A heat-sum model to determine yield and onset of internal heat necrosis for atlantic potato

The influence of temperature on tuber yield and development of internal heat necrosis (IHN) in Atlantic (Solanum tuberosum L.) was examined in field trials in two locations over three years (seven plantings). Under simulated commercial production, yield and development of IHN varied significantly between Virginia (VA) and New Jersey (NJ) in 1986, 1987, and 1988. Marketable yield ranged from 49.8 mt.ha^?1 for the early planting in 1986 in New Jersey (NJ86E) to 17.9 for VA87. Tubers developing IHN to a level which potato chip processors would rate unacceptable (off-grade) varied with year and location. Significant correlations were found between the number of days to off-grade and the mean maximum temperature for 0–30 (r = ?.83), 30–60 (r = ?.86) and 60–90 DAP (r = ?.81) as well as the mean minimum temperature for the same periods (r = ?.91,, ?.80 and ?.91, respectively). The relationship between yield or IHN and temperature was examined using heat-sum models with a penalty for maximum daily temperature > 25C but with or without a penalty for minimum temperature > 21C. The multiple coefficients of determination for yield were similar using either variables generated from the heat-sum model with maximum and minimum temperature penalties or from the model with maximum temperature penalty only (R² = 0.83 and R² = 0.82). The prediction of the time from first symptom of necrosis to off-grade (interval) was improved by including variables generated by the heat-sum model that included both the minimum and maximum temperature penalty (R² = 0.50 vs. R² = 0.27), respectively. High minimum temperatures as reflected in the days to maximum heat-sum were found to significantly affect tuber yield and the expression and development of IHN.