The team made the discovery while hunting for genes that boost hybrid vigor, a revolutionary breeding principle that spurred the production of outstanding hybrid crops like corn and rice a century ago. Hybrid vigor, also known as heterosis, is the phenomenon by which intercrossing two varieties of plants produces more vigorous hybrid offspring with higher yields
A theory for heterosis, supported by this new Hebrew University-Cold Spring discovery, postulates that improved vigor stems from only a single gene – an effect called "superdominance" or "overdominance."
To find such overdominant genes, the US-Israeli team developed a novel approach by turning to a vast tomato "mutant library" – a collection of 5000 plants, each of which has a single mutation in a single gene that causes defects in various aspects of tomato growth, such as fruit size, leaf shape, etc. Selecting 33 mutant plants, most of which produced low yield, the team crossed each mutant with its normal counterpart and searched for hybrids with improved yield. Among several cases, the most dramatic example increased yield by a whopping 60%.
