Ogbe F O, Dixon A G O, Hughes J d'A, Alabi O J, Okechukwu R
International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria and National Root Crops Research Institute (NRCRI), Umudike, Umuahia, Nigeria.
IITA, Ibadan, Nigeria.
Plant Dis. 2006 May;90(5):548-553. doi: 10.1094/PD-90-0548.
A diagnostic survey was conducted in 2002-03 to determine the status of cassava mosaic begomoviruses in Nigeria and to ascertain if the virulent Ugandan variant of East African cassava mosaic virus (EACMV-Ug2) was present. Of the 418 farms visited, 48% had cassava with moderately severe or severe symptoms, whereas 52% had cassava with mild symptoms. These distributions were at random. Of the 1,397 cassava leaf samples examined, 1,106 had symptoms. In polymerase chain reaction tests, 74.1% of the symptom-bearing samples tested positive for African cassava mosaic virus (ACMV) alone, 0.3% for EACMV alone, 24.4% for mixed infections by the two viruses, and 1.2% did not react with any of the primers used. The two viruses also were detected in 32% of the 291 symptomless plants and in the whitefly vector samples. EACMV-Ug2, Indian cassava mosaic virus, and South African cassava mosaic virus were not detected in any of the whitefly or leaf samples. Most farms had ACMV in single infection as well as in mixed infections with EACMV. Most doubly infected plants showed severe symptoms. Two biological variants of ACMV were identified based on symptom expression on cassava in the field. ACMV and EACMV were detected in the leguminous plant Senna occidentalis (L.) Link and the weed Combretum confertum Lams.; these are new natural hosts of the viruses. Although the virulent EACMV-Ug2 was not detected, the occurrence of variants of ACMV and a high proportion of mixed infections by ACMV and EACMV, which could result in recombination events such as the one that produced EACMV-Ug2, demands appropriate measures to safeguard cassava production in Nigeria.
2002 - 2003年进行了一项诊断调查，以确定尼日利亚木薯花叶双生病毒的状况，并查明东非木薯花叶病毒（EACMV）的强毒株乌干达变种（EACMV - Ug2）是否存在。在走访的418个农场中，48%的农场木薯有中度严重或严重症状，而52%的农场木薯有轻度症状。这些分布是随机的。在检测的1397份木薯叶样本中，1106份有症状。在聚合酶链反应测试中，74.1%有症状的样本仅对非洲木薯花叶病毒（ACMV）检测呈阳性，0.3%仅对EACMV检测呈阳性，24.4%为两种病毒混合感染，1.2%与所用任何引物均无反应。在291份无症状植株及粉虱载体样本中，也检测到了这两种病毒。在任何粉虱或叶片样本中均未检测到EACMV - Ug2、印度木薯花叶病毒和南非木薯花叶病毒。大多数农场的ACMV为单一感染以及与EACMV混合感染。大多数双重感染的植株表现出严重症状。根据田间木薯上的症状表现，鉴定出了ACMV的两个生物学变种。在豆科植物番泻决明（Senna occidentalis (L.) Link）和杂草聚果藤（Combretum confertum Lams.）中检测到了ACMV和EACMV；这些是该病毒新的自然寄主。尽管未检测到强毒株EACMV - Ug2，但ACMV变种的出现以及ACMV和EACMV的高比例混合感染，可能导致诸如产生EACMV - Ug2的重组事件，这就需要采取适当措施来保障尼日利亚的木薯生产。
