9.12. Yeheb, a wild food plant resistant to environmental odds of arid environments

Public examination of a doctoral dissertation in the field of environmental science

Doctoral candidate: M. Sc. Meseret Chimdessa Egigu

Date and venue: 9.12.2011, at 12 noon, ML2, Medistudia, Kuopio Campus 

In arid ecosystems, plants cope with high temperatures and globally increasing phytotoxic tropospheric ozone through modulation of the production/emission of secondary compounds and/or other enzymatic or non-enzymatic antioxidant compounds. Yeheb (Cordeauxia edulis), a wild, but a food and fodder plant, is a native shrub in arid ecosystems of tropical East Africa, where most common crops fail to establish due to abiotic and biotic stresses. Predictions show that temperature and concentration of tropospheric ozone will increase in the future all over the globe, and may further worsen the marginal situations of arid environments for crop production. This study investigated the impact of future predicted temperatures and tropospheric ozone concentrations on Yeheb in growth chambers, and the defensive role of its extract against phytophagous insect pests. 

The results showed that future predicted high temperatures or moderately high tropospheric ozone (120 ppb) does not negatively affect Yeheb. This could be attributed to the increased production/emission rate of highly reactive volatile isoprenoids and/or the enhancement of the ascorbate-glutathione antioxidant molecules that protect plants from oxidative stress. Therefore, Yeheb, which appeared to sustain abiotic stresses such as elevated temperatures and O3 concentrations, is a promising plant for domestication and cultivation to be used as food and fodder in arid ecosystems of East Africa where most other crop plants fail to establish. On the other hand, a substantial emission of highly reactive volatile organic compounds (e.g. isoprene and monoterpenes) under elevation of temperatures by Yeheb suggests that plants of tropical arid ecosystems may considerably contribute to the change of atmospheric chemistry, thus, need to be investigated more. The results also demonstrated that foliar extracts of Yeheb are rich in a phenolic compound cordeauxiaquinone, various monoterpenes and sesquiterpenes, and able to negatively affect the performance of the tested phytophagous insect pests. Particularly, besides deterring the feeding and oviposition by diamondback moth (DBM), foliar extract of Yeheb also attracts the natural enemy of DBM. Hence, it is effective in the control of DBM, which is an important pest of cruciferous crops worldwide.However, its efficacy and safety should be assessed under field conditions. 

The doctoral dissertation Master of Science Meseret Chimdessa Egigu entitled Secondary compounds of Yeheb (Cordeauxia edulis): production under abiotic stresses and their defensive role against phytophagous insects will be examined at the Faculty of Science and Forestry. The opponent in the public examination is Associate Professor Joop van Loon from the Wageningen University and the custos is Professor Jarmo Holopainen of the University of Eastern Finland.

Contact: Meseret Egigu, tel. + 358 44 919 2893, meseret.egigu@uef.fi

Publishing year: 2011

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