Characterization and evaluation of rice blast resistance of Chinese indica hybrid rice parental lines

The development of resistant varieties and hybrid combinations has been the most effective and economical strategy to control blast disease caused by Magnaporthe oryzae.However, the distribution of major R genes and blast resistance characterization in hybrid rice parents has not been well investigated, resulting in their limited use in hybrid rice blast-resistance breeding. In the present study, 88 elite indica hybrid rice parental lines were evaluated with 30 isolates of M. oryzae collected from the main planting area of indica hybrid rice in China and were characterized for the presence of 11 major resistance genes using molecular markers. The pathogenicity assays showed that four types of hybrid rice parent line showed some resistance to M. oryzae. However, the proportions of highly resistant lines and the mean resistance frequency(RF) varied among the four types, with resistance in decreasing order shown by three-line restorer lines, three-line maintainer lines, two-line sterile lines, and two-line restorer lines. All 88 hybrid rice parental lines carried more than one R gene, but none carried the R genes Pi1 and Pi2. Although Pid3 and Pi9 were present only in three-line restorer lines and Pigm only in three-line maintainer lines, the remaining six R genes(Pib, Pid2, Pi5, Pia, Pi54, and Pita) were present in the four types of hybrid rice parent with significantly different distribution frequencies. The correlation between R genes and resistance reactions was investigated. The results are expected to provide useful information for rational utilization of major R genes in hybrid rice breeding programs.

Pijx confers broad-spectrum seedling and panicle blast resistance by promoting the degradation of ATP b subunit and OsRbohC-mediated ROS burst in rice

(Molecular Plant 16,1832-1846,November 62023)The originally published version of this manuscript contained several small mistakes in the labels and legends of main and supplemental figures,along with a few small mistakes in the main text,that have now been corrected.Specifically,in Figure 6G,the label“NILGY31^(Pijx)”has been corrected to“NIL^(Pijx)”,and in the legend of Figure 6H,“PPL^(Pijx Piz-t)”and“PPL^(Pijx Pigm)”have been corrected to“NIL^(Piz-t Pijx)”and“PPL^(Pigm Pijx).”In Figure S8A。

CRISPR-Cas9-mediated editing of the OsHPPD 30 UTR confers enhanced resistance to HPPDinhibiting herbicides in rice

Dear Editor,Loss of yield because of competition from weeds restricts the production of rice(Oryza sativa L.)(Maeda et al.,2019).Application of chemical herbicides is currently the most effective method for controlling weeds during rice production,especially in modern simplified cultivation systems.However,long-term and extensive use of herbicides,such as inhibitors of the enzymes 5-enolpyruvylshikimate-3-phosphate synthase,acetolactate synthase,and acetyl-coenzyme A carboxylase,has resulted in the emergence of herbicide-resistant weed species as well as soils with high levels of herbicide residues,which limit crop rotation.Therefore,there is an urgent need for alternative herbicides and breeding of corresponding herbicideresistant rice varieties.

Pijx confers broad-spectrum seedling and panicle blast resistance by promoting the degradation of ATP β subunit and OsRbohC-mediated ROS burst in rice

Rice blast,caused by the fungal pathogen Magnaporthe oryzae,is one of the most important diseases of rice.Utilization of blast-resistance genes is the most economical,effective,and environmentally friendly way to control the disease.However,genetic resources with broad-spectrum resistance(BSR)that is effective throughout the rice growth period are rare.In this work,using a genome-wide association study,we identify a new blast-resistance gene,Pijx,which encodes a typical CC-NBS-LRR protein.Pijx is derived from a wild rice species and confers BSR to M.oryzae at both the seedling and panicle stages.The functions of the resistant haplotypes of Pijx are confirmed by gene knockout and overexpression experiments.Mechanistically,the LRR domain in Pijx interacts with and promotes the degradation of the ATP synthase β subunit(ATPb)via the 26S proteasome pathway.ATPb acts as a negative regulator of Pijx-mediated panicle blast resistance,and interacts with OsRbohC to promote its degradation.Consistently,loss of ATPb function causes an increase in NAPDH content and ROS burst.Remarkably,when Pijx is introgressed into two japonica rice varieties,the introgression lines show BSR and increased yields that are approximately 51.59%and 79.31%higher compared with those of their parents in a natural blast disease nursery.In addition,we generate PPL^(Pijx Pigm) and PPL^(Pijx Piz-t) pyramided lines and these lines also have higher BSR to panicle blast compared with Pigm-or Piz-t-containing rice plants.Collectively,this study demonstrates that Pijx not only confers BSR to M.oryzae but also maintains high and stable rice yield,providing new genetic resources and molecular targets for breeding rice varieties with broad-spectrum blast resistance.

Analysis of genetic architecture and favorable allele usage of agronomic traits in a large collection of Chinese rice accessions

Genotyping and phenotyping large natural populations provide opportunities for population genomic analysis and genome-wide association studies(GWAS). Several rice populations have been re-sequenced in the past decade;however, many major Chinese rice cultivars were not included in these studies. Here, we report large-scale genomic and phenotypic datasets for a collection mainly comprised of 1,275 rice accessions of widely planted cultivars and parental hybrid rice lines from China. The population was divided into three indica/Xian and three japonica/Geng phylogenetic subgroups that correlate strongly with their geographic or breeding origins. We acquired a total of 146 phenotypic datasets for 29 agronomic traits under multi-environments for different subpopulations. With GWAS, we identified a total of 143 significant association loci, including three newly identified candidate genes or alleles that control heading date or amylose content. Our genotypic analysis of agronomically important genes in the population revealed that many favorable alleles are underused in elite accessions, suggesting they may be used to provide improvements in future breeding efforts. Our study provides useful resources for rice genetics research and breeding.