Novel techniques to improve yield quantity and quality in common bean

Reflecting on current challenges, this research identified conceptual and practical shortcomings in our understanding of yield development, particularly under abiotic stress. Focusing on Phaseolus vulgaris L. (common bean), the most important grain legume for human consumption, this research investigated what factors determine yield with a focus on source-sink relationships under the imposition of abiotic stress. Given the importance of quantifying both source and sink strength, we developed a new method for the determination of sink development using portable nuclear magnetic resonance technology. Using this technique, we successfully measured dry matter and water loading into a P. vulgaris pod non-invasively in real-time. We characterised dry matter loading into P. vulgaris pods during the light and dark period and demonstrated that manipulating source strength does not impact on dry matter loading into the pod. Given the resilience of yield under changes to source strength, we sought to identify if drought and low phosphorus availability, impacted on yield and physiology along with nutritional quality. In a series of trials conducted in a controlled environment on P. vulgaris, water deficit and broad nutrient deficiency had no influence on nutrient content of the grain despite observed changes in nutrient concentration in the leaf and phloem tissue. Building on these findings we conducted a field trial and lysimeter trial on P. vulgaris genotypes at the International Centre for Tropical Agriculture to investigate the combined impact of drought and low phosphorus availability. These trials demonstrated that abiotic stress impacted on yield but did not dramatically impact on the grain nutrient content. Of particular interest, while genotypic variation was detected at the leaf level, no genotypic variability was detected in grain nutrient content. This research has substantial implications for the concept of sensitivity in yield development