Screening for Fusarium wilt resistance using banana meriplants
1995
Pedrosa, A.M. Jr.
Banana meriplants produced through tissue culture were tested for suitability as material for screening Fusarium wilt resistance. The reaction of the meriplants after inoculation with known isolates of Fusarium oxysporum f. sp. cubense was first compared with Musa balbisiana seedlings. Inoculation was initiated using a spore suspension (10 raise to fifth power conidia/ml) of 14-day old PDA fungal cultures. It was found that cultures of the fungus on corn meal-sand medium or on sterilized dried banana leaves were suitable to establish high populations in the soil. The disease reaction of the test meriplants, at the 6-8 leaf stage, was evaluated after 60 days by scoring the above ground symptoms using a rhizomes discoloration index. The number of discolored rhizomes from which F. oxysporum f. sp. cubense could be re-isolated was used as the basis for percentage infection. The results of the inoculation experiments established the standards for evaluating the resistance of candidate clones when inoculated with known isolates of F. oxysporum f. sp. cubense. The suitability of banana meriplants for screening of Panama Disease resistance has been verified. The clones that did not show rhizome discoloration were advanced to the second test in cement beds infested separately with identified virulent isolates. The plants were evaluated after another 60 days. Plants that were not infected in the secondary test were multiplied and further tested subjected to a broad collection of isolates in the culverts while their agronomic and commercial potential were being observed in the field. A 4-fold increase (35 percent) in the number of uninfected plants were obtained from the populations that were advanced to the secondary screening. Four clones that were identified as highly resistant in the secondary screening which advanced to field testing.
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