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Rapid screening for resistance against Pseudocercospora banana pathogens using relatively long detached banana leaves under controlled conditions

Alejandro Ortega-Beltran: International Institute of Tropical Agriculture

<div>Banana and plantain (<em>Musa</em> spp.) are important food and cash crops throughout the tropics and subtropics. However, they are threatened by the ‘Sigatoka Disease Complex’ (SDC) caused by <em>Pseudocercospora fijiensis,</em> <em>P. musae, </em>and <em>P. eumusae</em>. Invasion by these pathogens results in poorly filled fruits and smaller, lower yielding bunches. In addition, severe infections induce physiological changes that result in a heightened climacteric rise. This leads to reduced green life and is associated with premature and uneven fruit ripening, reduced pulp color clarity, and altered fruit taste. Although significant progress has been made in breeding for resistance to SDC, these efforts are constrained by lack of rapid, robust screening methods aimed to identify sources of resistance. We developed a robust, rapid, and reliable screening method to evaluate susceptibility to SDC using detached banana leaves ( 25 cm x 10 cm) placed in plastic boxes containing technical agar amended with 5 ppm gibberellic acid and separately inoculated with <em>P. fijiensis</em> and <em>P. musae</em>. Leaves remained viable >100 days and showed similar reaction as when infected in the field. For instance, the resistant accessions Calcutta 4 and Yangambi KM5 showed significantly lower (P ≤ 0.05) disease severity compared to the highly susceptible cultivars Gros Michel and Agbagba. The method allows both identifying resistant germplasm and studying host-pathogen interactions. This method will be useful to banana/plantain breeding programs across the globe to rapidly screen hundreds of banana and plantain accessions for resistance to SDC and other diseases under controlled conditions.</div>