Stability Estimates and Breeding for Eggplant Fruit Phenolic Acid Content

Eggplant genetic resources are a rich source of variation for secondary metabolites that influence fruit quality.  Phenolic acid conjugates are secondary metabolites that constitute the major dietary phenolics in eggplant and affect fruit culinary attributes as well.  Bioactive properties of these compounds are of considerable interest for human health.  Prior research indicated that these secondary metabolites are influenced by environmental stimuli that may positively or negatively influence performance of genotypes across environments.  Utilizing multiple open field and greenhouse production environments and a diverse collection of Solanum melongena hybrid and open-pollinated cultivars, land races, plus S. macrocarpon and S. aethiopicum accessions, twenty phenolic acid conjugates were identified in fruit flesh.  These compounds were assigned to six classes that included hydroxycinnamic acid amides, caffeoylquinic acid esters, hydroxycinnamoylquinic acid esters, malonylcaffeoylquinic acid esters, di-hydroxycinnamoylquinic acid esters, and other hydroxycinnamic acid conjugates.  We demonstrated that environmental variance was high but not significant for individual classes or total phenolic acid conjugate content in eggplant fruit.  Significant differences among genotypes and differential response of genotypes across environments were greater sources of variation relative to environment alone.  Partitioning genotype x environment interaction into stability statistics demonstrated a lack of stability in individual classes and total phenolic acid conjugates over environments.  Since variance components for genotypes exceeded those estimated for the genotype x environment interaction, our results suggested that it may be possible to develop genotypes that are uniform and stable for specific phenolic acid conjugate profiles.  Stability estimates provided a useful measure for selecting individual genotypes with predictable performance for phenolic acid conjugate content across environments.  Relatively high broad-sense heritability estimates (0.64 – 0.96) for individual classes and total phenolic acid conjugates further suggests that stability estimates may improve the efficiency of breeding new cultivars.  Progress in breeding eggplant genotypes with specific phenolic acid conjugate profiles will be discussed.