Effectiveness Study And Constitution Of Blast Resistance Genotype Of Hybrid Rice In Guangdong

Rice(Oryza sativa L.)is one of the most important grain crops,providing half of the world’s population.Rice blast disease is one of the most destructive diseases in rice growing region worldwide,which caused by the filamentous ascomycete fungus Magnaporthe oryzae.Utilization of resistance(R)genes is considered to be the primary and economic method for blast control.However,blast resistance will break down when resistance varieties released for 3 – 5 years.It is very important to dissect the resistance genes’ phenotypes and effectiveness and confirm the resistance spectrum and specificity of major resistance genes against M.oryzae in Guangdong for rational arrangement and alternation of resistance varieties and rice blast management.Since most of resistance genes phenotypes of varieties in China are unclear,it is very necessary to study it.The present research was to study the construction and effectiveness of resistance genes phenotypes of hybrid rice in Guangdong.The results are listed as follows:1.Resistance analysis of hybrid rice varieties in Guangdong578 hybrid rice new combinations from South China were carried out resistacne evaluation through field disease nursery identification and green house resistance spectrum test.The tested results showed that hybrid rice new combinations presented different resistant level,including high susceptible,susceptible,medially susceptible,medially resistant,resistant,high resistant,and their percentages were 15.92%,8.30%,11.42%,25.78%,26.30% and 12.28%,respectively.The combination over medially resistant accounted for 64.36%.Ratio of resistance and susceptibility was 1.8 :1.The tested male sterile lines and restorer lines were analyzed.The results indicated that the more resistant male sterile sets were Jifeng A,Anfeng A,Fengtian 1A,Hengfeng A,and the more resistant restorer sets were Yuehui 9802,Guanghui 618,Hanghui 1173,Minhui 3301,Hanghui 1179,Tai 766 etc..2.Rice blast resistance genotypes and effectiveness of hybrid rice in GuangdongPi1、Pik-p、Pik-h、Pi2、Pi9、Piz-t、Pita and Pii,the cloned rice blast resistant genes,which showed better rice blast resistance in different rice regions,have been widely used in rice blast resistance breeding.To define the distribution of these genes in hybrid rice in South China,the genotypes of resistance genes Pi1、Pik-p、Pik-h、Pi2、Pi9、Piz-t、Pita and Pii in 328 hybrid rice combinations were detected with functional markers.The results showed that the distribution frequency of Pita and Pii was the highest,accounting for 84.76% and 67.68% in 328 hybrid rice combinations,respectively;followed by Pi2 and Pik-p with the proportion as 22.87% and 13.72%,respectively;Pi1,Piz-t and Pik-h had the lower distribution frequency,accounting for 5.18%,3.35% and 2.13%,respectively.All of these varieties didn’t carry resistance gene Pi9.The number of blast resistance genes detected in hybrid rice combinations was at most four.The resistant evaluation showed that the more number of resistance genes in hybrid combinations of pyramids,the higher frequency of resistant varieties displayed.In the hybrid combinations with four resistance genes,the distribution frequency of varieties showing resistant was 91.67%.Blast resistance contribution assay of these eight resistance genes revealed that Pi2 and Pi1 displayed the greatest rice blast resistance contribution in the local rice region,followed by Pik-h,Pik-p,Pita,Pii and Piz-t,respectively.3.Rice blast resistance gene genotype analysis of high resistant combination Ningyou 1179Ningyou 1179(NY1179)is a new combination derived from native rice restorer line Hanghui 1179(HH1179)and male sterile line Ning A,which showed highly resistant to rice blast.HH1179 and its hybrid combinations show broad spectrum resistances against rice blast in South China.Dissection of the genetic background of HH1179 is very useful for making clear the resistance of NY1179.In present study,resistance genetic analysis of HH1179 against the blast isolate GD13-14 showed that it haboured a dominant rice blast R gene.A method based on bulked segregation analysis combined with high-throughput sequencing was used in association analysis to identify the blast R gene in HH1179.The association analysis indicaded that the target gene Pi-h(t)derived from HH1179 was located in chromosome 6.Linkage assay of the SSR and InDel markers on chromosome 6 and target gene showed that Pi-h(t)was mapped in 100.8 kb region between markers InDel-8 and RM19818,which belonged to Pi2/Pi9/Piz/Piz-t/Pi50 genes cluster.Further candidate genes prediction and genes cDNA sequecing indicated that Pi-h(t)was per se Pi2 gene.4.Interaction of major R genes of hybrid rice combinations in Guangdong and M.oryzae isolates125 M.oryzae isolates were selected to test the resistance spectrum of eight resistance genes of of hybrid rice combinations in Guangdong.The resistance value covered from 28.0% to 96.8%.The resistance spectrum of four blast resistance genes Pik-h,Pi1,Pi9 and Pi2 were 96.8%,96.0%,95.2% and 88.0%,respectively.These four genes showed broad resistance.The other rest four resistance genes Pik-p,Piz-t,Pii and Pita showed narrow resistance spectrum with 64.0%,55.2%,37.6% and 28.0%,respectively.The isogenic lines could be divided into three types among different years based on field resistance.The first type showed the highly susceptible,such as Pii and Pik-p.The second showed moderately susceptible as Pita and Piz-t.The third showed stablely resistant such as Pik-h,Pi1,Pi2 and Pi9.