GEOGRAPHIC-DISTRIBUTION OF INSECT RESISTANCE IN POTATOES

Potato germplasm accessions representing 92 Solanum species and associ ated with known coordinates of latitude, longitude, and elevation were rated for resistance to one or more of the following potato insect pe sts: green peach aphid, Myzus persicae (Sulzer); potato aphid, Macrosi phum euphorbiae (Thomas); Colorado potato beetle, Leptinotarsa decemli neata (Say); potato flea beetle, Epitrix cucumeris (Harris); and potat o leafhopper, Empoasca fabae (Harris), in Minnesota field trials (1966 -1986). Chi-square tests were used to determine if the proportion of r esistant accessions differed from expected among altitude classes, sma ll geographic quadrants (4 degrees latitude by 4 degrees longitude), a nd larger geographic regions (Mexico-USA, Colombia-Ecuador, Peru, Boli via, and Argentina). Resistant potatoes were not evenly distributed th roughout North and South America. Fourteen quadrants were identified t hat had greater or fewer resistant accessions than expected. The Mexic o-USA potatoes as a group had more resistance than expected to all ins ects except Colorado potato beetle. Potatoes from Colombia and Ecuador were less resistant than expected to all but green peach aphid. Potat oes from Peru were more resistant than expected to green peach aphid. Potatoes from Bolivia were less resistant than expected to potato aphi d, but more resistant than expected to Colorado potato beetle, potato flea beetle, and potato leafhopper. Potatoes from Argentina were more resistant than expected to Colorado potato beetle and green peach aphi d, but less resistant than expected to potato aphid and potato leafhop per. Potatoes from North America and collected at or below 2,500 m wer e more resistant than expected to green peach aphid, Colorado potato b eetle and potato flea beetle. Potatoes from South America and elevatio ns greater than 3,000 m were more resistant than expected to green pea ch aphid and potato aphid and those collected at or below 3,000 m were more resistant than expected to Colorado potato beetle, potato flea b eetle and potato leafhopper.