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Title: ASPERGILLUS BOMBYCIS GENOTYPES (RFLP) FROM SILKWORM CULTIVATION

Author
item GOTO, TETSUHISA - NATL FOOD RES INST, JAPAN
item Wicklow, Donald
item McAlpin, Cesaria
item Peterson, Stephen

Submitted to: Mycoscience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2003
Publication Date: 4/15/2003
Citation: Goto, T., Wicklow, D.T., McAlpin, C.E., Peterson, S.W. 2003. Aspergillus bombycis genotypes (RFLP) from silkworm cultivation. Mycoscience. 44: 209-215. 2003

Interpretive Summary: Aspergillus bombycis is a recently described aflatoxin producing species known only from domesticated silkworm rearing facilities in southeast Asia and Japan, and there is a need to determine if one or more `domesticated' forms of A. bombycis are common to such facilities having been spread with the transfer of diseased silkworms. Aflatoxin has been linked to increased virulence in Aspergillus disease of silkworms. Cultures of A. bombycis were examined for their ability to produce aflatoxins, and then subjected to DNA fingerprinting. Among 18 isolates analyzed, each of which produced B and G aflatoxins, seven distinct DNA fingerprint groups were identified, including GTAb-2 isolated from silkworm rearing facilities in four Prefectures of Japan. This research provides evidence that some forms of A. bombycis have become highly adapted to silkworm cultivation environments in Japan and have been spread among these facilities. Silkworm rearing companies can use this method to monitor the distribution and abundance of these problematic A. bombycis populations.

Technical Abstract: Eighteen isolates of Aspergillus bombycis from samples of dust, insect frass, and soil collected from 8 silkworm rearing facilities in Japan, as well as single silkworm rearing facilities in Indonesia and Malaysia, were subjected to DNA fingerprinting. PstI digests of total genomic DNA from each isolate were probed using the pAF 28 repetitive sequence. Among 18 isolates analyzed, 7 distinct DNA fingerprint groups were identified, including GTAb-2 isolated from rearing facilities in four Prefectures of Japan. Aspergillus bombycis isolates share several features in common with domesticated yellow-green aspergilli, koji molds, used in traditional Oriental food fermentations, including a loose and deep colony texture, smooth-walled stipes, and the absence of sclerotia. While aflatoxin is unknown from koji molds, all isolates of A. bombycis produced B and G aflatoxins. Aflatoxin has been linked to increased virulence in Aspergillus disease of silkworms and there should be strong selection for aflatoxin production among clonal populations of A. bombycis adapted to silkworm cultivation. A hypothesis is offered that A. bombycis isolates from silkworm cultivation represent domesticated forms of yet to be discovered `wild' populations that may infect Bombyx mandarina.