The Significance of Genetic Variation for Root Growth Within a Natural Population of White Clover (Trifolium Repens)

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Abstract
Significant genetic variation in root growth was found within a natural population of white clover T. repens. Heritability for this character was high. Subpopulations showing either long (L) or short (S) root growth were chosen from the total population. These plants were grown in a replacement-series competition experiment where the treatments were: L pure stand, pure stand, S and 1:1 mixture of L and S genotypes. The total number of stolons produced under the 3 treatments did not differ significantly. Within the mixture, 22% more stolons were produced by L genotypes than by S genotypes. Within treatments, significant differences in stolon number were found among individuals, and these differences were consistent over replicates. During a period of drought, dry matter yield was significantly different among the 3 treatments: mixture < L pure < S pure. Genetic variation for root growth within the population had significant effects on the fitness of individuals. Differences in fitness may be attributed to exploitation of slightly different soil layers by the L and S genotypes.