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. 2022 Mar 23;8(4):335.
doi: 10.3390/jof8040335.

Morphological and Molecular Identification of Plant Pathogenic Fungi Associated with Dirty Panicle Disease in Coconuts (Cocos nucifera) in Thailand

Anurag Sunpapao  1 , Nakarin Suwannarach  2 , Jaturong Kumla  2 , Reajina Dumhai  3 , Kanamon Riangwong  4 , Sunisa Sanguansub  5 , Samart Wanchana  6 , Siwaret Arikit  7
Affiliations

Affiliations

  • 1 Agricultural Innovation and Management Division (Pest Management), Faculty of Natural Resources, Prince of Songkla University, Songkhla 90110, Thailand.
  • 2 Research Center of Microbial Diversity and Sustainable Utilization, Chiang Mai University, Chiang Mai 50200, Thailand.
  • 3 Rice Science Center, Kamphaeng Saen Campus, Kasetsart University, Nakhon Pathom 73140, Thailand.
  • 4 Department of Biotechnology, Faculty of Engineering and Industrial Technology, Sanamchandra Palace Campus, Silpakorn University, Nakhon Pathom 73000, Thailand.
  • 5 Department of Entomology, Faculty of Agriculture at Kamphaeng Saen, Kamphaeng Saen Campus, Kasetsart University, Nakhon Pathom 73140, Thailand.
  • 6 National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), Pathum Thani 12120, Thailand.
  • 7 Department of Agronomy, Faculty of Agriculture at Kamphaeng Saen, Kamphaeng Saen Campus, Kasetsart University, Nakhon Pathom 73140, Thailand.

Morphological and Molecular Identification of Plant Pathogenic Fungi Associated with Dirty Panicle Disease in Coconuts (Cocos nucifera) in Thailand

Anurag Sunpapao et al. J Fungi (Basel). .
. 2022 Mar 23;8(4):335.
doi: 10.3390/jof8040335.

Authors

Anurag Sunpapao  1 , Nakarin Suwannarach  2 , Jaturong Kumla  2 , Reajina Dumhai  3 , Kanamon Riangwong  4 , Sunisa Sanguansub  5 , Samart Wanchana  6 , Siwaret Arikit  7

Affiliations

  • 1 Agricultural Innovation and Management Division (Pest Management), Faculty of Natural Resources, Prince of Songkla University, Songkhla 90110, Thailand.
  • 2 Research Center of Microbial Diversity and Sustainable Utilization, Chiang Mai University, Chiang Mai 50200, Thailand.
  • 3 Rice Science Center, Kamphaeng Saen Campus, Kasetsart University, Nakhon Pathom 73140, Thailand.
  • 4 Department of Biotechnology, Faculty of Engineering and Industrial Technology, Sanamchandra Palace Campus, Silpakorn University, Nakhon Pathom 73000, Thailand.
  • 5 Department of Entomology, Faculty of Agriculture at Kamphaeng Saen, Kamphaeng Saen Campus, Kasetsart University, Nakhon Pathom 73140, Thailand.
  • 6 National Center for Genetic Engineering and Biotechnology (BIOTEC), National Science and Technology Development Agency (NSTDA), Pathum Thani 12120, Thailand.
  • 7 Department of Agronomy, Faculty of Agriculture at Kamphaeng Saen, Kamphaeng Saen Campus, Kasetsart University, Nakhon Pathom 73140, Thailand.

