JWSS - Journal of Water and Soil Science

---

In order to study the parasitoid flies of Sunn pest in Isfahan, this research was conducted during the years 1997-1998. The results indicated that the dominant species of parasitoid fly is Phasia subcoleoptrata L. This species has two generations per year and over winters as pupae in soil under the shrubs of aestivation and hibernation places of Sunn pest and remains there until the following spring. The adults of the first generation of this parasitoid emerge from the pupae before the Sunn pest migrate to the grain fields and parasitize on the Sunn pest at the time of migration. About 6-8 days after the flies lay eggs in the body of Sunn pests, parasitoid larvae hatch from the eggs and grow in the body of their host. Larval period of parasitoid lasts about 15-20 days and then they fall on to the soil and pupate. In the laboratory, the length of pupal period for males and females is 17 and 18.5 days, respectively, for the first generation. Flies of the second generation of the parasitoid parasitize the fifth nymphal instar and the new adults of the Sunn pest.

---

In order to study the efficacy of Sunn pests' parasitoid flies, four overwintering sites of Sunn pest in Isfahan, including mountains of Kolahghazy, Panjeh, Jozdan and Sacepid were selected and from each site four different elevations were designated as sampling sites. During 1997, at least 6 and, in 1998, three samples were taken at each sampling site. In spring 1998, four wheat and barley fields were selected from Mahyar, Zeyar, Shahinshahr and Lavark regions and from each field eight samples were taken. In order to observe the larvae of parasitoids and to determine their efficiency, 100 Sunn pests were dissected from each sampling unit of aestivation, overwintering, wheat and barley fields.

The parasitism of prevalent species (Phasia subcoleoptrata L.) in spring 1998 was 15.39% for the 1st generation and 1.5% in 1997 and 3.5% in 1998 for the second generation of the pest. All other parasitoid species parasitized less than 1% of the pest population. In some regions, such as Lavark and Zeyar, chemical application against nymphs of Sunn pest were accomplished in spring 1998 at the peak of adult activity of parasitoids' 2nd generation. This application had negative effects on the population of parasitoids but in Shahinshahr where chemical application was accomplished at pupal stage of parasitoid, it did not have any direct adverse effects on the population of dominant parasitoid.

---

To study general combining ability(GCA) and gene action for resistance to sunn pest(Eurygaster integriceps) six lines of bread wheat numbered 7214 ,6412,c-75-4,18,14,12 plus azadi variety werw crossed in a half-diallel system. Seven parents and twenty-one hybrids were evaluated in a randomized complete block design with 3 replication at Tehran University Research Station during the years 2005-2006. Analysis of variance indicated that among all of traits except for weight of sunn pest damaged kernel, difference existed at 1% level of significant. Results of combining ability analysis showed that in all traits, additive and non- additive variances in inheritance is important. Considering GCA for resistance to sunn pest line 7214 was the best and line 18 was the worst. Considering specific combining ability(SCA) for resistance to sunn pest damage with regard to all of traits the azadi×c-75-4 hybrid was the best and the 18×12 hybrid was the worst. Study of Hayman genetics parameters confirmed the results of Griffing GCA analysis indicating that in all traits additive and non- additive components are effective in inheritance except 50 kernel weight damaged, sunn pest seed damaged percent and height. But dominant variance is more important in these traits. For all traits except awn length exist over dominance, furthermore in all traits nonsymmetrical distribution of negative and positive effects and environment effect is also important.