Differences in photosynthesis efficiency related parameters in a hybrid-parent barley germplasm set

Abstract

Crop productivity can be expressed as the product of the amount of radiation intercepted, radiation use efficiency and harvest index. Genetic variation for components of radiation use efficiency have rarely been explored due to the lack of appropriate equipment to determine parameters at the scale needed in plant breeding. On the other hand, responses of the photosynthetic apparatus to environmental conditions have not been extensively investigated under field conditions, due to the challenges posed by the fluctuating environmental conditions. The field fluorimeter MultispeQ was developed as a portable device that allows medium throughput measurements in any experimental conditions. This device provides the determination of a suite of chlorophyll fluorescence-derived photosynthetic parameters as photosystem II quantum efficiency (ɸII) or non-photochemical quenching (NPQ), absorbance-based parameters as relative chlorophyll content (SPAD), and water status indicators as leaf temperature differential (LTD) in less than 15 seconds, avoiding extensive dark acclimation periods required by traditional measurements.

Here we report genotypic differences found in a set of barley germplasm consisting of two female parents, 46 male parents, and the corresponding 92 hybrids. Each genotype was represented by a single plot. The analyses have been performed on the two sets of parents, and the set of hybrids. Therefore, genotypes in each set are considered as replicates. Extensive measurements were taken in two relevant moments, after a period of mild water stress, and after an episode of abundant rain. Significant differences were found for SPAD, ɸNPQ and LTD between groups of genotypes. Hybrids presented an asymmetric inheritance of traits, resembling the females in superior SPAD values, and resembling the males in higher LTD and ɸNPQ. The combination of traits detected in hybrids seems favorable, and could indicate higher plant nitrogen content and improved photoprotection.