Evidence that dicot-infecting mastreviruses are particularly prone to inter-species recombination and have likely been circulating in Australia for longer than in Africa and the Middle East

Viruses of the genus Mastrevirus (family Geminiviridae) are transmitted by leafhoppers and infect either mono- or dicotyledonous plants. Here we have determined the full length sequences of 49 dicot-infecting mastrevirus isolates sampled in Australia, Eritrea, India, Iran, Pakistan, Syria, Turkey and Yemen. Comprehensive analysis of all available dicot-infecting mastrevirus sequences showed the diversity of these viruses in Australia to be greater than in the rest of their known range, consistent with earlier studies, and that, in contrast with the situation in monocot-infecting mastreviruses, detected inter-species recombination events outnumbered intra-species recombination events. Consistent with Australia having the greatest diversity of known dicot-infecting mastreviruses phylogeographic analyses indicating the most plausible scheme for the spread of these viruses to their present locations, suggest that most recent common ancestor of these viruses is likely nearer Australia than it is to the other regions investigated.

Controlling Pythium in Ginger: Phase 2

The fungal disease Pythium Soft Rot is regarded by the ginger industry as their most serious disease threat. This project was developed to further investigate the factors contributing to the persistence and spread of Pythium Soft Rot on ginger farms and to identify measures for their control. The study demonstrated that the pathogen capable of causing Pythium Soft Rot in ginger was spread in contaminated ‘seed’, soil and water and that it can be managed through a combination of strategies that rely on early detection, reducing pathogen levels in soils, preventing water logging and restricting movement of contaminated ‘seed’, soil and water. However, in order to have an effective level of control, all strategies need to be integrated in an effective manner.

Screening and breeding for genetic resistance to anthracnose in mango

Postharvest diseases remain a significant constraint to the transport, storage and marketing of mangoes. The two main ones are anthracnose and stem end rot. Anthracnose caused by Colletotrichum gloeosporioides is the more wide-spread of the two. Varieties within Mangifera indica are known to vary in their level of reactions to anthracnose; however, the best tolerance in current commercial cultivars is not sufficient to eliminate the need for pre- and postharvest fungicides treatments. A screening program was initiated in mango accessions in the Australian National Mango Genebank to look for any significant resistance to C. gloeosporioides in fruit as they ripened. Screening was conducted by rating reactions to natural infection of anthracnose and reactions to artificially inoculating fruit with virulent isolates of C. gloeosporioides. A range of reactions to the pathogen were identified, with strong resistance found in one accession of the species M. laurina. This accession was used as the pollen parent in a controlled crossing program with a M. indica hybrid from the Australian Mango Breeding Program (AMBP). Sixty successful hybrids between the species have been generated. The hybrid population will be screened for resistance to anthracnose and used for gene discovery investigations to identify markers for anthracnose resistance.

The Jewel Beetle (Hylaeogena jureceki); a new biocontrol for cat’s claw creeper (Dolichandra unguis-cati) in Queensland

Cat’s claw creeper (Dolichandra unguis-cati (Bignoniaceae) is a serious environmental weed in Queensland and New South Wales. It presents a threat to riparian and rainforest ecosystems and is often found in inaccessible locations that are not suitable for chemical or physical control methods. This makes biological control an important tool for managing this weed. The jewel beetle Hylaeo¬gena jureceki was approved for release in Australia in May 2012. Since approval, approximately 35,000 insects have been released at 53 sites. Multiple and single releases have been made at sites with the number of insects released ranging from 20 to 1590. Post-release monitoring before and after winter found the beetle persisting at 73% of release sites in southeast Queensland. Within the release sites, the beetle appears to disperse widely, up to 100 m over a 15 month period. Based on these early field results, it appears that the beetle will establish and spread in Queensland and New South Wales. In addition to direct field releases, the beetle has been supplied to various community and Landcare groups for breeding and field release. This will hasten the spread of the insect to a wider area. It is expected that the jewel beetle will complement the leaf-sucking tingid (Carvalhotingis visenda) and leaf-tying moth (Hypocosmia pyrochroma) that were released in 2007.

A boat hitchhiker's guide to survival: Cabomba caroliniana desiccation resistance and survival ability

Cabomba caroliniana is a submersed macrophyte that has become a serious invader. Cabomba predominantly spreads by stem fragments, in particular through unintentional transport on boat trailers ('hitch hiking'). Desiccation resistance affects the potential dispersal radius. Therefore, knowledge of maximum survival times allows predicting future dispersal. Experiments were conducted to assess desiccation resistance and survival ability of cabomba fragments under various environmental scenarios. Cabomba fragments were highly tolerant of desiccation. However, even relatively low wind speeds resulted in rapid mass loss, indicating a low survival rate of fragments exposed to air currents, such as fragments transported on a boat trailer. The experiments indicated that cabomba could survive at least 3 h of overland transport if exposed to wind. However, even small clumps of cabomba could potentially survive up to 42 h. Thus, targeting the transport of clumps of macrophytes should receive high priority in management. The high resilience of cabomba to desiccation demonstrates the risk of continuing spread. Because of the high probability of fragment viability on arrival, preventing fragment uptake on boat trailers is paramount to reduce the risk of further spread. These findings will assist improving models that predict the spread of aquatic invasive macrophytes.

A boat hitchhiker’s guide to survival: Cabomba caroliniana desiccation resistance and survival ability

Cabomba caroliniana is a submersed macrophyte that has become a serious invader. Cabomba predominantly spreads by stem fragments, in particular through unintentional transport on boat trailers (‘hitch hiking’). Desiccation resistance affects the potential dispersal radius. Therefore, knowledge of maximum survival times allows predicting future dispersal. Experiments were conducted to assess desiccation resistance and survival ability of cabomba fragments under various environmental scenarios. Cabomba fragments were highly tolerant of desiccation. However, even relatively low wind speeds resulted in rapid mass loss, indicating a low survival rate of fragments exposed to air currents, such as fragments transported on a boat trailer. The experiments indicated that cabomba could survive at least 3 h of overland transport if exposed to wind. However, even small clumps of cabomba could potentially survive up to 42 h. Thus, targeting the transport of clumps of macrophytes should receive high priority in management. The high resilience of cabomba to desiccation demonstrates the risk of continuing spread. Because of the high probability of fragment viability on arrival, preventing fragment uptake on boat trailers is paramount to reduce the risk of further spread. These findings will assist improving models that predict the spread of aquatic invasive macrophytes.

Sirex woodwasp range expansion in Australia: performance and parasitism on two commercial pine species

Sirex woodwasp was detected in Queensland in 2009 and rapidly established in softwood plantations (Pinus radiata and P. taeda) in southern border regions. Biocontrol inoculations of Deladenus siricidicola began soon after, and adults were monitored to assess the success of the programme. Wasp size, sex ratios, emergence phenology and nematode parasitism rates were recorded, along with the assessment of wild-caught females. Patterns varied within and among seasons, but overall, P. taeda appeared to be a less suitable host than P. radiata, producing smaller adults, lower fat body content and fewer females. Sirex emerging from P. taeda also showed lower levels of nematode parasitism, possibly due to interactions with the more abundant blue-stain fungus in this host. Sirex adults generally emerged between November and March, with distinct peaks in January and March, separated by a marked drop in emergence in early February. Temperature provided the best correlate of seasonal emergence, with fortnights with higher mean minimum temperatures having higher numbers of Sirex emerging. This has implications for the anticipated northward spread of Sirex into sub-tropical coastal plantation regions. Following four seasons of inundative release of nematodes in Queensland, parasitism rates remain low and have resulted in only partial sterilization of infected females.