Author
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Fazio, Gennaro |
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ROBINSON, TERENCE - Cornell University |
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Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 10/19/2021 Publication Date: N/A Citation: N/A Interpretive Summary: The root systems of apple rootstocks vary in their ability to uptake mineral nutrients and water from the soil and shuttle them to grafted scion cultivars like Honeycrisp. This differential ability means that the fruit quality of apples can be affected by rootstocks. This experiment was designed to understand the timing of these influences during the growing season from fruit set to harvest. What was unique in this investigation was the comparison of three different tissues: leaves, fruit and pedicels (the stems that join apples to the tree). The analysis of nutrient content in pedicels provides an insight into what is moving into the fruit at a particular point in time. Important nutrients like potassium and calcium and their ratio featured seasonal content patterns that were influenced by rootstocks. Rootstock G.214 displayed a pattern that reduces the incidence of bitter pit (a disorder that makes Honeycrisp apples undesirable) whereas G.814 displayed a pattern that increased the disorder. This data contributes to the wealth of information needed by apple growers in the processes of selection and management of apple rootstocks. Technical Abstract: An experiment aimed at understanding the genotypic potential of certain rootstocks to influence the nutrient content of ‘Honeycrisp’ fruit was conducted over two years (2016 and 2017) on trees that had reached production maturity. Four or five replications of trees grafted on B.9, G.11, G.214, G.30, G.41, G.210, G.814, G.935, M.26, M.9 Pajam2 rootstocks were used as the source of tissues for this experiment. The nutrient content of leaves, pedicels, and fruit was monitored 8-10 times in two-week intervals from the time fruit reached 10 mm in diameter to harvest. Despite seasonal differences, nutrients like boron, potassium, sulfur, phosphorous and calcium showed good correlation among rootstock/tissue combinations. Overall, nutrient content changed in tissues over time. Some nutrients like boron and potassium displayed higher content early in the season decreasing over time in a similar way for all tissues. Other nutrients like calcium displayed discordance between tissue types as all tissues started from the same content, with leaves increasing content, pedicels remaining constant and fruit decreasing in content with time. Nutrient ratios like K/Ca and (K+Mg)/Ca showed starkly different trends in fruit tissues (increasing with time) compared to pedicel and leaves where the ratios remained relatively constant. These ratios were slightly influenced by rootstocks genotype over time, indicating effects that could be tied to rootstock specific influence on fruit quality parameters like bitter pit. While Ca increased in leaves, it was constant over time in the pedicel and slightly decreased in fruit, K in the pedicel decreased over time in a similar way as fruit and leaves. where calcium seems more mobile into the fruit. Rootstock genotype significantly affected the overall content of certain nutrients and as previously observed in similar experiment M.9 Pajam 2 displayed the lowest levels of boron in all tissues compared to other rootstocks. This work is part of a larger project aimed at understanding the connection between rootstocks and fruit quality being studied in the USDA NIFA Specialty Crop Project “AppleRoot2Fruit”. |
