Assessment of large population of cassava accessions for resistant to cassava bacterial blight infection in the screen house environment

Abstract

2International Institute of Tropical Agriculture (IITA), P. M. B. 5320, Ibadan, Nigeria. Accepted 1 April, 2010 Cassava bacterial blight (CBB) is caused by Xanthomonas axonopodis pv manihotis (Xam) a major cassava disease in all cassava growing area of the world. Resistance to the disease is found in Manihot esculenta and, in addition, has been introduced from a wild relative, M. glaziovii. We introduced a novel method of screening large population of cassava accessions in a screen-house environment using planting tray with a planting tree that can accommodate 68 different cassava stems cuttings in one planting tray. A total of 1,090 cassava accessions were screened with this method in the screen-house. The experimental design was augmented with randomized complete block design (ARCBD). Out of 490 land races cassava accessions that were assessed for susceptibility to CBB, 14.3 % were resistant to the disease. Land races populations were more susceptible to CBB infection having 30.1% highly susceptible and 12.3% susceptible cultivars. Six hundred cassava accessions of the improved and the new improved were screened in the greenhouse. Within the improved cultivars, 11.1% showed very strong resistance and 30.1% were resistant to the bacterial infections while 4.3% of these improved cassava accessions were observed as being highly susceptible to the disease and 36.6% were tolerant. Our results demonstrated that resistance to CBB is broadly distributed in cassava germplasm and for quick evaluation, the planting tray system should be employed.