Antixenosis is defined as a resistance Populus mechanism affecting pest establishment on their host plants. In this study, antixenosis mechanism were evaluated in ten poplar clones belonging to four species named, P.alba, Pnigra, P.deltoides and P.euramericana, against poplar stem aphid, Pterocomma populeum in laboratory condition in the year 2005. The study was carried out with four different experiments.Poplar cuts of each clone were provided from Alborz Research Center of Karaj. The length and diameters of poplar cuts were 20 and 1-1.50 centimeter respectively. In the first experiment a single cut of every poplar clone along whit two aphid-infested cuts were wrapped together with an elastic string. The bunch was then placed in plastic jars.The height and diameter of the jars were 22 and 14centimeter respectively.24 and 48 hours after aphid release, the number of established aphids on every clone's cuts were counted and recorded. In the second experiment the cuts of the clones were bounded around a cylindrical stick (3 cm diameter) with an elastic string and a Petri dish 3.5 cm diameter was placed on it. About 50 wingless aphids were placed in the Petri. The third experiment was similar to the second one, but, 50 alate aphids were released in the Petri dish. The fourth antixenosis experiment was done using an olfactometer. Fifty adult aphids were released in central container of the olfactometer. After 24 and 48, the number of aphids setteled on each clone cuts in lateral containers of the olfactometer were counted. Every experiment was replicated 10times. Statistical analysis revealed a significant differences (P<0.000) between tested clones in every four experiments.Comparison of means showed that numbers of aphid setteled on Populus nigra betolifolia and P.euramericana triplo clones were highest and lowest respectively.Other clones exhibited moderate level of aphid preference. All of the four experiments showed consistent results.

Schizaphis graminum (Rondani) (Hem.: Aphididae) is one of the seriously injurious pests of cereals particularly of barley. The population of the pest has been on the increase in recent years. Besides chemical control, another practically suitable method of controlling the pest is the use of resistant barley genotypes. In this research, 47 advanced lines along with 13 cultivars were screened in their seedling stages in greenhouse conditions (25±2oC, 55±10% relative humidity and 16:8 photo phase)while testing basis two mechanisms of antixenosis and tolerance on them. Screening was made on the basis of mean number of aphids (14 days after infection with the aphid). Rhaihan, Nosrat cultivars as well as line20 (Mall-4-3094- 2//Alpha/Cum/3/Victoria/…ICB01-1368-0AP), carrying the least, whileline13 (Legia/CWB117-5-9-5), line44 (Sls/Bda//Sararood-1) and Zarjo cultivar attracting the most mean number of aphids, were selected for antixenosis and for tolerance tests. Antixenosis experiment was carried out as based upon the number of attracted aphids to different cultivars within 24, 48, and 72 hours following insect release. Results indicated that Zarjo and Raihan cultivars bore the weakest vs the strongest antixenosis, respectively, as observed within all the three experimental times. Tolerance experiment was judged by the effect of aphid feeding on host plant height wise. Raihan cultivar had the most increase in its secondary height (compared with control) and the least percentage of decrease in its main height (%2.09). Conversely, Zarjo cultivar exhibited the least increase in its secondary height (compared with control) and the greatest percentage of decrease in its main height (%65.96), suggesting a least level of tolerance.

Antixenosis is defined as a resistance mechanism affecting pest establishment on their host plants. In this study, antixenosis mechanism were evaluated in twelve poplar clones belonging to four species namely, Populus alba, P. nigra, P. deltoides and P. x. euramericana against poplar woolly aphid Phloeomyzus passerinii Sign. Poplar cuts of each clone, placed in plastic jars containing water, were rest in growth chamber. The length and diameters of poplar cuts were 20 and 1-1.5 centimeter, respectively. A single cut of every poplar clones along with an aphid - infested cut were wrapped together with an elastic string. The bunch was then placed in controlled conditions of 60-70% RH, 20-22 Celsius and 16: 8 L: D photoperiods. After two days, the infested cut was taken away from the bunch, and aphid numbers were counted on each single cut. The cuts were placed together for second time, and the numbers of aphids were recorded on a two-day interval basis. Subsequently, the experiment was carried out with 18 replications. Statistical analysis revealed a significant difference (P<0.01) in aphid numbers among the clones. Number of aphids settled on Populus alba 58/57 (0.31 aphid/cut) was significantly less than the other clones. Consequently, a conclusion can be reached that this clone might be an immune poplar against the pest. Other than Populus alba 58/57,a number of clones including: Populus nigra 62/149; Populus nigra 62/72; Populus x euramericana 214; Populus deltoides 72/51 and Populus nigra 62/140 exhibited significantly low aphids density (2.54-4.91 aphid/cut). Therefore, it could be concluded that these clones contained a high level of antixenosis resistance. In contrast, aphid number recorded on P. nigra 56/72 (25.98 aphid/cut) was higher than the others, showing the most susceptible clone to P. passerinii establishment.

