Legg, J.P.

Milenovic, M.

Rapisarda, Carmelo

Wosula, Everlyne N.

Legg, James P.

CGSpace

Feeding behavior of cassava and non-cassava colonizing genotypes of Bemisia tabaci  Introduction The cassava-colonizing whitefly, Bemisia tabaci, is an economically important pest of cassava. It causes damage by feeding on plant vascular tissue and consequently spreading viruses that cause cassava mosaic disease (CMD) and cassava brown streak disease (CBSD). The feeding and whitefly-host interaction of cassava-colonizing whiteflies is not well understood. The electrical penetration graph (EPG) technique can be used to study these interactions in great detail. www.rtb.cgiar.org Milan Milenovic1, Everlyne Wosula2, Carmelo Rapisarda3, and James Legg2 1 University of Copenhagen, Denmark and University of Catania, Italy 2 International Institute of Tropical Agriculture (IITA), Tanzania 3 University of Catania, Italy  Materials and Methods  To study the details of stylet penetration into the plant, a DC voltage is applied to the soil in which the plant grows, and the whitefly is connected to a thin (<2.5µm) platinum wire which is then connected to the probe (Fig. 1 and  Fig. 2). When the insect feeds, it completes an electric circuit through the insect, plant and moist soil. The voltage fluctuation in the circuit is measured, producing a trace which describes the feeding behavior in great detail.  - + R = 109 Ω Ground Probe Amplifier Waveform Data recording and analysis Converter Faraday cage Fig. 1: Schematic diagram of DC-EPG. Objectives Determine why sweet potato whitefly genotypes are unable to survive and colonize cassava. In addition, determine ability of cassava colonizing genotypes to feed on other hosts. It has been hypothesized that cyanogenic glycosides from cassava are lethal to non-cassava genotypes of whiteflies. This was however never experimentally tested before.  Results and discussion The preliminary results show significant differences between sweet potato genotype feeding on sweet potato and cassava. However, the cassava-colonizing genotype does not show these differences suggesting the difference in host preference and suitability. When sweet potato genotype is feeding on cassava it has reduced number of phloem feeding events, and dramatically shorter mean and total phloem ingestion phase (Table 1). Conclusion Cassava colonizing whitefly can feed and survive on sweet potato when cassava is not available. This implies that controlling whiteflies only on cassava or applying rotation and isolation measures may not be very effective. On the other hand, sweet potato whiteflies reject the cassava host. The exact mechanism is unclear at the moment, but is likely related to taste perception and/or activation of plant resistance. Studying this interaction holds the potential to developing new methods for controlling the whiteflies. Fig. 2: Whitefly attached to a 12.5µm gold wire using water-based silver glue. Whitefly Genotype Host plant Number of phloem events Mean duration of the event  Total duration of the events Cassava type Cassava 1.9 257.5 min 5 h 39 min Cassava type Sweet Potato 2.5 145 min 4 h 18 min Sweet potato Cassava 1.5* 9.3 min* 16 min* Sweet potato Sweet Potato 6.5 77.5 min 6h 36 min Table 1: Selected phloem feeding parameters *Significantly different (p<0.05) 

Feeding behavior of cassava and non-cassava colonizing genotypes of Bemisia tabaci

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Feeding behavior of cassava and non-cassava colonizing genotypes of Bemisia tabaci

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