Origin and pathogenicity variation of Plasmopara viticola in China

Abstract

Grapevine downy mildew caused by Plasmopara viticola (Pv) is one of the most devastating diseases of grapevine in China. To understand the origin and pathogenicity of Chinese Pv, a total of 193 single-sporangiophore isolates were obtained from 14 Chinese major viticulture areas. Phylogenetic analyses suggest that Chinese Pv isolates originate from North America and belong to the P. viticola clade aestivalis. Host range experiments reveal that Chinese Pv are able to infect a wide range of Vitis species from different geographic origins, including Eurasian species Vitis vinifera, North American species V. aestivalis, V. riparia, and V. rupestris, and East Asian Vitis species V. davidii, V. amurensis, and V. hancockii. Analyses of the interactions between Pv isolates and grapevines reveal that the virulence of Pv isolates is correlated with the occurrence time and magnitude of hypersensitive response-mediating leaf necrosis in grape leaves caused by Pv. These understandings of genetic diversity and pathogenicity of Chinese Pv isolate would be useful to develop strategies for controlling grapevine downy mildew spread.

Keywords: Vitis species; downy mildew; hypersensitive response; pathogenicity test; plant-pathogen interaction.

Figure 1

Sampling of Plasmopara viticola on wild and cultivated species of the family Vitaceae in China. GS, Gansu Province; GX, Guangxi Province; GZ, Guizhou Province; HB, Hebei Province; HN, Henan Province; HN*, Hunan Province. JL, Jilin Province; SD, Shandong Province; SC, Sichuan Province; SH, Shanghai Province; SX, Shaanxi Province; SX*, Shaanxi Province; XJ, Xinjiang Province; ZJ, Zhejiang Province; Red numbers, number of obtained isolates.

Figure 2

Molecular Phylogenetic analysis of Chinese and North American isolates by Maximum Likelihood method. The percentage of replicate trees in which the associated taxa clustered together in the bootstrap test (1,000 replicates) are shown next to the branches. Bootstrap values are given when superior to 0.700 for both the maximum likelihood and parsimony analysis. Act-C1 to C7, Tub-C1 to C7, ITS-C1 to C2, and Cytb-C1 to C7 are the haplotypes of the Chinese Pv isolates.

Figure 3

Histochemical observation of LJ-Pv18001 in grapevines. Histochemical staining was performed to detect cell death and Hypha growth at 0 hpi, 12 hpi, 24 hpi, 48 hpi, and 96 hpi, with trypan blue and aniline blue staining. A1 to 5, C1 to 5, E1 to 5, G1 to 5, and I1 to 5, the development of hyphae of LJ-Pv18001 in grapevines. B1 to 5, D1 to 5, F1 to 5, H1 to 5, and J1 to 5, the leaf necrosis caused by LJ-Pv18001 in grapevines. B6, D6, F6, H6, and J6, symptom of LJ-Pv18001 on grapevines at 144 hpi. Mr., M. rotundifolia ‘Carlos’. Vam, V. amurensis ‘Shuanghong’. Vru, V. rupestris ‘SJTU123’. Vae: V. aestivalis ‘SJTU118’. Vv, V. vinifera ‘Thompson seedless’. Bars = 100 um.

Figure 4

The development of P. viticola hyphae and the leaf necrosis in V. amurensis ‘Shuanghong’. Histochemical staining was performed to detect cell death and Hypha growth at 0 hpi, 12 hpi, 24 hpi, 48 hpi, and 96 hpi, with trypan blue and aniline blue staining. A1 to 5, the development of hyphae of LJ-Pv18001 in V. amurensis ‘Shuanghong’. C1 to 5, the development of hyphae of LJ-Pv19056 in V. amurensis ‘Shuanghong’. B1 to 5, the leaf necrosis caused by LJ-Pv18001 in V. amurensis ‘Shuanghong’. D1 to 5, the leaf necrosis caused by LJ-Pv19056 in V. amurensis ‘Shuanghong’. B6, D6, symptom of LJ-Pv18001 and LJ-Pv19056 in V. amurensis ‘Shuanghong’ at 144 hpi. VI, Virulence Index. Bars = 100 um.