East Azarbaijan province is one of the most important areas for poplar production and has the highest suitability of poplar plantation in Iran. Three species of poplar trees includedPopulus alba, P. nigra and P. x. euramericanaare planted and usually attacked by different pests in this province. Melasoma populi L., Archips rosana (L.) and Pemphigus filaginis are some of important pests that cause direct and indirect damage on poplar trees. In this study were investigated antixenosis resistance of different poplar clones based on evaluation of pests accumulation on clones in natural condition. Based on the study results, clones includedP. nigra Shabestar, P. alba Marand and P. nigra 62.154 respectivelly had more susceptibility and P. nigra Maragheh, P. albaMaragheh, P. alba Bostanabad and P. x. euramericana Bostanabad clones were the most resistant against M. populi. P. alba Mianeh clone was the most susceptible to A. rosana while, P. nigra Miandoab, P. nigra Maragheh andP. alba Maragheh had the highest resistance. About P. filaginis only P. alba Miandoab, P. nigra Marand andP. nigra Mianeh clones were infested to the pest and none of the other clones infested to the aphid.

Leaf miner Liriomyza sativae has been widely distributed in the world in recent years and it is presently an important pest of vegetables and ornamentals. Because of its high potential for resistance to current insecticides, the use of resistant plant varieties seem to be an effective approach in developing IPM programs for the pest. Since bean is a preferred host for Liriomyza sativae, 19 varieties of bean were examined to study the antixenosis resistance mechanism to this insect and determining the damage rate in a growth chamber at 25± 1°C, 55± 5%RH and 16:8 (light dark) photoperiod. Bean varieties were evaluated in terms of indices such as number of feeding punctures, number of larval mines, proportion of mines to punctures and rate of damage. There was significant differences between varieties. Studied indices such as feeding punctures with larval mines (r=0.957) and larval mines with damage rating (r=0.869) showed high positive correlation among these varieties. Bean varieties were analyzed by cluster method based on all measured characters and were generally divided into three main groups including semi-resistant, moderately resistant and semi-susceptible. No variety was immune to the damage inflicted by L. sativae and Parastoo as a semi-resistant variety roughly sustained 31% damage. Meanwhile, Sayyad, a semi-susceptible variety, up to 61% damage was known as the most susceptible one among studied varieties.

The Colorado potato beetle, Leptinotarsa decemlineata (Say), is a serious pest of potato, Solanum tuberosum L. worldwidely. One of the methods used for controlling of it is deployment of resistant cultivars. Field experiments were conducted to evaluate the antixenosis resistance in 33 potato cultivars to this pest during 2007 - 2009. Research method in 2007 was similar to 2008 and was different from 2009. In a field choice test, the numbers of attracted beetles to the cultivars were determined as antixenosis index. Numbers of attracted beetles to the cultivars and numbers of egg masses on them were used as antixenosis indices during 2009. Cluster analysis of cultivars was performed with MINITAB15 statistical software using UPGMA procedure based on Euclidean distance. Combined analysis of variance of choice test data in 2007 and 2008 showed that with point of settled adult beetles on the studied cultivars, significant difference was observed between experimental years, blocks, times of counting, cultivars and reciprocal effect of cultivar´year (P<0.0001). Mean comparison showed that cultivars Bright, Delikat, Nicola, Sinja, Carlita and Cardinal in 2007 and Cardinal, Carlita, Sinja, Elles and Romina in 2008 had the highest antixenosis resistance with the least settled adult beetles on them. Cluster analysis showed that in two first years, cultivars Cardinal, Carlita, Sinja, Bright, Raja, Nicola, Romina, Santana, Elles, Fianna and Satina with the least attracted beetles were resistance group in antixenosis index. Also, cluster analysis based on the number of attracted beetles to the cultivars and number of egg masses on the cultivars showed that cultivars Bridjet, Baltica, Cardinal, Nicola, Raja, Bright, Delikat, Carlita, Provento, Cosima, Armada, Elles and Beluga were placed in one group and had the highest antixenosis effects compared to others cultivars in 2009. Mean comparison showed that cultivars Cardinal, Carlita and Bridjet had the highest antixenosis resistance with the least settled adult beetles on them in three experimental years.

