Integrated Management of Fusarium Wilt of Potato

Abstract

Fusarium wilt of potato caused by Fusarium oxysporum f.sp. tuberosi is an important disease that causes losses to potato growers in Pakistan. Limited information is available about the management of this disease. Therefore different control measures were investigated under lab. and green house conditions and then the best treatments were applied collectively in integrated management trial. To fulfill first objective, pathogenicity test was performed to check the virulence of the pathogen on susceptible variety “Desiree”. Isolate Okara-1 (O1) proved to be highly virulent and was used in all management trials. In screening of germplasm,. two varieties and eight lines were used for screening purpose. Cardinal and Karoda showed least mean disease severity index (MDSI) i.e. 22.67 and 16.00 % with the yield reduction of 23.2 and 25.5 % respectively. After varietal screening, chemical management was done by using 5 fungicides namely Topsin-M, Carbendazim, Score, Copper oxychloride and Ridomil under lab and green house conditions. In vitro results showed that Carbendazim and Topsin-M controlled maximum radial growth of fungus (100 %) as compared to rest of the fungicides. Green house results showed that Carbendazim followed by Topsin-M gave less MDSI (17.67% and19.00 %) as compared to Copper oxychloride (55.00 %). The yield reduction by Carbendazim and Topsin-M was 21.59% and 25.91 % as compared to copper oxychloride i.e. 60.91%. Efficacy of biological control agents Trichoderma hazianum and T. virens were checked under lab. condition. T. virens showed higher percent inhibition as compared to T. harzianum in dual culture assay on PDA. Green house results showed that application of T. virens at the time of sowing, 20 and 40 days after sowing (DAS) gave less MDSI (30.76 %) as compared to T. xv

harzianum (34.14 %) with yield reduction of 28.283 % and 32.56 % respectively. Efficacy of Brassica spp. was checked under lab. conditions, the macerated leaves of B. juncea significantly reduced the radial growth of pathogen i.e. 91.75 % as compared to B. napus (85.67 %). The roots of both brassica spp were less effective in controlling the disease. Under green house conditions, B. juncea leaf extracts reduced the MDSI by 42.95 % as compared to B. napus i.e. 45.61 % with no significant results by roots of both spp.As the management of the disease is difficult by single control measure therefore the best treatments from above mentioned experiments were applied together in integrated management trial. The integration of soil treatment with T. virens at the time of sowing, 20 and 40 DAS, green manuring with B. juncea and seed treatment with carbendazim exhibited significant results in reducing Fusariumwilt as compared to single or dual application of these in green house. The results of this study showed importance of integrating selective fungicide, microbial antagonists and biofumigant crop to achieve appropriate management of Fusarium wilt to increase yield of the crop.