding. [ABSTRACT FROM AUTHOR]