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The genotype + genotype × environment (GGE) biplot methodology has the potential to determine combining ability effects, identify efficient testers, and distinct heterotic groups in a line × tester study. However, it has not been adequately applied for such analysis. Therefore, this study was done to assess the combining ability of some maize inbred lines and testers for grain yield, identify most efficient testers and classify inbred lines into heterotic groups using GGE biplot. Fifteen experimental single cross hybrids, generated from a 5 × 3 line by line × tester crosses procedure, were evaluated across seven sites in Iran in 2018 using a randomized complete block design with three replicates per entry at each site. According to the pooled analysis of variance, crosses showed significant differences for grain yield. Also, the differences observed among the testers, inbred lines, and interactions for the line × tester, crosses × environments, line × tester × environment was significant. The inbred line L4 was recognized as outstanding for its general combining ability (GCA) effect and the tester K18 was highly efficient based on its discriminating power. It can be concluded that the crosses of L4 × K47/3 and L4 × B73 are suggested to release high grain yield hybrids. Results of the GGE biplot analyses were close to the conventional line × tester method in combining ability and heterotic patterns of the yield of lines, grouping, and identification of testers.

Lethal effect of the entomopathogenic nematode, Steinernema feltiae, against prepupae of Helicoverpa armigera (Hb) (Lepidoptera: Noctuidae) in soil was evaluated. Plasma phenoloxidase activity of H. armigera prepupae against S. feltiae also was evaluated. In brief, 20-25 infective juveniles (IJs) of S. feltiae in 20 μl Ringer's solution were injected into the hemolymph of H. armigera prepupae in different time intervals. In order to evaluate the effect of the Ringer's solution, it was also injected into the larvae in a separate experiment as positive control. A third group of non-injected insects was used as negative control. Hemolymph of the insects was collected in different time intervals (0 to 24 h post injection). Phenoloxidase (PO) activity of H. armigera hemolymph was determined spectrophotometrically, using L-Dopa as substrate. The LC 20 , LC 50 , and LC 80 values were 4.5, 19, and 76 IJs per insect, respectively. PO activity assay demonstrated higher levels of PO unit in nematode-injected insects compared to control groups. Nematode-injected insects showed the highest plasma PO activity 8 h post-injection.

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For evaluating lethal effects of abamectin on T. urticae leaf dipping method was used. Then T. brassicae adults were treated with LC 10 and LC 50 values obtained from probit analysis of the mite bioassay results using toxicity bioassay with fresh residue method. For evaluating residual effects of abamectin, bean plants were sprayed with twentieth of recommended field dose of abamectin (equal to 25 ppm of trade product). Leaf pieces were prepared from treated plants in different time intervals and the adult mites were transferred on them. Mortality was recorded after 24 h. Probit analysis of lethal experiment against T. urticae revealed 0.05, 0.417 and 3.26 ppm from trade product as LC 10 , LC 50 and LC 90 values, respectively. Results of residual effects experiment showed that mite mortality was 100% in 1 day after plant spraying which decreased to 55.62% in 21 days after spraying. LC 10 and LC 50 values of abamectin tended to 53.87 and 72.57% mortality of T. brassicae, respectively.