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Characterization of sugarcane resistance to Melanaphis sacchari using biological tests and Electrical Penetration Graph (DC-EPG)

Fartek B., Nibouche S., Costet L., Reynaud B.. 2008. In : Symposium on plant interactions with aphids, Wageningen (Netherlands), 18-20 August 2008. s.l. : s.n., 1 p.. Symposium on plant interactions with aphids, 2008-08-18/2008-08-20, Wageningen (Pays-Bas).

The sugarcane aphid, Melanaphis sacchari (Zehntner, 1895), is a major pest on sorghum and sugarcane worldwide, and the main vector of Sugarcane Yellow Leaf Virus (SCYLV) in Reunion Island. Very little is known about the feeding behaviour of M. sacchari, and plant resistance has been reported on sugarcane but never investigated. Our work was performed on two genotypes selected from field screening according to their resistance/susceptibility to aphids: MQ 76/53 (susceptible) and R 365 (resistant). Two biological experiments were performed to characterize aphid resistance : in the first one aphid life traits (fecundity, longevity, larvae survival and overall Rm trait) were measured on excised leaves; in the second one, the mean number of aphids per leave was scored on 3 week-old sugarcane plantlets between +8 and + 72 hours after deposit. DC-EPG were performed on both cultivars to characterize the effects of R 365 resistance on M. sacchari feeding behaviour.13 recordings (8 hour-long) per genotype of 5-day-old aphid larvae were performed on 3 week-old sugarcane plantlets. The EPG data were at first analysed by the EPG-soft ver.2, using an aphid expertised base provided by F. Tjallingii, and then corrected manually using the Matlab software. Biological experiments : the first test highlighted a great depreciation in life traits, showing a strong antibiosis effect on resistant genotype (R 365). The second test revealed an antixenosis occurring mainly between the first 8 and 24 hours, and peaking at 72 hours, with a strong decrease by three times of mean aphid number per leaves. EPG recordings : time to first E 1 and mean duration of E 1 waveform, correlated with watery salivation in phloem, did not differ significantly in both cultivars ; in contrast, none of the aphids on R 365 cultivar exhibited E2 waveform, indicating an absence of phloem sap ingestion. EPG data are consistent with results from biological experiments and suggest aphid resistance on R 365 should be phloem-located, and prevents any sustained sap ingestion although salivation in phloem occurs.

Mots-clés : saccharum officinarum; melanaphis; réunion; france; melanaphis sacchari

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