Screening of selected brazilian and tanzanian cotton (Gossypium spp.) cultivars for Fusarium wilt resistance.

Fusarium wilt of cotton caused by Fusarium oxysporum f.sp. vasinfectum Atk. Sny & Hans is one of the major diseases of cotton in Tanzania. Resistant varieties provide useful tools for management of this disease. Varieties developed at Lake Zone Agricultural Research and Development Institute with previous records of resistance are currently susceptible in areas with high level of inoculums warranting the need to search for additional sources of resistance. Further, cotton varieties of Brazil indicate some level of resistance against F. oxysporum f. sp. vasinfectum that can be exploited in breeding programmes. In present study, four varieties from Brazil and three from Tanzanian were screened under greenhouse conditions for resistance to Fusarium wilt. A population of 40 plants per variety was inoculated with a crude inoculum of F. oxysporum f. sp. vasinfectum by root - dip method. Randomized complete block design was used with four replications. Resistance was evaluated on basis of foliar symptoms (disease severity index) and plant survival percentage. Further, all plants showing wilting symptoms were examined for vascular discoloration. Among various tested varieties, two cultivars from Brazil (Ipê and Aroeira) had relatively lower disease severity index and higher plant survival, these results suggesting their potential candidature for use in br eeding programmes for Fusarium wilt resistance. On the other hand, two local cultivars (UK91 and UK08) presented the highest disease severity index and lowest plant survival