Evaluation of annual Medicago for Upper Midwest agroecosystems

Annual Medicago species (medics) have characteristics that may make them a valuable addition to agricultural systems in the Upper Midwest, USA, but few genotypes have been evaluated. The objective of this research was to identify medic germplasm exhibiting traits that are desirable for cultivars intended for multiple uses in the region. Australian annual medic cultivars and plant introductions (PI) representing seven species were evaluated for Phytophthora root rot (Phytophthora medicaginis Hansen et Maxwell) resistance, shade tolerance, growth habit, dry matter accumulation, maturity after 9-10 weeks of growth, and potato leafhopper (Empoasca fabae Harris) yellowing. Medicago polymorpha L. plant introductions PI 197346, PI 459135, and PI 283653 were resistant to Phytophthora root rot. Kelson [Medicago scutellata (L.) Mill.] and PI 419241 [Medicago tornata (L.) Mill.] were tolerant of shade, while M. polymorpha entries Santiago and SA 9032 were intolerant. In growth habit comparisons, PI 419241 and PI 368939 (M. polymorpha) grew less than 11 cm tall, while Kelson and SA 5762 (M. polymorpha) grew at least 27 cm tall. Dry matter production 10-12 weeks after emergence was greatest for PI 197339 (M. polymorpha) and Kelson. At that time, the earliest maturing entries, PI 226517 (M. polymorpha) and Sava (M. scutellata), had begun to senesce, while the latest maturing entry (PI 419241) was still vegetative. Paraponto (Medicago rugosa Desr.) was highly resistant to potato leafhopper yellowing. None of the medic entries evaluated combined all of the desirable traits for Upper Midwest cultivars, but the traits were all present within available germplasms. Plant breeders could develop adapted cultivars by combining favourable traits from several medic genotypes.