Biomass yield and heterosis of crosses within and between European winter cultivars of turnip rape (Brassica rapa L.)

Because of its high growth rate at low temperatures in early spring, there is renewed interest in Brassica rapa as a winter crop for biomass production in Europe. The available cultivars are not developed for this purpose however. An approach for breeding bioenergy cultivars of B. rapa could be to establish populations from two or more different cultivars with high combining ability. The objective of this study was to evaluate the heterosis for biomass yield in the European winter B. rapa genepool. The genetic variation and heterosis of the biomass parameters: dry matter content, fresh and dry biomass yields were investigated in three cultivars representing different eras of breeding by comparing full-sibs-within and full-sibs-between the cultivars. Field trials were performed at two locations in Germany in 2005–2006. Mean mid-parent heterosis was low with 2.5% in fresh and 3.0% in dry biomass yield in full-sibs-between cultivars. Mean values of individual crosses revealed a higher variation in mid-parent heterosis ranging from 14.6% to −7.5% in fresh biomass yield and from 19.7% to −12.7% in dry biomass yield. The low heterosis observed in hybrids between European winter cultivars can be explained by the low genetic variation between these cultivars as shown earlier with molecular markers. In conclusion, a B. rapa breeding program for biomass production in Europe should not only use European genetic resources, but should also utilize the much wider worldwide variation in this species

The virtual crop-modelling system 'VICA' specified for barley

The paper presents an improved version of the Virtual Canopy model VICA (Wernecke et al. 2000), which is developed to establish a generic functional-structural plant model (FSPM; cf. Vos et al. this volume) specified for barley (Hordeum vulgare L.). The model core is formulated as a set of hierarchically structured objects. These objects are related to morphological and functional ‘plant units’ (organs). The following processes are considered: i) organ initiation, ii) organ growth and senescence, iii) photon transfer, iv) photosynthesis, v) basic features of the carbon (C), and nitrogen (N) metabolism, and vi) mass fluxes between objects. Balance equations are defined for three different substrate classes with their mobile and immobile forms: i) substrates without N, ii) substrates without C, and iii) substrates containing both C and N. This approach leads to a set of coupled nonlinear ordinary differential equations (ODEs) to describe the balance equations of the plant–soil system in terms of the above-defined substrates. On this basis, algorithms can be specified to describe plant architecture as a function of substrate masses and organ age. The extended version of VICA discussed in the present paper is capable to simulate the influence of light and nitrogen supply on the dynamics of architecture and mass. The performance of the model system is demonstrated by simulation studies. A complete parameterization of the model with experimental data is subject to further work