Biodiversity of exserohilum turcicum leonard and suggs causing Northern corn leaf blight in Thailand

ความหลากหลายทางชีวภาพของเชื้อรา exserohilum turcicum leonard and suggs สาเหตุโรคใบไหม้แผลใหญ่ของข้าวโพดในประเทศไทย

Name: Sutthipong Wathaneeyawech

ThaSH: Corn -- Diseases and pests

Classification :.DDC: 632.3072

ThaSH: Plant diseases

Abstract: Northern Corn Leaf Blight (NCLB) disease caused by exserohilum turcicum is one of the most important diseases, damaging the corn worldwide. Symptoms normally start with a small water soaked spot with greenish gray and later turn to brownish yellow lesion, spindle shaped with the size of 1.5-2.0 x 10-15 cm., and the lesions expand and merging together to form larger lesions, the whole leaf showing necrosis and turn to blight. Under highly humid condition, dust-liked black spores can be lound on the lesions. Single spore isolations from diseased leaves were made and had pure cultures of 381 isolates from the samples collected from I I Nonhern provinces and 97 isolates from 6 Northeastern provinces in Thailand. The morphological studies showed that the conidia are spindle-shaped with slightly curve end, 3-8 septa, with 20±1 I .36x I 05± 2.25 µmin siLe. Single conidiumis formed at the tip of the 2-4 septate, olive green conidiophores with 7-9x 150-250 µ111 insize. The distinct protruding hilum found is typical of£. turcicum. Studying growth and sporulation of E. turcicum on 8 culture media e.g. CLIA CMA, MEA, OMA, PDA, PDYeA, RBA and V-8 agar, under 3 conditiuns ; I) natural light 2) fluorescent light and 3) nUV light. Results showed that the maximum growth vvas on PDA, but the best sporulation was onV-8 agar. Effect of temperature on the fungal development was conducted by culturing the fungus on PDA, RBA, and V-8 in the gradient temperature chamber from which best growth was achieved on PDA at 30° C and maximum sporulation was on V-8 agar at 24° C. Fungal toxin was obtained by using ethyl acetate for extraction of the culture in I JDB by rotary evaporator. Crude extract dissolved 111 water at the concentu1Lion of I: I (v/v) were sprayed on the 14 days old susceptible sweet corn plant. 1-lilrix 3, anu the similar lesions of NCLB were observed at 7 days after spraying. Three inoculation techniques I) spraying spore suspensiun 2) dusting spores on the leaves and 3) placing culture Jisc on the leaves, were compared. Results showed that all treatments giving clear NCLB-like symptoms. But sp1aying gave most satisfactory result because the symptoms spreaded throughout the plant. Host range was tested on 22 different Poaceae members and 21 specieswere inlected by E. 1urcic11111 only the sugarcane was found to be non-host of this pathogen. Pathogenicity test was conducted by inoculating 96 isolates of£. 1urcic11111 on corn Hibrix3. Results f rom grading symptom severity are at 4 levels i.e. HR, MR, MS and S. The most virulent isolate HI and isolate KL I were used for field screening test on 160 corn varieties. It was found that only 9 varieties were resistant to both isolates. Efficacy of five fungicides ; azoxystrobin, chlorothalonil, mancozeb, propineb and propiconazole mixed with PDA on growth inhibition of the fungus at 3 concentration levels ; recommended rate, higher anJ lower than recommended rate by hall ; was tested in the laboratory. Results showed that every concentration of tested fungicides could inhibit growth at 97.1-100% compared to controls. AFLP technique was applied for the biodiversity study of 96 isolates of E. turcicum using T-A primer. Results showed 8 distinct bands of polymorphisms that tell the significant difference. However, after grouping by the NYSYS-PCprogram, al1 96 isolates were clustered in the same group. This study can make understanding on suitable factors for growth and sporulation of the fungal pathogen, differences on pathogenicity of fungal isolates and host range, effect of toxin on disease development and effectiveness of fungicides for control of the disease. This can be used for setting up plan for disease control and breeding for resistant variety.

Chiang Mai University. Library

Address: CHIANG MAI

Email: cmulibref@cmu.ac.th

Name: Nuchnart Jonglaekha

Role: Chairperson

Name: Suchada Vearasilp

Role: Member

Name: Prasaiiporn Smitamana

Role: Member

Name: Pornchai Lueang-a-papong

Role: Member

Name: Sarunya Valyasevi

Role: Member

Created: 2013

Modified: 2023-01-22

Issued: 2023-01-22

วิทยานิพนธ์/Thesis

application/pdf

CallNumber: Th 632.3072 S967B

eng

DegreeName: Doctor of Philosophy

Descipline: Biotechnology

Grantor: Chiang Mai University

©copyrights Chiang Mai University

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