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Abstract
‘Coastal Red’ sweet potato [Ipomoea batatas (L.) Lam.] was developed by the Univ. of Georgia at the UGA Coastal Plain Experiment Station. This cultivar combines high yield with high resistance to fusarium wilt and root-knot nematodes, resistance to soil insects, excellent storage quality, profuse plant production from bedded roots, and good baking and canning quality in a red-skinned cultivar.
Abstract
Field experiments were conducted during 1979 and 1980 growing seasons with sweet potato [Ipomoea batatas (L.) Lam.] genotypes at different stages of growth to determine leaf net photosynthetic rates (Pn) and photosynthate partitioning patterns. Net photosynthesis was measured in an open system with an infrared analyzer on the youngest and the fully expanded leaves still attached to the plant. Photosynthesis rates differed significantly in both years. Photosynthesis varied from 19.1 to 32.4 mg CO2dm−2hr−1 in 1979 and from 25.8 to 36.9 mg CO2dm−1hr−1 in 1980. A new selection, 75-96-1, averaged highest both years. Percentages of photosynthate partitioning to storage roots also differed significantly. About 45 days after planting, ‘Centennial’ and ‘Georgia Jet’ diverted the highest percentage, about 28%, of the total dry matter to the storage roots. But ‘Georgia Red’ diverted the highest percentages of photosynthate (51.0 and 56.4) to the storage roots 75 and 90 days after planting, respectively. Photosynthate partitioning to storage roots ranged from 11.2 to 56.4%, 90 days after planting. Final root yield correlated significantly (r = 0.69 to 0.87) with photosynthate partitioning at all stages of growth. During 1980, Pn and total dry matter yield also were significantly correlated. Harvest index was significantly correlated (r = 0.89) with final storage root yield. But Pn did not significantly correlate with either storage root yield or photosynthate partitioned to roots. Stomatal density was 2 to 3 times more on the abaxial than the adaxial surface of the leaves. Percentages of neither leaf nitrogen nor chlorophyll content of leaves differed significantly. High-yielding genotypes generally initiated storage root formation earlier and also partitioned more photosynthate to storage roots than low-yielding genotypes.