Escape and true resistance to crenate broomrape (Orobanche crenata Forsk.) in grass pea (Lathyrus sativus L.) germplasm

Grass pea (Lathyrus sativus L) is an annual cool season legume widely grown as a pulse crop for human food and animal feed and as forage. Infection by the parasitic weed crenate broomrape (Orobanche crenata Forsk.) has been identified as major constraint for grass pea cultivation. We studied the response to O. crenata of a germplasm collection of grass pea in field trials over two seasons showing that the level of infection was highly influenced by environmental factors and plant growth cycle. Earlier or very late accessions were less infected. O. crenata infection increased with host plant vigour. O. crenata infection strongly reduced host biomass and grain yield. Even when resistance is scarce and masked by confounding environmental and plant growth cycle factors, calculation of the deviations from the polynomic nonlinear regression provided an improved approximation of the true genetic resistance levels present in the germplasm, here defined as resistance that do not depend on precocity. (C) 2011 Elsevier B.V. All rights reserved.