VIRULENCE ANALYSIS AND GENETIC DIVERSITY AMONG ISOLATES OF Fusarium oxysporum f. sp. Cicero.
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Date
2014-08-21
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Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola, Maharashtra.
Abstract
The present investigation entitled, “Virulence Analysis and Genetic Diversity Among Isolates of Fusarium oxysporum f. sp. ciceri” was carried out at Department of Plant Pathology, Dr. PDKV, Akola and Legume Pathology, ICRISAT, Patancheru. The rapid roving survey was carried out during Rabi - 2011 and 2012 season in the major chickpea growing region of India and revealed 0 to 40 per cent of variation for wilt incidence.
Thirty seven isolates of F. oxysporum f. sp. ciceri were purified by single spore isolation method and studied for morphological characters. The isolates were grouped based on variation for radial mycelial growth, sporulation intensity, pigmentation on PDA and filtrate colour in PDB. The study revealed no correlation for mycelium growth with sporulation intensity. However, isolates with thin intermediates mycelium growth recorded higher sporulation intensity than isolates with thick profuse mycelium.
For standardization of virulence assay, three method of inoculation viz., water culture, root dip and soil inoculation methods were used, among them root dip inoculation was found best. Virulence assay at 1x105 and 1x106 conidia/ml recorded revealed relatively higher wilt incidence at high inoculum dose. The study revealed that incubation period of less and moderately virulent isolates did not differ significantly at both the inoculum load. The highly virulent isolates required less incubation period (12-18 days) as compared to moderately virulent to less virulent isolates (16-28 days). At the high inoculation load, 16 isolates were highly virulent, 05 isolates were moderately virulent, 13 isolates were less virulent and 2 isolates were truly avirulent. Anatomical study showed early detection of pathogen before expression of external visible disease symptoms.
Interaction of 17 virulent isolates of F. oxysporum f. sp. ciceri on 10 host differential cultivars confirmed existence of four races (race-1, 2, 3 and 4) along with different disease behavior pattern by Foc-25, Foc-27, Foc-30 and Foc-31 isolates. The study revealed race-1 is the most prevalent in major chickpea growing area, confirmed presence of more than one race in Madhya Pradesh state (race-2 and race-4) and variant disease behavior by four isolates.
Among two marker systems employed during the experiment, 11 ISSR primers produced 73 amplicons; while 5 SSR primers to produced 19 amplicons. The level of polymorphism revealed by ISSR (97%) was higher than that of SSR (84%). Both the marker systems showed highest genetic similarity for race-1 isolates. In some isolates, phylogenetic grouping based on ISSR and SSR data did not appear to be congruent to virulence analysis and geographical locations. This study indicated the existence of pathogenic as well as genetically diverse population of F. oxysporum f. sp. ciceri. The isolates showing diverse pathogenic reaction need to study in depth for their racial behavior as the occurrence of new reaction is an alarming sign for pathologist and breeder.
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Keywords
Genetic diversity, Fusarium oxysporum f. sp. ciceri., Chickpea, Cicer arietinum L., Bengal gram, Leguminaceae, Chickpea wilt, Fusarium oxysporum,
Citation
MONDHE, MANISH KASHINATH. (2014). Virulence analysis and genetic diversity among isolates of Fusarium oxysporum f. sp. ciceri. Department of Plant Pathology. Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola. Ph. D. 2014. Print. xiii, 163p. (Unpublished).