Genetic analysis of growth, morphology and pathogenicity in the F 1 progeny of an interspecific cross between Fusarium circinatum and Fusarium subglutinans Lieschen DE VOS*, Magriet A. VAN DER NEST, Nicolaas A. VAN DER MERWE, Alexander A. MYBURG, Michael J. WINGFIELD, Brenda D. WINGFIELD Department of Genetics, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Lunnon Road, Hillcrest, Pretoria 0001, South Africa article info Article history: Received 5 April 2011 Received in revised form 4 July 2011 Accepted 6 July 2011 Available online 19 July 2011 Corresponding Editor: Michael Lorenz Keywords: Fusarium circinatum Fusarium subglutinans Interspecific cross Mycelial growth Pathogenicity QTLs abstract Fusarium circinatum and Fusarium subglutinans are two distinct species in the Gibberella fuji- kuroi species complex. A genetic linkage map produced from an interspecific cross between these species was used to identify quantitative trait loci (QTLs) associated with variation in mycelial growth and morphology of colony margins (CMs) in the 94 F 1 progeny. Mycelial growth was assessed by measuring culture size at 25  C and 30  C, while CM morphology was characterized in the parents and assessed in their F 1 progeny. In order to test the path- ogenicity of the progeny, Pinus patula seedlings were inoculated and lesion lengths were measured after 3 weeks. Seven putative QTLs were associated with mycelial growth, three for growth at 25  C and four at 30  C. One highly significant QTL (P < 0.001) was present at both growth temperatures. For CM morphology, a QTL was identified at the same position (P < 0.001) as the QTL responsible for growth at the two temperatures. The putative QTLs accounted for 45 and 41 % of the total mycelial growth variation at 25  C and 30  C, respec- tively, and for 21 % of the variation in CM morphology. Only one of the 94 F 1 progeny was pathogenic on P. patula seedlings. This observation could be explained by the genetic con- stitution of this F 1 isolate, namely that w96 % of its genome originated from the F. circina- tum parent. This F 1 individual also grew significantly faster at 25  C than the F. circinatum parent (P < 0.05), as well as more rapidly than the average growth for the remaining 93 F 1 progeny (P < 0.05). However, no association was found between mycelial growth and path- ogenicity at 25  C. The highly significant QTL associated with growth at two temperatures, suggests that this is a principal genomic region involved in mycelial growth at both tem- peratures, and that the same region is also responsible for CM morphology. ª 2011 British Mycological Society. Published by Elsevier Ltd. All rights reserved. Introduction Fusarium circinatum and Fusarium subglutinans are distinct fun- gal taxa that reside in the Gibberella fujikuroi species complex (Nelson et al. 1983; Nirenberg & O’Donnell 1998). This complex includes economically important pathogens of crops and trees. Based on the biological species concept, F. circinatum resides in mating population H (Nirenberg & O’Donnell 1998; Britz et al. 1999) and F. subglutinans in mating population E(Nelson et al. 1983). * Corresponding author. Tel.: þ27 12 420 3948; fax: þ27 12 420 3947. E-mail addresses: lbahlman@fabi.up.ac.za, magriet.vandernest@fabi.up.ac.za, albe.vdmerwe@fabi.up.ac.za, zander.myburg@ fabi.up.ac.za, mike.wingfield@fabi.up.ac.za, brenda.wingfield@fabi.up.ac.za journal homepage: www.elsevier.com/locate/funbio fungal biology 115 (2011) 902 e908 1878-6146/$ e see front matter ª 2011 British Mycological Society. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.funbio.2011.07.003