INHERITANCE OF NONNECROTIC RESISTANCE TO COWPEA CHLOROTIC MOTTLE VIRUS IN SOYBEAN

Inheritance of nonnecrotic resistance (inhibition of systemic movement) to cowpea chlorotic mottle virus was determined in a cross between susceptible soybean cultivar Davis and resistant Plant Introduction (Pl) 346304. Plants of the F1, F2, and F3 generations were mechanically inoculated with purified cowpea chlorotic mottle virus. F2 and F3 segregation ratios indicated that the nonnecrotic resistance is conditioned by two recessive genes. On the basis of data from a second cross between cultivar Bragg and Pl 346304, we could not conclude that allelism does not exist between the single dominant gene (Rcs) that controls hypersensitivity resistance in Bragg and the recessive genes that control inhibition of movement in Pl 346304. This appears to be the second report of double recessive genes controlling virus resistance.