Threshold of Soil pH for Occurrence of Tobacco Bacterial Will in Henan Province

Since 2015, Henan tobacco system has effectively controlled the occurrence and spread of bacterial wilt in Zhumadian and Xinyang cities by taking measures such as forced crop rotation. [...]whether bacterial wilt has occurred in other tobacco-growing areas and the geographical boundaries of bacterial wilt are not clear. Since R. solanacearum can survive in soil or compost for 2 -3 years or even longer111, the harm of bacterial wilt may re-occur under suitable climatic conditions. According to the principle of one repre sentative tobacco field each village (town), soil samples were collected from 91 tobacco fields, with plain tobacco area >30 hm2 and hilly tobacco area >15 hm2 in tobacco planting area of sampled villages and towns. The average soil pH of Wuyang was between those of Sheqi and Chengqu, but had no significant difference with those of Shangcai, Sheqi and Chengqu. 2.3Spatial distribution characteristics of soil pH The correlation analysis of soil pH and corresponding geographical location parameters (Fig.2) showed that the pH of tobacco-growing soil had very significant negative correlation with the longitude of sampling plots, very significant positive correlation with the latitude of sampling plots, and significant binomial correlation with the altitude. 2.4Clustering analysis /4 soil pH The 12 counties (districts) were roughly divided into three groups by dynamic clustering analysis of their average pH.