| Cucurbit crops are important economic crops in China.At present,more than 29 viruses that threaten the growth of cucurbit crops have been identified in China,causing huge economic losses every year.Among them,zucchini yellow mosaic virus(ZYMV)is considered one of the top10 important viruses that threaten crop yields and quality in the potato virus Y genus,which seriously threatens melon production and quality in northern China.In this study,22 ZYMV isolates were separated and purified from composite infections of ZYMV collected by our lab previously.Then,the purified virions were inoculated on three melon materials with different virus resistance: super-susceptible melon variety XMZ11,disease-resistant melon variety PI414723,and moderately susceptible melon variety Gantian No.3.The disease resistance of three melon materials was verified,and the pathogenic differentiation of different ZYMV isolates on melons was analyzed.The full-length genomic nucleotide sequences of 22 ZYMV isolates were obtained through RT-PCR amplification and Sanger sequencing,and then assembled.The full-length genomic sequence consistency,phylogenetic and recombination analyses of ZYMV isolates in China were carried out to analyze their genetic diversity and genetic exchange.The results are as follows:(1)22 ZYMV isolates were separated and purified from composite infections of ZYMV collected from Henan,Xinjiang,Guangxi,Chongqing,Sichuan and other provinces,using leaf-spot host or inoculation and detection methods.(2)22 ZYMV isolates were artificially inoculated on three melon materials,and the analysis of symptoms,morbidity and disease index showed that the symptoms of XMZ11 were mostly whole plant necrosis and vein necrosis,the symptoms of Gantan 3 were mostly blister spots and Mosaic,and the symptoms of PI414723 were mostly necrotic spots.XMZ11 had the highest incidence,with 6 cases reaching 100% and the lowest incidence exceeding 60%.The incidence of PI414723 was the lowest,with only 1 case reaching 75% and 7 cases reaching 12.5%.The incidence of Gan Tian 3 was between XMZ11 and PI414723,with the incidence of 100% in 7 samples and 12.5% in 2 samples.The disease index of XMZ11 was the highest,with the highest being 100 and the lowest being 28.33.The highest disease index of PI414723 was 54.16,and the lowest was 0.The highest disease index of Gan Tian 3 was 60,and the lowest was 5.Different isolates showed obvious pathogenicity differentiation in melons.For example,DB3,TN1 and JLP showed high pathogenicity in the three varieties,while JS5-23,KF34 and HX6-X6 showed low pathogenicity.Other isolates also showed certain differences.(3)The consistency analysis of the full-length genomic nucleotide sequences of 22 ZYMV strains in this study showed that the 22 ZYMV isolates belonged to the species of ZYMV from the full-length genomic nucleotide sequence level and had certain diversity.The phylogenetic analysis showed that the phylogenetic relationship of ZYMV worldwide was related to the geographical location of ZYMV isolates to some extent,but not to the host of isolates.17 out of 22 isolates were clustered in the G-C group,which was the dominant group in China.3 isolates from Guangxi and 1 from Sichuan were clustered in the G-D group.1 isolate from Kashgar,Xinjiang,was assigned to the G-A group,which further verified the rich diversity of ZYMV populations in this study.Recombination analysis found that there were 8 interspecific recombinant isolates in this study,indicating that genetic information exchange existed not only among domestic isolates but also between domestic and foreign isolates.This study analyzed the pathogenic differentiation of 22 ZYMV isolates from China on different melon hosts.At the same time,the consistency of their full-length genomic sequences,phylogenetic and recombination analyses clarified their genetic diversity and genetic information exchange,providing biological background and theoretical basis of clear viral materials for attempting to screen ZYMV resistant materials or breed resistant varieties. |
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