Plant Foods for Human Nutrition 51: 311–320, 1997. c 1997 Kluwer Academic Publishers. Printed in the Netherlands. Evaluation of growth of Neosartorya spp. on some Nigerian fruit products J. A. N. OBETA and J. O. UGWUANYI Department of Microbiology, University of Nigeria, Nsukka, Nigera ( author for correspondence) Received 13 March 1997; accepted in revised form 31 October 1997 Abstract. Growth of Neosartorya fischeri, N. fischeri var. spinosa and N. quadricincta on inoculated fruit juice agars (FJAs) consisting of 1% agar and juices from mango (MJA), orange (OJA) and pineapple (PJA) containing various levels of added sucrose was studied in terms of the average number of colonies produced by their ascospores, time (days) required before colonies were formed and developed to confluent mycelial mat as well as the level of reproductive spores produced. The means of the number of colonies on PJA and OJA without added sucrose were significantly ( 0 05) higher than that of MJA. Addition of sucrose at levels of 10% to PJA, 11.5% to OJA and 9% to MJA increased the numbers of colonies whereas sucrose levels of 30% or more in PJA, 31.5% or more in OJA and 29% or more in MJA decreased the number of colonies produced. At any level of added sucrose to FJAs, a significant ( 0 05) delay occurred before the colonies were formed and developed to confluent mycelial mat except in PJA containing 10% sucrose. All cultures produced abundant cleistothecia on all FJAs without added sucrose. Addition of sucrose at levels of 30% to PJA, 31.5% to OJA and 29% to MJA resulted in the production of abundant conidial heads with a corresponding decrease in the proportion of cleistothecia. Key words: Growth, Mango, Orange, Pineapple juice agar, Neosartorya spp., Sucrose Introduction Byssochlamys spp., the earliest known heat-resistant molds, are widely dis- tributed in developed countries of the temperate region [1, 2]. In contrast, studies in Nigeria have not yet revealed the presence of Byssochlamys spp., although one of their anamorphs, Paecilomyces variotii, has been found in the soil and heat-processed mango juice [3–5]. The most frequently isolated heat- resistant fungi in Nigeria are the species of Neosartorya and their anamorphs, Aspergillus spp. [3, 4]. Strains of N. fischeri are important spoilage organ- isms of heat-processed fruits and fruit products [6, 7]. Their ascospores are extremely heat-resistant compared to those of other molds [8]. The growth and production of ascospores by the organism have been documented in devel- oped countries [9, 10] but not in Nigeria where the incidence of the mold in the soil samples ranges from 77% in the semi-arid North to 98% in the