Phytopathology. 2014 May;104(5):520-31. doi: 10.1094/PHYTO-07-13-0213-R.
Bacterial leaf streak (BLS) caused by Xanthomonas oryzae pv. oryzicola was first reported in Africa in the 1980s. Recently, a substantial reemergence of this disease was observed in West Africa. Samples were collected at various sites in five and three different rice-growing regions of Burkina Faso and Mali, respectively. Sixty-seven X. oryzae pv. oryzicola strains were isolated from cultivated and wild rice varieties and from weeds showing BLS symptoms. X. oryzae pv. oryzicola strains were evaluated for virulence on rice and showed high variation in lesion length on a susceptible cultivar. X. oryzae pv. oryzicola strains were further characterized by multilocus sequence analysis (MLSA) using six housekeeping genes. Inferred dendrograms clearly indicated different groups among X. oryzae pv. oryzicola strains. Restriction fragment length polymorphism analysis using the transcriptional activator like effector avrXa7 as probe resulted in the identification of 18 haplotypes. Polymerase chain reaction-based analyses of two conserved type III effector (T3E) genes (xopAJ and xopW) differentiated the strains into distinct groups, with xopAJ not detected in most African X. oryzae pv. oryzicola strains. XopAJ functionality was confirmed by leaf infiltration on 'Kitaake' rice Rxo1 lines. Sequence analysis of xopW revealed four groups among X. oryzae pv. oryzicola strains. Distribution of 43 T3E genes shows variation in a subset of X. oryzae pv. oryzicola strains. Together, our results show that African X. oryzae pv. oryzicola strains are diverse and rapidly evolving, with a group endemic to Africa and another one that may have evolved from an Asian strain.
细菌性条斑病（BLS）由稻黄单胞菌引起，最初于 20 世纪 80 年代在非洲报道。最近，该疾病在西非大量重新出现。在布基纳法索和马里的五个和三个不同的水稻种植地区的不同地点采集了样本。从栽培和野生水稻品种以及表现出 BLS 症状的杂草中分离出 67 株稻黄单胞菌。稻黄单胞菌对水稻的致病力进行了评估，在感病品种上的病斑长度表现出高度变异。稻黄单胞菌进一步通过使用六个管家基因的多位点序列分析（MLSA）进行了特征描述。推断的系统发育树清楚地表明稻黄单胞菌菌株之间存在不同的群体。使用转录激活子样效应物 avrXa7 作为探针的限制性片段长度多态性分析导致鉴定出 18 个单倍型。基于聚合酶链反应的两种保守的 III 型效应物（T3E）基因（xopAJ 和 xopW）的分析将菌株分为不同的组，大多数非洲稻黄单胞菌菌株中未检测到 xopAJ。通过在 'Kitaake' 水稻 Rxo1 系上进行叶片渗透证实了 xopAJ 的功能。xopW 的序列分析显示稻黄单胞菌菌株存在四个群体。43 种 T3E 基因的分布表明在一组稻黄单胞菌菌株中存在变异。总之，我们的结果表明，非洲稻黄单胞菌菌株具有多样性和快速进化，其中一组是非洲特有，另一组可能是从亚洲菌株进化而来。
