Breeding of Brassica rapa for Biogas Production: Heterosis and Combining Ability of Biomass Yield
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Breeding of Brassica rapa for Biogas Production: Heterosis and Combining Ability of Biomass Yield Atta Ofori & Heiko C. Becker
Published online: 4 March 2008 # The Author(s) 2008
Abstract The use of plant biomass as substrate for biogas production has recently become of major interest in Europe. Winter Brassica rapa produces high early biomass and could be grown as a pre-crop harvested early in the year followed by a second crop such as maize. The objectives of this study were to estimate heterosis and combining ability of 15 European winter B. rapa cultivars for biomass yield at end of flowering. A half-diallel without reciprocals was conducted among cultivars to produce 105 crosses. These crosses and their parents were evaluated in two years at two locations in Northern Germany. Data collected were days to flowering (DTF), fresh biomass yield (FBY), dry matter content (DMC) and dry biomass yield (DBY). The mean DBY was 5.3 t/ha for the parental cultivars and 5.6 t/ha for their crosses. The crosses surpassed on average their parents by 7.6% for FBY and 5.9% for DBY whereas DMC was 1.4% higher in the parents. Maximum mid parent heterosis was 21.0% for FBY and 30.4% for DBY. Analysis of variance showed that genetic variance was mainly due to specific combining ability (SCA). The correlation between parental performance and general combining ability (GCA) was 0.42** for FBY and 0.53** for DBY. In conclusion, the amount of heterosis in crosses between European winter B. rapa cultivars is not very high on average, but can be up to 30% in the best crosses. Selection of parental combinations with high specific combining ability to produce synthetic cultivars can rapidly improve biomass yield. Keywords Biogas . Diallel . Full-sibs . General combining ability . Synthetic cultivars . Specific combining ability A. Ofori (*) : H. C. Becker Georg-August-University Göttingen, Göttingen, Germany e-mail: [email protected]
Introduction Different technologies to convert biomass to bioenergy have been developed and among them biogas production has gained major interest in the past years in Europe. The number of biogas plants operating in Germany at the end of 2006 was 3.500 [22], an increased of 75% between 2004 and 2006. Presently, over 350.000 ha, representing 2% of agricultural land in Germany is used for the cultivation of biogas energy crops. However, about 80% of the biogas substrate in Germany comes from maize [22], a crop of sub-tropical origin with low cold tolerance that can not be sown before May, and is harvested in September/October. For maximum utilisation of land and availability of biogas substrate through out the year, biomass crops that are winter hardy and can be harvested early in the year are required. This will give growers the option to grow two crops in one season: the first one sown in autumn and harvested in spring, followed by a second crop adapted to higher temperatures like maize, sorghum or sunflower [16]. Crops with high biomass production at low temperature are rye, some forage grasses, and also Bras
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