Breeding for Phytonutrient Content; Examples From Watermelon

Breeding for high phytonutrient fruits and vegetables can be a fairly straightforward endeavor when the compounds of interest produce a visible effect or the methods for quantifying the compounds simple and inexpensive.  Lycopene in tomatoes and watermelon is one such compound, since the amount of red corresponds well with the quantity of lycopene produced.  Because of this, breeders have developed high lycopene varieties.  High antioxidant concentration in these vegetables creates new marketing tools for improved sales, premium price options, and nutrient packed product.  Unfortunately, testing for many health promoting compounds is labor intensive and expensive.  For this reason, these compounds are usually not quantified or selected for in breeding lines.  Preliminary experiments on watermelon breeding lines showed a wide range in the amount of citrulline (6 fold differences between high and low) and the tripeptide antioxidant glutathione (24 fold differences) expressed within open pollinated varieties.  This divergent expression of health promoting amino acids and peptides makes it difficult for industry groups to make blanket health claims for individual crops.  By using new strategies and methods, it is becoming easier to test for many of these compounds to insure nutrient packed produce for the market place.  Our finding on citrulline and glutathione demonstrate the feasibility of new analytical technology to develop breeding strategies for developing more nutritive produce.