Resistance to Fusarium oxysporum f. sp. luffae in Luffa Germplasm Despite Hypocotyl Colonization

Fusarium wilt of Luffa, caused by Fusarium oxysporum f. sp. luffae (Folu), causes great losses in Luffa plants worldwide. In this study, 45 accessions of Luffa germplasm were used to determine their resistance to Folu isolates (FOLUST, FOLUSC, Fomh16, and Fol114) in two independent trials. In the first trial, only FOLUST was used to preliminarily identify resistant accessions. Nine accessions of L. acutangular and five of L. aegyptiaca were resistant to the FOLUST isolate. In the second trial, the other three isolates were then used to reevaluate the 14 resistant accessions. The results indicated that the 14 accessions were resistant to FOLUSC but exhibited variable resistance to the Fomh16 and Fol114 isolates. Eight accessions of L. acutangula and one accession of L. aegyptiaca were resistant to Fol114. Seven accessions of L. acutangula and one accession of L. aegyptiaca were resistant to Fomh16. Despite the lack of any symptoms, the Folu isolates were recovered from the hypocotyls of all resistant accessions at 28 days post inoculation, except for isolates FOLUSC and FOLUST on one accession (LA140). A high percentage (87.5%) of accessions collected from Bangladesh were identified as resistant, highlighting the effect of local adaptation on resistance. These results provide potentially valuable genetic resources for breeding programs to develop new varieties or rootstocks that could be beneficial for controlling soil-borne diseases in different cucurbit crops and further investigating the mechanisms of resistance to Folu in Luffa plants.