Determinants of yield and quality in winter rapeseed (Brassica napus L.) under Mediterranean conditions

Abstract

SUMMARYWinter rapeseed was introduced into Greece a decade ago to provide oil for biodiesel. To identify agronomic traits affecting yield and quality, three hybrids and an inbred line were tested over two seasons (2005–2006 and 2006–2007) and four locations, in central and northern Greece, varying in pedo-climatic conditions. The large variations in seed yield, quality and agronomic traits were largely ascribed to location; in contrast, cultivar accounted for ⩽0·010 of the variation for many traits. Below 40°N, rapeseed is a risky crop; short season, high temperatures and low rainfall during reproductive growth diminished seed yield and oil content, increased oleic and erucic acid and minimized linolenic acid. A hybrid, Exact, with tall stature and large seeds was adaptive to such conditions. The most productive location had dense stands with tall plants bearing numerous pods on the main raceme. At the site with the coldest winter, plant density (PD) was lowest (ca. 30 plants/m2) but rapeseed compensated by producing large seeds, with high oil content and harvest index (HI). A biplot revealed that the hybrid Excalibur, outperforming the other cultivars for oil content in six out of eight trials, produced the highest and most stable oil yield. Combined data showed that seed yield and oil yield were positively correlated with PD, seed size and HI and negatively to the number of pods on branches and per plant. Large seeds had high seed oil content. Oleic acid was negatively correlated to linolenic acid concentration. High temperatures and low rainfall favoured oleic acid, which was positively associated with seed number per pod.