Grain yield and quality of rapeseed to combined temperature and radiation stresses during post-flowering

RIVELLI, GONZALO M.; CALDERINI, DANIEL F.; ABELEDO, GABRIELA L.; MIRALLES, DANIEL J.; RONDANINI, DÉBORAH P.

Sidney

Congreso; International Rapeseed Congress; 2023

Australian Oilseeds Federation; The Global Council for Innovation in Rapeseed and Canola

Background:Events of high temperatures combined with cloudiness are more frequent during the post-flowering period of temperate crops in the Southern Cone of South America (Rivelli et al., 2021). Several studies evaluated the effect of either high temperature or shading in rapeseed,however, little is known about the sensitivity of the crop under the combined effect of bothstresses during post-flowering.Objective:The objective of this work was to analyse the limitations of combined abiotic stresses of hightemperature and low incident radiation during the post-flowering period of rapeseed on grainyield and quality.Methods:Field experiments were conducted in environments with different yield potentials: BuenosAires (Argentina) and Valdivia (Chile), medium and high, respectively. A spring rapeseed hybrid(Solar CL) was evaluated. The treatments were: control, shading (-60% incident solar radiation),high temperature (+5oC) during the midday hours and combined stress of shading and hightemperature, using portable chambers placed in each plot during 10 days from 14 days afterthe start of flowering. Experimental design was RCB with 4 replicates. Treatments overlappedthe critical period (Kirkegaard et al., 2018) for grain yield determination (190-330oCd inValdivia and 279-433oCd in Buenos Aires).Results:The climate differed between locations during the experiments. Moderate backgroundtemperatures and higher radiation levels caused a higher photothermal quotient during thecritical period of rapeseed in the control of Valdivia compared to Buenos Aires (1.7 and 1.2MJ m-2 d-1 °C-1, respectively). The grain yield in control was 9.3 and 4.5 t ha-1 in Valdiviaand Buenos Aires, respectively. It was significantly reduced under combined stress (-39%)in Buenos Aires, with no differences in Valdivia. Combined stress resulted in compensationbetween grain number (-40%) and thousand grain weight (+43%) in Valdivia, while in BuenosAires the thousand grain weight was significantly penalized (-25%). Regarding grain quality,differences were observed in the protein concentration in Buenos Aires, with an increaseof 15% for combined stress. By contrast, no significant effects on the oil concentration inrapeseed grain were observed in either experiment.Conclusions:Our results showed that combined stress of high midday temperature and shading significantlyaffected rapeseed grain yield in Buenos Aires, but had a milder impact in Valdivia, indicatinggreater stability under such conditions. More favourable environmental conditions in Valdivia,such as a moderate background temperature and higher levels of incident solar radiation,could be related to a high source/sink relationship post-flowering allowing a full compensationbetween grain weight and number. In summary, this work expands the present knowledgeof the effects of radiation reduction and high temperature on key yield and quality traits ofrapeseed obtained under field conditions and different environments.