HIGH ALPHA-TOMATINE CONTENT IN RIPE FRUIT OF ANDEAN LYCOPERSICON-ESCULENTUM VAR CERASIFORME - DEVELOPMENTAL AND GENETIC-ASPECTS

A variant of Lycopersion esculentum var. cerasiforme is described that deviates from the typical form of the entire species, including culti vated tomatoes, in possessing high levels (500-5000 mu g/g of dry weig ht) of the steroidal alkaloid alpha-tomatine in its ripe fruits. This biotype is restricted to a tiny enclave in the valley of Rio Mayo, Dep artment San Martin, Peru. Among 88 accessions of var. cerasiforme from its present distribution in the Andes, a 90% association was found be tween high tomatine and bitter flavor; within the Mayo watershed, all samples from the upper drainage had bitterness and high tomatine; the frequency of both traits decreased to low levels toward the lower end. Tomatine therefore probably is the source of bitterness. Throughout L . esculentum tomatine is present at very high concentrations in earlie st stages of fruit development, thereafter decreasing rapidly to midpe riod, and finally diminishing gradually to near zero at maturity as a result of catabolism to biologically inert compounds, except in the va riant described here. High tomatine content does not appear to affect adversely either the natives, among whom the bitter types are popular, or individuals who sampled them in this survey. Genetic determination of high tomatine in ripe fruits is totally recessive and appears to b e monogenic with interaction with genes of minor effect. The prevailin g pattern of glycoalkaloid synthesis and degradation in development of solanaceous fruits suggests a mechanism to protect against predation prior to ripening but to permit it afterward as a device to promote di spersal. In consideration of the nondegradative nature of the variant, its genetic determination, and very restricted geographic distributio n, mutation to this form appears to be a random event of doubtful evol utionary significance.