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Abstract
Plant surface chemistry is known to have a pronounced effect on the behavior of many agriculturally important insects. We assessed the qualitative and quantitative effects of N and K nutrition on storage root surface chemistry of three sweetpotato [Ipomoea batatas (L.) Lam.] cultivars: two displaying moderate resistance (Jewel and Regal), and one susceptible (Centennial) to the sweetpotato weevil, Cylas formcarius (Summers). One field and one pot experiments were conducted, Boehmerol and boehmeryl acetate identified by GC‐MS were found on the surface of Centennial but not Jewel or Regal roots. Another compound, previously identified as “peak 4”;, was found on Regal with a retention time very close to that of boehmeryl acetate. In the field, boehmerol increased quadratically with increases in K rate (0, 112, or 224 kg K/ha); the same was true for boehmeryl acetate, but at 112 kg N/ha only. “Peak 4”; increased linearly (pot experiment) or quadratically (field experiment) with increases in the K rate, while N did not have a significant effect. Nutrition was found to affect storage root surface chemistry and may be a significant factor modulating differences in weevil susceptibility over location and time. The effect may in part explain inconsistencies in published estimates of field resistance to the weevil. Nitrogen and K nutrition should be taken into account when selecting progeny for boehmeryl acetate content in a breeding program.
Notes
Current address: Instituto Nacional de Tecnologia Agropecuaria ‐ C.C.5, 3603 El Colorado (Fsa), Argentina.
Phytochemical Research Unit, Russell Research Center, USDA, Athens, GA 30613.