Penicillium species associated with barley grain in the U.K.

Abstract

Thirty-three Penicillium spp. and their teleomorphs, isolated from barley grain during ripening and subsequent storage, have been identified. Few species were isolated from the grain before harvest and these were mostly species characteristic of storage, but P. pedemontanum and Eupenicillium spp. (including E. shearit) were found only in the field. However, lodging could allow abundant development of P. hordei, P. granulatum and P. verrucosum var. cyclopium with probable penetration of grain tissue. P. hordei, P. piceum, P. roquefortii and P. verrucosum and its var. cyclopium were those most frequently isolated from stored grain. Penicillium spp., initially P. brevicompactum , increased only when grain was stored with more than 0.87 water activity ( a w ; = 18% water content). P. verrucosum occurred above 0.88 a w and other species were found as the water activity increased. Spontaneous heating occurred above 0.9 a w and limited growth of all except P. capsulatum, P. piceum, Talaromyces emersonii (P. emersonii) and T. thermophilus (P. dupontii). P. verrucosum became abundant when grain was incubated at 2–20 °C with 0.90 to 0.98 a w , and formed ochratoxin, especially at 0.98 a w and 10°. Restricting the aeration of stored grain enabled P. roquefortii to become abundant, especially at 1.00 a w causing the grain to become toxic.