In Vitro Evaluation of Banana cv. Mapilak ( AAA ) for Filtrate Sensitivity Phenotype Associated With Foc TR4 Response

Fusarium wilt, caused by Fusarium oxysporum f. sp. cubense Tropical Race 4 (Foc TR4), is a major threat to global banana production, necessitating host resistance as the most sustainable management option. This study evaluated the filtrate sensitivity phenotype of five NSIC‐registered Mapilak lines, derived from gamma‐irradiated Lakatan (AAA), which has been hypothesized to be associated with the response to Foc TR4. The aim was to determine whether filtrate sensitivity could serve as a proxy for potential field performance. Meriplants were subjected to 50% (v/v) Foc TR4 crude filtrate for 14 days with an effective concentration of ~150 ppm of fusaric acid and demonstrated phytotoxicity comparable to purified toxin. Disease response was assessed using a severity rating scale and quantified via ImageJ necrosis analysis. Four lines—NSIC 2017 Bn 01, NSIC 2021 Bn 02, NSIC 2021 Bn 04 and NSIC 2021 Bn 05—exhibited a moderately resistant (MR) response, statistically comparable to the resistant control, GCTCV 218 (MR). Line NSIC 2021 Bn 03, however, was sensitive (S), similar to the highly susceptible control (Lakatan Cavite), which was also categorized as highly sensitive (HS) to the filtrate. This research demonstrates the efficacy of the crude filtrate assay as a prescreening step to narrow down candidates for eventual pathogen‐challenge trials. The four identified MR lines show significant potential for Foc TR4 management and are recommended for field evaluation.