MICROPROPAGATED BANANAS ARE MORE SUSCEPTIBLE TO FUSARIUM-WILT THAN PLANTS GROWN FROM CONVENTIONAL MATERIAL

The reaction of field-grown micropropagated bananas, Musa cv. Williams (AAA, Cavendish subgroup) and cv. Goldfinger (AAAB, FHIA-01), to subt ropical race 4 Fusarium oxysporum f. sp. cubense (Foc) was compared wi th the reaction of plants grown from conventional planting material (s ections of the rhizome, termed bits). Leaf gas exchange of plants was determined, and growth and dry matter accumulation were measured. Comp arisons were made among these parameters from shortly after planting, throughout winter, and into spring when a high percentage of the plant s started to show external symptoms of fusarium wilt. Micropropagated bananas were significantly more susceptible to race 4 Foc than plants derived from bits. This was irrespective of planting times, cultivars used, or whether the bits had first been established in containers in the glasshouse (as for micropropagated plants) or been planted directl y in the field. This greater susceptibility does not appear to be a co nsequence of differences in maximum photoassimilation rates, greater p hotoassimilate demand, or lack of carbohydrate reserves once plants be came established.