STUDIES ON FUSARIUM WILT OF BANANAS: V. PATHOGENICITY AND DISTRIBUTION OF F. OXYSPORUM f. CUBENSE RACES 1 AND 2

Abstract

Two naturally occurring races of the Fusarium wilt or Panama disease fungus, F. oxysporum f. cubense (E.F.S.) Snyd. and Hans., have been identified. Race 1 is world-wide in distribution and attacks certain AAA triploids of Musa acuminata, of which variety 'Gros Michel? is the most important, and Musa textilis. Race 2 has been identified in Honduras, El Salvador, Puerto Rico, Virgin Islands, and the Dominican Republic and attacks certain ABB triploids of M. acuminata × M. balbisiana known as 'Chato', 'Bluggoe', 'Rulo', or 'Chamaluco'. Both races are pathogenic on 3- to 4-month-old seedlings of M. balbisiana, M. schizocarpa, and M. acuminata ssp. banksii, but the race 2 clone was less pathogenic than the race 1 clones tested. Mature M. balbisiana is immune to rhizome infection in the field. 'Odoratum' and 'Inodoratum' cultivars of F. oxysporum f. cubense are found within race 1; only the 'Inodoratum' cultivar is found within race 2. Circumstantial evidence indicates an independent development of race 2 in different areas. Race 2 wilt-susceptible ABB triploids hybridize and set seed with pollen from diploid M. balbisiana (BB) and M. acuminata (AA), the two ancestors of the cultivated banana. This will facilitate a study of the inheritance of wilt resistance to F. oxysporum f. cubense races 1 and 2.