ALBERT

Description: Background: Cowpea aphid (CPA; Aphis craccivora) is the most important insect pest of cowpea and alsocauses significant yield losses in other legume crops including alfalfa, beans, chickpea,lentils, lupins and peanuts. In many of these crops there is no natural genetic resistance to thissap-sucking insect or resistance genes have been overcome by newly emerged CPA biotypes. Results: In this study, we screened a subset of the Medicago truncatula core collection of the SouthAustralian Research and Development Institute (SARDI) and identified strong resistance toCPA in a M. truncatula accession SA30199, compared to all other M. truncatula accessionstested. The biology of resistance to CPA in SA30199 plants was characterised compared tothe highly susceptible accession Borung and showed that resistance occurred at the level ofthe phloem, required an intact plant and involved a combination of antixenosis and antibiosis.Quantitative trait loci (QTL) analysis using a F2 population (n = 150) from a cross betweenSA30199 and Borung revealed that resistance to CPA is controlled in part by a majorquantitative trait locus (QTL) on chromosome 2, explaining 39% of the antibiosis resistance. Conclusions: The identification of strong CPA resistance in M. truncatula allows for the identification ofkey regulators and genes important in this model legume to give effective CPA resistance thatmay have relevance for other legume crops. The identified locus will also facilitate marker assisted breeding of M. truncatula for increased resistance to CPA and potentially otherclosely related Medicago species such as alfalfa.