The mating efficiency of 50 Aspergillus fumigatus isolates from both clinical and environmental sources was analyzed. Forty isolates completed the sexual cycle in 4 weeks with variable levels of fertility designated high, medium, or low. Two opposite-mating-type strains exhibiting the highest fertility, AFB62 (MAT1-1), isolated from a case of invasive aspergillosis, and AFIR928 (MAT1-2), isolated from the environment, were chosen as the supermater pair. Single cleistothecia obtained from a cross of the two strains harbored a minimum of 1 × 104 ascospores. The viability of ascospores increased with the age of the fruiting body, 17% at 4 weeks and reaching 95% at 20 weeks. AFB62 and AFIR928 were equally virulent in two different murine models, despite differences in their sources. High recombination frequencies were observed when the closely linked genes alb1 (AFUA-2G17600) and abr2 (AFUA-2G17530) were used as genetic markers. Comparative genome hybridization analyses revealed that only 86 genes (ca. 0.86% of the genome) are significantly diverged between AFB62 and AFIR928. The high fertility in a relatively short period, combined with a high degree of virulence and a high recombination frequency, demonstrates that the mating pair AFB62 and AFIR928 provides an excellent tool for genetic studies of A. fumigatus.
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