| Mango anthracnose is one of the important diseases of mango,which has seriously affected the development of the mango industry.Studies have shown that breeding new varieties of disease-resistant and high-quality is one of the most efficient control measures.In this study,the highly anthracnose-resistant cultivar ‘Jinhuang’ and the highly anthracnose-susceptible cultivar ‘Aiwen’ were used as the parents and 170 F1 progeny lines of the hybrid population were used as materials,and use the indoor in vitro leaf inoculation method to identify the resistance of F1 progeny lines to mango anthracnose,and obtain the disease resistance of the F1 generation.Data;a high-density genetic linkage map of mango was constructed by whole-genome resequencing,and combined with disease resistance data,QTL for resistance to anthracnose was mapped,candidate genes for disease resistance were screened,and gene expression analysis was performed,and the following research results were obtained:1.Identification of disease resistance of hybrid F1 generation population with resistance to susceptible anthracnose: After using indoor leaf inoculation,lesion diameter measurement,disease index calculation and disease grade classification,170 progeny showed obvious resistance to infection.Among them,18 strains including A006 were highly resistant to disease,77 strains including A126 were resistant to disease,55 strains including A062 were susceptible,and 20 strains including A003 were highly susceptible.The results of the disease resistance assay of the progeny showed that the hybrid F1 generation had obvious resistance-susceptibility segregation.2.Construction of high-density genetic linkage map and disease resistance QTL mapping of mango based on whole-genome resequencing: After extracting mango DNA by CTAB method,whole-genome resequencing was performed using illumina novaseq 6000paired-end 150 bp,and a total of 5 240 062 markers were obtained indivual.Based on the deletion ratio and heterozygous ratio,1 507 262 markers were obtained by screening.Taking the completeness of the markers as the condition,6535 bin markers with high completeness were finally selected,and the high-density genetic map of mango was constructed by using the bin markers.The total length of the map was 2763.63 c M,covering 20 linkage groups,and the average genetic distance was 0.42 c M.The linkage groups with the longest and shortest genetic distances in the map were the 11 th and 2nd linkage groups,and the genetic lengths were 210.39 c M and 92.62 c M,respectively.The number of bin markers contained in each linkage group was between 208 and 597,among which the 11 th linkage group contained the largest number of bin markers,and the ninth linkage group contained the least number of bin markers.There are 21 gaps in the genetic linkage map,which are distributed in 9 linkage groups.The gap length in linkage group LG18 is the largest,which is 23.42 c M.Through compound interval mapping,the genetic map and disease resistance data were used for QTL mapping,and two QTL intervals for disease resistance,KB1 and KB2,were detected,which were located in the LG5 linkage group and the LG8 linkage group,respectively.A total of 303 genes were annotated in the interval.The functions involved in the genes are involved in encoding proteins rich in repetitive leucine structures.3.Expression analysis of candidate genes for resistance to anthracnose: In order to mine the functional genes of resistance to anthracnose,the gene LRR1 encoding the disease resistance protein in the QTL mapping interval and the gene CPK6 involved in the interaction between plants and pathogens were selected as the objects.Jinhuang’ and’Aiwen’)were used as experimental materials for real-time fluorescence quantitative analysis.The experimental results showed that the relative expression levels of LRR1 gene and CPK6 gene in ’Jinhuang’ were much higher than that in ’Aiwen’.The relative expression levels of the genes in the two varieties were the highest 24 hours after inoculation with the bacteria.At this time,the expression levels of CPK6 and LRR genes in’Jinhuang’ were 8.36 and 5.81,respectively,which were 22.59 of the gene expression levels when they were not inoculated(0 time).The expression levels of CPK6 and LRR genes in’Aiwen’ were 1.54 and 1.21 times,respectively,which were 1.86 times and 1.42 times of the expression levels when they were not inoculated,indicating that the two genes have certain effects on the occurrence of mango anthracnose resistance.The high-density genetic map constructed in this study,the mapping of anthracnoseresistance-related QTL intervals and the expression analysis of candidate genes have certain guiding significance for the mining and functional identification of anthracnoseresistance genes,and provide a theoretical basis for in-depth study of the genetic mechanism of mango disease resistance. |
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