اثر ویژگی‌های برگ ارقام مختلف گلابی بر ساختار و ثبات جمعیت پسیل گلابی [cacopsylla pyricola (foester)]

پسیل گلابی [cacopsylla pyricola (foerster)] یکی از آفات مهم گلابی است. اولین گام در دستیابی به ارقام مقاوم، شناسایی عوامل موثر بر تغییر ساختار و پایداری جمعیت آفت بر روی میزبان است. این پژوهش در سال‌های 1399 تا 1402 انجام شد. در این بررسی، نُه رقم گلابی شامل بوهمه، شاه‌میوه، نطنزی، سبری، درگزی، لوئیزبون، هاروست کوئین، پوتوماک و کوشیا مورد مطالعه قرار گرفتند. جمعیت تخم، پوره و حشرات کامل پسیل گلابی در اوایل فرورین تا آبان نمونه برداری شد. شاخص های رنگ برگ شامل r (قرمز)، g (سبز) و b (آبی و زرد )، سطح برگ، میزان کلروفیل و تراکم پرز برگ نیز مطالعه شدند. ارتباط بین صفات برگ با شاخص پایداری جمعیت از طریق همبستگی وتاثیرتغییرات فصلی صفات با تحلیل سری زمانی بررسی شدند. نتایج نشان داد که بالاترین و پایین ترین ثبات جمعیتی در تخم حشره در ارقام شاه میوه و نطنزی به ترتیب معادل 4.470و 7.33تخم در مهر و اردیبهشت بود. بالاترین و پایین ترین ثبات جمعیتی پوره به ترتیب در ارقام شاه میوه و درگزی معادل 2.1399و 6.8عدد در شهریور و اردیبهشت بود. در حشره کامل نیز بالاترین و پایین ترین ثبات جمعیتی در ارقام شاه میوه و درگزی به ترتیب معادل 5.126و 3.3 حشره بود. بالاترین همبستگی تقاطعی شاخص های رنگ شامل r، g وb در اردیبهشت و 92.0-91.0و در سطح برگ معادل 74.0و در خرداد ثبت شد. تراکم پرز در ابتدای فصل تا مرداد دارای آثار منفی و معنی دار بر ثبات جمعیت بود. این صفات می‌توانند برای غربالگری ارقام گلابی برای مقاومت به پسیل گلابی استفاده شوند.

effect of leaf characteristics of different pear cultivars on the population structure and stability of pear psylla [cacopsylla pyricola (foester)]

