HOST RESPONSE TO BLACK SIGATOKA IN MUSA GERMPLASM OF DIFFERENT AGES UNDER NATURAL INOCULATION CONDITIONS

The development of an early evaluation method for host response of dif ferent Musa clones to black sigatoka was investigated under natural in oculation conditions in southeastern Nigeria. Two months old tissue-cu lture-derived plants of three plantain hybrids and parents of the hybr ids were exposed to the natural inoculum of Mycosphaerella fijiensis i n a field planted with a susceptible plantain cultivar. The response t o M. fijiensis was evaluated on these young plants and on the same clo nes of mature, field-established plants. Young plants expressed simila r resistance responses as mature plants and allowed an earlier evaluat ion of host-plant response to M. fijiensis. The male diploid banana pa rent, 'Calcutta 4', was highly resistant to black sigatoka. The three hybrids displayed partial resistance before flowering while the female parent, a triploid plantain, was susceptible. Disease responses of bo th mature and young plants ranked in the same order and were highly co rrelated (P = 0.01). Young-plant response to black sigatoka in Musa ge rmplasm was shown to be a reliable indicator of mature-plant response and a quick means of disease reaction assessment. This could accelerat e progress made by breeding programs when producing new black sigatoka -resistant germplasm. (C) 1997 Elsevier Science Ltd.