Effects of Brown Streak Virus Disease on Yield and Quality of Cassava in Tanzania

Abstract

Brown streak virus disease is the most important biotic constraint to cassava production in the coastal areas of southern Tanzania. Symptoms include foliar chlorosis and sometimes stem lesions. The disease also aects the tuberous roots which develop a yellow/brown, dry, corky necrosis within the starch-bearing tissues, sometimes accompanied by pitting and distortion, that is visible externally. The foliar symptoms of the disease often do not greatly aect plant growth, although the most sensitive cultivars may be stunted and defoliated. The main impact of the disease on the crop is by causing root necrosis. Field experiments were conducted at two sites in Tanzania to determine the eect of the disease on yield and quality of the roots. Cassava brown streak disease (CBSD) decreased root weight and patches of root necrosis made roots unmarketable, although the unaected parts might still have been suitable for home consumption. The disease therefore has two eects, one on total root yield and one on root quality, which aects marketability. The ®eld trials showed that CBSD can decrease root weight in the most sensitive cultivars by up to 70%. The length of time between the appearance of foliar symptoms and the development of root necrosis is a varietal characteristic. In the most susceptible cultivars, root necrosis may appear within 6 months of planting cuttings derived from symptomatic mother plants. A local cultivar known as cv. Nachinyaya exhibited a form of tolerance to CBSD in which foliar symptoms appeared but the development of root necrosis was delayed allowing the full yield potential to be realized.U. S.

Characterization of Brown Streak Virus–Resistant Cassava

“…The symptom severity differed between susceptible varieties. In particular, variety MTAI 25 was highly susceptible with early CBSD symptoms followed by dieback of the scions-an observation previously made in the field on highly susceptible cassava varieties (Hillocks et al, 1996;Hillocks et al, 2001) Table 2). …”

“…CBSD resistance originating from Manihot glaziovii, Manihot melanobasis and a few cassava varieties of Brazilian origin, was initially reported in the cassava improvement programmes at the Amani Research Station throughout the 1940's and 1950's (Hillocks et al, 2001;Jennings and Iglesias, 2002). However, recent evaluations of the cassava germplasm have identified only tolerance rather than resistance to CBSD .…”

“…However, recent evaluations of the cassava germplasm have identified only tolerance rather than resistance to CBSD . It remains unclear whether the CBSD resistance was lost through selective breeding for CMD (Hillocks et al, 2001) or that initial reports of CBSD resistance were actually referring to CBSD tolerance due to inconsistent use of the terminology (Cooper and Jones, 1983).…”

Recent Biotechnological Advances in the Improvement of Cassava

“…The most damaging symptoms of CBSD are found in tuberous roots, including brown, corky necrosis of the starchy tissue, occasional radial constrictions and a reduction in the content of starch and cyanide [32,34]. Yield losses are estimated to be up to 70% in highly susceptible cultivars [37]. In additional to viral pathogens, is cassava bacterial blight (CBB), caused by Xanthomonas axonopodis pv.…”

Approaches to diagnosis and detection of cassava brown streak virus (<i>potiviridae: ipomovirus</i>) in field-grown cassava crop.

“…More than 70 % of tuberous yield loss per plant has been attributed to CBSD [2]. The disease is caused by Cassava brown streak virus (CBSV) (family, Potyviridae: genus, Ipomovirus), [3,4].…”