Development And Evaluation Of Rice Disease And Insect-resistant Lines By Molecular Marker Assisted Selection

Huanghuazhan is one of the conventional rice varieties cultivated on a large scale in southern China.This variety has been approved in many provinces,with excellent comprehensive characters and wide adaptability.It is suitable for direct seeding practice,making an important contribution to ensuring food security.However,the production of Huanghuazhan is still threatened by rice diseases such as blast,bacterial blight,brown planthopper and so on.Compared with chemical control methods to solve the above problems,breeding multi-resistant rice varieties by use of the disease and insect resistance genes from rice gene resource bank,can not only reduce the cost of disease and insect control in rice production,but also benefit environmental protection on green development.In this study,rice blast resistance genes Pi1 and Pi2,bacterial blight resistance genes xa5,and brown planthopper resistance genes Bph14 and Bph15 were introduced into Huanghuazhan by Hybridization and genome-wide marker-assisted selection.At the same time,the genetic background of the improved lines was analyzed and screened by the SNP chip GSR40 K.With the original excellent characters of Huanghuazhan,a batch of multi-resistance lines with high resistance to disease and insect were developed.The main results are as follows:1.Five near-isogenic lines,two bigenic lines and one five-gene line were successfully developed.The introgressed fragments of Pi1,Pi2,Bph14,Bph15,and xa5 are less than 481.5 kb,934.5 kb,401.7 kb,1054.2 kb,and 225.5 kb respectively.The genetic background recovery rate of five-gene line is 98.01%,and those of other near-isogenic lines and bigenic lines range from 99.06% to 99.72%.2.The resistance of rice blast,brown planthopper,bacterial blight and streptosis were tested.Pi1+Pi2 under the background of Huanghuazhan had the highest resistance frequency 97.30% to 37 isolates of M.oryzae,Pi1 also showed the 97.30%of resistance frequency while Pi2 had the lowest resistance frequency 78.38%.Bph14 and Bph15 showed the high resistance,followed by Bph14(resistance)and Bph15(susceptible).xa5 can simultaneously improve the resistance of rice blast,bacterial leaf blight and bacterial streak in Huanghuazhan,showing pleiotropism.The five genes interact with each other.3.Huanghuazhan(Pi1Pi1+Pi2Pi2+Bph14Bph14+Bph15Bph15+xa5xa5)showed blast resistance frequency of 100%,resistance to brown planthopper with the average damage grade of 2.7,and resistance to bacterial blight with the lesion length ranging from 0.5 cm to 2.8 cm.Compared with Huanghuazhan,its bacterial streak resistances to both GX01 and RH3 were significantly increased.The pyramiding line maintained the desirable agronomic traits of Huanghuazhan,showing the first-class grain quality(see NY/T 593-2021 Cooking Rice Variety Quality).These results indicated that Pi1,Pi2,Bph14,Bph15 and xa5 were accurately introduced into the genetic background of Huanghuazhan by marker-assisted selection,and the disease-and insect-resistance of the improved lines was increased with the major agronomic traits and grain quality of the original Huanghuazhan.