Seed health status and germination of Eucalyptus spp.
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Seed health status and germination of Eucalyptus spp. E. Mangwende & P. W. Chirwa & T. A. S. Aveling
Received: 18 March 2020 / Revised: 14 October 2020 / Accepted: 15 October 2020 # Koninklijke Nederlandse Planteziektenkundige Vereniging 2020
Abstract The presence of disease causing microorganisms on seeds raises serious quarantine and economic concerns to nurserymen, foresters and seed traders. The agar plate method was used to examine seed-borne mycoflora associated with Eucalyptus seed lots and their effect on seed germination was determined. A total of 35 fungal species from 29 genera were identified from 12 different Eucalyptus species. The Eucalyptus nitens seed lot was the most infested, whereas the lowest incidence of fungi was from the E. dorrigoensis seed lot. Penicillium was the most abundant fungus. Colletotrichum, Aureobasidium and Disculoides were recorded for the first time associated with Eucalyptus seeds. There was a significant reduction in seed germination of seed lots inoculated with selected seed-borne fungi compared to non-inoculated controls. Fusarium oxysporum and F. solani reduced seed germination the most on E. badjensis, E. dorrigoensis, E. nitens, E. pellita, E. teritecomis and E. urophylla seed lots with percentage germination of 31.3 and 33.5; 30.5 and 30.0; 38.8 and 37.0; 30.5 and 32.3; 25.0 and 26.8; 33.3 and 31.8; 31.3 and 33.5%, respectively. Similarly, seed germination was lowest on the E. benthamii seed lot (29.8%) inoculated with C. gloeosporioides, whilst E. Mangwende : P. W. Chirwa : T. A. S. Aveling Department of Plant and Soil Sciences, University of Pretoria, Pretoria 0002, South Africa E. Mangwende : T. A. S. Aveling (*) Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria 0002, South Africa e-mail: [email protected]
germination of E. grandis, E. smithii and E. viminalis seed lots inoculated with Botrytis sp. and F. solani were 37.0 and 37.5%; 35.8 and 36.3%; 28.3 and 30.0%, respectively. This study has shown that commercial Eucalyptus seed lots carry a wide diversity of fungi and suggests that infested seeds may be a primary reason for poor seed germination. Keywords Seed-borne . Seed germination . Colletotrichum . Disculoides . Fusarium
Introduction The ideal for foresters is to obtain high Eucalyptus seedling survival rates above 85% (Stape et al. 2001), but delay of seedling emergence and poor survival of seedlings remain a common nursery challenge. Several factors can reduce seedling emergence, among them is seed health status (Brown and Ferreira 2000; Lilja et al. 2010). In almost every harvested seed lot, chaff and other debris together with a variety of microorganisms are naturally present at least in small quantities (Boland et al. 1980). Seed-borne fungi can cause seed rot, delay seed germination or threaten establishment of plant stands due to pre- and/or post-emergence damping-off (Cram and Fraedrich 2010; Evira-Recuenco et al. 2015; Tobias et al. 2017). During processing or storage, infested seed batches may contami
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