The influence of temperature, inoculum level and race of Fusarium oxysporum f.sp. cubense on the disease reaction of banana cv. Cavendish

Abstract

Cavendish banana plants were grown in soil infested with different levels of microconidia of races 1 and 4 of Fusarium oxyspomm Schlect. f. sp. cubense (E.F. Smith) Snyd. & Hans. The 4-week-old plants were incubated at 20¦ and 28¦C in temperature controlled cabinets subject to natural light fluctuations. Race 1, which does not normally infect Cavendish in the field, infected the plants at both temperatures, as did race 4. Results indicated that temperature was primarily affecting plant growth rather than influencing the aggressiveness of the pathogen. Inoculum levels were also found to influence disease severity with a minimum of 4.5 x l04 microconidia/g dry weight of soil required before macroscopic symptoms were observed. The suitability of month-old tissue culture derived plants for screening for resistance and the evolution of the Cavendish attacking race 4 strains are discussed in the light of these findings.