Oviposition preference, larval and pupal Development and adult fecundity of the Sorghum shootfly, atherigona soccata rondani (diptera muscidae) on selected sorghum lines

Abstract

The sorghum shootfly, Atherigona soccata Rondani is one of the most important pests of sorghum. Since control measures like the use of insecticides are not very effective or economical breeding for resistance could be the answer to the problem in the future. In this study, the possible mechanisms of resistance in 5 selected sorghum lines to the sorghum shootfly, were investigated under greenhouse and field conditions. These lines: IS-1054, IS-1082, IS-2195, IS-2312 and IS-3962 were selected for their promising performance in earlier screening tests.CSH-l, a hybrid variety from India and susceptible to shoot fly attack

was included as control.

Oviposition preference was studied in a single choice o~iposition test involving the control (CSH-l) and each one of the 5 test lines. For antibiosis studies, the following parameters were considered: growth and mortality of larvae raised on the test lines and control, the extent of damage to the shoot, fecundity, longevity, preoviposition period in the adult flies and hatching of the resulting eggs.

A randomised complete block design consisting of 4 blocks was employed in the field experiment in which the test lines and control were subjected to a natural insect pest infestation. Observations on germination, oviposition, dead-heart formation both in the main plants and in tillers, tillering ability, • flowering and damage by pests other than the shoot fly were recorded. Results of this investigation show that IS-3962 was strongly non-prefe-rred for oviposition by the shootfly followed by IS-2312. Oviposition non-preference was present at a higher level in IS-I082 and at low level in IS-2195 whil~it was lacking altogether in IS-I054. IS-2312 was very strong in ahtibiosis followed by IS-3962. IS-2195 had ~ low level of antibiosis, IS-I054 had the lowest level while it was lacking in IS-I082. IS-2195 also showed sane tolerance characteristic In conclusion the best material in terms of shoot fly resistance is IS-3962 and IS-2312 followed by IS-2195. IS-I082 has a moderate resistance rating while IS-I054 has the lowest rating.

The next step in this field of research is to learn more about the factors responsible for various mechanisms of resistance identified in these lines and incorporate them into high yielding agronomically recommended sorghum varieties. Further investigation on sources of multiple resistance , for shootfly, stemborers and midge would be of great importance in the breeding of these resistant sorghum varieties.