Oil concentration in canola (Brassica napus L.) as a function of environmental conditions during seed filling period

Oil concentration (OC) in canola (B. napus L.) is determined during seed fillingperiod (SFP), and the variation in OC is greatly related to environmental conditionsduring that period. To determine factors affecting OC in canola, 12 fieldexperiments were conducted at Agricultural Research Station of Gonbad, Iran,during 2000-07. The experiments were carried out under different growingconditions. The regression functions were fitted to the data of each group ofgenotypes, over years and experiments. Increasing SFP was a determinant factorfor increasing OC. Oil concentration was affected by the duration of SFP, whichwas maximized when plants of both genotypes (open pollinates and hybrids) wereexposed to lower temperatures. There was a linear negative relationship betweenair temperature during SFP and OC. High temperatures, accelerated the rate ofplant development, lowered the length of SFP, and reduced OC potential. In bothgroup of genotypes, the variation of OC was explained by rainfall during SFP, andtemperature and radiation interactions during the period, as showed byphotothermal quotient (PTQ). There was a positive logarithmic relationshipbetween PTQ during SFP and OC. The relationships of OC with duration of SFP,and temperature, PTQ and rainfall during SFP over years, sowing dates andgenotypes showed that these variables are generally applicable in canola OCdetermination.