Evaluation of Yield and Agronomic Performance of Leafed and Semi-leafless Pea Blends

Abstract

Field pea has two distinct leaf morphologies: leafed (L) and semi-leafless (SL). The leafed pea is more susceptible to lodging, but it may have high yield potential when lodging is prevented. In contrast, the semi-leafless pea is bred for lodging resistance and has greater yield stability. However, it has reduced leaf area which may be related to yield potential. When grown together, the semi-leafless type improves the lodging resistance of leafed pea and also gains a weed competition advantage with the leafed blend. There is some evidence that growing blends of leafed and semi-leafless pea may lead to higher crop yield than sole crops of either leaf type. However, previous studies used two different semi-leafless and leafed varieties to compose the leaf-type blend, which identified confounding factors. The effect of pea leaf blends has not yet been clarified, whether the agronomic and yield improvements were from the blends and/or the mixture of different genotypes. An optimum blending ratio has also not been determined. The objective of this thesis was to determine the yield and agronomic performance of near-isogenic pairs of leafed and semi-leafless pea varieties. Two field studies were conducted in Saskatchewan, Canada, from 2017 to 2019. The pea leaf blends reduced leafed pea lodging and prevented leafed pea yield loss compared to the leafed monoculture; however, the blend did not affect light interception, disease, lodging, and yield relative to the semi-leafless monoculture. The estimated optimal blending ratio, 86:14% SL/L, had a 13% yield increase compared to the leafed monoculture, but no yield and agronomic advantage compared with the semi-leafless monoculture. When comparing the pea leaf blends that consisted of the near-isogenic pairs or non-isogenic pairs, light interception, lodging, disease severity, and yield responses of the variety mixtures were not significant. The results of the relative yield in variety mixture to monoculture showed that the blends’ yield was generally intermediate to the mean of the two varieties in the monocultures, and no consistent agronomic improvements or yield increases could be attributed to the variety mixture. To explore the effect of leaf type blend on lodging, crop canopy was captured pre-and post- lodging by UAV-imagining. The canopy height was determined using canopy reconstruction of a time-series reduction from UAV-image analysis, which was compared to the lodging index from the ground measures. The image-derived lodging index was more precise than ground reference measures of lodging, and the pure semi-leafless pea was the most lodging resistant ratio. Lodging increased significantly when the leafed percentage in the blend exceeded 33%. This thesis project grew four pairs of near-isogenic lines in the two experiments at eleven site years and did not find significant yield and agronomic benefits to the current semi-leafless pea production.