Supressividade de um solo a murcha-de-fusário do caupi e influência da doença no rendimento da cultura

• Autor(a) principal: ELOY, Arlinda Pereira
• Data de Publicação: 2003
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFRPE
• dARK ID: ark:/57462/0013000007nfn
• Texto Completo: http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/6483
• topic: Murcha-de-fusário; Ecologia do solo; Inóculo; Vigna unguiculata; FITOSSANIDADE::FITOPATOLOGIA

The Fusarium wilt, caused by Fusarium oxysporum f. sp. tracheiphilum, reduces cowpea yield in Northeastern Brazil. This work aimed to characterize the nature and ability to transfer cowpea Fusarium wilt suppressiveness of a soil; to analyze populational dynamic of F. oxysporum f. sp. tracheiphilum and others soilborne microorganisms in two soils with different levels of suppressiveness, as well as to determine the relation of disease severity and the reductions of yield in cowpea seeds, in two plant seasons. In the nature and transfer of suppressiveness analyses the two soils samples used were previously classified as suppressive (CAC) and conducive (GOI) to cowpea Fusarium wilt, and did not slown indigenous populations of Fusarium oxysporum. When the samples were infested with the pathogen and sown with BR 17 Gurguéia (highly susceptible) and IPA 206 (moderately susceptible) cowpea cultivars, total populations of both fungi and bacteria, and Bacillus spp. were higherin rhizosphere of the suppressive soil samples than in the conducive ones. The suppressiveness was not related to a suppressive effect on the pathogen population. Soil sterilization did not change the suppressive capability, pointing out its abiotic origin. The ability suppressiveness transfer to a conducive soil was demonstrated only. In the suppressive soil, a significant influence of pH levels on Fusarium wilt severity was verified, which decreased in increasing pH. The inoculum density alone did not determine the severity of Fusarium wilt on plants cultivated in both soils, due to the influence of the efficiency of the inoculum, which was significantly lower in the suppressive soil. Aiming to determine the linkage of disease severity to the reduction of cowpea seed yield, cultivated during two different period of time, an essay was carried out using plots artificially infested with the pathogen. The first planting was made in April 2002, while the second one in October, in thesame year. At the harvest, yield for each plot was determined through the total weight of seed per plant. After harvesting the severity of Fusarium wilt was evaluated in all plants. There was no significant correlation between inoculum densities of the pathogen that was present in the soil before planting and the disease severity. The yield in the first planting period was higher than in the second one, in non-infested plots, what may have been due to the water stress to which the plants were submitted right before the blossom.Differences between the severity average levels and yield losses were not verified for both essays. Fusarium wilt severity ranged between 3.2 and 93.3%, while the yield losses ranged between 2.2 and 98.1%.