Analysis of morphological, physiological and molecular aspects of bud outgrowth to dissect branching in red clover (Trifolium pratense)

Red clover has several advantages in agriculture: the ability to fixate nitrogen, a high seedling vigour and a high nutritional value for feed and indirectly for food (high protein and polyunsaturated fatty acid levels). However, the current red clover cultivars have a low persistence. Plant architecture, which is under genetic and environmental control, may have a strong influence on traits such as forage yield, re-growth capacity, seed yield and persistence in fodder crops. We have studied the plant architecture of a limited number of red clover genotypes with contrasting branching phenotypes. A detailed morphological analysis showed differences in the number of buds and the quantity and position of bud outgrowth. In a physiological approach, isolated single node fragments were used to study the influence of the branching hormones auxin, cytokinin and strigolactone on bud outgrowth without having to deal with the complex architecture of a complete red clover plant (non outgrowing main axis, many first order branches). The different genotypes differed in the level of inhibition or outgrowth for the three hormone applications. Finally some data will be presented from the translational approach where red clover sequences of important branching genes were isolated and used in expression studies of isolated single node fragments to analyze their role in bud outgrowth. Future challenge will be to identify the important genes in branching of red clover and to apply this knowledge in breeding programs for high yielding and more persistent plants.