The use of resistant plant cultivars and parasitoids could be an effective strategy in IPM of Liriomyza sativa Blanchard. Cucumber is a preferable host for this insect. In this research, antixenosis resistance of 17 cultivars of cucumber was evaluated toL. sativae under greenhouse condition. Results indicated that there were significant differences between cultivars with regard to the number of feeding sting and larval tunnels (p<0.01).Cucumber cultivars were ranked by cluster method based on all measured characters and were classified to four groups: susceptible, semi-susceptible, semi-resistant and resistance. Density of leaf hairs and trichomes of cucumber cultivars were evaluated and the result showed that the density of glandular hairs on leaves of field cultivars was higher in comparison to greenhouse cultivars. These results suggested that the local and field cultivars are generally more resistant to leafminer than the greenhouse cultivars. In this study, a wide range of genetic variation in traits related to leafminer resistance was found in cucumber germplasm. Also in tritrophic level system, the effects of first level (cucumber cultivars) on third level (parasitoid wasps) were studied and the results showed no significant differences between cultivars in attracting parasitoid wasps.

Pear psylla [(Cacopsylla pyricola (Foerster)] is one of the most important pests affecting pear production. The main purpose of this research was to investigate the resistance of pear cultivars to pear psylla for recommendation in integrated pest management and national pear breeding programs. This research was carried out using randomized complete block design with foure replications in Kamalshahr research station in Karaj, Iran, in four growing seasons from 2019 to 2023. Nine pear cultivars; Boheme, Shah Mieveh, Natanzi, Sebri, Dargazi, Louis Bonne, Harvest Queen, Potomac and Coscia. Data about psyllids population at different stages; eggs, nymphs, and dult, was collected and recorded at the peak of its activity, i.e., from early February to November, every seven days. Antixenosis resistance indices included; attraction index, mean crowding intensity, relative abundance establishment rate, non-preference index and prevalence index of eggs, nymphs and adults were calculated. Tree characteristics; form, one year old branches growth, leaves, flowers and fruits were examined. The results showed that the most resistant cultivars to pear psylla were; Cosia, Boheme, Sabri, Natanzi and Potomac. Atteraction index was 0.99, 0.99 and 0.95, crowding intensity index was 58.30, 149.14 and 16.13, relative establishment rate was 3.68, 3.65 and 3.40 for egg, nymph and adult stages, respectively. Non-perference index was 98.04, 98.06 and 19.98 and the prevalence index was 49.66, 49.47 and 47.50 for egg, nymph and adult stages, respectively. Keywords: Pear, Psylla, Host finding, Host acceptance, Cultivar sensitivity. IntroductionCurrent management practices are sufficient to effectively control pear psylla (Murray et al., 2021). In many countries, collections of pear cultivars have been established in some important pear-growing areas with a wide range of cultivars of national, local and foreign origin to evaluate resistance to diseases and pests (Braniste and Militaru, 2007). Antixenosis resistance of pear cultivars to pear psylla has been described with non-preferential egg laying. It has also been found that this type of resistance mechanism affects the size of the initial nymph population (Bell and Puterka, 2003). The main goal of this research was to investigate the details of the host preference and resistance mechanism of nine pear cultivars to pear psylla for recommendation in integrated pest management and national pear breeding programs. Materials and MethodsThis research was carried out using randomized complete block design with foure replications in Kamalshahr research station in Karaj, Iran, in four growing seasons from 2019 to 2023. Nine pear cultivars; Boheme, Shah Mieveh, Natanzi, Sebri, Dargazi, Beiruti (Louis Bonne), Harvest Queen, Potomac and Coscia. Data about psyllids population at different stages; eggs, nymphs, and dult, was collected and recorded at the peak of its activity, i.e., from early February to November, every 7 days. Antixenosis resistance indices included; attraction index, mean crowding intensity, relative abundance establishment rate, non-preference index and prevalence index of eggs, nymphs and adults were calculated. Tree characteristics; form, one year old branches growth, leaves, flowers and fruits were examined. After testing normality of the data Kolmogorov-Smirnov test, analysis of variance was performed based on priciples of random complete block design using IBM SPSS Statistics 27.0.1.0 software. For grouping pear cultivars based on the level of sensitivity to pear psylla, cluster analysis was employed. The relationship between characteristics of pear cultivars and antixenosis resistance indices was studied using correlation analysis. Factor analysis was performed to identify unobservable effective combined factors on resistance mechanism based on sets of observable indices. The accuracy of cluster analysis method was examined using linear discriminant analysis (LDA), normal discriminant analysis (NDA), or discriminant function analysis and Fisher's linear discriminant analysis. Results and DiscussionShah Miveh pear cultivar was the most sensitive cultivar to pear psylla. The most resistant cultivars to pear psylla were; Coscia, Boheme, Sebri, Natanzi and Potomac. Increase in host antixenosis properties based on reduction of attraction index led to increase in the time spent in egg-laying activities, decrease in the egg-laying rate, and as its consequences, decrease in attractiveness of the host for egg-laying in resistant pear cultivars. In host-finding stage, adult psylla must randomly search in a habitat until it finds one of the important stimuli for selection of pear cultivars.Morphological stimuli of pear cultivars for host-finding include different growth characteristics of the tree, flower, leaves and availability of host. Pear cultivars resistant to pear psylla can be good alternatives to chemical control and manage the pest. It has been reported that the genetic control of resistance to pear psylla is polygenic trait (Dondini et al., 2015). This genetic mechanism reduces the possibility of the emergence of resistant biotypes of the pest, and rewards investing in development and use of resistant pear cultivars to psylla in integrated pest management and control. This approach is very important and eco-friendly. ReferencesBell, R.L. and Puterka, G.L. 2003. Modes of host plant resistance to pear psylla: a review. Proceedings of the XI Eucarpia Symposium on Fruit Breeding and Genetics 663 (pp. 183-188). DOI: 10.17660/ActaHortic.2004.663.26Branişte, N. and Militaru, M. 2007. Germplasm fund of Pyrus sp. presently in ex situ Romanian collections. In X International Pear Symposium 800 (pp. 497-502). DOI: 10.17660/ActaHortic.2008.800.63Dondini, L., De Franceschi, P., Ancarani, V., Civolani, S., Fano, E.A. and Musacchi, S. 2015. Identification of a QTL for psylla resistance in pear via genome scanning approach. Scientia Horticulturae, 197, pp.568-572. DOI: 10.1016/j.scienta.2015.10.018Murray, K., Jepson, P.C. and Hedstrom, C. 2021. Integrated pest management strategic plan for Oregon and Washington pears: Summary of a Workshop Held on March 5, 2020 in Hood River, Oregon. Oregon State University Extension Service. 80 pp.

