Document Type : Research and Full Length Article
Scientific Member of Institute of Forests and Rangelands, Tehran,
Institute of Forests and Rangelands, Tehran
Medicago spp. is the most important forage crop in many regions of the world.
Annual medics have distinct advantages over perennial Medicago. These species have faster
growth rate in cultivation year, higher crude protein percentage, tolerance to pests and more
vigorous seedlings. Morphological and physical aspects of pod and seeds of annual medics
play a major role in the tolerance of the plants to over grazing and establishing in different
type of rangelands i.e., plants with small seeds can establish better in heavy grazed rangelands,
spiny pods establish better in dense compact clay soil, hard seeds increase seed bank of the
soil and maintain the pasture for the next years. In order to study the variation in seeds and
pods morphological traits of five annual Medicago spp. seeds of 50 accessions of M. rigidula,
M. polymorpha, M. orbicularis, M. radiata and M. minima, provided from natural resources
gene bank of Iran, were sown in pots. Data were collected for size of the seeds, spins and
pods, number of seeds per pod, levels of hardseededness and elevation of the seed origin.
Results showed that M. rigidula 1000-seed weight had the most variation. Largest seeds were
17 times bigger than the smallest one in this species. M. polymorpha showed the most
variation in the elevation of seed origin (upper=2280 m, lower=5 m above sea level). M.
radiata showed the most variation in the amount of hard seeds. M. rigidula showed the least
amount of hard seeds (mean=59.93). M. radiata had the largest pods. M. radiata and M.
orbicularis showed the highest variation in pod size. M. polymorpha showed the highest
variation of spine length. The correlation between 1000-seed weight and the elevation of seed
origin was positive and significant for M. polymorpha and negative and significant for M.
orbicularis. Based on Ward clustering method, the five species were grouped into two clusters
in a dendrogram. First cluster included M. minima and M. polymorpha and the second cluster
included M. rigidula, M. orbicularis, and M. radiata. This result indicated that it may possible
of interspecific hybridization between species of the same cluster.