Improving birdsfoot trefoil for resistance to Fusarium wilt

Fusarium wilt (caused by Fusarium oxysporum f. sp. loti) is a serious disease of birdsfoot trefoil, Lotus corniculatus L., reducing yield of forage and seed. In the early 1990s a breeding program was begun to breed a Fusarium wilt-resistant birdsfoot trefoil. Our objectives were to (i) determine progress from recurrent phenotypic selection for resistance to Fusarium wilt in six birdsfoot trefoil populations and (ii) compare forage yield and persistence of Fusarium wilt-resistant populations to unselected populations in field trials. Recurrent phenotypic selection was effective in improving resistance in the greenhouse, with mean improvement of 35% across all populations after three cycles of selection. In a field with high natural disease pressure, a population developed after two cycles of selection for resistance had lower levels of disease incidence and yielded 1.33 Mg ha^-1 more than the mean of nine cultivars in the seeding year. The Fusarium wilt-resistant population had 52% higher plant stand than the mean of the other cultivars at the end of the first production year. In a trial inoculated with the Fusarium wilt organism, two cycle 3 populations averaged 28% more yield by June of the fourth production year and 22 more plants per m2 than the mean of the unselected populations. Birdsfoot trefoil with resistance to Fusarium wilt yielded more and persisted longer than other cultivars under Fusarium wilt-infested field conditions.