Discrimination of banana genotypes for Fusarium wilt resistance in the greenhouse

• Published in: Acta horticulturae no. 897; pp. 381 - 385
• Main Authors: Ribeiro, L.R, Amorim, E.P, Cordeiro, Z.J.M, Silva, S. de Oliveira, Dita, M.A
• Format: Journal Article
• Language: English
• Published: International Society for Horticultural Science 01.01.2011
• Subjects: bananas; breeding; cultivars; discoloration; Fusarium wilt; genotype; greenhouses; inoculum; plantlets; sand; screening; vermiculite
• ISSN: 0567-7572
• DOI: 10.17660/actahortic.2011.897.52

Among the major constrains to banana breeding for Fusarium wilt (FW) resistance is the long period necessary for evaluations in the field and the lack of an effective method for early detection of resistant genotypes. This work aimed to establish a screening method for FW resistance under greenhouse conditions and validate its reliability by challenging cultivars with different levels of FW resistance. Two types of substrates (vermiculite and washed river sand) and three inoculum sources (conidial suspension from 1-week-old colonies grown in Potato-Dextrose-Agar-PDA, conidial suspension produced after stress of 1-week-old colonies and Foc-colonised corn meal-sand (CMS) medium) were studied by inoculating 45-day-old plantlets of ‘Silk’ (AAB, susceptible) in a double-tray system. Symptoms were observed in plants grown in both substrates, but highest incidence occurred in washed river sand. Low infection rates were observed using conidial suspension from PDA-grown colonies. By contrast, inocula from stressed colonies and CMS caused consistent symptom expression. Using washed river sand as substrate and inoculum from PDA-grown stressed colonies and/or Foc-colonised CMS, plantlets of the cultivars ‘Tropical’ (AAAB) and ‘Thap Maeo’ (AAB) (field intermediary resistance) were challenged. Plantlets of ‘Silk’ and ‘Grande Naine’ (AAA) were used as susceptible and resistant controls, respectively. While the incubation period in ‘Silk’ was 13 days after inoculation (dai), initial symptoms were only observed at 17 dai in ‘Tropical’ and ‘Thap Maeo’. No symptoms were observed in ‘Grande Naine’. The disease progress evaluated based on external symptoms and rhizome discolouration scales allowed discriminating cultivars according to resistance levels. Since experiments were repeated three times with similar results, our research suggests that the method here described could be suitable for early detection of banana genotypes resistant to Fusarium wilt.