Strong indication of susceptibility of faba bean (Vicia faba) genotypes to the root-lesion nematode Pratylenchus thornei, under field conditions

Abstract

Faba beans (Vicia faba) are susceptible to the root-lesion nematode Pratylenchus thornei, therefore a range of cultivars and advanced lines were tested to determine if there was genetic variation in resistance to potentially exploit in breeding programs. Two field experiments in Queensland measured the resistance to P. thornei of faba bean cultivars and compared them with wheat cultivars (Triticum aestivum) ranging from moderately-resistant to susceptible, and a very susceptible narbon bean cultivar (Vicia narbonensis). In the first experiment, in-crop rainfall was 271 mm and plant biomass ranged from 7.3 to 9.2 t/ha, whereas the second experiment, in-crop rainfall was 116 mm and plant biomass ranged from 3.9 to 4.6 t/ha. Despite the differences in seasonal conditions and plant growth, the effect of cultivars on nematode populations was consistent in an across site analysis (P<0.001). All faba bean cultivars were susceptible with final P. thornei populations increased 7 to 14-fold (48 P. thornei/g soil after cv. 11NF001-10 to 90/g soil after cv. Cairo at 0–30 cm soil depth at harvest) when compared with the moderately resistant wheat cultivar (6 P. thornei/g soil). There was a 10-fold increase after the susceptible wheat cultivar (73/g soil) and 22-fold increase after narbon bean (148/g soil). Screening cultivars for resistance to diseases in the field can be confounded by environmental constraints, but not so in these experiments, reflecting the strong genetic control of crop genotypes on P. thornei reproduction. The range of P. thornei populations measured after growing the faba bean cultivars means that targeted breeding can be used to improve resistance levels of all faba bean cultivars so that growers will be able to derive the maximum benefit from this valuable pulse crop in the farming systems of the Australian northern grain region.