Genetic and environmental variation for corolla traits in Portulaca grandiflora

A commercial seed lot of Portulaca grandiflora was sampled and the variation for several flower traits was analysed. A genotypic component of variance was estimated for the traits petal length, petal width, and petal number. The heritability for petal number was high (64 · 3), for petal width was intermediate (31 · 3), and for petal length was low (12–3). The environmental variance was partitioned into three components, but more than 90% of it was unaccountable. A significant positive correlation between petal length and petal width was found. A covariance analysis was used to test for genetic variance for petal length and petal width after the effects of covariance had been removed. No relationship was found between total corolla area and flower production. Thus, selection for larger flowers is not expected to reduce the number of flowers produced. Selection responses are predicted for different selection differentials and the assumptions are discussed. The results suggest that selection for increased petal number will be very effective.