Effect of plant variety, plant age and photoperiod on glandular pubescence and host-plant resistance to potato moth (Phthorimaea operculella) in lycopersion spp.

G. M. Gurr, D. McGrath

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The effect of plant age and daylength on glandular pubescence was determined for two lines of tomato derived from Lycopersicon hirsutum (BTN 979 and LA 1777A) and a variety of L. esculentum (N 91-1-1-1-1). Densities of type I, IV, VI and VII glandular trichomes were lowest in N 91-1-1-1-1 and, over all varieties, were more dense on plants aged greater than 6 wk. Daylength interacted with variety to significantly affect densities of type VII trichomes only. Host-plant resistance to Phthorimaea operculella was determined in preliminary tests using insects cultured from founders from a potato crop and in confirmatory tests using (less readily available) insects recovered from foliage of a tomato crop. Mortality of ex-potato neonates on LA 1777 A and BTN 979 foliage was higher 18 h after placement than for N 91-1-1-1-1, with no effect of day length or plant age. Mortality for ex-tomato neonates followed a similar trend. Ten days later, two-thirds of ex-tomato larvae had established mines on N 91-1-1-1-1 but fewer (16.7 %) were live on other varieties. Stepwise multiple regression using variety as the sole factor was significant (P < 0.001) in accounting for 61.4% of the variation in ex-tomato larval survival but addition of other factors to the regression model was not significant. BTN 979 supported fewer, smaller adults to develop than did N 91-1-1-1-1, whilst no adults developed on LA 1777 A. In a non-choice test using ex-potato adults, significantly more eggs were laid on N 91-1-1-1-1 than on L. hirsutum varieties and 9-wk-old plants were preferred over plants three weeks older or younger. The same variety and plant age trends were evident in a free-choice test using ex-tomato adults.
Original languageEnglish
Pages (from-to)221-230
Number of pages10
JournalAnnals of Applied Biology
Issue number2
Publication statusPublished - 20 Jul 2001

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