Abstract

Dirty panicle disease in coconuts (Cocos nucifera) was first observed in the KU-BEDO Coconut BioBank, Nakhon Pathom province, Thailand. The occurrence of the disease covers more than 30% of the total coconut plantation area. The symptoms include small brown to dark brown spots and discoloration of male flowers. Herein, three fungal strains were isolated from infected samples. Based on the morphological characteristics the fungal isolates, they were classified into two genera, namely, Alternaria (Al01) and Fusarium (FUO01 and FUP01). DNA sequences of internal transcribed spacer (ITS), glyceraldehyde 3-phosphate dehydrogenase (GAPDH), translation elongation factor 1-α (tef1-α), and RNA polymerase II second largest subunit (rpb2) revealed Al01 as Alternaria burnsii, whereas DNA sequences of ITS, rpb2, and tef1-α identified FUO01 and FUP01 as Fusarium clavum and F. tricinctum, respectively. A pathogenicity test by the agar plug method demonstrated that these pathogens cause dirty panicle disease similar to that observed in natural infections. To the best of our knowledge, this is the first report on the novel dirty panicle disease in coconuts in Thailand or elsewhere, demonstrating that it is associated with the plant pathogenic fungi A. burnsii, F. clavum, and F. tricinctum.

Keywords: flower discoloration; fungi; molecular techniques; morphology; pathogenicity test.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1

Figure 1

Dirty panicle disease observed on…

Figure 1

Dirty panicle disease observed on coconuts in KU-BEDO Coconut BioBank: Discoloration of male…

Figure 1
Dirty panicle disease observed on coconuts in KU-BEDO Coconut BioBank: Discoloration of male flowers (A) and zoomed-in view of infected flowers (B), flower drop (C), and infected panicles (D,E).
Figure 2

Figure 2

Pathogenicity test of Alternaria sp.…

Figure 2

Pathogenicity test of Alternaria sp. and Fusarium sp. on coconut panicles: Control group…

Figure 2
Pathogenicity test of Alternaria sp. and Fusarium sp. on coconut panicles: Control group (A), coconut panicles inoculated with Alternaria sp. Al01 (B), Fusarium sp. FUO01 (C), and Fusarium sp. FUP01 (D).
Figure 3

Figure 3

General morphology of Alternaria sp.…

Figure 3

General morphology of Alternaria sp. (Al01): Colony on PDA from the top ( …

Figure 3
General morphology of Alternaria sp. (Al01): Colony on PDA from the top (A) and bottom view (B); hyphae and diverse shape of conidia (C–G).
Figure 4

Figure 4

General morphology of Fusarium sp.…

Figure 4

General morphology of Fusarium sp. FUO01 ( A – D ) and FUP01…

Figure 4
General morphology of Fusarium sp. FUO01 (A–D) and FUP01 (E–H): Colony on PDA from the top (A,E) and bottom view (B,F); hyphae and diverse shape of conidia (C,D,G,H).
Figure 5

Figure 5

Phylogram derived from the maximum…

Figure 5

Phylogram derived from the maximum likelihood analysis of 18 taxa of the combined…

Figure 5
Phylogram derived from the maximum likelihood analysis of 18 taxa of the combined ITS, GAPDH, tef1, and rpb2 sequences. Curvularia arcana CBS 127224 and C. moringae CPC 38873 were used as the outgroups. The numbers above the branches represent bootstrap percentages (left) and Bayesian posterior probabilities (right). Bootstrap values ≥75% and Bayesian posterior probabilities ≥0.90 are shown. The scale bar represents the expected number of nucleotide substitutions per site. The sequence of the fungal species obtained in this study is in red. The type species are in bold.
Figure 6

Figure 6

Phylogram derived from the maximum…

Figure 6

Phylogram derived from the maximum likelihood analysis of 23 taxa of the combined…

Figure 6
Phylogram derived from the maximum likelihood analysis of 23 taxa of the combined ITS, rpb2, and tef1 sequences. Nectria eustromatica CBS 121896 and N. mariae CBS 125294 were used as the outgroups. The numbers above the branches represent bootstrap percentages (left) and Bayesian posterior probabilities (right). Bootstrap values ≥75% and Bayesian posterior probabilities ≥0.90 are shown. The scale bar represents the expected number of nucleotide substitutions per site. The sequences of the fungal species obtained in this study are in red. The type species are in bold.
See this image and copyright information in PMC

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