Onion thrips, Thrips tabaci Lindeman, is one of the most common and important pests of agricultural products including eggplant. In present study, we investigated the mechanism of antixenosis, trichomes density and chlorophyll content of 10 eggplant genotypes (Black beauty, Blacky, Yalda, Lady, Linda, Lyma, Kyme, Borazjan, Siah-Mashhad and Mahali-Zabol) to the thrips in festationin a selection test. Experiments were performed in a greenhouse at 25±1oC, 65±5 RH and 16L: 8D photoperiod. Total protein of the cultivars was isolated and electrophoresed using SDS-PAGE to determine the protein-electrophoresis pattern and its relation to the quantity of attracted thrips. Protein-electrophoresis showed differences in the number and type of the protein bands which are related to the variation among the cultivars in which the thrips-resistant cultivars can be used in the inbreeding programs. The genotypes were significantly different in terms of trichome densities and chlorophyll content as well as thrips-mediated damage percentage. There was no significant correlation between morphological attributions and molecular data. We believe that Lima and Linda genotypes, with highest genetic distance (0.454), can be successfully used in cross breeding programs, although complementary tests are required to improve the efficiency of the programs.

Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the most important and devastating pest of tomato crops throughout South and Central America, Europe and recently Iran that caused severe damages to tomato crops in greenhouses and fields. Since antixenosis and antibiosis are the two important resistance mechanisms in Lycopersicon hirsutum to tomato leafminer, these mechanisms were evaluated on 12 tomato cultivars of Lycopersicon esculentum Mill. (Petomech, Mobil, superstain-B, kingstone, Redstone, Early urbana-Y, Early urbana, Riogrande, Cal-J-N3, Primo early, Falat-111 and Dehghan) in greenhouse with daily temperature fluctuations of 18–27oC during November and December 2013. The first experiment was carried out to appraise the oviposistion preference of tomato leafminer on different parts of those 12 cultivars. Survival and duration of eggs, larvae and pupae, weight of pupae, sex ratio of progeny, visual injury rating and number of mines of tomato leafminer on 12 tomato cultivars were examined in the second experiment. The higher and lower ovposition were observed on Falat-111 (30 eggs) and Kingstone (5.33 eggs), respectively, on the fourth day of the experiment. Incubation period, larval and pupal stadia, pupal weight, visual injury rating and number of mines were significantly affected by tomato cultivars. Based on all examined characteristics, tomato cultivars were clustered into three main groups. We concluded that three cultivars Mobil, Riogrande and Cal-J-N3 appeared to be relatively more resistant to the damage inflicted.