PEA CULTIVAR SUSCEPTIBILITY AND INHERITANCE OF RESISTANCE TO THE LENTIL STRAIN (PATHOTYPE P2) OF PEA SEED-BORNE MOSAIC-VIRUS

Commercial pea (Pisum sativum L.) cultivars, plant introduction (PI) l ines, and Oregon State Univ. (OSU) breeding lines were tested for resi stance to pathotype P2 (lentil strain) and pathotype P1 (type strain) of pea seedborne mosaic virus (PSbMV) and to bean yellow mosaic virus (BYMV) to assess the relative proportion of resistant and susceptible pea genotypes. Of the 161 commercial cultivars tested, 117 (73%) were resistant and 44 were susceptible to PSbMV-P2. Of these PSbMV-P2-resis tant cultivars, 115 were tested for resistance to BYMV and all were re sistant. Of the 44 PSbMV-P2-susceptible cultivars, 43 were tested for BYMV susceptibility and all were infected except two, 'Quincy' and 'Av on', both of which were susceptible to a BYMV isolate in another labor atory. Of 138 commercial cultivars inoculated with PSbMV-P1, all were susceptible. All PI lines and OSU breeding lines that were resistant t o PSbMV-P1 were resistant also to PSbMV-P2. The high percentage of com mercial cultivars resistant to PSbMV-P2 was probably attributable to t he close linkage of genes sbm-2 and mo and the widespread use by breed ers of BYMV-resistant 'Perfection' and 'Dark Skin Perfection' in devel oping new pea cultivars. Segregation ratios in progenies of three sepa rate crosses between PSbMV-P2-resistant and PSbMV-P2-susceptible culti vars closely fit the expected 3 susceptible : 1 resistant ratio expect ed for resistance conferred by a single recessive gene.