N O V E M B E R / D E C E M B E R 2 0 1 7 POTATO GROWER 11 Turning Back The Clock A Look Back 25 Years Ago at Excerpts from The December 1992 Issue of The Valley Potato Grower Magazine Variety Development For Resistance To Colorado Potato Beetle The Colorado Potato Beetle (CPB) is one of the most destructive insect pests of potatoes. Potato fields can be com- pletely defoliated if the insect is left unchecked resulting in serious yield losses. The Colorado potato beetle also has been known to develop resistance to insecticides, making long term con- trol difficult. Breeding for resistance offers the possi- bility of not only developing a more durable means of control, but also would cost less than chemical control and be enviromentally safe. The North Dakota State University breeding program has expanded its efforts to develop varieties resistant to the Colorado potato beetle. Wild species including S. fendleri, S. vernei, S. polytrichon, and S. chacoense have been utilized in crosses with commercial vari- eties and the resulting progeny screened for CPB resistance. In addition, somatic hybrids obtained from the University of Wisconsin are being screened for CPB resistance for use in our crossing program. These somatic hybrids incorporate the wild species S. bulbocastanum, S bethaultil, and S.etuberosum in fusions with potato. The CPB evaluation program is also developing greenhouse assays so that preliminary screening can eliminate non-resistant material prior to field planting. The mechanism of CPB resist- ance in CPB resistant breeding lines is being determined by testing for gly- coakaloids and trichomes. In the 1992 season, over 400 breeding lines and several thousand seedlings were evaluated in unsprayed field plots at Fargo and Grand Forks, North Dakota. Two different sets of somatic hybrids were transplanted and evaluat- ed at Crookston, Minnesota. CPB dam- age was scored on a per plot basis as percent defoliation on a one to 100 per- cent scale. Ratings were taken approxi- mately weekly beginning after the emergence of overwintered adults until mid-August. Results of the screening trials showed that progeny derived from the wild species S. fendleri showed the highest level of reistance to CPB. Several of these lines had significantly less feeding damage than standard varieties grown in this region. Somatic hybrids with S. etuberosum and S. berthaultil in the fusion showed much less feeding dam- age than other somatic hybrids. CERTIFIED SEED POTATOES Contact Kevin Waller 701.402.2833 [email protected] Multi-Year Contracts Available 4320 18th Ave. S., Grand Forks, ND 58201 www.blackgoldfarms.com Specializing in Atlantic & Snowden Chip Seed. Other Red/Chip/Russet varieties also available.