Evaluation of cucurbit rootstocks and screening of bitter gourd genotypes for resistance to Fusarium wilt
Fusarium wilt, caused by Fusarium oxysporum f. sp. momordicae (FOM), is one of the major constraints to bitter gourd (Momordica charantia L.) cultivation in Taiwan. Bitter gourd is commonly grafted to pumpkin or other cucurbit rootstocks to avoid the disease, but this is becoming less effective now as grafted plants are now observed wilting in the field and there is concern that FOM is cross-infective to the rootstocks. Thus, this study first assessed the disease reaction of bitter gourd and other cucurbit species, commonly used for rootstock, to a virulent FOM strain, FOM6, from Taiwan. The assessments were based on the disease symptom severity scoring and fungal colonization assays at lower stem near cotyledons after inoculation by both a root dipping and a root pruning method on 10-day-old seedlings. FOM6 killed almost all inoculated bitter gourd plants, caused some infection of the bottle gourds (Lagenaria siceraria) and fig-leaf gourd (Cucurbita ficifolia), but only caused cotyledon yellowing on the tropical pumpkins (C. moschata). The pathogen infected and colonized the plant stem tissue including in symptomless plants. This highlights the potential risk when inappropriate rootstocks are used for disease management. Subsequently, 92 bitter gourd genotypes, comprising 12 commercial F1 cultivars, 15 breeding lines, and 65 germplasm accessions, and one accession of M. balsamina, were screened by root-pruning inoculation to identify sources of resistance. Based on rate of disease development (area under the disease progress curve; AUDPC), five genotypes were identified as resistant, five as moderately susceptible, and the remaining as susceptible. The resistant genotypes are potentially useful sources of resistance for breeding Fusarium wilt resistant bitter gourd.
Sheu, Z.-M., Cheng, H.-C., Chiu, M.-S., Yu, C.-C., Huang, H.-Y., Barchenger, D.W. and Kenyon, L. (2019). Evaluation of cucurbit rootstocks and screening of bitter gourd genotypes for resistance to Fusarium wilt. Acta Hortic. 1257, 57-62
Momordica charantia, cross infectivity, germplasm, colonization, Fusarium oxysporum, Cucurbita