| In rapeseed(Brassica.napus L)strong heterosis has been reported for seed and agronomic traits. The level of genetic diversity between parents as estimated using isozymic and molecular markers is considered a tool for predicting the hybrid performance and heterosis of crosses. To explore this possibility, GD(genetic distance) on three different level, including morphological, isozymic and RAPD markers, were used to predict the performance of hybrids. Eleven elite rapeseed lines, including 6 maintainer lines to Shaan2A Cytoplasmic Male Sterility and 5 restorer lines espectively, were selected on the basis of different geographic origin, and the corresponding male sterile lines were crossed with restorer lines in a 6x5 NC II model to produce 30 Fl hybrids which were evaluated for seven agronomically important traits in a replicated field trials in Yangling. General combining ability (GCA) and specific combining ability (SCA) for seed yield and mid-parent heterosis (MPH) estimates were calculated on the basis of hybrid performance during the two year. Genetic distances (GD) for pairs of the 11 genotypes were calculated with diversity information based on morphological, isozymic and RAPD, and correlated with MPH estimates.The objectives of this paper were to (i) estimate heterosis for agronomic traits in rapeseed (Brassica napus L.) adapted to the region near Huanghe river and Huaihe river of China, and (ii) predict heterosis by means of morphological character, isozyme and RAPD as genetic distance measures.The results were described as follow:1. In cotyledonal stage of rapeseed, isozymes of ACP, CAT, POD, and EST showed nine, six, six, seventeen bands in PAGE respectively. In sprouted rapeseed both GOT and a -AMY showed three bands. Eighteen soluble protein bands of seed were detected in SDS-PAGE. The biochemical polymorphic ratio was 66.13%2. The eleven parents were assayed for random amplified polymorphic DNA (RAPD) with thirty-four primers, which generated 136 polymorphic bands and the polymorphic.ratio was 52.18%.3. The parental lines were assayed for polymorphisms using three classes of markers. GD(genetic distance) estimates were computed using Nei's similarity coefficient based on these data considering each molecular marker set separately (GDIso, GDRapd, GDMor). Range of GDMor was 0.333-0.812, average GDMor was 0.641. Range of GDIso was 0.143-0.535, the average value of GD was 0.297. GDRapd between parents ranged from 0.309-0.553, the average value of GDRapd was 0.434. Genetic similarity among the eleven parents based on isozymes and soluble proteins was higher. The three measurements were not significantly correlated.4. Diversity in morphology, isozyme loci and RAPD were evaluated using UPGMA cluster. The eleven parents can be clustered into three groups by a threshold value equal to 0.390: group I including six maintainer lines and 3 restorer lines; group II and group III including one restorer line C2 and C4 respectively. The result cannot showthe relationship of the materials origination.5. Significant heterotic effects were detected for seed yield and other traits.. Highly significant GCA and SCA effects were observed for yield. Correlation between parents' average GD and GCA was not significant.Meanwhile, the correlation between SCA and yield, and yield MPH were significant coefficent was 0.670 and 0.560). In 2002 and average of two year data , SCA did not correlate with GD though it did in 2003.6. It was significant negative, negative and positive that the correlation were tested between GDIso and number of branch, 1000-seed-weight and flowering respectively(P=0.01, P=0.01,P=0.05). Significant positive, positive, negative and negative correlation were checked out between GDaapd and plant height, number of branch, number of silique, mumber seed per silique respectively(P=0.05, P=0.05, P=0.01, P=0.05). Significant positive, positive, and negative correlation were checked out between GDTotal and plant height, mumber of s...
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