Response of winter common wheat genotypes to metabolite pool manipulations
Abstract
The purpose of the study was to establish the characteristicsof the response of a broad set of winter commonwheat(Triticum aestivum L.) genotypes of diverse originto contrasting metabolite pool manipulations (half-spikeremoval, complete defoliation) in order to assess their breedingvalue and substantiate directions for their further use inbreeding programs.Methods. The study was conducted in 2024–2025on a collection of 55 genotypes, including 31 cultivars ofdomestic, Chinese, and European breeding and 24 breedinglines. Three treatments were applied to the main stem of each genotype: control (intact plants), complete defoliationat heading, and removal of half the spikelets. At full grainmaturity, 1000-kernel weight (TKW) and stem dry mass weredetermined. The significance of control-treatment differenceswas assessed by paired t-test with Cohen's d; four responseindices (R1–R4) were calculated for each genotype as theratio of the treatment value to the control. The structure ofrelationships among the indices was established by principalcomponent analysis (PCA), with prior verification ofdata suitability (Bartlett's test, KMO measure). Genotypetypology was determined by hierarchical clustering (Ward'smethod), followed by testing of inter-type differences usingone-way ANOVA.Results. Half-spike removal caused a significant increasein TKW (+7.0% relative to control; Cohen's d=1.04), whereascomplete defoliation caused its decrease (-15.9%; d=2.44) –the effect size of defoliation was twice that of spikelet removal,indicating a predominance of source limitation of grain fillingin the studied germplasm. Stem mass showed a mirroredpattern, confirming the involvement of stem reserves in compensatingfor source deficit. PCA revealed two independentaxes of variability: stem reserve plasticity (40.1% of variance)and the type of source–sink limitation of the kernel (30.9%).Cluster analysis identified four statistically distinct responsetypes (p<0.01 for all indices): one with enhanced sensitivityto source limitation, one with consistently high stem massunder both treatments, one with intermediate index values(the most numerous), and one with a reduced stem response.Conclusions. The identified typology of winter commonwheat genotypes by the nature of source–sink relationsreflects a genuine physiological differentiation rather than astatistical artifact, providing a differentiated basis for selectingbreeding material for specific objectives – increasing yieldpotential, lodging resistance, or tolerance to stresses associatedwith loss of photosynthetic surface area.
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