Morphology, pathogenicity and phylogeny of corn downy mildew fungi in Thailand

Name: Pattama Janruang

LCSH: Kasetsart University -- Dissertations. Ph.D. (Plant Pathology) 2020

Classification :.LCCS: SB608.M2

LCSH: Kasetsart University. -- Department of Plant Pathology -- Dissertations

LCSH: Corn -- Diseases and pests

LCSH: Fungal diseases of plants

LCSH: Downy mildew diseases

LCSH: Mildew

LCSH: Single nucleotide polymorphisms

Abstract: In Thailand, corn downy mildew has been reported to be caused by six species of fungi using morphological characteristics. The purposes of this study were (1) to identify the fungal species of corn downy mildew distributed in Thailand based on morphological and molecular identification (2) to determine the physiological races an genetic variation of corn downy mildew fungi occurred in different localities of Thailand (3) to screen the resistant of field corn varieties to different downy mildew fungal strains (races) in greenhouse condition and (4) to identify specific alleles of resistant source associated with corn downy mildew resistance in sweet corn and waxy corn varieties. The results showed that all fungal isolates possessed large, hyaline and long conidiophores with dichotomously branched, hyaline and oval to almost spherical conidia. The D1/D2 domains of 28S rDNA sequences analysis indicated that all sequences of this study were clustered with Peronosclerospora sp. sequences obtained from GenBank database with 86 % bootstrap value supporting, and they were separated from other Peronosclerospora species included P. sorghi. While, ITS1 rDNA based sequences analysis revealed that sequences of present study were grouped with sequences obtained from GenBank database including of P. maydis, P. australensis and P. sargae. On the other hand, based on cox 2 sequence analysis, six sequences of this study were clustered together with 99% bootstrap value and were separated from sequences of P. australensis, P. sargae, P. sorghi and other species. Therefore, based on morphological observation, pathogenicity test and DNA sequences analysis, the main corn downy mildew fungi distributed in Thailand should be recorded as P. maydis. The physiological races identification of corn downy mildew fungi on six differential corn varieties revealed that there were three physiological races. Kanchanaburi isolates had three races (races1, 2 and 3) that high genetic differentiation within population. This data correlated with the data of genetic variation using ISSRs markers showed ten groups with high genetic differentiation within population at 57 % (ɸPT = 0.429). Although, the present study suggested that the corn downy mildew fungi distributed in Thailand as P. maydis, the ISSR markers analysis indicated that there was genetic differentiation between P. maydis isolates from Thailand and Indonesia. Moreover, sixty-eight varieties of sweet corn and waxy corn identified highly significant SNPs located on chromosome 2, 5, and 9 based on 35,404 significant SNPs of disease response P values ≤0.05.

Kasetsart University. Office of the University Library

Address: Bangkok

Email: tdckulib@ku.ac.th

Name: Jintana Unartngam

Role: Thesis Advisor

Name: Sansern Jampatong

Role: Thesis CO-Advisor

Name: Sithichoke Tangphatsornruang

Role: Thesis CO-Advisor

Name: Patcharavipa Chaijuckam

Role: Thesis CO-Advisor

Created: 2020

Modified: 2025-08-02

Issued: 2025-08-02

วิทยานิพนธ์/Thesis

application/pdf

URL: https://www.lib.ku.ac.th/KUthesis/2563/pattama-jan-all.pdf

CallNumber: SB608.M2 .P38

eng

DegreeName: Doctor of Philosophy

Level: Doctoral Degraee

Descipline: Plant Pathology

Grantor: Kasetsart University

©copyrights Kasetsart University

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