Identifying and evaluating competitive traits in wheat for sustainable weed management (PhD)

Abstract

The management of weed species Alopecurus myosuroides (black-grass) in arable agriculture is largely achieved through use of herbicides. However, resistant populations are increasingly commonplace and new modes of action are proving elusive. Growers use integrated weed management (IWM) strategies to manage the weed seedbank, such as rotational ploughing to bury seed and delayed drilling to reduce weed numbers within a crop. Competitive cultivars may contribute to IWM, but testing cultivars is a long, expensive process.

The aims of this studentship were to identify the traits that confer enhanced crop competitive ability and determine if these can be used to predict competitive ability of new cultivars. This was investigated on outdoor sand-beds and in field trials. Commercial wheat cultivars were grown alongside A. myosuroides. Various wheat traits were measured throughout growth. The seed return of A. myosuroides was quantified at maturity, and yield was harvested in the field. Pearson’s correlations and multivariate analysis were used to identify traits related to competition, and Linear Mixed Models (LMM) were used to identify predictive traits. Two models of crop-weed interactions were parameterised for the cultivars. Potential interactions between cultivar choice and other IWM strategies (delayed sowing and increased sowing rate) was assessed experimentally and through simulation models.

Cultivar differences in suppressive ability were most evident between the extreme ends. Various traits were related to a cultivar’s ability to suppress A. myosuroides seed return, such as early height and tillering parameters, though no traits were consistent across all experiments. Few traits could be related to tolerance to yield loss. Suppressive ability can be ascertained early in the growing season, but the relationship with individual traits can change direction, possibly depending on the availability of belowground resources. Generally, earlier maturity and a conserved tillering strategy appears to be more suppressive. Cultivar choice is largely compatible with delayed sowing and increased sowing date. The effect of environmental variability on relationships between traits and competitive ability requires further investigation before they can be employed as predictors, particularly in the context of belowground competition.