Ground Cover North : Ground Cover 048 February-March 2004 - North
By JOOP van LEUR, ANGELA FREEMAN and SAFAA KUMARI Surveys for faba bean viruses in 2003 showed an unusually high incidence of subterranean clover stunt virus (SCSV), a potentially serious disease. With 11 viruses reported on faba bean in Australia, it is essential that regular surveys are made to monitor virus incidence and to set priorities for virus research. Such surveys require diagnostic tests because different viruses can cause similar symptoms. Also, nutrient deficiencies, herbicide damage and water stress can produce symptoms almost indistinguishable from those caused by viruses. The 2003 survey was based on a large number of plants in random paddock sampling, and testing for a wide range of viruses. In the southern region, testing of samples by ELISA (enzyme-linked immunosorbent assay) was used, but for the northern region (where virus incidences are generally higher) plants were tested individually using Tissue Blot Immuno Assays (TBIA). The TBIA membranes were processed in the virology laboratory of the International Centre for Agricultural Research in the Dry Areas (ICARDA, Syria) as part of a GRDC-funded collaborative project. Preliminary reports show that both the magnitude of virus infection as well as the range of viruses detected were larger than assumed. The most frequently found -- and likely most damaging -- virus in 2003 was Bean yellow mosaic virus (BYMV), while incidences of the destructive Bean leafroll virus (BLRV) were low. The unique feature in 2003 was widespread infections by SCSV. On faba bean this closely resembles BLRV; yellowing, thickening and rolling of leaves and stunting of the plant -- hence the need for serological tests to differentiate. However, the SCSV infection pattern was unlike that normally observed for BLRV. While BLRV is usually randomly distributed through a field, the SCSV-affected plants were clustered. This suggests that the aphid vectors of BLRV fly into the crop, feed and fly off, whereas the SCSV vectors fly into the crop, feed and move to neighbouring plants. This makes SCSV potentially more dangerous than BLRV at lower infection levels. Single stunted plants can be overgrown by healthy plants, but clusters of virus infected plants will remain a source of infection until the end of the season. SCSV infection on faba bean in 2003 appeared to be widespread in eastern Australia. Incidences in the surveyed paddocks in northern New South Wales were below one percent in all but a single paddock near Moree with nine percent infection. Although SCSV infection levels in most faba bean crops in Victoria were below one percent, a number of paddocks around Horsham showed very high incidences (20-80 percent) and severe yield losses (up to 100 percent). SCSV is indigenous to Australia and has not been reported anywhere else in the world. It is normally thought of as a destructive pathogen of subterranean clover, but is known to severely affect faba bean, french bean and field pea. Studies during the 1970s on the epidemiology of this virus in subterranean clover demonstrated huge year-to- year fluctuations, caused largely by the population dynamics of its main vector, the cowpea aphid (Aphis craccivora). Causes for the higher than normal infection levels in faba bean were not investigated, but are likely related to the exceptionally high aphid populations observed throughout eastern Australia early in the season. Whether the infection originated from local sources or was the result of large-distance aphid migration is not clear. In Victoria, a build-up of aphids was observed on volunteer pulse crops. Volunteers were abundant after heavy February 2003 rains, as many paddocks were not harvested in 2002 due to the drought. Aphid populations moved from the volunteers into newly sown pulse crops soon after germination, and could have picked up SCSV from infected medic and/or clover paddocks. SCSV-infected clover and medic plants were found in paddocks adjacent to the severely infected faba bean crops in Victoria. Comparing SCSV infection levels between varieties in yield trials in an experimental site in northern NSW indicated the existence of large genotypic differences. Established varieties like Fiord, Fiesta and Icarus had around one percent infection levels, but some experimental lines showed over 10 percent SCSV-infested plants. The presence of highly susceptible germplasm among advanced breeding lines is a reminder to breeding programs to continuously test material not only for major but also for (perceived) minor pathogens. Incidental epidemics of SCSV are likely to happen again and continuous monitoring of viruses in experimental and commercial pulse crops will remain necessary. RESEARCH UPDATE 13 FEBRUARY 2004 FABA BEAN VIRUSES More common than expected: Faba bean damaged by subterranean clover stunt virus. Disease threat needs constant vigilance The Grains Research and Development Corporation (GRDC) invests in research and development on behalf of the Australian grains industry and the Federal Government. APPLICATIONS FOR CONFERENCE SPONSORSHIP 2004-05 The GRDC invites and assesses Conference Sponsorship Applications twice a year. Applications for funding support for conferences not forming an element within a research project, do not require a Research Proposal, but are to be made on the Conference Sponsorship application form. For conferences that are held annually/biennially the GRDC requires a new application each year. For conferences that occur infrequently, for example major international conferences, where Australia is the convenor or conferences, which are held every 5 years, the GRDC will consider dispersing funds in advance of the conference date over a number of years. Conference Sponsorship Applications are being considered for the period July to December 2004 and must be submitted by Friday, 26 March 2004. Applications must be submitted at least three months prior to the conference. These applications should not be included as a part of any other GRDC research project or attached to other GRDC applications. Applicants interested in preparing Conference Sponsorship Applications will be required to use the GRDC's Word 6 template (see details below). INDUSTRY DEVELOPMENT AWARDS (IDA) APPLICATIONS 2004-05 The GRDC invites and assesses Industry Development Award applications twice a year. This award is aimed at developing the skills and information bases required to achieve growers and GRDC's objectives. The Industry Development Award is available specifically for growers. Several awards are available to growers, processors and others in the grains industry not engaged in R&D activities who are seeking to enhance their experience and potential to contribute to the work of the Australian grains industry. The awards may be for study tours within Australia or overseas, or for other purposes approved by the GRDC. Support will be for up to six months and will not exceed $15,000. HOW TO APPLY Applicants will be required to use the GRDC's Word 6 templates. These documents can be opened and completed on any computer that has Microsoft Word 6 (or a later version of Word) or any word processing software that can convert from Word 6. When complete, the GRDC will require Six (6) paper copies (A4 size, double sided, stapled) to be submitted. These should be addressed to: Program Coordinator Product and Service Delivery Grains R&D Corporation PO Box 5367 KINGSTON ACT 2604 In addition to the "hard" copies, an electronic copy should be emailed to firstname.lastname@example.org. The name of the word document should incorporate the applicant's name and the award eg smith IDA.doc These Word templates can be found at the 'Applying and Reporting' section on our Website: http://www.grdc.com.au/researchers/forms.htm Applications will close on 26 March 2004. No late applications will be accepted. TRAVEL/CONFERENCE ATTENDANCE APPLICATIONS 2004-05 The GRDC invites and assesses Travel/Conference Attendance applications twice a year. This means that travel applications must be submitted with closing dates of 26 March 2004 (for the six months July 2004 to December 2004) and 24 September 2004 (for the six months January 2005 to June 2005 and so on). The GRDC's preference is for travel requests to be incorporated into project applications wherever possible. Applications for financial support for travel or conference attendance not forming an element within a research project may be made on the Travel/Conference Attendance Application form (see details below). GRDC RESEARCH CODE DAV411, program 3 For more information: Joop van Leur, NSW Agriculture, email@example.com; Angela Freeman, Department of Primary Industries Victoria, firstname.lastname@example.org; Safaa Kumari, International Center for Agricultural Research in the Dry Areas, email@example.com.
Ground Cover 049 April-May 2004 - North
Ground Cover 047 November-December 2003 - North