Morphology, Phenology, Yield, and Quality of Durum Wheat Cultivated within Organic Olive Orchards of the Mediterranean Area

Abstract

In the current context of climate change, tree–crop combinations in agroforestry systems are suggested to mitigate water and heat stresses, particularly in semi-arid environments of the Mediterranean area. In this framework, a 3-year trial was conducted at the French National Research Institute for Agriculture, Food and the Environment (INRAE) in Mauguio (Southern France) in order to investigate the response of twenty-five durum wheat genotypes under a yearly pruned (AF) and a never-pruned alley olive orchard (AF+), in comparison with an open field without trees (control, C). The grain yield of wheat was markedly reduced in both the agroforestry systems AF (average −43%) and AF+ (−83%), according to the shading level. Among the yield components, the plant density at harvest was enhanced in AF (+22%) and AF+ (+3%), although with a significant reduction in the number of grains per spike (−37% in AF and −62% in AF+), and the number of spikes per plant (−32% in AF and −52% in AF+). The thousand-grain weight (TGW) and harvest index (HI) were slightly higher under moderate shade (AF; +12% vs. C) and severe shading (AF+; +6%). Plant biomass and spike size were significantly reduced in both agroforestry systems, while the flag leaf–spike distance (last internode) increased in AF. It was concluded that the moderate shading conditions of AF may create a sustainable agricultural system, and the wide intraspecific variability suggested a large scope for screening suitable genotypes, helping to produce ideotypes to implement agroforestry-oriented breeding programs.