ANALYSIS OF GENOTYPIC DIFFERENCES IN DEVELOPMENTAL STABILITY IN ANNONA CHERIMOLA.

Abstract

The genetic basis of developmental stability, measured as asymmetry (fluctuating asymmetry in leaves), was analyzed in leaves and flowers of cherimoya (Annona cherimola Mill) and atemoya (A. cherimola × A. squamosa). The individuals analyzed belonged to a controlled collection of cultivars (clones) that had previously been characterized by means of isozymes. We used a nested design to analyze the differences in asymmetry at several sampling levels: individual leaves and flowers, individual trees, and genotypes. The clonal repeatability of developmental stability was not significantly different from zero, thus suggesting the absence of heritability of the asymmetry for leaves and flowers under these environmental conditions. No relationship between asymmetry and individual heterozygosity was found, but leaf fluctuating asymmetry was significantly related to particular isozymic genes. Petal and leaf size showed a phenotypically plastic response to the exposure zone of the tree (mainly due to light). Leaf fluctuating asymmetry also showed such a plastic response. No significant correlation was found between asymmetry and any pomological characters (some of these being fitness related). Finally, the hybrid species (atemoya) did not show larger developmental instability than did the parental species (cherimoya). All these data show that cherimoya asymmetry reveals the random nature of developmental noise, with developmental stability for leaves being possibly related to specific chromosome regions, but with weak evidence for genotypic differences in developmental stability.