Evaluation of rain-shelter cultivation mode effects on microbial diversity during Cabernet Sauvignon (Vitis vinifera L.) maturation in Jingyang, Shaanxi, China

Abstract

Rainfall particularly under continental climates with monsoonal tendency impacts the vineyard microbial niches during grapevine growth. With microbial community shifts, vine traits (grape flavor and yield) cultivated/protected under rain-shelter may ultimately be altered. Such cultivation may influence microflora dynamics via meteorological parameter variations, however this is unclear yet. Here, we used Cabernet Sauvignon, a prevalent red cultivar among wine growing regions, to evaluate the effects of the rain-shelter cultivation on the microorganism diversity. We found that average air temperature under rain-shelter conditions was 2-3 °C higher than the non-covered group, while air humidity the maximum reduction was 5.79% (p < 0.05). After grape setting stage, similar trends were observed on soil temperature (increased) and humidity (lowered) under the treatments (p < 0.05). UV and precipitation of rain-shelter treatment were less by a total of 72% and 96%, respectively (p < 0.05). The rain-shelter management presented lower fungal and bacterial OTUs. The fungal alpha diversity on leaves and branches under rain-shelter was lower (p < 0.05) than the control as the grape ripeness, with Ascomycota, Mycosphaerella and Cladosporium as the principal fungi. Our results revealed that the fungal microbiota patterns were differentiated by the cultivations from setting stage to the entire véraison and then tended to be similar at harvesting. Only branch fungal patterns were observed asymmetrically at all stages. Meanwhile, bacterial diversity and distribution varied on colonization locations where Proteobacteria and Actinobacteria were the primary bacteria phyla. Bacterial community structures overlapped at harvest, while the differences were observed between two cultivations at other stages, excluding grape berry. The rain-shelter cultivation reduced the abundance of Alternaria and Colletotrichum that may adversely affect grapevine health. Multivariate statistical analysis suggested that the effect of vineyard microclimate on microbiota distribution and succession were influenced by cultivation modes and grapevine developmental stages. This research provides evidence to address the dynamics of microbial ecology from vineyard to grape under rain-shelter cultivation, and its benefits as a sustainable vineyard management.

Keywords: Cabernet Sauvignon; Meteorological factors; Microbial diversity; Microclimate; Rain-shelter; Vineyard.