Forage Quality of Perential Glandular‐Haired and Eglandular Medicago Populations

Abstract

Current alfalfa (Medicago sativa L.) cultivars have inadequate resistance to the alfalfa weevil [Hypera postica (Gyilenhal)] and the potato leafhopper [Empoasca fabae (Harris)], the two most injurious arthropod pests of alfalfa in North America. Resistance to both insects has been documented in other Medicago species having erect, glandular hairs. These hairs have been transferred to alfalfa. The effects of glandular hairs and their exudates on forage quality of alfalfa are unknown. A field trial was established in 1985 to determine the effects of erect glandular hairs and their exudates on forage quality of some perennial Medicagos. Glandular and eglandular plant populations were selected from the diploids M. glandulosa David and M. prostrata Jacq. and tetraploids M. glutinosa Bieb., M. sativa (MS4n) × M. glutinosa, and MS4n × M. prostrata. (Medicago glutinosa is the first label given to PI 346919, a plant introduction from Russia. In 1978, USDA Tech. Bull. 1574 identified it as a mixture of the following M. sativa L. subspecies: sativa, praefalcata, glomerata, and X varia.) Eglandular M. sativa ‘Riley’ and diploid M. sativa subsp. caerulea (Less. ex Ledeb.) Schmalh. were included as controls. The test was planted in an area mapped as Wymore silty clay loam (fine, montmorillonitic, mesic Aquic Argiadolls) 1 to 4% slopes. Foliar diseases and insects were controlled. Leaves were separated from stems for three harvests in 1985 and one harvest in 1986. In vitro dry matter disappearance (IVDMD) and crude protein (CP) were determined on each component. The presence of glandular hairs on the wild Medicago species (glandulosa, prostrata, and glutinosa) did not significantly affect the IVDMD or CP contents of leaves or stems. Stem digestibilities and crude protein contents of the diploid populations exceeded those of Riley.