Journal of Advances in Biology & Biotechnology

Background: Fusarium wilt, caused by soil-borne formae speciales of Fusarium oxysporum, is among the most persistent constraints on yardlong bean (Vigna unguiculata ssp. sesquipedalis) production across East and Southeast Asia, where the crop is grown intensively as a vegetable legume. Despite decades of research on the disease in African and North American cowpea (ssp. unguiculata), the evidence base specific to the long-podded vegetable subspecies remains comparatively fragmented and has not previously been synthesised critically.

Purpose: This review evaluates the state of knowledge on the biology of the causal pathogen or pathogens, the epidemiology of the disease, and the genetic and genomic basis of host resistance in yardlong bean, situating subspecies-specific findings within the broader cowpea and grain-legume literature.

Methods: Evidence was identified through structured searches of open-access, indexed scholarly databases and repositories, supplemented by citation tracking, and appraised for methodological adequacy, source credibility and relevance; only bibliographically verified sources were retained.

Findings: Molecular and genomic studies confirm that F. oxysporum pathogenicity toward cowpea and its Asian vegetable subspecies is governed by transferable, transposon-rich accessory chromosomes bearing effector genes, a mechanism that helps explain the instability of the forma specialis and physiological race concepts applied to this pathosystem, including an unresolved discrepancy between reports attributing yardlong bean wilt in China to F. oxysporum forma specialis tracheiphilum and to forma specialis phaseoli. Resistance in cowpea is conditioned predominantly by race-specific, largely monogenic or oligogenic loci mapped through biparental and association approaches, several validated through synteny with soybean and common bean, although genomic resources and mapped loci remain markedly sparser for the sesquipedalis gene pool than for African cowpea. Non-genetic management options, principally biological control and cultural practices, show mechanistic promise but rest on a comparatively thin and geographically narrow evidence base for this specific pathosystem.

Conclusions: Confidence is high for the genomic mechanisms of host specificity and for several race-specific resistance loci in cowpea; confidence remains provisional for the taxonomic identity of the yardlong bean pathogen and for the transferability of African cowpea resistance sources into Asian vegetable germplasm, marking priority directions for future research.