To characterize the prevalence of viruses associated with grapevine leafroll disease in China, 249 grapevine (Vitis spp.) samples (86 popular cultivars and a rootstock) from 19 provinces and regions were collected and tested for Grapevine leafroll-associated virus 1 (GLRaV-1), GLRaV-2, GLRaV-3, GLRaV-4, and GLRaV-4 strain 5 by SYBR Green real-time reverse-transcription polymerase chain reaction (RT-PCR), and RT-PCR and sequencing. GLRaV-3 was found in 100% of the samples while GLRaV-1, GLRaV-2, and GLRaV-4 were detected in 24.9% (62/249), 15.3% (38/249), and 0.80% (2/249) of the samples, respectively. Single infections with GLRaV-3 were found in 66.3% (165/249) of the samples, and the remaining samples were mixed infections of GLRaV-3 with one or two other GLRaVs, those with GLRaV-1 being the most common (18.5%, 46/249). The genetic variability of Chinese GLRaV-3 isolates was characterized based on the coat protein (CP) gene. In total, 153 full-length CP gene sequences (94 sequences newly generated) of Chinese GLRaV-3 isolates from different grapevine-growing regions showed 89.3 to 100.0% and 92.7 to 100.0% identity at the nucleotide and amino acid levels, respectively. The average nucleotide diversity for the population of Chinese GLRaV-3 isolates was estimated at 0.037 (standard error = 0.0032). GLRaV-3 isolates from China segregated into five distinct phylogenetic groups and two novel recombination events were found in the viral population. This is the first and most extensive report of the prevalent species of GLRaV in China, which also provides an assessment of genetic variability of GLRaV-3 Chinese isolates.

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To determine prevalence and distribution of Grapevine leafroll-associated virus 7 (GLRaV-7) in China, a total of 213 grapevine (Vitis spp.) samples (92 popular cultivars) from 13 Chinese provinces and regions were tested for the presence of GLRaV-7 by reverse transcription polymerase chain reaction (RT-PCR) assays and sequencing. GLRaV-7 was found in 40Á4% of the samples, and shown to be widely distributed in major grapevine growing areas in China. GLRaV-7 was found in more than 50 grapevine cultivars. Some popular grape cultivars showed a high incidence of GLRaV-7 infection, such as Manicure Finger (100%), Cabernet Sauvignon (83Á3%), Merlot (60%), Fujimineri (60%) and Red Globe (50%). The genetic variability of GLRaV-7 isolates was characterized based on partial nucleotide sequences (nucleotides 945-1329 and 97-598 of the ORF) of heat shock protein 70 homologue (HSP70h) and 61-kDa protein (p61) (nucleotides 1073-1572 of the ORF) genes. The overall mean values of nucleotide diversity were low (ranging from 0Á009 to 0Á066), and phylogenetic analysis based on p61 showed that the GLRaV-7 isolates segregated into three phylogenetic clusters. The results also showed that two previously described primer pairs failed to amplify a wide range of GLRaV-7 isolates present in China. However, a new primer pair reported here, based on the p61 gene and its associated downstream intergenic region, detected more GLRaV-7 Chinese isolates. This is the first report on the prevalence and distribution of GLRaV-7 in China, and also provides an improved RT-PCR assay for detecting the virus.

Soil salt-alkalization seriously impacts crop growth and productivity worldwide. Breeding and applying tolerant varieties is the most economical and effective way to address soil alkalization. However, genetic resources for breeders to improve alkali tolerance are limited in mung bean. Here, a genome-wide association study (GWAS) was performed to detect alkali-tolerant genetic loci and candidate genes in 277 mung bean accessions during germination. Using the relative values of two germination traits, 19 QTLs containing 32 SNPs significantly associated with alkali tolerance on nine chromosomes were identified, and they explained 3.6 to 14.6% of the phenotypic variance. Moreover, 691 candidate genes were mined within the LD intervals containing significant trait-associated SNPs. Transcriptome sequencing of alkali-tolerant accession 132–346 under alkali and control conditions after 24 h of treatment was conducted, and 2565 DEGs were identified. An integrated analysis of the GWAS and DEGs revealed six hub genes involved in alkali tolerance responses. Moreover, the expression of hub genes was further validated by qRT-PCR. These findings improve our understanding of the molecular mechanism of alkali stress tolerance and provide potential resources (SNPs and genes) for the genetic improvement of alkali tolerance in mung bean.