Genotypic diversity in a South African population of the pitch canker fungus Fusarium subglutinans f.sp. pini

Abstract

The genotypic diversity in a South African population of Fusarium subglutinans f.sp. pini (F.s. pini) was determined, based on the number of vegetative compatibility groups (VCGs). Isolates of F.s. pini from South Africa (69), California (five) and Florida (19) were included in the study. The nit1 (or nit3) and NitM mutants were selected as chlorate resistant sectors and paired on minimal medium. The South African isolates of F.s. pini were assigned to 23 different VCGs. No heterokaryons formed between isolates from South Africa, California and Florida. The high degree of genotypic diversity in the South African population of F.s. pini is probably due to some level of sexual reproduction in the population.

Evidence for a new introduction of the pitch canker fungus Fusarium circinatum in South Africa

“…Together with F. circinatum isolates representing the known VCGs in South Africa (Viljoen et al ., ; Britz et al ., ), the AFLP analysis included an isolate representing each of the VCGs obtained from the WCP. In cases where a VCG was associated with both mating types or occurred in more than one location, representative isolates for both mating types and from all the locations were also included.…”

“…Clusters 1 and 2 (indicated by the digits at the nodes) were also recovered with the distance analysis employing the simple matching similarity coefficient (Kosman & Leonard, ). The W estern C ape P rovince ( WCP ) isolates from the three collection areas are indicated in yellow ( T okai), pink ( G eorge area) and blue ( WCP nursery), whilst those from nurseries elsewhere in S outh A frica (SA; Britz et al ., ; Viljoen et al ., ) or from the USA and M exico (Wikler & Gordon, ) are indicated in grey and green, respectively. In each case, the VCG designation is followed in parentheses by the representative isolate used to generate the AFLP data.…”

“…For comparative purposes, two additional sets of F. circinatum isolates were included. The first set of 27 isolates represented the known VCGs originally identified from nurseries elsewhere in South Africa (Viljoen et al ., ; Britz et al ., ). The second set of 42 isolates represented known VCGs from California (10 isolates), Florida (25 isolates) and Mexico (seven isolates) (Wikler & Gordon, ).…”

“…A set of isolates representing each of the different VCGs detected at each location in the WCP were subjected to AFLP analysis. The analysis also included representative isolates for VCGs from other parts of South Africa (Viljoen et al ., ; Britz et al ., ) and those from California, Florida and Mexico (Wikler & Gordon, ). The analysis was carried out as described by De Vos et al .…”

“…For this purpose a collection of F. circinatum isolates was obtained from diseased P. radiata seedlings in a nursery as well as from plantation trees. To determine their possible origin(s), this collection of isolates was compared with representative isolates obtained from diseased seedlings elsewhere in the country (Viljoen et al ., ; Britz et al ., ), as well as the USA and Mexico (Wikler & Gordon, ). Comparisons were made using vegetative compatibility group (VCG) assays (Leslie & Summerell, ) and amplified fragment length polymorphism (AFLP) analysis (Vos et al ., ).…”