Recently, the maize gene editing and breeding research team of the Institute of Crop Science of Chinese Academy of Agricultural Sciences created mutants with obvious resistance to Fusarium oxysporum ear rot in various environments through directional editing of maize endogenous genes, which provided important germplasm materials and breeding techniques for disease-resistant breeding. A few days ago, related papers were published online in Plant Biotechnology.
There is no effective control method for maize ear rot.
"Ear rot of corn mainly causes ear rot and grain rot of corn, and improper storage of corn after harvest can also cause grain rot. In China, ear rot of maize occurs widely in various maize planting areas, with an incidence rate of 5%- 10% in general and 30%-40% in recurrent years, and even as high as 100% in some areas. " Xie Chuanxiao, the correspondent of the paper and a researcher at the Institute of Crop Science of the Chinese Academy of Agricultural Sciences, said in an interview with the reporter of Science and Technology Daily.
At present, there are more than 70 kinds of pathogens that can cause corn ear rot at home and abroad, and these pathogens can be infected individually or jointly. Among them, Fusarium verticillium and Fusarium graminearum are the two most harmful dominant pathogens in the world, and they are also the dominant pathogens of corn ear rot in China. In recent years, the occurrence frequency and damage degree of maize ear rot in China have increased year by year, and once maize occurs, the incidence rate can be as high as 50%.
"At present, there is no effective method to control corn ear rot in production, and reasonable cultivation measures, timely sowing, pest control and seed coating agent are mainly adopted to reduce the harm of corn ear rot. However, cultivating and popularizing disease-resistant varieties is the most economical and effective way to solve the harm of corn ear rot. " Xie Chuanxiao said.
The traditional breeding techniques of maize ear rot resistance mainly include screening of resistant germplasm resources, analysis of genetic law of resistance, backcross breeding or polymerization of resistance sites (genes). The screening and identification of a large number of germplasm resources at home and abroad show that the resources with high resistance to maize ear rot are relatively scarce, and most germplasm, especially maize backbone inbred lines, are highly susceptible to maize ear rot.
"Affected by factors such as environment, pathogenic bacteria and resistance identification methods, it is difficult to find consistent genes with high resistance and multi-resistance. Therefore, there are few high-resistance varieties bred at home and abroad. " Xie Chuanxiao said.
After improvement, the resistance of maize was improved.
In this study, a series of target gene mutants were constructed by using CRISPR/Cas9 gene editing technology, among which three recessive homozygous mutants of ZmFER 1 gene were obtained, including E 1( 1bp insertion), E2( 1bp insertion) and E3(5bp deletion) deletion CRISPR/Cas gene editing. In 2020, in Beijing, 202 1 in Hainan and 202 1 in Beijing, researchers artificially inoculated Verticillium pseudoverticillium with blind samples of mutant and wild-type seeds 1: 1, carried out genotype identification and phenotype identification of individual plants, and analyzed their resistance. Liu Changlin, the first author of the paper and an associate researcher at the Institute of Crop Science of the Chinese Academy of Agricultural Sciences, told the reporter.
The results showed that compared with the wild type, the mutants all showed moderate resistance. Verified and identified the diseased seeds, it was found that fumonisin in infected wild-type diseased seeds was thousands of times higher than that in uninfected seeds, which was consistent with the pathogenic characteristics of Fusarium oxysporum. Pathogen identification showed that the disease phenotype came from inoculated Fusarium oxysporum. No significant negative effects of mutation on other agronomic traits were found.
"Compared with traditional breeding methods, this method can quickly improve the resistance of maize backbone germplasm resources, reduce the harm of maize ear rot, have clear objectives and significantly shorten the time required for improvement. Compared with traditional backcross breeding, gene editing technology can improve the disease resistance of recipient maize germplasm and overcome the problem of chain burden. " Liu Changlin pointed out. (Science and Technology Daily reporter Ma Aiping)