Field evaluation of lucerne (Medicago sativa L.) for resistance to aphids in northern China

Abstract

Resistance of 9 lucerne cultivars and lines of predominantly overseas introductions to an aphid complex was evaluated in field experiments at Lanzhou city in Gansu province of northern China in 2004. The aphid complex, consisting of 3 aphid species, the spotted alfalfa aphid (SAA) Therioaphis trifolii Monell, black bean aphid (BBA) Aphis craccivora Koch, and pea aphid (PA) Acyrthosiphon pisum Harris, was found to be dominated by BBA at the early stage of plant growth in spring and by SAA at other stages. Plants infested by SAA showed the symptoms of either chlorotic leaf veins or yellow leaf. Cultivars performed similarly in Gansu as in their country of origin, with minor differences (e.g. Hunter River). ‘Aphid damage index’ and ‘% of resistant plants’ were found to be useful parameters for specifying the resistance of a given cultivar to the aphid complex. Based on the ‘% of resistant plants’, cvv. HA–3, Cropper 9, 8925MF, SARDI 7, and SARDI 10 were classified as highly resistant; HA–1 and Gannong 3, resistant; Jindera, moderately resistant; and Hunter River, low resistance.

Biology and trophic interactions of lucerne aphids

“…Lucerne‐feeding aphids are the most devastating insect pests of lucerne, causing an estimated production loss of 25% worldwide (He & Zhang, ). They present a significant problem for the lucerne industry by inhibiting seedling establishment, plant growth and persistence, and by reducing the quality and quantity of lucerne produced (Irwin et al , ).…”

“…Because of the costly nature and negative environmental impacts of insecticide applications, the use of cultivar resistance (i.e. bottom‐up control) against aphids presents a more economical and practical option for increasing lucerne yield, quality and stand persistence (Irwin et al , ; Edwards & Singh, ; He & Zhang, ; Gao et al , ). Aphid‐resistant varieties of lucerne were selected by plant breeders soon after the late 1950s when SAA devastated lucerne stands in the U.S.A., which at that time, were dominated by the cultivars ‘Vernal’ and ‘CUF101’ (Hughes & Hughes, ; Bouton, ).…”

“…‘Trifecta’, released in 1983, was the first cultivar to achieve at least moderate (>20% of plants) levels of aphid resistance (Oram, ), which led to significant yield increases over ‘Hunter River’ and ‘CUF101’ (Clements et al , ). The problem with cultivar introductions overseas, however, is that aphid responses can vary outside their country of origin (He & Zhang, ) and so further studies are required to assess local levels of lucerne resistance, environmental adaptation and mechanisms for resistance to aphids. After more than 30 years of breeding and variety introductions, over 50 lucerne varieties are now available for Australian growers (Lattimore, ).…”

“…seedling biomass) under aphid infestation. He and Zhang () evaluated the resistance of nine lucerne cultivars to three aphid species (SAA, CA and PA) in China, focussing primarily on ‘aphid damage index’ and ‘percentage of resistant plants’ as parameters to evaluate cultivar resistance.…”

(E)‐β‐farnesene synthase gene affects aphid behavior in transgenic Medicago sativa

“…A few pest species can cause substantial yield and quality losses if present in high numbers, including alfalfa weevil ( Hypera postica Gyllenhal) (Coleoptera: Curculionidae), alfalfa caterpillar ( Colias eurytheme Boisduval) (Lepidoptera: Pieridae), Empoasca leafhoppers (Hemiptera: Cicadellidae) and aphids . As one of the major insect pests of alfalfa, aphids have the potential to cause worldwide production losses of 25% …”