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Biological activities of antagonistic fungi to control fusarium wilt of tomato
Dissertation Abstract:
The research findings on tomato wilt collected from infested fields in Bangkok, Phetchaboun, Tak, Nakhoratchasima, Burirum, Nongkhai, Sakonnakhon, and Khonkaen Provinces resulted to isolate and identify the causal agent as Fusarium oxysporum f. sp. lycopersici race 2 according to confirmation work on morphological and molecular phylogeny by sequencing the internal transcribed spacer (ITS) region ITS1, 5.8S, and ITS2; a small portion of 18S rDNA; and a small portion of 28S rDNA and AFLP marker.
The pathogenicity test and AFLP analysis revealed that 11 isolates were categorized as non-pathogenic or avirulent group and 14 isolates were categorized as pathogenic group, which is divided into three subgroups, namely: low virulent (L), moderate virulent (M), and high virulent (H). As a result, the isolates of KSoC02, NKRC09, SSoC03, and SSoC04 were shown to be non-pathogenic. Isolate KK2 from the northeast part of Thailand was tested for pathogenicity to cause wilt symptom on tomato Sida var., which is susceptible to standard tested isolate F. oxysporum f. sp. lycopersici race 2. This work provided new information on formae specialis of F. oxysporum f. sp. lycopersici which could classify as race 2 that can cause wilt to different varieties of tomato (i.e., Cheery and Sida varieties) rather one variety.
The antagonistic fungi of Chaetomium brasilense CB01, Ch. cupreum CC03, Ch. elatum ChE0, Ch. lucknowense CLT01, Emericella nidulans En01, and E. rugulosa ER01 were proved to antagonize F. oxysporum f. sp. lycopersici NKSC02. The antagonism test demonstrated the antagonistic activity of Ch. brasilense CB01, Ch. cupreum CC03, Ch. cupreum CC03, Ch. elatum ChE01, Ch. lucknowense CLT01, E. nidulans EN01, and E. rugulosa ER01 to inhibit the conidial production of F. oxyspoprum f. sp lycopersici NKSC02. Bioactivities tests of crude extracts and pure compounds form tested antagonistic fungi were proven as a control mechanism. To elucidate the control mechanism involved in the inhibitation of F. oxysporum f. sp. lycopersici, crude extracts of Ch. brasilense CB01, Ch. cupreum CC03, Ch. elatum ChE01, Ch. lucknowense CLT01, E. nidulans EN01, and E.rugulosa ER01 were confirmed for antifungal activity against of F. oxysporum f. sp. lycopersici NKSC02. The other control mechanism involved in releasing antibiotic substances of inhibits F. oxysporum f. sp. lycopersici. All tested crude extracts of Ch. brasilense CB01, Ch. cupreum CC03, Ch. elatum ChE01, Ch. lucknowense CLT01, E. nidulans EN01, and E. rugulosa ER01 were significantly inihibited conidia production of F.oxysporum f. sp. lycopersici.
It was clearly demonstrated that a pure compound produced by E. rugulosa ER01, Chaetoglobosin C, a pure compound produced by Ch. elatum ChE01 and Ch. luckowense CLT01, inhibited conidia production of F. oxysporum f. sp. lycopersici NKSC02 with the ED50 value of 5.94 μg/ml. Moreover, tajixanthone, a pure compound produced by E. rugulosa ER01, inhibited conidia production of F. oxysporum f. sp. lycopersici NKSC02 with an ED50 value of 167 μg/ml. Chaetoglobosin C and tajixanthone are expressed as an antibiotic substances to destroy the pathogen cells implies antibiosis.
Inocula of F. oxysporum f. sp lycopersici (1 × 107 spores/ml) were mixed with chaetoglobosin-C and tajixanthone and inoculated to tomato seedlings caused no symptoms at day 21 while the treatment with pathogen alone showed significantly highest disease severity index. With this, no wilt incidences appeared at all tested concentrations of 10, 50, and 100 μg/ml of either Chaetoglobosin C or tajixanthone. Chaetoglobosin C and tajixanthone affected directly to the pathogen inocula implies which occurrences of ruptured cells and abnormal conidia of pathogen.
The research findings indicated that treated seedlings var. Sida with crude EtOAc of E. rugulosa at 1,000 μg/ml gave significant lower DSI form treated with crude EtoAC of E. rugulosa at 500 μg/ml when compared to the inoculated with F. oxysporum f. sp. lycopersici NKSC02. Disease immunity of Fusarium wilt in Sida variety appeared the highest immunity when treated with crude EtOAc at 1,000 μg/ml and followed by treated with crude EtOAc at 500 μg/ml microbial extracts expressed to induce immunity in term of microbial elicitors.
Ch. elatum ChE01, E. nidulans EN01, and to E. rugulosa ER01, which were formulated as oil powder bioformulations, gave a good result to control wilt of tomato var. Sida caused by F. oxysporum f. sp. lycopersici NKSC02 race 2. The treated tomatoes showed the lowest wilt incidence in oil and powder bioformulations from Ch. elatum ChE01, E. nidulans EN01, and to E. rugulosa ER01, which significantly differed from Prochoraz and inoculated control. The application of oil bioformulation from E. rugulosa could reduce wilt incidence, followed by application of powder bioformulation and Prochoraz, which also reduced wilt incidence. Based on the results, oil bioformulation from Ch. elatum ChE01, E. nidulans EN01, and E. rugulosa ER01 gave significantly better plant parameters in terms of plant height, plant weight, root weight, number of fruits, and fruit weight than powder bioformulation and Prochoraz when compared with the inoculated control with F. oxysporum f. sp. lycopersici. These new reports of bioformulation of Ch. elatum ChE01, E. nidulans EN01, and E. regulosa ER01 could be applied to control tomato wilt caused by F. oxysporm f. sp. lycopersici in the fields.