The traits of sugar and acid levels in tomatoes are key to perceptions of flavour, US researchers have confirmed.
This suggests that breeding for improved flavour "shouldn't be that difficult" because both levels can be reliably and inexpensively measured, the researchers at the US Department of Agriculture's Agricultural Research Service (ARS) said.
This was the main outcome of what ARS described as "one of the most comprehensive efforts to identify the sources of genes for boosting flavour among both commercial tomato varieties and breeding lines", yielding "a treasure trove for breeders".
In all, 173 varieties of tomato taken from the 6,000 held by ARS, including commercial and heritage varieties, were open-grown in North Carolina.
Volunteer taste testers were then asked to rate each variety on a range of characteristics, while the researchers also measured each for traits including levels of sugar, acid and vitamin C.
This showed considerable variability in sugars (three-to-nine per cent) and acid (0.2-0.64 per cent), and that these levels correlated with positive flavour perceptions.
"Commercial tomato varieties have a narrow genetic base," said ARS researcher Joanne Labate. "To find ways to improve their flavour, we need to broaden that base and begin looking among our entire stock of tomatoes for new sources of beneficial genes," she added.
Resistance to late blight can be bred into commercial tomatoes through crossing with the wild species Solanum habrochaites, according to researchers at the University of California. But such resistance is conferred by a complex interaction of genes that can affect yield, maturity and fruit size, presenting "challenges and opportunities for breeding efforts", they said.