Assessment of Tolerance to Zebra Chip in Potato Breeding Lines under Different Insecticide Regimes in New Zealand

Fourteen potato lines, including some indicating reduced susceptibility to zebra chip (ZC), were assessed in trials over three seasons at Pukekohe (New Zealand) under three insecticide regimes: FULL (pre-plant plus 14-15 foliar applications through the season), REDUCED (4-5 foliar applications) and NIL (no insecticide). In all three seasons there were consistent reductions in tuber yield, dry matter and tuber size from the FULL to the REDUCED to the NIL insecticide treatment. ZC severity recorded in crisp slices before and after frying tended to be highest in the NIL treatment and lowest in the FULL treatment. All lines had symptoms of ZC in both raw and fried crisp samples but there were clear differences between lines, with some showing significantly fewer symptoms of ZC than current widely grown potato lines in New Zealand. The potential of these ZC-symptom tolerant lines, both as parents in a breeding programme and for possible release, is discussed. CLso titre of individual tubers of three lines was also determined from the 2014 NIL plots using qPCR. There was little relationship between CLso titres and ZC scores in either raw or fried crisp slices both within and between lines.