High temperature patterns at the onset of seed maturation determine seed yield and quality in oilseed rape (Brassica napus L.) in relation to sulphur nutrition

High temperatures during the crop reproductive stage impact seed yield and quality. The changing climate will require consideration of the effects of high temperature events that differ from their intensity, their duration and their frequency over the seed quality-building stages. The impact of these features deserve to be investigated at the light of induced thermo-sensitization which can lead to alleviate expected negative impacts. In our work, maturing seeds of the sulphur-demanding crop, oilseed rape, were exposed to several temperature sequences that varied in intensity, duration and frequency at the onset of seed maturation. Results-measured in seeds that were at the onset of maturation when the temperature stress occurred-indicated that (i) the longer the cumulated duration of the temperature stress, the more negatively impacted the quality criteria with decreased fatty acids (FAs) concentration, increased ω6:ω3 ratio, lower seed membrane integrity and increased seed dormancy and (ii) a mild stress event prior to heat peaks had an alleviating effect on the negative impact of the later heat peaks (priming effect) on seed nitrogen, desiccation tolerance and the phytohormones involved in thermoinhibition. Sulphur restriction was positive on FAs, protein concentration and negative on breaking dormancy. In addition, sulphur supply interfered with temperature modality, features such that positive impact of sulphur limitation on boosting oxidative response were cancelled with intense late heat peaks. This work provides insights to define thermopriming protocols in relation to the timing of quality building processes, their respective optimal temperature and adequate sulphur supply.