Botryosphaeriaceae species overlap on four unrelated, native South African hosts

Abstract

The Botryosphaeriaceae represents an important and diverse family of latent fungal pathogens of woody plants. While some species appear to have wide host ranges, others are reported only from single hosts. It is, however, not clear whether apparently narrow host ranges reflect specificity or if this is an artifact of sampling. We address this question by sampling leaves and branches of native South African trees from four different families, including Acacia karroo (Fabaceae), Celtis africana (Cannabaceae), Searsia lancea (Anacardiaceae) and Gymnosporia buxifolia (Celastraceae). As part of this process, two new species of the Botryosphaeriaceae, namely Tiarosporella africana sp. nov. and Aplosporella javeedii sp. nov., emerged from sequence comparisons based on the ITS rDNA, TEF-1α, β-tubulin and LSU rDNA gene regions. An additional five known species were identified including Neofusicoccum parvum, N. kwambonambiense, Spencermartinsia viticola, Diplodia pseudoseriata and Botryosphaeria dothidea. Despite extensive sampling of the trees, some of these species were not isolated on many of the hosts as was expected. For example, B. dothidea, which is known to have a broad host range but was found only on A. karroo. This could have resulted from the fact that it is a rare species in the region. With the exception of S. lancea, which was infected by A. javeedii all the hosts were infected by more than one Botryosphaeriaceae species. Collectively, the results suggest that some intrinsic host factors, possibly combined with local environmental conditions, affect the distribution and co-infectivity of various hosts by the Botryosphaeriaceae. 2This would counteract the general ability of a species in the Botryosphaeriaceae to infect a broad range of plants. The combination of host and environmental factors might also explain why some Botryosphaeriaceae with apparently broad host ranges, are found on different suites of hosts in different areas of the world.

Overlap of latent pathogens in the Botryosphaeriaceae on a native and agricultural host

“…Of these, been isolated previously from other hosts in the country, including both native (Jami et al 2012(Jami et al , 2014Mehl et al 2011;Pavlic et al 2007) and non-native (Begoude et al 2010;Damm et al 2007;Mehl et al 2014;Pavlic et al 2007;van Niekerk et al 2004) trees. This is, however, the first time that any of them have been recorded from S. birrea.…”

“…Examples include B. fabicerciana that was first described in China from Eucalyptus species (Chen et al 2011) and has been recorded from M. indica trees in Brazil (Marques et al 2013), and L. theobromae that has been recovered from various native tree hosts and non-native fruit trees in South Africa (Jami et al 2014). Apart from these, L. crassispora is possibly also alien as it was first described from Santalum album in Western Australia and Eucalyptus urophylla in Acarigua, Venezuela (Burgess et al 2006a), and is also known to infect grapevine in California, USA (Úrbez-Torres et al 2010).…”

“…Most of the Botryosphaeriaceae isolated in this study are capable of infecting both S. birrea and M. indica simultaneously, including Botryosphaeria dothidea, L. crassispora, L. theobromae, N. mediterraneum, and N. parvum. Previous studies have noted the ability of these fungi to infect multiple tree species concurrently, including natives and non-natives (Begoude et al 2012;Jami et al 2014;Sakalidis et al 2011). Added to this is the concern of introducing novel genotypes of a species already present in an area, which can become established and/or recombine with other genotypes already present to produce novel genotypes capable of infecting naïve hosts (Gladieux et al 2015).…”

“…These fungi infect plants via wounds or through natural plant openings such as buds, lenticels and stomata . Many species in the family have a wide range of plant hosts, including commercial fruit crops (Chen et al 2014;Slippers et al 2005;van Niekerk et al 2004), forest trees (Burgess et al 2006b;Slippers et al 2009), and plants in native woody ecosystems (Jami et al 2014;Mehl et al 2011;Pavlic et al 2007). These fungi occur in healthy plant tissues as latent pathogens and persist endophytically until stress occurs, after which disease symptoms can manifest .…”

“…Since many of the Botryosphaeriaceae have broad host ranges (Jami et al 2014;Slippers and Wingfield 2007), these fungi can spread to and infect both related and unrelated plants. There are many examples of interhost exchanges of the Botryosphaeriaceae, and these include those amongst and between native and non-native trees.…”