15 décembre 1993
auteur
On a évalué les capacités de multiplication du puceron du pois (Acyrthosiphon pisum Harris) sur 6 cultivars de luzerne de teneurs variées en saponines. Cette teneur a été appréciée par un test biologique utilisant le champignon Trichoderma viride. En conditions contrôlées (température de 20°C, photophase de 16 heures), les taux nets de reproduction d'adultes aptères du puceron ne diffèrent pas entre les variétés lors des deux premières semaines de leur vie imaginale. Des prélèvements de populations naturelles du puceron du pois dans un essai bloc installé en conditions agronomiques n'ont pas montré de différence de contamination des variétés durant les trois années de l'exploitation des parcelles. On en déduit que la teneur globale des variétés en saponines n'est pas un facteur qui détermine le niveau de résistance des cultivars de luzerne au puceron du pois.
Several authors reported an effect of Lucerne saponins on various species of Homoptera ; we therefore tested the reaction of the pea aphid, Acyrthosiphon pisum Harris on 6 different cultivars of Lucerne, bed either in Europe or the USA. Three groups of cultivars were distinguished according to their saponin contents : those with high levels (cv. Europe, Du Puits), those with medium levels (cv. Lutèce, Ruro), and those with low levels (Lahontan, Robot). The contents were measured by a biological test using the fungus Trichoderma viride. The texts were carried out with pea aphids under two different conditions : controlled in a growth chamber, or outdoors in the field. In the growth chamber (temperature : 20°C, photophase : 16 hours), the net reproductive rate of apterous adults on the 14th day of their imaginal life was tested ; there was no difference between the 6 cultivars ; neither did the weight of adults differ on the 7th day of their imaginal life. The trial in the field consisted of a randomized complete block design with 6 replications, which lasted for 3 years. At mid-June, pea aphids were sampled with a sweep net (10 strokes per replicate). Aphid populations were rather low : between 70 and 300 aphids per 10 strokes, but no differences were observed in any year between the mean values of the 6 cultivars. It is concluded that resistance to the pea aphid is not associated with the saponin concentration of the host plant.
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