The temporal and spatial progress of sheath blight was assessed on a set of mega rice varieties of South Asia and local varieties of North India in field experiments for two consecutive years. With artificially created disease focus disease severity was recorded on five un-inoculated plants from the focus in four directions after two, four and six weeks of inoculation. The mega varieties differed in their level of susceptibility to sheath blight. The temporal progression of the disease was significantly increased in Swarna and Swarna Sub-1 followed by PR 114 and PR 121 varieties. Area under disease progress curve (AUDPC) ranged 184.92 – 683.67 in tested varieties. The disease severity decreased as the distance from the disease focus increased in all varieties, the significance of the spatial spread depended on the susceptibility level of the variety. Swarna and Swarna Sub-1 showed higher level of susceptibility. The exponential regression model explained the increased severity with time which get decreased with increase in distance from the disease focus. Relationship of week after inoculation with disease severity indicated that model explained 96.0% variability of the response data in Swarna. The morphological traits like plant height, number of tillers per hill and tiller angle of the varieties had a significant correlation with the disease severity and incidence. In the absence of genetic resistance, this study provides evidence of requirement of a six-week period for differentiating the susceptible or resistant response of rice varieties to sheath blight under field conditions. Plant morphological traits are the key factor which can be consider in disease resistant breeding programme.

在连续两年的田间试验中，对一组南亚大型水稻品种和北印度地方品种的纹枯病时空进展进行了评估。在接种 2、4 和 6 周后，在四个方向上的 5 个未接种的植物上记录了人工创建的病灶的病害严重程度。大型品种对纹枯病的易感性水平不同。疾病的时间进展在 Swarna 和 Swarna Sub-1 中显着增加，其次是 PR 114 和 PR 121 品种。受试品种的疾病进展曲线下面积 (AUDPC) 范围为 184.92 – 683.67。所有品种的病害严重程度随着距病灶距离的增加而降低，空间传播的重要性取决于品种的易感性水平。Swarna 和 Swarna Sub-1 显示出更高的易感性水平。指数回归模型解释了随时间增加的严重程度，随着与疾病焦点距离的增加而降低。接种后一周与疾病严重程度的关系表明，该模型解释了 Swarna 中响应数据的 96.0% 变异性。品种株高、分蘖数、分蘖角等形态性状与病害严重程度和发病率呈显着相关。在没有遗传抗性的情况下，这项研究提供了需要六周时间来区分水稻品种在田间条件下对纹枯病的敏感或抗性反应的证据。