THE INFLUENCE OF TEMPERATURE, INOCULUM LEVEL AND TRACE OF FUSARIUM-OXYSPORUM F SP CUBENSE ON THE DISEASE REACTION OF BANANA CV CAVENDISH

Cavendish banana plants were grown in soil infested with different lev els of microconidia of races 1 and 4 of Fusarium oxysporum Schlect. f. sp. cubense (E.F. Smith) Snyd. and Hans. The 4-week-old plants were i ncubated at 20 degrees and 28 degrees C in temperature controlled cabi nets subject to natural light fluctuations. Race 1, which does not nor mally infect Cavendish in the field, infected the plants at both tempe ratures, as did race 4. Results indicated that temperature was primari ly affecting plant growth rather than influencing the aggressiveness o f the pathogen. Inoculum levels were also found to influence disease s everity with a minimum of 4.5 x 10(4) microconidia/g dry weight of soi l required before macroscopic symptoms were observed. The suitability of month-old tissue culture derived plants for screening for resistanc e and the evolution of the Cavendish attacking race 4 strains are disc ussed in the light of these findings.