Title : Fusarium wilt disease- A threat to cucurbits
Abstract:
Fusarium wilt is a common vascular wilt fungal disease of cucurbits which poses a serious threat to its cultivation. It is responsible for causing huge economic losses to cucurbits around the world. Cucurbits are one of the oldest cultivated vegetable crops which are rich in vitamins, minerals as well as dietary fibre. Among cucurbitaceae family, the most important crops which are infected by Fusarium wilt disease are cucumber, watermelon, muskmelon, bitter gourd, pumpkin, bottle gourd etc. Fusarium wilt caused by Fusarium oxysporum is a soil-borne fungus which produces resting spores that can survive in the soil for many years. This pathogen, F. oxysporum has a high level of host specificity, which is classified as a formae specialis. The formae speciales are morphologically similar, but they are strictly host-specific like in cucumber (F. oxysporum f. sp. cucumerinum), bittergourd (F. oxysporum f. sp. momordicae), muskmelon (F. oxysporum f. sp. melonis) etc. All stages of the plant growth are susceptible to the fungus, and disease symptoms may appear in the form of yellowing of the leaves, stunted and poor growth, chlorotic foliage, and defoliation. In case of high disease severity, whole root become dark brown in colour, soft rot symptoms develop near the crown and it ultimately lead to death of the plant. The disease is favoured by high temperature as well as warm moist soils. F. oxysporum attacks vascular tissues of the plant and chokes the vessels with the spores thereby, preventing the water uptake by the plants. The pathogen causes losses to cucurbits in terms of quality as well as quantity because along with the reduction in yield it reduces the sugar content of the fruits and make them appear dull also which reduces the market value of cucurbits. The long-term survival of Fusarium in the soil and the evolution of new races make its management difficult. Although there are resistant varieties available, but the threat of more new virulent strains or mutations to harm formerly resistant crops is of major concern.
