Use of Glandless Breeding Stocks to Evaluate Unknown Heliothis Growth Inhibitors (X‐Factors) in Cotton1

Abstract

A significant linear relationship (r = 0.86 to 0.90) was found between reduction in larval weight of tobacco budworm, Heliothis virescens (F•), and flowerbud gossypol content of 1) F3 progenies of Upland stocks crossed with three Texas race stocks (Texas 216, Texas 490, and Texas 1134) of cotton, Gossypium hirsutum L., and 2) 221 entries from the race stock collection. Most of the suppression of growth of larvae which fed on diets containing extracts of progenies from the three race stocks could be attributed to gossypol or to other compounds that occur in pigment glands and can be measured by the colorimetric method for gossypol involving reaction with aniline. Subsequently, 317 glandless progenies from glandless strains crossed with derivatives of Texas 27, Texas 194 and Texas 254 were assayed for their effect on larval growth. None of the glandless selections tested caused a reduction in larval growth compared with insects feeding on a casein‐wheat germ diet, which suggest that the X‐factor effect results from one of the following: 1) gossypol; 2) synergist or additive effects of gossypol and other toxic compounds in flowerbuds; 3) gossypol‐related compound that gives the same colorimetric test as gossypol but is more toxic than gossypol. Some of the glanded sister lines from the crosses suppressed larval weight by more than 50%, but generally this reduction was within the confidence limits of the reduction expected fxom gossypol content.