SURVEILLANCE AND MORPHOLOGICAL CHARACTERIZATION OF FUSARIUM ISOLATES ASSOCIATED WITH LENTIL WILT

Abstract

Lentil (Lens culinaris Medikus) is an important dietary source of protein in many parts of the world, especially South Asia including Pakistan. The crop is vulnerable to wilt, a serious soil-borne threat incited by the fungus Fusarium oxysporum f. sp. lentis. In view of the potential threat Fusarium wilt can pose to lentils, these studies were considered essential, and consequently this project was initiated for the disease assessment, morphological characterization of recovered isolates the pathogen and determination of their pathogenicity. Nine districts with 28 locations were surveyed during the crop season of year 2012-13, out of which 21 showed 100% disease prevalence. In total, 15 isolates of F. oxysporumf. sp. lentis were recovered. The length and width of micro-conidia of these isolates ranged from 4.38 to 6.65 µm and 2.31 to 3.2µm, respectively. These were oval shaped for all the isolates except for isolate FOL-6 (2 celled oval) and FOL-10 (oval pyriform). The length and width of macro-conidia ranged from 9.90 to 29.73 µm and 3.02 to 5.06 µm, respectively. The shape of macro-conidia was straight for all the isolates except FOL-6 and FOL-12, which were slightly curved. The mean diameter of chlamydospores ranged from 7.0 to 15.8 µm. During pathogenicity testing of 15 isolates on cv. Masoor-93, the mean disease severity index ranged from 0 (FOL-1, FOL-8 and FOL-11) to 0.72% (FOL-3) and on line ILL 4605 ranged from 0 (FOL-1, FOL-3, FOL-5, FOL-8, FOL-10 and FOL-13) to 0.66% (FOL-2). This line proved to be more resistant than Masoor-93.