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Wayne T. Iwaoka, Xiaorong Zhang, Richard A. Hamilton, C.L. Chia and C.S. Tang

The volatile compounds in soursop (Annona muricata L.) were obtained by a liquid-liquid continuous extraction procedure from the aqueous solution of blended soursop pulp and analyzed by gas chromatography (GC) and GC-mass spectrometry (MS). Twelve volatiles were identified by comparing their mass spectra and Kovats retention indexes with those of standard compounds: five were identified tentatively from MS data only, eight are being reported for the first time. (Z) -3-hexen-l-ol was the main volatile present in mature-green fruit, while methyl (E) -2-hexenoate, methyl (E) -2-butenoate, methyl butanoate, and methyl hexanoate were the four main volatiles present in ripe fruit. Concentrations of these five volatiles decreased and several other unidentified volatiles appeared when the fruit became overripe.

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Brian K. Hamilton, Leonard M. Pike, Alton N. Sparks, David A. Bender and Richard W. Jones

Thrips are the major insect pest of onions grown in South Texas. Four cultivars, `IPA-3', `TG1015Y', `1664' (glossy control), and `1900B' (waxy control), were grown in a split-plot design with insecticide sprayed or nonsprayed treatments as the main plots and cultivar as the subplots. The experiment was conducted at the Texas Agricultural Experiment Station, Weslaco, Texas, in the 1995-96 season. The objectives of the study were to compare `IPA-3' and `TG1015Y' for thrips resistance and evaluate possible resistance mechanisms that may be present in `IPA-3'. The average number of thrips per plant and leaf damage rating were significantly higher for `TG1015Y', indicating that some resistance is present in `IPA-3'. However, there were no significant differences in yield between the two cultivars. A comparison of leaf wax characteristics indicated no significant difference between `TG1015Y' and `IPA-3' using gravimetric or gas chromatography techniques. However, scanning electron micrographs of `TG1015Y' leaves appeared more similar to `1900B' and `IPA-3' appeared more similar to `1664'. The insecticide spray treatment had significantly fewer thrips, less damage, and higher yield than the nonsprayed treatment.