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ARS Home » Midwest Area » Madison, Wisconsin » Vegetable Crops Research » Research » Publications at this Location » Publication #313734
Title: Leaf waxes and thrips resistance in onion

Author
item Havey, Michael

Submitted to: Onion World
Publication Type: Trade Journal
Publication Acceptance Date: 2/25/2015
Publication Date: 3/1/2015
Citation: Havey, M.J. 2015. Leaf waxes and thrips resistance in onion. Onion World. 31(3):10-11.

Interpretive Summary:

Technical Abstract: Onion thrips is an important insect pest of onion that damages leaves and bulbs, reduces yields, and transmits important diseases such as iris yellow spot virus and bacterial rots. Growers would benefit from onions resistant to thrips in order to reduce insecticide applications and provide more sustainable management strategies. In plants, insect resistances are often associated with amounts and types of epicuticular waxes on the leaves. We studied types and amounts of epicuticular waxes on onion leaves and assessed numbers of thrips. Overall three different foliage types (waxy, semi-glossy, and glossy onions) possess the same types of waxes; however their amounts vary significantly. The ketone hentriacontanone-16 is the main epicuticular wax on onion leaves, and is responsible for the visual waxiness of the leaves. Semi-glossy and glossy onions have significantly less of this ketone than waxy onions. The epicuticular waxes of onion also include specific fatty alcohols and alkanes. Genetic studies revealed that the amount of hentriacontanone-16 is controlled by one region on chromosome 5, while amounts of the fatty alcohols and alkanes primarily by a region on chromosome 2. This means that we should be able to breed onions with significantly less hentriacontanone-16, but can still accumulate significant amounts of the other waxes to protect the leaves from pathogens and spray damage. In field studies, numbers of adult and larval thrips were significantly different between waxy onions versus the glossy and semi-glossy types; however there were no differences for numbers of thrips on the leaves of glossy and semi-glossy onions. Therefore semi-glossy onions should be useful in an integrated approach to manage onion thrips by reducing the number of sprays required to control the insect as well as the incidence of thrips-transmitted diseases, while maintaining the protection of intermediate amounts of waxes on leaves.