Nashef, K. | Search bioRxiv

bioRxiv2023

Pre-anthesis spike growth dynamics and its association to yield components among elite bread wheat cultivars (Triticum aestivum L. spp.) under Mediterranean climate

Wheat (Triticum spp.) grain yield (GY) is highly associated with grain number per unit area (GN m-2). Biomass accumulation and partitioning are essential to understand pre-anthesis spike growth dynamics which determines spike dry matter at anthesis (SDMa) - a GN determinant. Spike growth takes place during the stem elongation period (SE), from terminal spikelet to anthesis, following leaf and spikelet initiation (LS) from sowing to terminal spikelet. In this study, bread wheat cultivars were examined under Mediterranean semi-arid conditions to determine (i) the varietal differences in pre-anthesis phase duration, (ii) whether this variability influences biomass partitioning and spike-related traits, and (iii) to what extent, the genotypic variations in pre-anthesis phase duration and spike growth are associated with yield components. A panel of Israeli commercial bread wheat cultivars were grown in the field during 2016-17 (three environments) and 2017-18 (two environments) and characterized for pre-anthesis phases, floral conditions and spike fertility via histological measurements, spike traits and dry matter accumulation and partitioning at anthesis and maturity and for yield components. Significant variability in the timing of pre-anthesis phases was detected within the tested panel. LS duration, and occasionally SE, favourably related with a better dry matter of fertile florets spike-1 (at anthesis) and SDM (at both anthesis and maturity). Two cultivar pairs Zahir-Yuval and Negev-Gedera, which flowered concurrently, revealed significant differences in the durations of LS and SE phases across the environments. Longer LS (e.g., in cultivars Zahir and Negev) exhibited increased spikelets number spike-1, whereas longer SE (e.g., in Yuval and Gedera) enhanced spike fertility through improving the survival rate of floret primordia (FSR%) of central spikelets. However, there was a trade-off for FSR at the proximal and distal spike portions, resulting reduction of final GN (or GY) in cultivars with longer SE. It is concluded that, in this panel, the duration of both LS and SE contribute to spike fertility. However, under short wheat growing cycle, LS duration seemed a stronger driver than SE for GN and yield enhancement. These highlights the novel importance of pre-anthesis phases, especially the role of LS in wheat yield increment during the short growing cycle. The varietal combination with variable LS and SE duration could be implemented in the breeding pipeline and used as pre-breeding materials for GN improvement. Furthermore, the findings will improve pre-anthesis traits adoption in Mediterranean bread wheat future breeding programs.

plant biology↗

bioRxiv2020

Genetic improvement of wheat early vigor promote weed-competitiveness under Mediterranean climate

Chemical weed-control is the most effective practice for wheat, however, rapid evolution of herbicide-resistant weeds threat food-security and calls for integration of non-chemical practices. We hypothesis that integration of GAR dwarfing-genes into elite wheat cultivars can promote early vigor and weed-competitiveness under Mediterranean climate. We develop near-isogenic lines of bread wheat cultivars with GAR dwarfing genes and evaluate them for early vigor and weed-competitiveness under various environmental and management conditions to identify promising NIL for weed-competitiveness and grain yield. While all three NILs, OC1 (Rht8,12), ZC4 (Rht12,13), and BNMF12 (Rht12), responded to gibberellic acid, they exhibited differences in early vigor. Greenhouse and field evaluation highlighted OC1 as a promising line, with significant advantage in early vigor over its parental. To facilitate accurate and continuous early vigor data collection, we applied non-destructive image-based phenotyping approaches which offers non-expensive and end-user friendly solution for selection. NIL OC1 was tested under different weed density level, infestation waves, and temperatures and highlight the complex genotypic x environmental x management interactions. Our findings demonstrate the potential of genetic modification of dwarfing genes as promising approach to improve weed-competitiveness, and serve as basis for future breeding efforts to support sustainable wheat production under semi-arid Mediterranean climate.

plant biology↗