Oblonga …a clonal olive rootstock resistant to verticillium wilt
A field planting in Tulare county of Sevillano olives grafted on various rootstocks provided opportunity for observations on susceptibility to verticillium wilt. In this 16-year test period, trees growing on the Oblonga clonal rootstock remained free of symptoms while 20 to 100 percent of the trees grafted on other olive species and varieties were killed by verticillium. None of the trees with the highly susceptible Sevillano as the scion variety on the Oblonga root showed symptoms of verticillium wilt…suggesting that the pathogen is not transmitted through the graft. Several trials with two major strains of Verticillium albo-atrum taken from cotton and olives in Tulare county, using controlled inoculation techniques and greenhouse conditions at Davis, confirmed the resistance of Oblonga to verticillium wilt. Sevillano, Ascolano, and Mission develop to normal sized trees on Oblonga roots. However, in studies at Winters this rootstock exerted some dwarfing influence on Manzanillo. No evidence of graft incompatibility or a weak graft union has appeared in any of these combinations.