yield difference and radiation use efficiency in spring cultivars of the oilseed rape

in order to study of yield, yield component, plant height, total dry matter and radiation use efficiency with 13 spring varieties of rapeseed ,an experiment was carried out in 2007 growing season at agriculture and natural resources research station of torogh,mashhad. these cultivars were from three rapeseed species belonged to brassica napus, brassica rapa and brassica juncea. experimental design was randomized complete block with 4 replication. result showed that a significant difference was existed among cultivars for yield, yield component, plant height and total dry matter. with exception of number of pod, hyolla hybrids had more yield components than other cultivars. meanwhile cultivars of b.napus had more yield components than cultivars of b.rapa. hyolla 330 with average of 1475 kg.ha-1, bp18 with average of 1277kg.ha-1 and hyolla 401 with average of 1274 kg.ha-1 had the most yields in this experiment respectively. we concluded that cultivars of b.napus had more yield than varieties of b.rapa. cultivars in this trial presented considerable difference regarding radiation use efficiency. the value of radiation use efficiency under this investigation ranged from 0.4487±0.201 dm. mj-1 to 1.8355±0.07 dm. mj-1. hyolla 330 with average of 1.8355+0.07 dm. mj-1 and zarfam with average of 1.32+0.725 dm. mj-1 had the most radiation use efficiency. at this experimental condition, generally cultivars of b.nupus had greater slope of dry matter expansion in unit of cumulative received radiation than both b.rapa and b.juncea cultivars.