BRIEF REPORT Alternate hosts of African cassava mosaic virus and East African cassava mosaic Cameroon virus in Nigeria Olufemi J. Alabi Æ Francis O. Ogbe Æ Ranajit Bandyopadhyay Æ P. Lava Kumar Æ Alfred G. O. Dixon Æ Jaqueline d’A. Hughes Æ Rayapati A. Naidu Received: 2 May 2008 / Accepted: 22 June 2008 / Published online: 26 July 2008 Ó Springer-Verlag 2008 Abstract Cassava mosaic disease (CMD) caused by African cassava mosaic virus (ACMV) and East African cassava mosaic Cameroon virus (EACMCV) is the major constraint to cassava production in Nigeria. Sequences of the DNA-A component of ACMV and EACMCV isolates from leguminous plant species (Senna occidentalis, Leu- cana leucocephala and Glycine max), castor oil plant (Ricinus communis), a weed host (Combretum confertum) and a wild species of cassava (Manihot glaziovii) were determined. All ACMV isolates from these hosts showed 96–98% nucleotide sequence identity with cassava isolates from West Africa. EACMCV was found only in four hosts (S. occidentalis, L. leucocephala, C. confertum, M. glazi- ovii), and sequences of these isolates showed 96–99% identity with cassava isolates from West Africa. These results provide definitive evidence for the natural occur- rence of ACMV and EACMCV in plant species besides cassava. Cassava (Manihot esculenta Crantz.) is a staple food crop grown by subsistence farmers in Sub-Saharan Africa and contributes significantly to the household food security in the region. Cassava mosaic disease (CMD) is an important constraint to cassava production in Sub-Saharan Africa, with an estimated annual yield loss of US $1.5 billion [9, 18]. Six distinct cassava mosaic begomoviruses (CMBs, family Geminiviridae, genus Begomovirus) have been found occurring in CMD-infected cassava plants in the region [4]. Among them, only African cassava mosaic virus (ACMV) and East African cassava mosaic Cameroon virus (EACMCV) have so far been documented in CMD-infec- ted cassava plants in West Africa [2]. The whitefly vector, Bemisia tabaci (Gennadius) (Aleyrodidae, Hemiptera) transmits CMBs from plant-to-plant. Long-distance spread of CMD occurs by the distribution of infected stem cuttings. One of the key gaps in knowledge on the epidemiology of CMD in Nigeria, and indeed on a regional scale, is the potential role of non-cassava plant species as alternate/ reservoir hosts in the perpetuation of CMBs. Since cassava was introduced from South America in the 16th Century, it is likely that CMBs endemic to Africa infecting indigenous African plant species have become adapted to cassava upon its introduction [16]. Thus, it is plausible that native plant species could act as alternative and/or reservoir hosts for CMBs and contribute to virus evolution and disease epi- demics. Available information on the natural host range of CMBs indicates that they are largely restricted to cassava and a few of its wild relatives such as Manihot glaziovii Mu ¨ll. Arg. Previously, ACMV was detected in Jatropha multifida L. (Euphorbiaceae) [6] and suspected to infect Hewittia sublobata (Convolvulaceae) in Kenya [3] and Laportea (=Fluerya) aestuans (Urticaceae) in Nigeria [13]. Recently, Ogbe et al. [12] documented both ACMV and O. J. Alabi Á R. A. Naidu (&) Department of Plant Pathology, Washington State University, Irrigated Agriculture Research and Extension Center, 24106 N. Bunn Rd, Prosser, WA 99350, USA e-mail: naidu@wsu.edu R. Bandyopadhyay Á P. Lava Kumar Á A. G. O. Dixon Á J. d’A. Hughes International Institute of Tropical Agriculture, Oyo Road, PMB 5320, Ibadan, Nigeria F. O. Ogbe National Root Crops Research Institute, Umuahia, Nigeria Present Address: J. d’A. Hughes AVRDC-The World Vegetable Center, PO Box 42, Shanhua, Tainan 74199, Taiwan, ROC 123 Arch Virol (2008) 153:1743–1747 DOI 10.1007/s00705-008-0169-8