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Background and Objectives Wheat (Triticum aestivum L.) holds crucial significance as a primary global food source, providing approximately 18% of required calories and 19% of essential protein for human consumption. The greenbug, Schizaphis graminum, poses a substantial threat to wheat crops worldwide, including in Iran, causing significant annual damage. Traditional methods for identifying induced resistance in host plants involve pest pre-infestation and the assessment of demographic parameters. Considering the adverse environmental and health implications of excessive pesticide use in wheat fields, the exploration of "induced resistance" as a biorational method has gained notable attention in recent years within the wheat-integrated pest management domain. This study's main objectives included examining induced responses in three distinct wheat varieties to S. graminum and determining the optimal pre-infestation period to activate this defensive reaction in the host varieties. Materials and Methods Seeds from three wheat varieties (Kohdasht, Morvarid, and Aseman) were planted in growth chamber conditions (temperature: 25±2°C, relative humidity: 60±5%, and a photoperiod of 14:10 L: D). Upon reaching the two-leaf stage, five one-day-old female apterus aphids were introduced to each plant, allowing them to feed for 0, 2, 4, 6, and 8 days (considered as the experimental pre-infestation treatment duration). After the designated pre-infestation period, aphids were removed from the wheat plants, and the plants remained aphid-free for 48 hours. Following this interval, an age-specific two-sex life table of aphids was separately constructed for each wheat variety and pre-infestation duration. Using a cohort of 30 one-day-old first-instar nymphs, the biological and demographic parameters of aphids were measured and compared using the paired bootstrap test. Results The Aseman variety exhibited heightened resistance to S. graminum in comparison to Morvarid and Kohdasht varieties, as evidenced by the demographic parameter values. Notably, Aseman's extended nymphal developmental time and mean generation time (T), coupled with decreased longevity and fecundity, resulted in a significantly lower intrinsic rate of increase (rm) at 0.245 1/day, in contrast to Morvarid and Kohdasht varieties (0.348 and 0.358 1/day, respectively). Across all varieties, pre-infestation by aphids led to reductions in biological and demographic parameters, with the effective pre-infestation duration varying based on the variety and specific parameters studied. The nymphal developmental time increased, while fecundity and intrinsic rm significantly decreased as the pre-infestation duration progressed from 0 to 8 days. In Aseman, Morvarid, and Kohdasht varieties, rm decreased from 0.245 to 0.187, 0.348 to 0.275, and 0.385 to 0.335 1/day, respectively, with an increase in pre-infestation duration from 0 to 8 days. In the relatively more resistant Aseman variety, significant changes in nymphal developmental time and intrinsic rm occurred after a 2-day pre-infestation period, while aphid fecundity changed significantly after a 6-day pre-infestation duration. Morvarid exhibited significant changes in nymphal developmental time, female fecundity, and intrinsic rate of increase after 6, 4, and 2-day pre-infestation durations, respectively. Across all three varieties, the intrinsic rm, identified as a crucial demographic parameter, experienced significant changes after a 2-day pre-infestation period. Discussion Diverse demographic responses were observed for S. graminum across the studied wheat varieties, with the Aseman variety exhibiting heightened relative resistance to wheat green aphid. Pre-infestation of wheat plants with aphids induced resistance in all three varieties, resulting in a reduction in the biological and demographic potential of green aphid. Due to their favorable induction reactions to S. graminum, it is recommended to cultivate Kohdasht (resistant to pathogenic fungi, suitable for dry and semi-arid drylands) and Morvarid (resistant to pathogenic fungi, suitable for humid and plain areas) varieties. This approach can contribute to diminishing the aphid population and enhancing wheat production in these specified regions. The research outcomes offer valuable insights into identifying sources of resistance, understanding mechanisms, and facilitating the implementation of integrated aphid management strategies in wheat fields across Iran. [ABSTRACT FROM AUTHOR]

The biology of greenbug, Schizaphis graminum Rondani, one of the most important pests of cereals in Varamin region of Iran, was studied in laboratory at 20 ± 1ËC, 60-70% R.H. and a photoperiod of 16: 8 (L: D) hours. The experiment was carried out by rearing aphids on the leaves of six common wheat varieties including: Mahdavi, Kavir, Niknezhad, Azadi, Tabasi, and Ghods using leaf cages. The nymphal development time, mortality, longevity and adult fertility of the aphid were recorded daily. The intrinsic rate of increase (rm), finite rate of increase (λ), and doubling time (DT) parameters were calculated. Results revealed that nymphal mortality rate was very low resembling that on sensitive wheat varieties. The aphid had relatively high longevity and short nymphal development time on all mentioned wheat varieties. The lowest aphid fertility rate was obtained on Kavir comparing to the fertility yielded on Mahdavi and Tabasi that was significantly higher (P < 0.01). Estimation of the intrinsic rate of increase revealed that the wheat varieties studied were susceptible to aphid, for the reason that the aphid population increased by constant exponential rate of 0.252-0.310 female/female/day. This showed high population increase potential at suitable conditions in the absence of natural enemies. Results proved that the Niknezhad, Tabasi and Ghods were the most suitable wheat varieties for rearing the aphid. The lowest rate of fertility, intrinsic rate of increase, and finite rate of increase, and the longest doubling time of aphid population were observed on Kavir, due to lower fecundity and longer nymphal development period. Therefore, the aphid population increase potential on Kavir was lower than that on the other varieties and so, expansion of sowing Kavir in Varamin region most probably may not result in aphid population increase.