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Morpho-physiological adaptations to weed competition impair green bean (Phaseolus vulgaris) ability to overcome moderate salt stress

Valerio Cirillo , Marco Esposito, Matteo Lentini, Claudio Russo, Nausicaa Pollaro, Albino Maggio

Abstract

Weeds are a constant component of the agricultural environment, causing significant yield losses if not adequately controlled. Similarly, salt stress is an ever-expanding phenomenon that affects agricultural land. The coexistence of these two constraints represents a threat for the future of food production, also because weeds are more salt stress tolerant than most crops. Moreover, the current climate change scenario will lead to an increase of soil salinity worldwide, and therefore it will possibly exacerbate the competition between weeds and crops. Notwithstanding these predictions, this aspect has been scarcely investigated in the context of weed-crop competition. For this reason, an open field experiment on green beans (Phaseolus vulgaris L.) has been performed to shed light on the impact of the combination of weed competition and salt stress on different key morpho-physiological traits, as well as on the final crop yield. We demonstrated that soil salinity shifted weed composition toward salt tolerant species such as Portulaca oleracea and Cynodon dactylon, while it reduced the presence of other species with lower levels of tolerance. In addition, weed competition activated adaptation responses in green bean such as reduced leaf mass per area and biomass allocation to the stem, unchanged stomatal density and instantaneous water use efficiency which diverge from those that are typically observed as a consequence of salt stress. The morpho-physiological modifications caused by the presence of weeds can be ascribed to the effects of alterations of light intensity and/or quality, further confirming the pivotal role of the light in crop response to weeds. Therefore, we concluded that higher yield loss caused by the combination of salt stress and weed competition is a consequence of impaired morpho-physiological responses of green bean to salt stress which highlights the negative interaction between salt stress and weed competition for green bean yield. This phenomenon will most likely be more frequent in the future and potentially reduce the efficacy of the current methods for weed control.

FP23202  Accepted 01 May 2024

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