α-Tomatine and resistance of tomato cultivars toward the nematode,Meloidogyne incognita.

Susceptible and resistant tomato cultivars were assayed for root tomatine concentrations at different developmental times. No correlation between high tomatine levels and resistance towardMeloidogyne incognita was apparent. In plants infected with nematodes, tomatine in the roots was the same as in uninfected controls. Tomatine concentration, as measured by bulk analysis, does not appear to play an important role in resistance toward the nematode studied.

Effects of cotton condensed tannin, maysin (Corn) and pinitol (soybeans) onHeliothis zea growth and development.

Maysin, a flavone glycoside from corn silks, inhibits ingestion, and thus growth, ofHeliothis zea (Boddie) larvae. Pinitol from soybeans inhibitedH. zea growth by the same mechanism. Despite the widely held assumption that tannins inhibit growth by inhibiting assimilation, cotton condensed tannin inhibitedH. zea growth by reducing ingestion; no evidence was found for a reduction in assimilation. Neonate larvae are shown to be much more sensitive to allelochemics than larvae that have fed on control diet before being transferred to diet containing plant allelochemics.

Growth inhibitors in tomato (Lycopersicon) to tomato fruitworm (Heliothis zea).

Several compounds that retard the larval growth of the tomato fruitworm,Heliothis zea (Boddie) have been isolated and identified from tomato leaves,Lycopersicon esculentum Mill. The major allelochemics are α-tomatine (I), chlorogenic acid (II), rutin (III), and a new caffeyl derivative of an aldaric acid (IV). The isolation, analyses, and toxicity of these compounds toH. zea are presented.

Pinitol, a larval growth inhibitor for Heliothis zea in soybeans.

A search for insect growth inhibitors in methanol extracts of soybean leaves resulted in isolation of pinitol. Pinitol caused a 50% reduction in weight gain (ED50) of Heliothis zea larvae at about 0.7% when added to a synthetic diet. Although myo-inositol is a normal component of the insect diet, it also caused growth inhibition at higher concentrations; ED50 4%.

Diterpene acids as larval growth inhibitors.

Kaurenoic and trachylobanoic acids from sunflower inhibited larval development in several Lepidoptera species. The tricyclic resin acids were also effective in curtailing growth of Pectinophora gossypiella and either reduction to carbinol or esterification of the carboxyl group lowered activity. Partial reversal of growth inhibition in the presence of relatively large amounts of cholesterol suggests an interaction with the insects' hormonal system.