Inheritance of Resistance to Ascochyta Blight in Lentil

Abstract

Lentil (Lens culinaris) is a major grain legume (pulse) crop in Canada. Ascochyta blight, caused by Ascochyta lentis Kaiser et aI. (1997) (syn. Ascochyta fabae Speg. f sp. lentis Gossen et aI., 1986) is an important disease of lentil in Canada and worldwide. This disease can be serious, especially in wet growing seasons, and losses can be as high as 70% due to reduction in yield and quality. The main objective of this study was to determine the mode of inheritance of resistance to seedborne ascochyta blight in lentil. Seven lentil cultivars/lines, four resistant (ILL 5588, Indianhead, PI 339283 and PI 374118 (tentative)) and three susceptible (Eston, Laird and ZT4), were crossed in all possible combinations, excluding reciprocals. Fl plants were grown in the greenhouse and spaced F2 plants were grown in an irrigated ascochyta nursery. F2 plants were harvested individually and seeds were plated on agar media to determine percentage seedborne ascochyta infection. F2 plants with [greater than or equal too] 12% seedborne ascochyta infection were considered resistant and those with > 12% seedborne ascochyta infection were considered susceptible. F3 rows were grown in an irrigated ascochyta nursery in the field and harvested in bulk. One hundred seeds from each of the F3 rows were plated on agar media and percentage seedborne ascochyta infection was determined. F3 families with [greater than or equal to] 12% seedborne ascochyta infection were considered resistant and those with > 12% seedborne ascochyta infection were considered susceptible. Chi-squared test of goodness-of-fit to various one and two gene ratios showed that the resistance in Indianhead lentil was governed by a single recessive gene. Resistance in ILL 5588 lentil was governed by a single dominant gene. The resistance in PI 339283 was governed by at least one dominant gene. Lentil line PI 374118 showed a high level of seedborne ascochyta infection and was regarded as susceptible. The recessive gene governing resistance in Indianhead lentil was epistatic to the dominant genes for resistance in ILL 5588 and PI 339283 lentil. Indianhead lentil showed high foliage infection by ascochyta, suggesting that resistance to seedborne ascochyta infection and resistance to foliage infection are controlled by two different genetic systems.