Resistance to bacterial blight (Pseudomonas syringae pv. pisi) in Spanish pea (Pisum sativum) landraces

Pea bacterial blight ( Pseudomonas syringae pv. pisi) has long been known t o be present in pea growing areas of Spain and to cause serious crop losses , although there is no published record of its occurrence. A collection of 16 isolates from a winter pea trial in Valladolid in 1991 which were shown in this study to be P.s. pv. pisi races 4 and 6 would appear to be the firs t published record of the disease in Spain. This occurrence of races 4 and 6 is the same as reported for winter-sown peas in the South of France. Ten Pisum sativum landraces from different geographical areas of Spain and considered to be representative of the traditional pea crop, were tested fo r resistance to seven races of P.s. pv. pisi. Seedlings of each landrace we re stem inoculated with the type strain of each race in a glasshouse. Resis tance exhibited by the different landraces mainly conformed to those previo usly described in pea cultivars indicating various combinations of the main resistance genes: R3, R2+4, R3+4 and R2+3+4. R3 was the most frequent R ge ne, being present in all landraces. R4 was present in four and R2 in three of the landraces tested. Variation for resistance within landraces was limi ted except for landrace accessions ZP-0102, ZP-0109 and ZP-0137 which also showed variation for morphological traits. The resistance responses of land race ZP-0109 were difficult to interpret, but suggested a genetic mixture w ith some evidence of less well documented R genes, R5 and/or R6, and possib ly some unknown resistance to race 6.