VG02035 Capsicum – virus resistance

Capsicum crops in all Australian States have sustained major production losses from Tospoviruses over the last 12 or so years.

Capsicum chlorosis virus (CaCV) and Tomato spotted wilt virus (TSWV), two of the species of tospoviruses found in Australia, were studied in a project with two major objectives :

  1. Understand their distribution in horticultural crops and weed hosts
  2. Identification of germplasm resistant to CaCV and the transfer of resistance to suitable lines of bell capsicum by conventional breeding methods.

The increasing importance of tospoviruses in Australian capsicum crops was addressed in this project by seeking germplasm resistant to CaCV.

Incorporating this resistance into bell capsicum lines in combination with the Tsw gene to provide broad protection against tospoviruses.

This report details about the identification of resistances to Tospoviruses affecting capsicums in Australia and the integration of resistance into capsicum breeding material.

Research identified a single gene for natural Capsicum chlorisis virus resistance in wild capsicum stock.

Lines with this gene were cross-bred with lines that had a natural resistance to tomato spotted wilt virus, creating cultivars that demonstrate resistance to both viruses.

Des McGrath Stephen Garland
Murray Sharman Denis Persley
Ian Walker  

VG06140 Capsicum breeding for
tospo virus resistance - 2007
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Findings :

Tospoviruses belong to the virus family Bunyaviridae many of which are transmitted by mosquitoes and other insects.

All viruses within the family that infect plants are assigned to the Tospovirus genus. The genus name is derived from the type species, Tomato spotted wilt virus (TSWV), which was first found and described from Australia around 1920 .

There are currently 16 recognised or proposed tospovirus species with three being recorded in Australia – TSWV, Capsicum chlorosis virus (CaCV) and Iris yellow spot virus (IYSV).

  1. Surveys of CaCV revealed that it is endemic in all major capsicum production districts of Queensland, including Bundaberg, Bowen, Gumlu and Ayr.

    It has been the dominant tospovirus of capsicum at Bundaberg since 2000.

    CaCV was also recorded at Kununurra, WA, and in tomato at Coffs Harbour, NSW.

  2. The high incidence of CaCV in tomato and capsicum crops at Bundaberg is likely to be related to the presence of two thrips vector species,

    Thrips palmi and Frankliniella schulezi and the frequent infection of the common weed species Ageratum conyzoides.

    The control of this weed species will be a critical component of a broader strategy for the management of CaCV.

  3. One Plant Introduction accession with high levels of resistance to both CaCV and Tomato spotted wilt virus was found in a screening of more than 100 accessions from several uncultivated Capsicum species.

    One major resistance gene was identified in this parent and transferred to a series of breeding lines in four cycles of hybridization and selection.

  4. In associated work, a DNA marker was developed to enable faster and more efficient selection of the resistance gene in breeding programs.
  5. The most advanced lines have good fruit quality and yield similar to commercial cultivars, but need a further cycle of breeding to improve fruit size.

    Resistant breeding lines and populations from this project will be commercialised.

    They should be valuable either as parents in hybrid cultivars or as a source of resistance in new breeding populations.

    Given the extent of CaCV in Queensland and South East Asia, resistance may soon be an essential attribute of new cultivars for these areas.

Acknowledgements :

The advice and assistance of Dr John Thomas and Lee McMichael is gratefully acknowledged.

Staff from Bowen Crop Monitoring and Crop Tech Bundaberg assisted with the virus disease surveys.

This project was funded by Horticulture Australia Ltd through the National Vegetable R&D Levy and the Department of Primary Industries and Fisheries, Queensland.

The Australian Government provides matched funding for all HAL’s R&D activities.

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