The NC State cucumber, watermelon and stevia breeding program has provided environmental sustainability for growers as follows. We have incorporated new germplasm sources into populations and breeding lines, and made those available to plant breeders and growers. The new germplasm expands the base of diversity for the crop, and decreases the vulnerability to diseases, insects, and environmental stresses such as chilling. In addition, we have screened hundreds of accessions for resistance to important diseases. The most resistant accessions have been selected and distributed to plant breeders for use in developing new cultivars. Those improved cultivars will reduce our reliance on chemicals for disease control.
We have obtained germplasm from other public and private breeding programs, from the USDA germplasm system, and from primary, secondary and tertiary centers of diversity. The primary center of diversity for cucumber is India, and the secondary center is China. There are more than 1200 accessions in the cucumber germplasm collection at NC State, including more than 1000 plant introduction accessions and more than 200 available cultivars and breeding lines. For watermelon, the primary center of diversity is Africa, with secondary center in China and tertiary in Central Asia. There are more than 1500 Citrullus accessions, including cultivars collected from around the world.
Some of the traits evaluated so far for cucumber include resistance to anthracnose, gummy stem blight, downy mildew, belly rot, and root-knot nematode (Meloidogyne hapla, M. javanica, and M. arenaria races 1 and 2). We have also evaluated the collection for chilling resistance, keeping ability, early flowering, root size, and high yield.
In order to improve environmental sustainability, it is necessary to have renewable inputs for fertilizer and pest control, and superior cultivars with high yielding ability and resistance to pests. Our research has provided answers to the part of the puzzle involving superior cultivars of cucumber, watermelon and stevia.