Aphid Resistance and Leaf Surface Chemistry of Sugar Ester Producing Tobaccos1

Abstract

Sugar ester producing tobacco lines were evaluated for aphid resistance and other surface chemicals. The cembrenoid and labdenoid diterpenes, α- and β-4,8,13-duvatrien-1-ols, α- and β-4,8,13-duvatriene-1,3-diols, (12Z)-labda-12,14-diene-8α-ol (cis-abienol), (13E)-labda-13-ene-8α,15-diol (labdenediol), docosanol, and sugar esters were quantified using high pressure liquid chromatography and compared with aphid infestation ratings. Regression analysis of aphid [Myzus persicae (Sulzer)] infestation rating and leaf surface chemistry was statistically significant and showed that surface chemicals were important in explaining the observed variation in the aphid infestation ratings. A significant negative correlation was found between aphid ratings and sugar ester levels among the 62 entries evaluated (r = −0.2758, P = 0.0301). α and β monols (α- and β-4,8,13-duvatrien-1-ols) were also significantly correlated with aphid infestations in this study (r = −0.2743, P = 0.0310 and r = −0.2797, P= 0.0109, respectively). None of the other surface chemicals were statistically correlated with aphid resistance. Although high sugar ester levels were correlated with aphid resistance, not all tobacco entries with high levels of sugar esters, such as Tl 1568 were resistant. This would suggest that there may be different types of sugar esters present in these tobaccos, and total sugar ester levels alone could not be used to predict aphid resistance. Also, some tobacco lines, like Tl 1674 and Tl 59 with lower sugar ester levels, were resistant in this study because of high monol levels. The ten tobacco entries with the highest levels of sugar esters in this study were Tl 698, Tl 675, Tl 704, Tl 998, Tl 193, JA 389, Tl 722R, Tl 1092, Tl 711, and Tl 1007. All of these lines exhibited high levels of aphid resistance, but some also had low-to-moderate levels of monols that may have elevated the aphid resistance level. A number of these tobaccos could be used for production of natural sugar ester biorationals or used in a breeding program for development of aphid resistant cultivars.