Resilience of rapeseed to cope with heat and light stress during post flowering

RIVELLI, GONZALO MARTÍN; CALDERINI, DANIEL FERNANDO; ABELEDO, LEONOR GABRIELA; MIRALLES, DANIEL JULIO; RONDANINI, DEBORAH PAOLA

Buenos Aires

Simposio; Frontiers in Bioscience 4; 2023

CONICET

High temperature combined with cloudiness during a few days are frequent during the post-flowering period of temperate crops in the Southern Cone. Several studies evaluated the effect of either high temperature or shading in rapeseed productivity, but little is known about combined stresses. Recent findings show that effects of combined stresses are well described by photothermal quotient, and there is evidence of high reproductive plasticity in rapeseed and compensatory mechanisms between grain weight and grain number. Whether compensatory mechanisms operate only in benign, high-yield potential environments is unknown. To quantify the effects of combined abiotic stresses of high temperature and low incident radiation during the post-flowering period of rapeseed on grain yield, watered crops were growing in environments with high (Valdivia, Chile) and medium (Buenos Aires, Argentina) productivity. Treatments were applied to a spring rapeseed hybrid (Solar CL) using portable chambers placed during 10 days from 14 days after the start of flowering: unstressed (control), shading (-60% incident solar radiation), high temperature (+5ºC) during 5 hours at midday, and combined stress of shading and high temperature, in a RCB with 4 replicates. Moderate background temperatures and higher radiation levels caused a higher photothermal quotient during the critical period of rapeseed in the control of Valdivia compared to Buenos Aires, with grain yield in controls of 9.3 and 4.5 tn/ha, respectively. It was significantly reduced under combined stress (-39%) in Buenos Aires, with no differences in Valdivia. Combined stresses resulted in compensation between grain number (-40%) and thousand grain weight (+43%) in Valdivia, while in Buenos Aires the thousand grain weight was significantly penalized (-25%). It is concluded that combined stress affected rapeseed grain yield in Buenos Aires, with a milder impact in Valdivia probably related to a high source/sink relationship post-flowering allowing a full compensation between grain weight and number.