Contribution of main culm and tillers to grain yield of durum wheat:Influence of sowing date and plant traits

摘要

The question of whether tillers are a burden or a resource indurum wheat is of concern in the variable Mediterranean climates.The contribution of tillers to grain yield was investigated in commercialcultivars differing in time to anthesis, tillering and spikesize, in response to three sowing dates:mid-autumn (recommended),winter, and early spring. The thermal time of phenologicalphases was calculated, and yield-components and floret productionwere analysed separately in main culm and tillers. Tiller spikesshowed higher spikelet abortion coupled to lower spikelet fertilityand mean kernel weight, so that grain yield was 40-60% lower thanin main culm spikes. Despite this, tillers contributed 35 to 50% toplant yield. The sowing date affected tiller number rather than onetiller yield. In winter sowings (December), lower main culm yieldwas fully compensated by increased tiller yield, whereas shifts ofsowing date to early spring (February) reduced tillering, whichcaused a yield loss ranging from 12 to 20%. Cultivars differed inone tiller yield rather than in tiller number, and higher grain yieldof tillers was primarily due to increased grain recovery. A moreequal partitioning of resources within main culm and tillers correspondedto better yield stability across sowing dates. Starting fromthis, we suggest that early anthesis, a long stem elongation phase,a high primordium initiation-rate and small spikes, could be positivetraits for durum wheat yield stability in changing environments,since they allow plants directing more time and resources tofloret production and grain filling both in main culm and tillerspikes. From a methodological point of view, our results show thatthe number of fertile florets per spike is highly correlated with theaverage floret number of five given spikelets.