Comparison of eggplant landraces and commercial varieties for fruit content of phenolics, minerals, dry matter and protein

Development of eggplant (Solanum melongena) varieties with an improved content in phenolics and nutritionally relevant minerals in the fruit is an increasingly important breeding objective. We analyzed several proximate composition traits (dry matter and protein content), content in phenolics, and eight minerals (P, K, Ca, Mg, Na, Fe, Cu, and Zn) in 31 varieties of eggplant from three different varietal groups (commercial varieties, landraces, and hybrids between the landraces). Considerable differences in the composition among varieties were detected in all the traits studied, with relative differences between the lowest and highest values of 42.9% for dry matter and 156.3% for Ca. Results show that eggplant provides relevant quantities of phenolics, P, K, and Cu to the diet, with global mean values of 48.26 mg/100 g, 26.6 mg/100 g, 198.5 mg/100 g, and 0.062 mg/100 g of fresh weight, respectively. Landraces had, as a mean, higher contents in phenolics (16.4%), P (34.6%), and Zn (30.0%) than commercial varieties. Positive mean heterosis was detected for dry matter content (8.4%) and Na concentration (12.1%), and negative mean heterosis for P (-16.0%), K (-5.5%), and Ca (-38.5%) concentrations. Mean heterosis was not significant for the content in phenolics, although positive values were found for some individual hybrids. Contents in dry matter, protein and the main macrominerals were positively correlated. Also, positive correlations between mid-parent and hybrid values were found for dry matter (r=0.596), P (r=0.658) and K (r=0.599). The results obtained indicate that there is ample variation within eggplant for composition traits and this can be exploited for the selection of varieties with nutritionally improved characteristics. In this respect, we have identified several landraces with high nutritional quality.