Diversity and species overlap of Botryosphaeriaceae on some trees of Anacardiaceae in disturbed and undisturbed ecosystems in South Africa
The Botryosphaeriaceae are common and diverse on native and non-native plants. It has been established that the ability of Botryosphaeriaceae fungi to exist in healthy plant tissues as endophytes facilitates their global movement during the international trade of plants and plant products. It is important to understand whether fungi in the Botryosphaeriaceae have a restricted host range or a limited geographic distribution once introduced into new areas, and how ecosystem disturbances through human activities influence species diversity and distribution of fungi in the Botryosphaeriaceae. The current study explored Botryosphaeriaceae species diversity on native and non-native tree species of Anacardiaceae found in disturbed and undisturbed ecosystems, as well as species overlap of the Botryosphaeriaceae as endophytes and as pathogens in asymptomatic and symptomatic tissues of these trees. In addition, the genetic diversity and population structure of N. parvum, the dominant species occurring on asymptomatic mango fruit were assessed. These questions were addressed by sampling three tree species of Anacardiaceae, namely Sclerocarya birrea (marula), Mangifera indica (mango) and Lannea Schweinfurthii (false marula) in disturbed and undisturbed ecosystems in the Limpopo and Mpumalanga provinces, South Africa. The ecosystem disturbance study identified 11 species of Botryosphaeriaceae, namely Diplodia allocellula, Dothiorella brevicollis, Dothiorella dulcispinae, Dothiorella viticola, Lasiodiplodia crassispora, Lasiodiplodia exigua, Lasiodiplodia gonubiensis, Lasiodiplodia mahajangana, Neofusicoccum parvum, Oblongocollomyces ednahkunjekuae and Oblongocollomyces sp. 1 occurring on native and non-native Anacardiaceae in disturbed and undisturbed ecosystems. Ten of the 11 species were identified on trees in undisturbed ecosystems, while three were identified on trees in disturbed ecosystems. Lasiodiplodia crassispora and L. mahajangana were generalists on trees in disturbed and undisturbed ecosystems. The results from this study also indicated the ability of some species to cross-infect native and non-native Anacardiaceae growing next to each other. For example, N. parvum isolates occurred on both S. birrea (a native species) and M. indica (a non-native species) trees adjacent to each other in disturbed ecosystems. An investigation on species occurrence of the Botryosphaeriaceae as endophytes and as pathogens on the Anacardiaceae identified 12 species of Botryosphaeriaceae, D. allocellula, Dothiorella brevicollis, Do. dulcispinae, Do. viticola, Lasiodiplodia crassispora, L. exigua, L. gonubiensis, L. mahajangana, L. pseudotheobromae, Neofusicoccum parvum, Oblongocollomyces ednahkunjekuae and Oblongocollomyces sp. 1 in asymptomatic and symptomatic tissues. Dothiorella dulcispinae, L. exigua, L. gonubiensis, Oblongocollomyces ednahkunjekuae and Oblongocollomyces sp. 1 were exclusive to asymptomatic Anacardiaceae, while D. allocellula, Do. brevicollis, Do. viticola, L. crassispora, L. mahajangana and N. parvum occurred in asymptomatic and symptomatic Anacardiaceae indicating the ability to occupy healthy plant tissues as latent opportunistic pathogens on these trees. The N. parvum population genetics data was assessed based on nine microsatellite markers. This study indicated that the N. parvum population consists of three distinct genetic clusters characterized by high levels of genetic diversity. The three clusters were not correlated to host or geographic location indicating the lack of barrier on the movement of the fungus between the hosts and locations sampled. The study highlights the potential of mango fruit to serve as a source of international spread of Botryosphaeriaceae, especially of N. parvum.
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