Pre-Screening of Banana Genotypes for Fusarium Wilt Resistance by Using an In Vitro Bioassay

Abstract

In the process of breeding and selection of banana for resistance to Fusarium wilt, it is important to conduct an efficient resistance screening test by artificial inoculation with Fusarium oxysporum f. sp. cubense (Foc) Tropical Race 4. So far, there are two types of early bioassays for screening Musa genotypes against Foc: a greenhouse and an in vitro bioassay. The most commonly used greenhouse bioassay is a pot-based system followed by a hydroponic system. Here we describe an in vitro bioassay characterized by in vitro inoculation of rooted banana plantlets grown on medium consisting of half-strength MS macronutrients and MS micronutrients. The disease response and evaluation results obtained through this in vitro bioassay correlates with that from a greenhouse screen and/or field evaluation. Given the importance of in vitro cell and tissue culture techniques for banana (mutation) breeding, promising resistant clones could be screened directly. This in vitro bioassay is a totally contained system compared with greenhouse methods and does not require an acclimatization step, thereby improving banana breeding efficiency. The in vitro pre-screening protocol and bioassay for Fusarium wilt resistance presented here is fast, space-effective, and accurate.