Effects of two-generational heat stress exposure at the onset of seed maturation on seed yield and quality in Brassica napus L.

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Many studies point out the deleterious effect of high temperatures during the crop reproductive stages on seed yield and quality. However, the response of plants to repeated stressing events across plant generations remains poorly investigated, especially in a context of climate change characterized by increased interseasonal variability frequency in terms of spring and summer heat waves. In our study, we attempted to gain a better insight on the effects of repeated heat stresses over two plant generations (i.e. Mother and Progeny plants) on yield components, seed nutritional and physiological quality criteria, under two contrasting sulphur supplies. Results measured in seeds that were at the onset of maturation when the temperature stress was applied indicated that (i) Progeny effects were predominant over Mother effects on most measured variables, thus indicating no intergenerational effects, (ii) the extent of the Progeny effects was modulated by the Mother effects e.g. amplified or attenuated differences on the desiccation tolerance proxy, according to the Mother plant origin, and (iii) the longer the cumulated duration of the temperature stress over the two plant cycles, the more negatively impacted the quality criteria with decreased fatty acids concentration, increased ω6:ω3 ratio, lower desiccation tolerance and increased seed dormancy. Sulphur limitation had little effect on the Progeny responses to heat stress, thus maintaining similar trends to those observed under well-supplied plants. This work provides insights to define thermopriming protocols over multiple plant generations to stabilize or even improve yield and seed quality in a context of stress exposure fluctuations. • Multiple heat stress exposures over two generations modify seed yield and quality in oilseed rape. • Progeny effects were predominant over Mother effects. • The most negative heat stress sequences matched the longest stress duration over the two generations. • The most impacted variables were seed weight, oil, storage capacity and seed dormancy. • Thermopriming protocols are challenging acclimation strategies due to their fine tuning in terms of stress features.