Abstract
Apple mosaic disease has a great influence on apple production. In this study, an investigation into the incidence of apple mosaic disease in southwest China was performed, and the pathogen associated with the disease was detected. The results show that 2869 apple trees with mosaic disease were found in the Sichuan, Yunnan, and Guizhou Provinces, with an average incidence of 9.6%. Although apple mosaic virus (ApMV) is widespread in apples worldwide, the diseased samples were negative when tested for ApMV. However, a novel ilarvirus (apple necrotic mosaic virus, ApNMV) was identified in mosaic apple leaves which tested negative for ApMV. RT-PCR analysis indicated that ApNMV was detected in 322 out of 357 samples with mosaic symptoms. Phylogenetic analysis of coat protein (CP) sequences of ApNMV isolates suggested that, compared with ApMV, ApNMV was closer to prunus necrotic ringspot virus (PNRSV). The CP sequences of the isolates showed the diversity of ApNMV, which may enable the virus to adapt to the changeable environments. In addition, the pathology of mosaic disease was observed by microscope, and the result showed that the arrangement of the tissue and the shape of the cell, including the organelle, were seriously destroyed or drastically changed.
Highlights
As a member of the Rosaceae, the apple (Malus domestica) is one of the most widely cultivated fruit trees in the world, with high nutritional value and economic benefits
Four virus species and one viroid species were common in China, including apple stem pitting virus (ASPV), apple stem grooving virus (ASGV), apple chlorotic leaf spot virus (ACLSV), apple mosaic virus (ApMV), and apple scar skin viroid (ASSVd) [3,4,5,6]
RNAs were subjected to RT-PCR using virus specific primers, and the results revealed the association of appleyielded necrotic mosaic virus (ApNMV) with the apple mosaic disease in southwest China instead of ApMV, with a positive rate of
Summary
As a member of the Rosaceae, the apple (Malus domestica) is one of the most widely cultivated fruit trees in the world, with high nutritional value and economic benefits. China is the world’s largest producer of apples, accounting for more than 50 percent of global production in recent years (USDA, 2017). According to the national modern apple industrial system, apple producing areas in China are divided into five regions, namely the Bohai Bay producing area, the Loess Plateau producing area, the Yellow River producing area, the Southwest Cool and High producing area, and the Characteristic producing area, and it is apparent that the Chinese apple production center is moving westward [1]. Four virus species and one viroid species were common in China, including apple stem pitting virus (ASPV), apple stem grooving virus (ASGV), apple chlorotic leaf spot virus (ACLSV), apple mosaic virus (ApMV), and apple scar skin viroid (ASSVd) [3,4,5,6].
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