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Two isolates of Trichoderma viride (L4 and S17A) were assessed for biological control of Allium white rot (AWR) with different onion accessions and cultivars, alone and in combination with a tebuconazole-based seed treatment or composted onion waste. In glasshouse tests, 23 new bulb-onion accessions from previous work to detect resistance to Sclerotium cepivorum showed no differences in susceptibility to AWR but, when combined with S17A, disease was reduced by up to two-thirds over all accessions. Trichoderma viride L4 and S17A also reduced the proportion of infected plants for five commercial bulb-onion cultivars and one advanced breeding line by at least one-third. Further glasshouse tests using a salad-onion cultivar showed that L4, S17A, tebuconazole or composted onion waste controlled AWR and at least halved the proportion of diseased plants. Combination treatments of T. viride with either tebuconazole or compost enhanced control and, in some treatments, disease was almost eliminated. In field trials, control of AWR by S17A was significant for 17 out of 18 individual or mixed bulb-onion accessions, with disease reduced overall by more than half. In another field experiment, S17A failed significantly to reduce AWR for two out of three commercial bulb-onion cultivars, while tebuconazole reduced the final proportion of AWR-infected plants over all cultivars from 0·47 to 0·09. Combining S17A and tebuconazole resulted in a similar level of AWR to using tebuconazole alone. The use of T. viride in an integrated strategy with other treatments to enhance control of S. cepivorum is discussed.

MycologyPhylogeny Systematics Taxonomy a b s t r a c t Novel species of Cercospora and Pseudocercospora are described from Australian native plant species. These taxa are Cercospora ischaemi sp. nov. on Ischaemum australe (Poaceae); Pseudocercospora airliensis sp. nov. on Polyalthia nitidissima (Annonaceae); Pseudocercospora proiphydis sp. nov. on Proiphys amboinensis (Amaryllidaceae); and Pseudocercospora jagerae sp. nov. on Jagera pseudorhus var. pseudorhus (Sapindaceae). These species were characterised by morphology and an analysis of partial nucleotide sequence data for the three gene loci, ITS, LSU and EF-1a. Recent divergence of closely related Australian species of Pseudocercospora on native plants is proposed.Crown

Khaya senegalensis (African mahogany or dry-zone mahogany) is a high-value hardwood timber species with great potential for forest plantations in northern Australia. The species is distributed across the sub-Saharan belt from Senegal to Sudan and Uganda. Because of heavy exploitation and constraints on natural regeneration and sustainable planting, it is now classified as a vulnerable species. Here, we describe the development of microsatellite markers for K. senegalensis using next-generation sequencing to assess its intra-specific diversity across its natural range, which is a key for successful breeding programs and effective conservation management of the species. Next-generation sequencing yielded 93,943 sequences with an average read length of 234 bp. The assembled sequences contained 1030 simple sequence repeats, with primers designed for 522 microsatellite loci. Twenty-one microsatellite loci were tested with 11 showing reliable amplification and polymorphism in K. senegalensis. The 11 novel microsatellites, together with one previously published, were used to assess 73 accessions belonging to the Australian K. senegalensis domestication program, sampled from across the natural range of the species. STRUCTURE analysis shows two major clusters, one comprising mainly accessions from west Africa (Senegal to Benin) and the second based in the far eastern limits of the range in Sudan and Uganda. Higher levels of genetic diversity were found in material from western Africa. This suggests that new seed collections from this region may yield more diverse genotypes than those originating from Sudan and Uganda in eastern Africa.