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

Morphological and Molecular Characterization of Calonectria foliicola Associated with Leaf Blight on Rubber Tree (Hevea brasiliensis) in Thailand

“…Currently, the identification of fungal pathogens causing diseases in plants relies on both morphology and molecular techniques in addition to pathogenicity testing to determine whether Koch’s postulates are fulfilled [ 19 , 31 , 46 ]. The molecular details of multiple DNA sequences have been applied in identifying fungal species [ 42 , 43 ].…”

“…To test whether fungal isolates can cause disease in rubber tree leaves, pathogenicity testing was conducted according to the agar plug (0.5 mm) method [ 30 , 31 ] to determine fulfillment of Koch’s postulates. Healthy rubber tree leaves were disinfected using 70% ethanol.…”

A New Species of Neoscytalidium hylocereum sp. nov. Causing Canker on Red-Fleshed Dragon Fruit (Hylocereus polyrhizus) in Southern Thailand

“…A total of ten symptomatic samples were collected. The causal fungus was isolated using the tissue transplanting method [ 15 , 16 ]. The infected tissue samples were cut into small pieces (0.3 × 0.3 cm), and their surfaces were disinfected with 70% ethanol followed by 1% sodium hypochlorite (NaOCl).…”

Identification of New Fusarium sulawense Strains Causing Soybean Pod Blight in China and Their Control Using Carbendazim, Dipicolinic Acid and Kojic Acid

“…The three isolates were grown in 100 mL potato-dextrose broth (PDB; prepared as PDA medium but in the absence of agar) at 26 °C and 200 rpm in darkness for 48 h. The genomic DNA was extracted using the Ezup Column Fungi Genomic DNA Purification Kit (Sangon Biotech, China) according to the manufacturer’s instructions. Internal transcribed spacer ( ITS ) region of rDNA, elongation factor 1-α ( EF1-α ) and RNA polymerase II second largest subunit ( RPB2 ) partial sequences were amplified using the ITS1/ITS4 (5′-TCCGTAGCTGAACCTGCGG-3′ and 5′-TCCTCCGCTTATTGATATGC-3′, respectively), EF1-728F/EF1-986R (5′-CATCGAGAAGTTCGAGAAGG-3′ and 5′-TACTTGAAGGAACCCTTACC-3′, respectively) and fRPB2-7CF/fRPB2-11aR (5′-ATGGGYAARCAAGCYATGGG-3′ and 5′-GCRTGGATCTTRTCRTCSACC-3′, respectively) primers [ 27 , 28 , 29 ].…”