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ARS Home » Southeast Area » Fort Pierce, Florida » U.S. Horticultural Research Laboratory » Subtropical Insects and Horticulture Research » Research » Publications at this Location » Publication #318686
Title: Expression of Bacillus thuringiensis cytolytic toxin (Cyt2Ca1) in citrus roots to control Diaprepes abbreviatus larvae

Author
item MAHMOUD, SULLEY BEN - University Of Florida
item Ramos, John
item Shatters, Robert - Bob
item Hall, David
item Lapointe, Stephen
item Niedz, Randall
item ROUGE, PIERRE - University Of Toulouse
item BOROVSKY, D. - Dov Borovsky

Submitted to: Pesticide Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/25/2016
Publication Date: 7/26/2016
Citation: Mahmoud, S., Ramos, J.E., Shatters, R.G., Hall, D.G., Lapointe, S.L., Niedz, R.P., Rouge, P., Borovsky, D. 2016. Expression of Bacillus thuringiensis cytolytic toxin (Cyt2Ca1) in citrus roots to control Diaprepes abbreviatus larvae. Pesticide Biochemistry and Physiology. 136:1-11.

Interpretive Summary: Citrus root weevil cause damage to citrus root and is difficult to control using conventional insecticides. In this report we expressed a bacterial toxin in the roots of citrus. Larval weevil are killed when they feed on these roots. The level of the toxin in the plant was also determined and we show that medium expression of the toxin in citrus does not affect citrus growth. In the future this approach could be used to protect citrus from larval attack of the roots without the use of insecticides.

Technical Abstract: Diaprepes abbreviatus (L.) is an important pest of citrus in the USA. Currently, no effective management strategies of Diaprepes abbreviatus exist in citriculture. To protect citrus against Diaprepes abbreviatus a transgenic citrus rootstock expressing Bacillus thuringiensis Cyt2Ca1, an insect toxin protein, was developed using Agrobacterium-mediated transformation of ‘Carrizo’ citrange [Citrus sinensis (L) Osbeck x Poncirus trifoliate (L) Raf]. The transgenic citrus root stock expressed the cytolic toxin Cyt2Ca1 uniformly under the control of a 35S promoter in the transgenic Carrizo citrange trifoliate hybrid including the roots that are the food source of larval Diaprepes abbreviatus. The engineered citrus was screened by Western blot and RT-qPCR analyses for cyt2Ca1 and positive citrus identified. Seven citrus trees expressing different levels (high, medium and low) of cyt2Ca1 transcripts were identified. High expression of the toxin, however, retarded plant growth. The transgenic plants were grown in pots and the roots exposed to 3 week old Diaprepes abbreviatus larvae using no-choice plant bioassays. Three cyt2Ca1 transgenic plants were identified that sustained less root damage all belonging to the medium-expressing group. One plant caused death to 43 percent of the larvae that fed on its roots. These results show, for the first time, that Cyt2Ca1 expressed in moderate amounts by the roots of citrus does not retard citrus growth and can protect it from larval Diaprepes abbreviatus.