Agronomic evaluation of Medicago ruthenica collected in Inner Mongolia

Medicago ruthenica (L.) Ledebour has long been recognized as a potential new forage crop, which may also have potential as a source of genes for improving abiotic stress tolerance in cultivated alfalfa (M. sativa L.). This study was designed to assess the genetic variation among 50 M. ruthenica accessions, collected in Inner Mongolia in 1991 from 15 environments ranging from sand dunes to lush grassland, and to assess the agronomic potential of the species in the humid eastern USA. Accessions were evaluated in the field at Beltsville, MD, in 1993 and 1994 on an Iuka sandy loam (coarse-loamy, siliceous, acid, thermic, Aquic Udigluvent; pH 6.4) in boron and potassium deficient soil. Stand retention was only 47% (compared with 94% for M. sativa checks) after the winter of 1993, indicating that the species is not well adapted to the humid eastern USA. Significant variation was noted for reaction to environmental stress (possibly boron deficiency), days from seeding to tillering, dry matter yield, growth habit, leaf shape, and plant height and width. No disease symptoms were noted; however, a detailed pathological examination was not conducted. A positive relationship was noted between plant width and yield, and between uprightness and narrow leaves. The more procumbent plants with broader leaves may have been less susceptible to winter damage under Beltsville conditions. Some of the most agronomically desirable accessions could have resulted from genetic shifts due to selection. Analyses indicate that M. ruthenica may have the potential to become a new forage crop, perhaps for low input systems, and that semi-erect (for hay production) or procumbent (grazing tolerant) populations with improved seedling vigor and yield could be developed. Considering the antiquity and isolation of M. ruthenica, its harsh native environment, and the stress tolerance and yield of elite accessions under low-input conditions, M. ruthenica may provide genes that could be of considerable value to cultivated alfalfa.