The effect of ozone fumigation and different Brassica rapa lines on the feeding behaviour of Pieris brassicae larvae

Abstract

Elevated levels of tropospheric ozone and their effects on plants have been studied for a great number of years. Ozone is a gaseous pollutant and acts as a phytotoxin. Even though ozone is known to change the physiology of plants, little attention has been given to the indirect effects of ozone on plant-insect interactions. This paper addresses this question by investigating the interactive effects of ozone and plant genotype on insects. Lines of rapid-cycling Brassica rapa (L.) selected for their contrasting sensitivity to ozone and Pieris brassicae (L.) (Lepidoptera: Pieridae) were used as a model system. The effect of differences in ozone sensitivity and ozone fumigation on the plant's carbon and nitrogen pools, the feeding preference, and behaviour of P. brassicae larvae were investigated. The results show that the plant's susceptibility to ozone interacts in a complex way with ozone induced alterations in the suitability of the plant for the insect. Only the larval performance on the sensitive line was affected by ozone exposure. Biochemical changes in the resistant B. rapa line made the plant a better food source for the insects, since the digestibility of this plant was significantly higher than that of the sensitive line, and the larvae pupated more quickly and were heavier.

Ozone affects growth and development of Pieris brassicae on the wild host plant Brassica nigra

“…It appears that 120 ppb might be beyond a critical threshold, altering the phenotype of plants and having adverse effects on P. brassicae performance beyond the point of recovery. These results support a previous study by Jøndrup et al (2002) in which they observed similar negative effects of ozone on the performance of P. brassicae on B. rapa plants, but the effects depended on the plant's sensitivity to ozone. On ozone-sensitive lines, P. brassicae larvae took longer to reach pupation on 75 ppb ozone-fumigated plants than clean air-fumigated controls, but there was no effect on pupal mass.…”

“…Foliar sucrose levels increase dose dependently in response to ozone exposure in both Beta vulgaris and Brassica napus (K€ ollner and Krause, 2003). In B. rapa, ozone induced starch accumulation was observed in resistant and sensitive lines, while soluble sugars increased in sensitive lines (Jøndrup et al, 2002). We did not deeply explore the nutritive properties of B. nigra, but found that ozone exposure had no significant effect on water or carbon content while a reduction in nitrogen content occurred at both elevated concentrations.…”

“…A significant increase in the time to pupation was observed for larvae feeding on ozone-fumigated ozone sensitive plants, but not for the resistant variety. In the same study, 3rd and 4th instar larvae showed no preference for either ozone treated or control leaf discs (Jøndrup et al, 2002).…”

“…However, the effects on plantherbivore interactions are variable, with enhancement (Chappelka et al, 1988;Bolsinger et al, 1992), reduction Jøndrup et al, 2002) or no effect on (Fortin et al, 1997;Lindroth et al, 1993) herbivore performance for different plant-herbivore combinations. The only previous study to address such questions in a brassicaceous system used ozone sensitive and resistant varieties of field mustard (Brassica rapa L.) and large cabbage white butterfly larvae (Pieris brassicae) (Jøndrup et al, 2002). A significant increase in the time to pupation was observed for larvae feeding on ozone-fumigated ozone sensitive plants, but not for the resistant variety.…”

Constitutive and herbivore-inducible glucosinolate concentrations in oilseed rape (Brassica napus) leaves are not affected by Bt Cry1Ac insertion but change under elevated atmospheric CO2 and O3

“…The quantitatively altered GS proWle of plants resulting from elevated CO 2 and O 3 could aVect the performance of various adapted and non-adapted herbivores and also involve predation eYciency of insects of higher trophic levels through altered emissions of volatile GS degradation products (Potting et al 1999;Schuler et al 1999b) in the future. DiVerential herbivore performance has been noted under elevated CO 2 (Reddy et al 2004) and O 3 (Jondrup et al 2002), but until now the role of secondary compounds such as glucosinolates in this response has not been Fig. 4 Interactions linking O 3 stress, plant hormones involved in signal transduction and glucosinolates (GSs).…”