Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/1996
Publication Date: N/A
Interpretive Summary: The clover root curculio is a small, broad nosed weevil that attacks alfalfa roots and predisposes the plant to the invasion of root diseases. It is widely spread and can do much damage to alfalfa crops. This paper describes techniques that can be used to locate plant resistance in foreign and domestic alfalfa plant material designated plant introductions. Alfalfa plant introductions (PIs), were grown in the field two years and their taproots evaluated for injury by larvae. Several PI's showed substantially reduced taproot injury and promise for providing resistance or tolerance for this insect. We also developed an improved strategy and method for isolating PIs with resistance from the general alfalfa population.
Technical Abstract: Medicago sativa L., plant introductions (PIs), were grown in field nurseries for two years and their taproots evaluated for injury by larvae of the clover root curculio, Sitona hispidulus (F.). Most plants had about 20-25% of the tap root surface injured by larvae. PIs 183060, and PI 183263, averaged significantly lower taproot injury (<10%) than the check cultivar 'WL316' (24%). Half-sib progenies of individual plants selected in the field with less than 10% taproot injury were infested with clover root curculio eggs in the laboratory and grown in the growth chamber in cone containers for five weeks. Significantly lower amounts of taproot injury were found on PIs 183060, 183263, and 183404 and larval survival was lower on PI 315456-3 compared to WL316, respectively. Half-sib progeny and hand pollinated crosses of other PIs selected in the field for low amounts of tap root feeding were seeded in an advanced nursery. Progeny of one cross between PI464719 x PI445871 had significantly less taproot injury than WL316. Choice tests for antixenosis to adult feeding on first trifoliates in the greenhouse showed PI494661 and PI516906, with significantly less feeding than the control. Overall, there was no correlation between adult feeding in the greenhouse and larval injury to the taproot in the field. Evaluating alfalfa PIs in the field for two years followed by evaluation of their half-sib progenies in both cone containers and advanced nurseries appears to be a useful strategy for identifying sources of resistance to taproot injury by the clover root curculio.