Isolation and Identification of Fungal Species from the Insect Pest Tribolium castaneum in Rice Processing Complexes in Korea

Abstract

The red flour beetle, Tribolium castaneum, is one of the most common and economically important pests of stored cereal products worldwide. Furthermore, these beetles can act as vectors for several fungal post-harvest diseases. In this study, we collected T. castaneum from 49 rice processing complexes (RPCs) nationwide during 2016-2017 and identified contaminating fungal species on the surface of the beetles. Five beetles from each region were placed on potato dextrose agar media or Fusarium selection media after wet processing with 100% relative humidity at 27°C for one week. A total of 142 fungal isolates were thus collected. By sequence analysis of the internal transcribed spacer region, 23 fungal genera including one unidentified taxon were found to be associated with T. castaneum. The genus Aspergillus spp. (28.9%) was the most frequently present, followed by Cladosporium spp. (12.0%), Hyphopichia burtonii (9.2%), Penicillium spp. (8.5%), Mucor spp. (6.3%), Rhizopus spp. (5.6%), Cephaliophora spp. (3.5%), Alternaria alternata (2.8%) and Monascus sp. (2.8%). Less commonly identified were genera Fusarium, Nigrospora, Beauveria, Chaetomium, Coprinellus, Irpex, Lichtheimia, Trichoderma, Byssochlamys, Cochliobolus, Cunninghamella, Mortierella, Polyporales, Rhizomucor and Talaromyces. Among the isolates, two known mycotoxin-producing fungi, Aspergillus flavus and Fusarium spp. were also identified. This result is consistent with previous studies that surveyed fungal and mycotoxin contamination in rice from RPCs. Our study indicates that the storage pest, T. castaneum, would play an important role in spreading fungal contaminants and consequently increasing mycotoxin contamination in stored rice.

Keywords: Tribolium castaneum; fungi; mycotoxin; rice processing complexes.

Fig. 1

Collation map of fungal isolates from the insect pest Tribolium castaneum in rice processing complexes (RPCs) during 2016 to 2017 in Korea. (A) Distribution map of 49 RPCs in Korea. The 49 RPCs are indicated by gray circles. The name of RPCs are noted by two capitalized letter just below the gray circles. The blue-colored letter indicates 8 provinces in Korea and two capitalized letters in parentheses indicates the abbreviation of provinces (See Table 1). The obtained fungal isolates and distribution map from (B) the first round (44 isolates from 17 RPCs), (C) the second round (46 isolates from 22 RPCs), and (D) the third round (52 isolates from 26 RPCs) of collection. The yellow colored circles indicates the location that obtained fungal isolates from the collected T. castaneum. A total number of fungal isolates is noted in the yellow colored circles. The percentage distribution of different fungal isolates from (E) the first round, (F) the second round, and (G) the third round of collection.

Fig. 2

Summary of fungal isolates from Tribolium castaneum. (A) Distribution map of 142 fungal isolates were identified from 40 RPCs. (B) The percentage distribution of different fungal isolates among the collected 142 isolates between April 2016 and August 2017. Distribution map of (C) Aspergillus flavus (collected from 12 RPCs), (D) Aspergillus spp. (16 RPCs) (E) Penicillum spp. (9 RPCs), Alternaria alternate and Fusarium spp. were collected from T. castaneum in this study. The number in the circles indicates a total number of identified isolates.