Sentence:  In a paper published Thursday in the journal Science, a team of researchers say they analyzed the genetic code of nearly 400 varieties of tomatoes ― from the common red supermarket types to the funky <WSD>heirlooms</WSD> found in farmers markets. 
Meaning of the word marked with <WSD> tags:  An old crop variety that has been passed down through generations of farmers by seed saving and cultivation, in contrast to modern cultivars used in large-scale agriculture.