In Pisum sativum, two independently inherited single recessive genes were found to confer resistance to the same pathotype of pea seed-borne mosaic virus from lentil (PSbMV-L1). The gene sbm-2, present in the domestic cuttivar Bonneville, was determined to be closely linked to mo, which conditions resistance to bean yellow mosaic virus and watermelon mosaic virus 2 and is known to be located In Pisum linkage group 2. The second gene, sbm-3, was found in PI 347492, a bean yellow mosaic virus-susceptible line from India, and apparently is located in a different linkage group. Both genes, independently of each other, confer resistance to PSbMV-L1, but whether they are repetitive entities remains to be determined. Pea seed-borne mosaic virus (PSbMV) was characterized by Musil in Czechoslovakia and by Inouye in Japan. 1518 In 1968, this virus was found in the United States, 917-22 and since then, its presence has been ascertained in several other countries. 13 In searching for sources of resistance to PSbMV, Stevenson and Hagedorn, Baggett and Hampton, and Hampton and Braverman screened hundreds of accessions of Pisum sativum L. with the standard strain (PSbMV-ST) and found resistant germ plasm among foreign introductions. 312-23 Hagedorn and Gritton determined that, in PI 193586 and PI 193835 accessions from Ethiopia, resistance was conferred by a single recessive gene (sftm). 8 Recently, Goodell and Hampton and Ashby et al reported that PSbMV isolates from lentils (PSbMV-L) and from New Zealand peas (PSbMV-NZ) were unable to infect pea cultivars possessing mo, the gene for resistance to bean yellow mosaic virus (BYMV). 26-24 Alconero et al demonstrated that resistance to PSbMV-Pl and PSbMV-P4 (from pea), and to PSbMV-Ll (from lentil), was pathotype specific. 1 Consequently, it appears that in P. sativum, there are distinct genetic entities for resistance to PSbMV, with each factor capable of controlling only a specific pathotype of the virus. Alone or in combination, these resistance factors were found in a number of plant introductions (Pis), mostly from. India and Ethiopia. 1 '"