Root and stem rot caused by Rhizoctonia solani is a serious fungal disease of sugar beet and dry bean production in Nebraska. Rhizoctonia root rot and crown rot in sugar beet and dry bean have reduced the yield significantly and has also created problems in storage. The objective of this study was to analyze morpho-genetic diversity of 38 Rhizoctonia solani isolates from sugar beet and dry bean fields in western Nebraska collected over 10 years. Morphological features and ISSR-based DNA markers were used to study the morphogenetic diversity. Fungal colonies were morphologically diverse in shapes, aerial hyphae formation, colony, and sclerotia color. Marker analysis using 19 polymorphic ISSR markers showed polymorphic bands ranged from 15 to 28 with molecular weight of 100 bp to 3 kb. Polymorphic loci ranged from 43.26–92.88%. Nei genetic distance within the population ranged from 0.03–0.09 and Shannon diversity index varied from 0.24–0.28. AMOVA analysis based on ΦPT values showed 87% variation within and 13% among the population with statistical significance (p < 0.05). Majority of the isolates from sugar beet showed nearby association within the population. A significant number of isolates showed similarity with isolates of both the crops suggesting their broad pathogenicity. Isolates were grouped into three different clusters in UPGMA based cluster analysis using marker information. Interestingly, there was no geographical correlation among the isolates. Principal component analysis showed randomized distribution of isolates from the same geographical origin. Identities of the isolates were confirmed by both ITS-rDNA sequences and pathogenicity tests. Identification and categorization of the pathogen will be helpful in designing integrated disease management guidelines for sugar beet and dry beans of mid western America.

中文翻译：

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内布拉斯加州西部甜菜和干豆病原丝核菌形态遗传多样性的纵向研究

由立枯丝核菌引起的根茎腐烂是内布拉斯加州甜菜和干豆生产的严重真菌病害。甜菜和干豆中的丝核菌根腐病和冠腐病显着降低了产量，也造成了储存问题。本研究的目的是分析内布拉斯加州西部 10 年来收集的来自内布拉斯加州西部甜菜和干豆田的 38 株茄属丝核菌分离株的形态遗传多样性。形态特征和基于 ISSR 的 DNA 标记用于研究形态发生多样性。真菌菌落在形状、气生菌丝形成、菌落和菌核颜色方面形态多样。使用 19 个多态 ISSR 标记的标记分析显示多态条带范围为 15 至 28，分子量为 100 bp 至 3 kb。多态位点的范围为 43.26-92.88%。种群内的内遗传距离为0.03-0.09，香农多样性指数为0.24-0.28。基于 ΦPT 值的 AMOVA 分析显示，具有统计学显着性的群体内部和 13% 的变异为 87% (p < 0.05)。大多数来自甜菜的分离株在人群中表现出附近的关联。大量分离株与两种作物的分离株表现出相似性，表明它们具有广泛的致病性。在使用标记信息的基于 UPGMA 的聚类分析中，分离物被分为三个不同的聚类。有趣的是，分离株之间没有地理相关性。主成分分析显示来自同一地理来源的分离株的随机分布。通过 ITS-rDNA 序列和致病性测试确认了分离株的身份。