|De Haan, R|
|Samac, Deborah - Debby|
Submitted to: Journal of Agronomy and Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2002
Publication Date: 12/1/2002
Citation: DE HAAN, R.L., SHEAFFER, C.C., SAMAC, D.A., MOYNIHAN, J.M., BARNES, D.K. 2002. EVALUATION OF ANNUAL MEDIC GERMPLASM FOR UPPER MIDWEST AGROECOSYSTEMS. JOURNAL OF AGRONOMY AND CROP SCIENCE. 188:417-425. Interpretive Summary: Annual medics (Medicago species) have been shown to be useful in providing nitrogen, smothering weeds, and stabilizing soil in a number of cropping systems. However, few varieties have been tested for growth in the Upper Midwest. Twelve Australian annual medic cultivars and 23 USA and Australian plant introductions representing 7 species were evaluated for characteristics needed for productive growth in this environment. Plants were identified that had adequate levels of Phytophthora root rot resistance, although the majority of varieties were highly susceptible. This trait is required in the cooler, wet soils of the region. Varieties were identified that were shade tolerant and with a low growth habit, enabling them to grow between crop rows to provide weed suppression and supplemental nitrogen. Varieties differed widely in dry matter accumulation. Generally, plants with a more upright habit had higher yields. Both yield and an upright habit are needed for varieties to be used for hay or forage. A number of varieties matured after 9 to 10 weeks of growth, which would enable them to be used as cover crops after removal of the primary crop. Varieties were also found with resistance to potato leafhopper yellowing, a common insect pest in the Midwest. None of the varieties evaluated combined all of the desirable characteristics for Upper Midwest cultivars, but the characteristics were all present within available varieties. Plant breeders could develop adapted cultivars by combining favorable traits from several varieties. Such adapted cultivars will enable growers to utilize annual medics in cropping systems for economical weed control, erosion control, and to increase soil nitrogen for subsequent crops.
Technical Abstract: 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. Twelve Australian annual medic cultivars and 23 USA and Australian plant introductions representing 7 species were evaluated for Phytophthora root rot (Phytophthora medicaginis Hansen et Maxwell) resistance, shade tolerance, growth habit, dry matter accumulation, maturity after 9 to 10 wk of growth, and potato leafhopper (Empoasca fabae Harris) yellowing. Several plant introductions (PI 197346, PI 459135, and PI 283653) were resistant to Phytophthora root rot. Entries most tolerant of shade were Kelson and PI 419241, while Santiago and SA 9032 were intolerant. In growth habit comparisons, PI 419241 and PI 368939 grew less than 11 cm tall, while Kelson and SA 5762 grew at least 27 cm tall. Dry matter production 10 to 12 wk after emergence was greatest for PI 197339 and Kelson. At that time the earliest maturing entries (PI 226517 and Sava) had begun to senesce, while the latest maturing entry (PI 419241) was still vegetative. Paraponto 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 favorable traits from several medic genotypes.