Yield and quality traits of wheat and rapeseed in response to source-sink ratio and heat stress in post-flowering

Abstract

The probability of occurrence of high temperatures and cloudiness events increases during the post-flowering period of temperate crops in the southern cone of South America. Several studies have evaluated the effect of high temperature or shading on wheat and rapeseed, but little is known about the impact of the combined effect of both stresses on the yield and grain quality of these crops during the post-flowering phase. This study aims to analyze the sensitivity and stability of wheat and rapeseed grain yield and quality in response to shading, high temperature and the combined stresses during post-flowering in two contrasting environments. Field experiments were carried out using the same wheat and rapeseed genotypes in environments with high (Valdivia, Chile) and medium (Buenos Aires, Argentina) yield potential. The treatments consisted of i) control, ii) shading stress, iii) heat stress and iv) combined shading and heat stress during the central hours of day. Portable chambers were placed on the plots at 7–10 days from anthesis in wheat and 14 days from the beginning of flowering in rapeseed, throughout 10 days. Grain yield was significantly reduced for the combined stress in wheat (−46%) and rapeseed (−39%) in Buenos Aires, but there were no differences between treatments in any crop in Valdivia. Combined stress in rapeseed produced a trade-off between grain number (−40%) and grain thousand weight (+43%) in Valdivia, while grain thousand weight was penalized (−25%) in Buenos Aires. For wheat there were no differences in grain protein in both locations, while for rapeseed protein increased due to the combined stress in Buenos Aires (+15%), no effects were recorded for grain oil in either location. Our results showed a high stability of grain weight in rapeseed to single and combined environmental stresses, with better environmental conditions during grain filling.