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Article|02 Aug 2017|OPEN
Pathogen development and host responses to Plasmopara viticola in resistant and susceptible grapevines: an ultrastructural study
Xiao Yin1,2,3 , Rui-Qi Liu1,2,3 , Hang Su1,2,3 , Li Su1,2,3 , Yu-Rui Guo1,2,3 , Zi-Jia Wang3 , Wei Du3 , Mei-Jie Li3 , Xi Zhang3 , Yue-Jin Wang1,2,3 , Guo-Tian Liu1,2,3 , , Yan Xu,1,2,3 ,
1State Key Laboratory of Crop Stress Biology in Arid Areas, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China
2College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China
3Key Laboratory of Horticultural Plant Biology and Germplasm Innovation in Northwest China, Ministry of Agriculture, College of Horticulture, Northwest A&F University, Yangling, Shaanxi 712100, China
*Corresponding author. E-mail: liuguotian555@163.com,yan.xu@nwsuaf.edu.cn

Horticulture Research 4,
Article number: 33 (2017)
doi: https://doi.org/10.1038/hortres.2017.33
Views: 727

Received: 02 Mar 2017
Revised: 09 Jun 2017
Accepted: 27 Jun 2017
Published online: 02 Aug 2017

Abstract

The downy mildew disease in grapevines is caused by Plasmopara viticola. This disease poses a serious threat wherever viticulture is practiced. Wild Vitis species showing resistance to P. viticola offer a promising pathway to develop new grapevine cultivars resistant to P. viticola which will allow reduced use of environmentally unfriendly fungicides. Here, transmission and scanning microscopy was used to compare the resistance responses to downy mildew of three resistant genotypes of V. davidii var. cyanocarpa, V. piasesezkii and V. pseudoreticulata and the suceptible V. vinifera cultivar ‘Pinot Noir’. Following inoculation with sporangia of P. viticola isolate ‘YL’ on V. vinifera cv. ‘Pinot Noir’, the infection was characterized by a rapid spread of intercellular hyphae, a high frequency of haustorium formation within the host’s mesophyll cells, the production of sporangia and by the absence of host-cell necrosis. In contrast zoospores were collapsed in the resistant V. pseudoreticulata ‘Baihe-35-1’, or secretions appeared arround stomata at the beginning of the infection period in V. davidii var. cyanocarpa ‘Langao-5’ and V. piasezkii ‘Liuba-8’. The main characteristics of the resistance responses were the rapid depositions of callose and the appearance of empty hyphae and the plasmolysis of penetrated tissue. Moreover, collapsed haustoria were observed in V. davidii var. cyanocarpa ‘Langao-5’ at 5 days post inoculation (dpi) and in V. piasezkii ‘Liuba-8’ at 7 dpi. Lastly, necrosis extended beyond the zone of restricted colonization in all three resistant genotypes. Sporangia were absent in V. piasezkii ‘Liuba-8’ and greatly decreased in V. davidii var. cyanocarpa ‘Langao-5’ and in V. pseudoreticulata ‘Baihe-35-1’ compared with in V. vinifera cv. ‘Pinot Noir’. Overall, these results provide insights into the cellular biological basis of the incompatible interactions between the pathogen and the host. They indicate a number of several resistant Chinese wild species that could be used in developing new cultivars having good levels of downy mildew resistance.