Variability epidemiology and management of Fusarium oxysporum f sp lini

Abstract

newline The investigation entitled Variability, epidemiology and management of Fusarium oxysporum f.sp. lini was conducted at Department of Plant Pathology, CSKHPKV Palampur and Shivalik Agricultural Research and Extension Centre, Kangra during 2015-2018. 35 isolates of Fusarium oxysporum f.sp. lini were obtained from the diseased samples collected from Kangra and Mandi districts of Himachal Pradesh and other parts of India. Three isolates were categorized as weakly pathogenic, 7 as moderately pathogenic and 25 as highly pathogenic during pathogenicity test. All the isolates showed variability in morphological and cultural characteristics. To identify the wilt resistant sources, 176 linseed genotypes were evaluated under field conditions. Among these 5 genotypes viz., KL-215, KL-261, EC541213, H-18 and TL-50 showed highly resistant,7 genotypes showed resistant and 21 genotypes showed moderately resistant disease reactions. A set of 17 genotypes i.e. TL-9, R-552, H-34, Janaki, Himalini, Polf-24, TL-22, EC-541213, KL-187, POLF-16, EC-541212, H-18, EC-541211, POLF-22, Kangra local, Baner and Chambal was standardized as differential hosts. Pathogenic variability among 35 isolates was determined on differential set and 5 pathotypes were recorded and designated as Pathotype-1 to Pathotype-5. 32 promising genotypes of linseed were evaluated against the 5 pathotypes and 13 genotypes viz., EC-541199, H-18, H-36, Him Alsi-1, Jeevan, Janaki, KL-215, KL-227, KL-265, Nagarkot, Natazo, POLF-19 and Surbhi showed resistant disease reaction against all the 5 pathotypes. Maximum in vitro growth of the Fusarium oxysporum f.sp. lini on PDA was observed at 24ºC and pH 5.5 with highest growth rate and sporulation. Lowest wilt incidence was recorded in clay loam soil compared to sandy, sandy clay loam and loam soils. Disease incidence during the crop season 2015-16 and 2016-17 showed positive correlation with minimum temperature and soil temperature at 10 cm and negative correlation with relative humidity at evening time. Delay in date of sowing from 16 October to 26 November resulted decrease in wilt incidence in varieties Chambal and Janaki. Trichoderma viride (Strain Tr-3) and Carbendazim 50 WP were found most effective for mycelial growth inhibition of the Fusarium oxysporum f.sp. lini during in vitro studies and Tr-3 (Trichoderma viride) showed highest compatibility with fungicides among three tested bioagents. In pot studies, the highest seedling emergence and lowest linseed wilt incidence was observed with Tr-4 (Trichoderma harzianum) (seed treatment + soil application), Thiram 75WP seed treatment and Thiram 75 WP + Tr-4 (Trichoderma harzianum) (seed treatment + soil application). In field studies, Carbendazim (50%) + Tr-4 (T. harzianum) (seed treatment + soil application) showed highest disease reduction and yield increase over control.