Islam Md Rashidul, Alam Md Samiul, Khan Ashik Iqbal, Hossain Ismail, Adam Lorne R, Daayf Fouad
Department of Plant Pathology, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh.
Department of Plant Pathology, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh.
C R Biol. 2016 Sep-Oct;339(9-10):399-407. doi: 10.1016/j.crvi.2016.06.002. Epub 2016 Aug 1.
Bacterial blight (BB) is caused by Xanthomonas oryzae pv. oryzae (Xoo), a most destructive disease of rice, mostly in Asia, including Bangladesh. Altogether 96 isolates of Xoo were collected from 19 rice-growing districts of Bangladesh in both the rain-fed and irrigated seasons of 2014 to assess their pathotypic and genetic variation. Pathotypic analyses were carried out on a set of 12 Near Isogenic Lines (NILs) of rice containing a single resistance gene and two check varieties IR24 and TN1 by the leaf clipping inoculation method. A total of 24 pathotypes were identified based on their virulence patterns on the NILs tested. Among these, pathotypes VII, XII and XIV, considered as major, containing a maximum number of isolates (9.38% each), are frequently distributed in seven northern to mid-eastern districts of Bangladesh. The most virulent pathotype I was recorded in the Habiganj and Brahmanbaria districts. The molecular analysis of variability among the isolates was carried out through PCR analysis using multi-locus primers Jel1 and Jel2 (based on the repetitive element IS1112 in the Xoo genome). Using the genotypic data, a dendrogram was constructed with 17 clusters along with 17 molecular haplotypes at the 65% similarity index. Cluster I was composed of 46 isolates considered as major, whereas clusters X, XI, XII and XVII were represented by a single isolate. A phenogram was constructed based on virulence to interpret the relationship between the pathotypes and the molecular haplotypes. At the 50% similarity level, among 10 clusters, cluster I, considered as major, consisted of a maximum of 10 pathotypes out of 24. In case of haplotypes, a maximum of 7 haplotypes were obtained from pathotype XII, whereas pathotypes IX, X, XV, XXII and XXIV were represented by a single haplotype. However, the present study revealed that different isolates belonging to the same pathotypes belonged to different haplotypes. Conversely, genetically similar haplotypes were also detected from different pathotypes collected from separate districts. This relationship appeared due to a high degree of DNA polymorphism among strains within many pathotypes existing in Bangladesh.
白叶枯病（BB）由稻黄单胞菌水稻致病变种（Xoo）引起，是水稻最具毁灭性的病害，主要发生在包括孟加拉国在内的亚洲地区。2014年，在孟加拉国雨养和灌溉季节，从19个水稻种植区共采集了96株Xoo分离株，以评估它们的致病型和遗传变异。通过剪叶接种法，对一组含有单个抗性基因的12个水稻近等基因系（NILs）以及两个对照品种IR24和TN1进行致病型分析。根据它们在测试的NILs上的毒力模式，共鉴定出24种致病型。其中，致病型VII、XII和XIV被认为是主要致病型，每种含有最多数量的分离株（各占9.38%），在孟加拉国北部至中东部的七个地区分布频繁。毒性最强的致病型I出现在哈比甘杰和婆罗门巴里亚地区。通过使用多位点引物Jel1和Jel2（基于Xoo基因组中的重复元件IS1112）进行PCR分析，对分离株之间的变异性进行分子分析。利用基因型数据，构建了一个相似性指数为65%的包含17个聚类和17个分子单倍型的树状图。聚类I由46个被视为主要的分离株组成，而聚类X、XI、XII和XVII由单个分离株代表。基于毒力构建了一个表型图，以解释致病型和分子单倍型之间的关系。在50%的相似性水平上，在10个聚类中，被视为主要聚类的聚类I在24种致病型中最多包含10种。就单倍型而言，致病型XII最多获得7种单倍型，而致病型IX、X、XV、XXII和XXIV由单个单倍型代表。然而，本研究表明，属于相同致病型的不同分离株属于不同的单倍型。相反，从不同地区收集的不同致病型中也检测到了遗传上相似的单倍型。这种关系的出现是由于孟加拉国存在的许多致病型内菌株之间高度的DNA多态性。
