Comparison of biparental and melting pot methods of crossing sugarcane in Hawaii

Abstract

Sugarcane (Saccharum hybrid spp.) breeders at the Hawaiian Sugar Planters’ Association used biparental and melting pot (modified polycross) crossing methods concurrently from 1935 to 1985. While the annual effort expended to make biparental crosses exceeded the effort to make melting pot crosses over this 50-year period, annual viable seed yield from biparental crosses was usually less than 15% of that from melting pot crosses and hence, the numbers of seedlings planted to the field from those crosses usually accounted for less than 20% of the total seedling population. In 1985, nine of the 10 sugarcane cultivars listed in Hawaii’s variety census originated from melting pot crosses; only one originated from a biparental cross. In the face of a shrinking sugar industry in Hawaii and a smaller work force in the breeding program, the decision was made in 1985 to rely primarily on melting pot crosses for the production of commercial cultivars. From 1985 to 2005, twelve additional clones that were bred prior to 1985 eventually attained “commercial cultivar” status by exceeding 1% of the total cane growing area. All twelve originated from melting pot crosses. Over the 50-year period that the two crossing methods were used, the melting pot method proved to be more labour efficient and ultimately contributed more than the biparental crossing procedure toward the development of new commercial cultivars for the Hawaiian sugar industry. From 1985 forward, the biparental crossing method was used more for introgressing desired traits from exotic germplasm than for the development of commercial cultivars.