**6. Mediterranean crop modification techniques: from the laboratory to the field**

#### **6.1 Marker-assisted breeding (MAB)**

This method/strategy selects plants and animals for breeding programs early in their development by exploiting DNA markers linked with desirable features. Thus, it significantly shortens the time required in a breeding cycle, to locate/identify variations or breeds that display the desired trait. Two separate studies in tomatoes recorded before, one using a mutant inbred line and the other using an interspecific *Solanum Chmielewski* population, discovered that the colorless-peely mutant on chromosome 1 is controlled by a *SlMYB12*-regulated transcriptional network that controls the accumulation of yellow-colored flavonoid (naringenin chalcone) in the fruit epidermis [134, 135].

### **6.2 Crop plants that have undergone genetic modification**

Overexpression and competition with the target route, overriding rate-limiting steps, preventing the catabolism pathway of the desired product, and blocking other pathways are all part of the process of maximizing the synthesis of specialized target molecules [136]. For example, the principal flavonoid metabolic route has been studied to optimize these critical molecules in *Solanum lycopersicum*. Flavonoids (such as naringenin, chalcone, and rutin) are predominantly found in tomato peel, with just trace levels found in tomato flesh [137]. Ectopic expression of a single structural gene (*CHI*) or many structural genes (*CHS*, *CHI*, *F3H*, and *FLS*) increased the number of flavonols (quercetin- and kaempferol- glycosides) in tomato peel and flesh. The co-expression of onion *CHI* in the purple tomato *Delila* bHLH and *Rosea1* R2R3-MYB recently transformed flavonoid to flavanol and boosted anthocyanin concentration [138].
