Gummy stem blight of bottle gourd: Pathogen identification, host screening, and management strategies

Abstract

Gummy stem blight, caused by Stagonosporopsis cucurbitacearum (syn. Phoma cucurbitacearum; teleomorph - Didymella bryoniae), is becoming a major problem for the cultivation and seed production of bottle gourd, including almost all gourds and melons. During May-June, 2021-2024, severe disease incidence of gummy stem blight occurred on bottle gourd (Lagenaria siceraria; Family: Cucurbitaceae) at Indian Council of Agricultural Research – Indian Institute of Vegetable Research, Varanasi, Uttar Pradesh. Its infection is noted on green and ripe fruits and has become considered a serious threat for bottle gourd cultivation and its seed production. Initially, typical symptoms of gummy stem blight appeared as circular dark brown-tan spots at the margin of the leaves and water-soaked areas on the stem near the soil line, including defoliation, wilting, and death of plant vines. The pathogen was isolated from diseased stems and leaves of bottle gourd (var. Kashi Ganga). The pathogen produced white aerial mycelial growth with an undulated colony with cylindrical non-septate to monoseptate conidia. 14-day-old plants of bottle gourd were inoculated by spraying a conidial suspension (2.3 × 106 cfu/mL) of pathogen isolate to test pathogenicity. Based on the detailed cultural, morphological, pathological, microscopic characteristics and pathogenicity test, the causal pathogen was identified as S. cucurbitacearum. Twelve cultigens of cucurbits were screened against gummy stem blight pathogen under net-house conditions. On the basis of disease reaction among tested cultigens namely summer fit, cucumber- Cucumis hardwickii and bitter gourd (IC-21250044) were found highly resistant. The treatments comprises spot application of Trichoderma asperellum + Bacillus subtillis (CRB-7) @ 10 gram per pit at the time of planting and soil drenching @1% in the root zone near collar region at the time of each earthing recorded highest in vivo seed germination (84%), lowest gummy stem blight percent disease severity index (7.0) and maximum yields (31.66 tonnes/ha) with highest BC ratio (1: 2.73) in comparison to control.