Endophytes as potential pathogens of the baobab species Adansonia gregorii: a focus on the Botryosphaeriaceae

Abstract

Adansonia gregorii (baobab) is an iconic tree species occurring in the NW of Australia. Dying baobabs, A. digitata, have been reported from southern Africa and as A. gregorii is closely related to A. digitata, surveys were conducted to assess the health of the Australian baobab. The endophytic microflora of A. gregorii and surrounding tree species was sampled and the ability of these endophytes to cause disease in A. gregorii was determined. Endophytes were isolated from asymptomatic baobabs across 24 sites in the Kimberley region, north-west Australia (NW Australia). Material was also taken from surrounding native tree species at three sites. Material was also collected from asymptomatic and dying Adansonia species in the George Brown Darwin Botanic Gardens and from a dying baobab in a nursery in Broome. Endophytic fungi isolated from these samples were identified using morphological and molecular methods.Eleven botryosphaeriaceous species were identified along with 18 other nonbotryosphaeriaceous species; L. theobromae 1 was the most common species. The pathogenicity of the botryosphaeriaceous species to baobabs was determined by inoculating the taproot of seedlings and stems of young baobab trees. Lasiodiplodia theobromae was confirmed as a potentially significant pathogen of baobabs.2

Botryosphaeriaceae species overlap on four unrelated, native South African hosts

“…For example, C. africana had the most diverse assemblage of these fungi while S. lancea had the lowest level of diversity. These results are similar to the study of Sakalidis et al (2011a) where 11 Botryosphaeriaceae species were found on both Adansonia gregorii and native surrounding trees at three sites in Australia. In that study, each host showed a different Botryosphaeriaceae species diversity.…”

“…In this study, S. viticola was isolated from three different families of trees Fabaceae, Cannabaceae and Celastraceae but not from the Anacardiaceae. Although some previous studies have considered larger numbers of potential host plants and were conducted over larger areas (Sakalidis et al 2011a;Taylor et al 2009), patterns of host association were not clear. For example, Sakalidis et al (2011a) showed that at one site, Pseudofusicoccum kimberleyense overlapped on hosts residing in three families (Fabaceae, Myrtaceae and Moraceae), but similar levels of overlap were not observed at other sites.…”

“…Although some previous studies have considered larger numbers of potential host plants and were conducted over larger areas (Sakalidis et al 2011a;Taylor et al 2009), patterns of host association were not clear. For example, Sakalidis et al (2011a) showed that at one site, Pseudofusicoccum kimberleyense overlapped on hosts residing in three families (Fabaceae, Myrtaceae and Moraceae), but similar levels of overlap were not observed at other sites. Taylor et al (2009) showed similar results with Aplosporella yalgorensis that were found on two tree species E. gomphocephala (Myrtaceae) and Acacia cochlearis (Fabaceae) at one site but it was not found on these trees at another sampling location.…”

“…were infected only by one species. Furthermore, the overlapping seven species was inconsistently found on hosts at the various sites (Sakalidis et al 2011a). Taylor et al (2009) showed similar results where some native Australian trees were hosts to numerous Botryosphaeriaceae while other native trees were host to only a single species.…”

Characterization of Phytophthora hybrids from ITS clade 6 associated with riparian ecosystems in South Africa and Australia

“…PCR and sequencing reactions were purified either by sodium acetate and ethanol precipitation 190 (Zeugin and Hartley 1985) or using sephadex, as described previously (Sakalidis et al 2011). PCR 191 amplicons were sequenced in both directions using the T7 and SP6 primers.…”