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ARS Home » Research » Publications at this Location » Publication #148516
Title: A NEW STRAIN OF MUCOR ISOLATED FROM GUAVA FRUIT IN HAWAII

Author
item Nishijima, Kate
item CHAN, JR, HARVEY - RETIRED ARS EMPLOYEE
item NISHIJIMA, WAYNE - UH MANOA, COOP EXT SVC

Submitted to: Phytopathology
Publication Type: Other
Publication Acceptance Date: 4/22/2003
Publication Date: 6/1/2004
Citation: Nishijima, K.A., Chan, Jr, H.T., Nishijima, W.T. A new strain of Mucor isolated from guava fruit in Hawaii. 2004:Phytopathology 94(6)S153.

Interpretive Summary: Guava puree is one of the major products in the tropical fruit beverage industry in Hawaii. In 1997, a food quality concern of high mold counts in fresh guava puree from Kauai led to an investigation into the source and identification of the contaminant. A gray-colored strain of the fungus Mucor (GMS) was isolated from puree samples and was identified as Mucor hiemalis f. hiemalis Wehmer (identified by CABI, England), or M. hiemalis f. luteus (Linnemann) Schipper (identified by CBS, Netherlands). The GMS fungus was not found at the processing plant or it¿s equipment, but was isolated from the surface of non-wounded guava fruit in the field. In 1999 surveys using a fruit core bioassay technique, GMS occurred in 11-25% and 33-44% of guava fruit from the islands of Kauai and Hawaii, respectively. Inoculation, thermal and cultural studies indicated that GMS does not cause disease on artificially wounded guava fruit (Beaumont B-30) and GMS differs from the Muror rot pathogen, yellow-colored M. hiemalis. We conclude that GMS is a non-pathogenic fungus of guava fruit that occurs on the surface or in sub-surface tissue without producing rot symptoms and infested fruit are difficult to cull out during harvesting and processing.

Technical Abstract: Guava puree is one of the major products in the tropical fruit beverage industry in Hawaii. In 1997, concern over high mold counts (>103 cfu/g) in fresh guava puree from Kauai led to an investigation into the source and identification of the contaminant. A gray-colored Mucor strain (GMS), isolated consistently from puree samples and the surface of fruit in the field, was identified as M. hiemalis f. hiemalis Wehmer (CABI, England) or M. hiemalis f. luteus (Linnemann) Schipper (CBS, Netherlands). In 1999 surveys using a fruit core bioassay technique, GMS was isolated from 11-25% and 33-44% of guava fruit from the islands of Kauai and Hawaii, respectively. Inoculation, cultural, and thermal studies indicated that GMS is not pathogenic to artificially wounded guava fruit (Beaumont B-30) and differs morphologically and physiologically from the Mucor rot pathogen, yellow-colored M. hiemalis (YM). We conclude that GMS is an endophyte of guava fruit that inhabits exocarp and mesocarp tissue without producing decay symptoms and infested fruit are difficult to cull out during harvesting and processing.