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  • Author or Editor: Robert E. Thornton x
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A controlled environment study was conducted to determine if ‘Russet Burbank’ potatoes (Solanum tuberosum L.) were more tolerant of NH4-N as established plants than as young plants. When grown on one N source for 86 days, root and shoot growth were best with NO3-N, intermediate with NH4 + NO3, and least with NH4-N. Changing the N source from NO3-N or NH4 + NO3 to NH4-N at tuber initiation (58 days after planting) reduced both shoot and root growth. Conversely, changing the N source from NH4-N to NH4 + NO3 improved growth. The highest tuber weights were obtained with continuous NH4 + NO3 or when NH4-N was applied at tuber initiation to plants previously grown on NO3-N alone. Nitrogen source also influenced absorption of other nutrients. Changing the N source once plants were established, however, did not have a consistent effect on mineral composition. We conclude that when NH4-N is the sole form of N available to the plant, it is detrimental to potato growth regardless of stage of development.

Open Access

Ascorbic acid (vitamin C) is an essential nutrient in the human diet and potatoes are a valuable source. As a first step in breeding for potatoes (Solanum tuberosum L.) with higher levels of ascorbic acid, 75 clones from 12 North American potato-breeding programs were evaluated for concentration, and 10 of those for stability of expression. Trials were grown in Idaho, Oregon, and Washington in 1999 and 2000, tubers sampled, and ascorbic acid quantified. There were significant differences among clones and clone by environment interaction was also significant. Concentration of ascorbic acid of the clones was continuously distributed over a range of 11.5 to 29.8 mg/100 g. A subgroup of 10 clones was analyzed using an additive main effects and multiplicative interaction (AMMI) model, to diagnose interaction patterns and measure clone stability. The first two principal component axes accounted for over 80% of the variability. Bi-plot analysis showed `Ranger Russet' to be highly unstable across the environments tested. A plot of Tai's stability statistics found six of the 10 clones to be stable for ascorbic acid expression. Appropriate evaluation methods for ascorbic acid concentration must involve multi-year testing.

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