SINGLE-PLANT SELECTION AT ULTRA-LOW DENSITY OF FIRST GENERATION LINES OF THREE BEAN CULTIVARS UNDER WATER STRESS

Nil-competition (ultra-low plant density) has been asserted to highlight individual genotypes of high yielding potential. This was tested preliminary on three determinate type bean varieties (Phaseolus vulgaris L.), two genetically non-uniform and with unstable yields Greek cultivars, Iro and Pirgetos and a “Great northern” type imported variety. Single-plant selection under ultra-low density (interplant distance of 100 cm) was performed in a honeycomb design experiment established during 2017 in the main farm of the University of Western Macedonia in Florina. Eighteen high yielding plants were selected and seed of each constituted a separate first generation line. In 2018, progeny evaluation was conducted in two R21 honeycomb design trials under normal and deficit irrigation treatments respectively. Compared to the original variety Iro, four of the high yielding progeny lines had higher yield plant^-1 (by 20 to 39%) under water deficit with two being significantly different, where for the variety Pyrgetos only one first generation sister line significantly outperformed the original cultivar by 28%. Water stress affected significantly total chlorophyll content measured at 10 day intervals from start of flowering until physiological maturity with the best performing progeny lines showing higher chlorophyll concentrations especially during the seed filling stage. Significant differences between progeny lines and the original varieties were also shown on CO2 assimilation rate under water deficit especially within the genotype Iro. Further research is needed so that any existing variation is beneficially exploited.