Tropicultura (Jan 2007)
Tolérance de quelques cultivars de manioc (Manihot esculenta Crantz) et de l'espèce sauvage (Manihot glaziovii) à la mosaïque virale africaine et à la cercosporiose du manioc
Abstract
Tolerance of some Cassava Cultivars (Manihot esculenta Crantz) and the Wild Species (M. Glaziovii) to Cassava Mosaic Virus Disease and Brown Leaf Spot. A study of the tolerance of three cultivars of Manihot esculenta Crantz (one local cultivar, Alot-Bikon, and two improved: IITA 8034, IITA 8061) and wild cassava (M. glaziovii) collected from the Mbam and Kim forest (Cameroon) towards the cassava mosaic virus disease (CMVD) and brown leaf spot (BLS), was carried out in Yaoundé. CMVD was studied under natural conditions, whereas BLS was inoculated through a solution of Cercospora henningsii in concentration around 20 × 10² conidia/ml. Sixteen weeks after planting the cuttings, M. glaziovii plants were tallest (156 cm), whereas highest number of leaves (113) was obtained on the IITA 8061 cultivar. The lowest infection degrees by CMVD (17.2%) and BLS (2.7%) were registered on the wild species. Consequently, wild species seem to be more tolerant of the diseases studied. IITA 8061 cultivar is moderately resistant to CMVD (28.9%) and rather resistant to BLS (7.8%). Cultivars IITA 8034 and the local variety are more sensitive respectively to CMVD (53.1 and 54.5%) and BLS (18.8 and 32.8%). The highest yield in tubers was obtained from cultivar IITA 8061 (34.5 t/ha) followed by IITA 8034 (32.1 t/ha) and local cultivar, Alot-Bbikon (15.6 t/ha). These results show that the tolerance of cassava cultivars to disease has a large influence on tuber yield.
