Temporal and spatial characterization of Botrytis leaf blight of onion

ABSTRACT Onion cultivation has intensified due to in natura consumption and industrial processing. However, Botrytis leaf blight (Botrytis squamosa Walker) is the main disease in the seedling period and has compromised the crop. As the epidemiology of the disease in Brazil is unknown, the objective of this study was to characterize the temporal and spatial progression of this disease under cultivation conditions in the southern region of Brazil. Three grams of onion seeds of the cultivar EMPASC 352- Bola Precoce were sown in eight blocks of one square meter each. The initial incidence of the disease at the planting site was used for the spatial analysis through the negative binomial test. The severity of the disease during the cultivation was analyzed based on the percentage of leaf area affected by the disease in ten randomized plants previously demarcated in each replicate and the severity data were adjusted to a nonlinear model throughout the crop cycle. The spatial pattern of the disease was random and the disease progress curve was fitted to the Gompertz model, represented by y = 0.51830 * (exp (5.95660 * exp (-0.47392 * x))). This study will serve as a model for research related to the disease.

摘要
由于鲜食与工业加工需求的增长，洋葱栽培规模持续扩大。然而，葱鳞葡萄孢灰叶斑病（Botrytis squamosa Walker）是洋葱苗期的主要病害，已对作物生产造成不利影响。鉴于巴西境内该病害的流行病学特征尚不明确，本研究旨在明确巴西南部地区栽培条件下该病害的时间与空间发生动态。
本试验将3克‘EMPASC 352- Bola Precoce’品种的洋葱种子播种于8个面积均为1平方米的小区中。以种植位点的病害初始发病率作为空间分析数据，采用负二项检验开展空间格局分析；于每个重复中随机选取10株预先标记的植株，统计其发病叶面积占比以评估栽培期间的病害严重度，并将全作物生育期的病情数据拟合至非线性模型中。
结果表明，该病害的空间格局呈随机分布，病情进展曲线可通过龚珀兹模型（Gompertz model）拟合，拟合方程为 y = 0.51830 * (exp (5.95660 * exp (-0.47392 * x)))。本研究可为该病害相关的后续研究提供参考模型。