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EVALUATION OF BANANA GENOTYPES FOR RESISTANCE TO YELLOW SIGATOKA AND PANAMA DISEASE
EVALUATION OF BANANA GENOTYPES FOR RESISTANCE TO YELLOW SIGATOKA AND PANAMA DISEASE
J.A. VENTURA & J.A.GOMES
EMCAPA, Caixa Postal 391, Vitbria-ES, 29010-901, Brazil
Background and objectives
Banana (Musa) is a popular fruit in Brazil playing an important role as a socioeconomic crop. Panama disease (Fusarium wilt) caused by the soilborne fungus Fusarium oxysporum f. sp. cubense is a destructive disease of many important Brazilian banana cultivars such 'Prata' (Pome-AAB) and 'Silk' (AAB). Yellow Sigatoka is a banana leaf spot disease caused by the fungus Mycosphaerella musicola (Pseudocercospora musae>). The first observable symptoms are pale yellow specks on leaf surface that enlarge into mature spots and cause defoliation. Recent attention has focused on the development of resistant replacements for different cultivars.
Materials and methods
Five cultivars Prata [AAB], Ouro da Mata [AAABJ, Mysore tMB], Thap Maeo [AAB] and Yangambi km5 [AAA]) and three tetraploid hybrids (PA 03-22, PA 12-03 and PV 03-44), supplied by EMCAPA and banana genetic breeding programm of CNPMF/EMBRAPA, were evaluated for resistance to Yellow Sigatoka and Panama Disease, under field conditions. Experiment was conducted on a natural infection site at EMCAPA, Alfredo Chaves County, in the Espirito Santo State, and arranged in a randomized complete block design, with three replicates. The normal management practices of the region were adapted. No pesticides were applied to the trial. Yellow Sigatoka was evaluated by Youngest Leaf Spotted (YLS), that is the number of the first fully unfurled leaf with 10 or more necrotic lesions, and by the percentage of leaf area killed by the disease. Fusarium wilt severity was scored by external symptoms according to the apropriate scale 0-5 (0 = no symptoms and 5 = severe wilting with petiole buckling) and internal symptoms taken at harvest and determined by slicing-off the lower portion of the corm horizontally and examined for discoloration using a scale 0 - 5 (0 = completely clean, no vascular discoloration and 5 = total discoloration of vascular tissue). The treatment means were compared by Duncan's multiple range test.
Results and conclusions
The most resistant genotypes to Yellow Sigatoka were PV 03-44 and Yangambi km 5 which did not show necrotic leaf spots at flowering. YLS rating from 4.03 with cv. Prata (susceptible) to 11.3 with PV 03-44 and Yangambi km 5. Results showed that there were no a significative difference among the Musa types 'Mysore', 'Thap Maeo', PA 03-22 and PA 12-03. The Panama index ranged from 0.0 with resistant genotypes PV 03-44, Ouro da Mata, Mysore, Yangambi km 5 and Thap Maeo, and 6.7 with PA 12-03 and 'Prata'. The hybrid PA 03-22 was intermediate (5.0). The survey revealed that the tetraploid hybrid PV 03-44 had multiple resistance to the diseases. Based on early observations on agronomic evaluations, it appears a promising commercial banana and it would be of local interest to the Brazilian farmers.