Relationships of grain carbon isotope discrimination (Δ) and ash content with yield and quality in dry bean

Abstract

SUM M ARYDry bean (Phaseolus vulgaris L.) is a traditional crop of north-western Macedonia, Greece, where two landraces ( plaki Prespas and Chrisoupoli) in particular are grown. The aim of this study was to test whether the grain carbon isotope discrimination (Δ) and ash content (ASH) are related to grain yield (GY), protein content (PC) and mean grain weight (MGW) in dry bean. As a part of a honeycomb selection programme, 21 genotypes (19 lines derived via intra-landrace honeycomb selection for single plant yield at low density plus the two original populations) were grown at two densities, 1·2 and 4·8 plants/m 2 under non-limiting water conditions in a glasshouse and in the field. Genotypes differed significantly for Δ, ASH and PC under the low density. In the dense stand, genotypes differed significantly only for ASH and PC. The environment (glasshouse or field conditions) affected all the traits significantly. Neither Δ nor ASH showed strong or consistent relationships with GY and thus, they cannot serve as reliable, indirect selection criteria for GY. Strong, negative relationships between Δ and PC were found especially in the dense stand, confirming analogous results in C 3 cereals. Inconsistent genotypic ranking for grain physiological traits under the different densities and environments was indicative of large genotype × environment interaction. Genotypes performed consistently for GY and MGW under both densities, showing the strong stability of these traits.

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“…Conversely, ΔG m was higher in Season 1, probably because of the enhanced re-mobilization of C products having high Δ value, contributing to an increase of Δ in the grain ( Figure 2 and Table 4 ). The correlation across genotypes between ΔG m and yield (r = 0.84, p < 0.01) confirmed previous [ 24 , 25 , 26 ] and was stronger when rainfall distribution corresponded to typical post-anthesis water stress (i.e., Season 1), as has already noted by Monneveux et al [ 25 ] in wheat and Tsialtas et al [ 27 ] in dry bean. The close association between GY and dry matter Δ across treatments confirmed the potential interest of Δ as an indicator of yield effects of source–sink manipulations [ 3 , 21 ].…”