Variation in growth rates and aggressiveness of naturally occurring self-fertile and self-sterile isolates and the wilt pathogen Ceratocystis albifundus

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Authors

Lee, Dong Hyeon
Roux, Jolanda
Wingfield, Brenda D.
Wingfield, Michael J.

Journal Title

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Volume Title

Publisher

Wiley

Abstract

Ceratocystis albifundus is the most important fungal pathogen of black wattle (Acacia mearnsii) grown in plantations in southern and eastern Africa. It is a homothallic fungus but also undergoes unidirectional mating type switching. As a result, the ascospore progeny can be either self-fertile or self-sterile. The only apparent difference between these mating types is the deletion of the MAT1-2-1 gene in self-sterile isolates. There is some evidence suggesting that self-sterile isolates grow more slowly than self-fertile isolates, but this has not been tested rigorously. The aim of this study was to determine whether self-sterile isolates are less fit by examining growth rate, relative germination rate and pathogenicity. Five self-sterile isolates were generated from each of five self-fertile isolates of C. albifundus and these 30 isolates were compared. The results showed that the self-sterile isolates grew consistently slower and were less pathogenic than the self-fertile isolates. The germination ratio of self-fertile to self-sterile isolates from single ascospores collected from the ascomata of five self-fertile isolates was on average 7:3. This could be a consequence of the self-sterile isolates having a lower germination rate. This observation, and the lower growth and pathogenicity levels, suggests that self-sterile isolates are not likely to compete effectively in nature, raising intriguing questions regarding their role and value to C. albifundus and other fungi having a similar mating system.

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Keywords

Ceratocystis albifundus, Fitness, Self-fertile mating type, Self-sterile mating type, Black wattle (Acacia mearnsii)

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Citation

Lee, DH, Roux, J, Wingfield, BD & Wingfield, MJ 2015, 'Variation in growth rates and aggressiveness of naturally occurring self-fertile and self-sterile isolates and the wilt pathogen Ceratocystis albifundus', Plant Pathology, vol. 64, no. 5, pp. 1103-1109.