pear psylla [cacopsylla pyricola (foerster)] is one of the important pest of pear trees. understanding of effective factors on population structure and stability of the pest is the first step in selection and development of resistant pear cultivars. this research was conducted from 2020 to 2023. nine pears cultivars including: boheme, shah miveh, natanzi, sebri, dargazi, louis bonne, harvest queen, potomac, and coscia were studied. the pear psylla populations were sampled from early march to november. leaf traits were also studied. the results showed that the highest and the lowest population stability of in the egg in cv. shah miveh and cv. natanzi were 470.4 and 33.7 in october and may, respectively. the highest cross-correlation coefficient (0.91-0.92) of color indices including r (red), g (green), and b (blue and yellow) observed in may, and for the leaf surface are was 0.74 in june. the lint density had significant effect on the population stability from the beginning of the season until august.these traits can be used to screen resistance pear cultivar against pear psylla. keywords: pear, adult insect, leaf surface area, lint density, esistance. introductionthe pear psylla [(cacopsylla pyricola (foerster)] is an important pest of pear trees and has a worldwide distribution (luo et al., 2012). in the climatic conditions of iran, where spring and summer are dry and rainfall is low, the indirect damage caused by honeydew is more than the damage caused by sucking plant sap (behdad, 1991). researches that have been conducted on different pests have shown that leaf morphological characteristics, such as leaf size, leaf thickness, presence of villi, thickness of cuticle, presence of waxy material on the epidermis, color, chlorophyll content, water content, overall shape, and other traits are effective on pest population changes during growing season (khalil et al., 2017; rutledge et al., 2003). understanding the effective factors that drive changes in population structure and stability is the initial step in selection and development resistant pear cultivars. the characteristics of the host plant affect the abundance, structure, stability and diversity of the pest population (steffan-dewenter et al., 2001). therefore, this research was conducted to determine the effect of morphological characteristics of leaf of nine pear cultivars on population structure and stability of pear psylla and their relationship in different growth stages of pear psylla. materials and methodsnine pear cultivars including: boheme, shah miveh, natanzi, sebri, dargazi, louise bonne, harvest queen, potomac, and coscia were used in this study. this research was conducted from 2020 to 2023. data of the population of different stages of development of psylla pear was scored at the peak of its activity, i.e. from the beginning of april to november, every seven days. from each cultivar, 10 leaves were randomly selected from the crown’s lower, middle, and upper parts. the monthly average of the effective population at different growth stages and the percentage of each stage relative to the total population density were calculated. the population stability index for the active pear psylla population on each pear cultivars was estimated. the leaf color index including r (red), g (green), and b (blue and yellow) were determined using the mobile phone software called color grab 3.9.2 with constant light and at a distance of 15 cm from the leaf surface. a relatively accurate leaf surface area was estimated using the mobile phone software easy leaf area. the leaf chlorophyll content was evaluated using the opti-sciences ccm-200 chlorophyll meter. results and discussionthe maximum population density in the first and second activity periods was 242.3 and 359.3, respectively. the minimum density in the first and second activity periods was 73.2 and 175.5, respectively. the lowest and highest percentage of egg density in the population structure was recorded at 16% and 18 %, respectively, in may and september. the highest and lowest population stability, in different growth stage, of pear psylla eggs were in cv. shah miveh (470.4 eggs) and cv. natanzi (33.7eggs), in october and may respectively. the highest and the lowest population stability index of nymphs and beloged to cv. shah miveh (2.2 nymphs) and cv. dargazi (8.6 nymphs), in october and may respectively. the highest and lowest population stability index of adult insects recorded in cv. shah miveh (126.5 adult insects) and cv. darghazi (3.3 adult insect), respectively.leaf color indices (r, g, and b) with correlation coefficients of more than 0.9, leaf surface area index and lint density with correlation coefficients of -0.84 and 0.63, respectively, had significant relationship with the population stability index of pear psylla. considering the resuts of this study, it was found that different leaf characteristics, especially color and lint density, were highly effective on population density and stability indices of pear psyll. these characteristics can be used in pear breeding programs for selction and development of new resistant cutivars to pear psylla. referencesbehdad, e. 1991. iran pests of fruit trees (2nd edition), bahman nashr press, esfahan, iran, 826 pp. (in persian).khalil, h., raza, a. b. m., afzal, m., aqueel, m. a., khalil, m. s. and mansoor, m. m. 2017. effects of plant morphology on the incidence of sucking insect pests complex in few genotypes of cotton. journal of the saudi society of agricultural sciences, 16(4), pp.344-349. doi: 10.1016/j.jssas.2015.11.003luo, x., li, f., ma, y. and cai, w. 2012. a revision of chinese pear psyllids (hemiptera: psylloidea) associated with pyrus ussuriensis. zootaxa, 3489(1), pp.58-80. doi: 10.11646/zootaxa.3489.1.4rutledge, c. e., robinson, a. p. and eigenbrode, s. d. 2003. effects of a simple plant morphological mutation on the arthropod community and the impacts of predators on a principal insect herbivore. oecologia, 135, pp.39-50. doi: 10.1007/s00442-002-1114-2steffan-dewenter, i., münzenberg, u. and tscharntke, t. 2001. pollination, seed set and seed predation on a landscape scale. proceedings of the royal society of london. series b: biological sciences, 268(1477), pp.1685-1690. doi: 10.1098/rspb.2001.1737