The systemic expressions of certain defense-related genes in cucumber plants induced by culture filtrate (CF) of the plant growth-promoting fungus (PGPF), Penicillium simplicissimum GP17-2, and challenging with Sio₂ nanoparticles against Papaya ring spot virus (PRSV) and its vector the green peach aphid Myzus persicae were investigated. CF and Sio₂ were topically applied to cucumber plants by soil drench method. Results showed that the severity of PRSV and its accumulation in cucumber leaves were significantly reduced in all treated cucumber plants compared with the control. The expression of pathogenesis-related genes showed strong activations of peroxidases (POX) and phenylalanineammonia lyase (PAL) genes and moderate expression of PR-1 one day after inoculation, while, six days after inoculation a high activation of PAL and PR-1 genes and moderate activation of POX gene were detected. No expression was detected in plants infected with PRSV alone without any treatments. These results suggested that CF and Sio₂ treatments mediated the expression of the majority of various pathogen-related genes, which may contribute to the increased defense mechanism against PRSV infection in cucumber.

The pink stem borer (PSB), Sesamia cretica (Lepidoptera: Noctuidae) purple-lined borer (PLB), Chilo agamemnon (Lepidoptera: Crambidae) and European corn borer Ostrinia nubilalis, (Lepidoptera: Crambidae) are considered the most devastating insect pests of maize production in the Mediterranean region. The frequent use of chemical insecticides has resulted in the evolution of resistance to various insect pests as well as the pernicious impact on natural enemies and environmental hazardousness. Therefore, developing resistant and high-yielding hybrids is the best economic and environmental approach to cope with these destructive insects. Accordingly, the objective of the study was to estimate the combining ability of maize inbred lines (ILs), identify promising hybrids, determine gene action controlling agronomic traits and resistance to PSB and PLB, and investigate inter-relationships among evaluated traits. A half-diallel mating design was employed to cross seven diverse maize inbreds to generate 21 F₁ hybrids. The developed F₁ hybrids, alongside high-yielding commercial check hybrid (SC-132), were assessed in field trials for two years under natural infestation. Substantial variations were obtained among the evaluated hybrids for all recorded characteristics. The non-additive gene action was major for grain yield and its contributing traits, while the additive gene action was more important in controlling the inheritance of PSB and PLB resistance. The inbred line IL1 was identified to be a good combiner for earliness and developing short-stature genotypes. Additionally, IL6 and IL7 were recognized as excellent combiners to enhance resistance to PSB, PLB and grain yield. The hybrid combinations IL1×IL6, IL3×IL6, and IL3×IL7 were determined to be excellent specific combiners for resistance to PSB, PLB and grain yield. Strong positive associations were identified among grain yield, its related traits, and resistance to PSB and PLB. This implies their importance as useful traits for indirect selection for improving grain yield. Otherwise, the resistance against PSB and PLB was negatively associated with the silking date, indicating that earliness would be favorable for escaping from the borer’s attack. It could be concluded that the inheritance of PSB and PLB resistance can be governed by the additive gene effects, and the IL1×IL6, IL3×IL6, and IL3×IL7 hybrid combinations can be recommended as excellent combiners for resistance to PSB and PLB and good yield.

Water stress and nitrogen deficiency are two constraints that negatively affect growth and productivity of wheat plants. Moreover, the interaction between these two stresses could affect the susceptibility of wheat plants to insect attack. In order to examine the influence of drought stress and nitrogen fertilization on piercing-sucking insect pests, the population abundance of four cereal aphid species; English grain aphid Sitobion avenae, wheat aphid Schizaphis graminum, Bird cherry-oat aphid Rhopalosiphum padi, and corn leaf aphid Rhopalosiphum maidis has been monitored in two water treatments (water stress and well-watered) and two nitrogen levels (120 and 180 kg N ha-1). Results revealed that S. graminum was the most dominant specie in all treatments, followed by S. avenae. The population of all aphids tends to increase in the second half of the season coinciding with the emergence of wheat spikes. Stressed-wheat plants attracted more aphids, especially when water deficit synchronizes with an increase in N fertilization. Aphids vigorously thrive better on stressed plants amended with high nitrogen level. Contrary, the lower infestation rate was observed in well-watered plots with lower nitrogen rate. Plant characteristics, such as days to heading, plant height, and chlorophyll content were significantly decreased in drought-stressed plants, while higher N rates increased such parameters. Grain yield and its components were reduced with drought stress and reduced nitrogen fertilization. The current study advocates avoiding severe drought concurrently with an increasing in nutritional augmentation which it might contribute in an increase in insect pest infestation and decreasing in wheat plant traits.

The biotic and abiotic factors including the agricultural implementation can modify soil acidification. We hypothesized that soil pH should as repercussion, alter the plant physiological and physical properties and eventually affect insect herbivores including agricultural pests. This study aimed to evaluate the impact of seven levels of soil pH on the performance of cowpea aphid Aphis craccivora on Vicia faba. Significant relationships between soil pH and growth of host bean seedlings or development and reproduction of the aphid were detected. Data demonstrated significant differences in the total longevity, the pre-reproductive, reproductive, post-reproductive and pre-viviparity periods. Within a suitable range of pH for bean growth between pH 5.3 and pH 7.2, the aphid performance was worse on seedlings growing better, however, under unfavorable extreme pH conditions, plant quality measured as height did not affect the aphids anymore and their performance was uniformly low except the case in pH 8.1 condition in which the best aphid reproduction was observed. The results confirm that soil pH affect the performance of cowpea aphid A. craccivora and also exhibited strong influence on the growth of broad bean plants.