Influence of Climatic Variables on Incidence of Whitefly-Transmitted Begomovirus in Soybean and Bean Crops in North-Western Argentina.

Over the last 20 years, begomoviruses have emerged as devastating pathogens, limiting the production of different crops worldwide. Weather conditions increase vector populations, with negative effects on crop production. In this work we evaluate the relationship between the incidence of begomovirus and weather before and during the crop cycle. Soybean and bean fields from north-western (NW) Argentina were monitored between 2001 and 2018 and classified as moderate (≤50%) or severe (>50%) according to the begomovirus incidence. Bean golden mosaic virus (BGMV) and soybean blistering mosaic virus (SbBMV) were the predominant begomovirus in bean and soybean crops, respectively. Nearly 200 bio-meteorological variables were constructed by summarizing climatic variables in 10-day periods from July to November of each crop year. The studied variables included temperature, precipitation, relative humidity, wind (speed and direction), pressure, cloudiness, and visibility. For bean, high maximum winter temperatures, low spring humidity, and precipitation 10 days before planting correlated with severe incidence. In soybeans, high temperatures in late winter and in the pre-sowing period, and low spring precipitations were found to be good predictors of high incidence of begomovirus. The results suggest that temperature and pre-sowing precipitations can be used to predict the incidence status [predictive accuracy: 80% (bean) and 75% (soybean)]. Thus, these variables can be incorporated in early warning systems for crop management decision-making to reduce the virus impact on bean and soybean crops.

Biological and molecular characterization of bean bushy stunt virus, a novel bipartite begomovirus infecting common bean in northwestern Argentina.

Common bean plants (Phaseolus vulgaris L.) showing different virus-like symptoms were collected in northwestern Argentina. Dot-blot hybridization tests showed that the begomoviruses bean golden mosaic virus and tomato yellow vein streak virus were the most prevalent, but they also revealed the presence of unknown begomoviruses. The complete genome sequence of one of these unknown begomoviruses was determined. Sequence analysis showed that the virus is a typical New World begomovirus, for which the name "bean bushy stunt virus" (BBSV) is proposed. Biological assays based on biolistic inoculations showed that BBSV induced leaf roll and stunting symptoms similar to those observed in the field-collected common bean sample.