GENETICS OF RESISTANCE TO ALFALFA MOSAIC VIRUS IN RED CLOVER

Virus diseases are known to reduce the yield and persistence of stands of red clover (Trifolium pratense L.). Alfalfa mosaic virus (AMV) is one of the causes of mosaic in red clover and may also cause mottling and leaf distortion. The goals of this study were to identify genotypes resistant to AMV within commercial red clover cultivars and to determine the inheritance of this resistance. Cultivars and progenies were screened for resistance by means of mechanical inoculations. Plants showing no symptoms after three successive inoculations were assayed for the presence of the virus using ELISA (enzyme-linked immunosorbent assay). Resistant plants were detected at a frequency of just over 1% in the five cultivars screened. Crosses among and between resistant (R) and susceptible (S) plants were carried out over two successive cycles of selection. In cycle 1, R × R crosses produced a higher frequency of resistant plants (19.8%) in the progenies than R × S crosses (10.9%). S × S crosses produced no resistant pr...