Evaluation of resistance in wheat against Rhopalosiphumpadi (L.) (Homoptera:Aphididae) Under laboratory Conditions

Abstract

Aims and introduction
All over the world aphids are pests of economic importance, affecting all varieties of plants like cereal crops, vegetables, ornamental plants and fruits. Aphids damage plants either directly or indirectly. Aphids are one of the major agricultural pests. There are only a few plants that are not susceptible to infestation by this destructive pest. They cause direct damage by sucking the sap of leaves, blocking photosynthesis which results in leaf distortion, gall production, discoloration, stunting, leaf curling, wilting, twisting and premature leaf falls. They are directly involved in transmission of plant viruses and indirectly by depositing honey dew that reduces photosynthetic activity and induces sooty mold production and premature leaf senescence.
	
Methodology
Hosts were wheat and maize. There was twenty varieties of National Uniform Wheat Yield Trials (NUWYT) Normal (N) of year 2004-05, and twelve varieties of (NUWYT) Rain Fed (R.F) of year 2004-05 while there were twenty-two varieties of maize of year 2005-06. All these varieties were evaluated against bird cherry oat aphid R. padi L pest. Evaluation for resistance was done by seedling bulk test and by comparing the results of components of resistance like antibiosis, antixenosis and tolerance tests. These experiments were performed under controlled environmental conditions. Experiments were of randomized complete design and replicated. The data obtained was statistically analyzed of variance (ANOVA) and the mean values were compared by Duncan’s new multiple range test (DMRT) at 5 percent level of significance (Steel and Torrie, 1980).

Results
Among the tested germplasm (one variety and 11 lines of wheat), the V-5 line was found resistant and the NRL-2017 line was found susceptible to Rhopalosiphum padi. The results of the Antixenosis Test indicated that two wheat lines, V-5 and PR-83 were least preferred and three lines viz., NRL-2017, V-00055 and V-00BT004 were highly preferred by the test insect. The results of the Antibiosis Test showed that PR-83 line was least fecund whereas NR-241 and V-00055 lines were highly fecund. The results of the Tolerance Test indicated that four varieties, PR-83, V-5, SN-128 and NR-241 were highly tolerant, while only one line, V-00BT004 was least tolerant.

Conclusion
To avoid harmful effects of this insect pest, only resistant, least preferred, least fecund and highly tolerant lines must be used in wheat breeding programs