Occurrence, Pathogenic Variability and Cultivar Response to Fusarium Wilt of Cucumber in High Plastic Tunnels of Balochistan, Pakistan

Abstract

Fusarium wilt, caused by Fusarium oxysporum f. sp. cucumerinum (FOC), is an emerging constraint on tunnel-grown cucumber (Cucumis sativus L.) in Balochistan, Pakistan. Limited field-level information is available in the literature on its distribution, aggressiveness, and cultivar reaction in this region. A survey of high tunnels across the upland districts of Balochistan, namely Quetta, Pishin and Mastung was conducted in 2022 and 2023. Fusarium wilt was recorded at every location, with incidence ranging from 21.80 to 57.20%; Quetta was the most severely affected. Nine isolates recovered from infected tissue were morphologically identified as F. oxysporum associated with cucumber wilt and confirmed pathogenic by soil-infestation pot assays. All nine isolates were pathogenic, with plant mortality ranging from 21.25 to 92.00% and root infection from 32.50 to 98.00%; five isolates (FOC1, FOC2, FOC6, FOC8 and FOC9) were classified as highly pathogenic on the basis of mortality, with FOC2 the most aggressive, causing the highest mortality (92%) and root infection (98%). When five commercial cultivars (Arista, R-Yield, Star One, Subhan and Mawasem) were challenged with FOC2, all were susceptible but differed significantly in degree: Mawasem was most susceptible (95.00% mortality, 96.50% root infection) with the greatest growth suppression, while Arista was comparatively less susceptible (32.25% mortality, 40.00% root infection) with the best growth performance. None of the five evaluated commercial cultivars showed complete resistance to FOC2, although Arista and R-Yield exhibited comparatively lower disease severity and better growth. These findings indicate that Fusarium wilt is an important disease constraint in the surveyed cucumber tunnels of Balochistan, underscoring the need for integrated management and further resistance-breeding work.