مروری بر ژرم پلاسم گلابی معمولی (.pyrus communis l) و استفاده از آن در برنامه به نژادی و گزینش ارقام جدید در ایران

در میان میوه های مختلف، گلابی در رده پنجم اهمیت در سطح جهان طبقه بندی شده است و این محصول در سه گروه گلابی معمولی، سیائی و چینی تولید می شود. جنس گلابی (pyrus)، دارای حداقل 36 گونه و هیبرید بین گونه ای است که در چهار مرکز تنوع ژنتیکی شرق آسیا، آسیای مرکزی و ایران، اروپا و حوزه مدیترانه، پراکنده اند. وجود یکی از مراکز مهم تنوع ژنتیکی جنس گلابی در ایران و همپوشانی برخی از مراکز، نظیر مرکز تنوع ژنتیکی اروپا در نواحی غربی سبب شده تا هشت گونه آن، در این ناحیه موجود و تنوع ژنتیکی بسیار گسترده ای از گونه گلابی معمولی (.p. communis l) در نواحی شمالی و غربی ایران وجود داشته باشد. تنوع گسترده این گونه می تواند به عنوان یکی از اصلی ترین منابع گزینش اولیه ارقام بومی گلابی نظیر ارقام شاه میوه، سبری، نطنزی، دمکج، شاهک و درگزی و همچنین انواع خوج موجود در مناطق شمالی کشور باشد. این تنوع ژنتیکی گسترده و به موازات آن، واردات ژرم پلاسم گلابی تجاری طی چند دهه اخیر، پتانسیل فراوانی برای برنامه های به نژادی گلابی با اهداف گزینش برای مقاومت به بیماری آتشک، برای مقاومت به پسیل گلابی، عادت باردهی و پاکوتاهی، پیش رسی و بهبود کیفیت میوه، فراهم آورده است. در این مقاله مروری، با توجه به استقبال باغداران گلابی در دو دهه اخیر و توسعه باغ های مدرن این محصول در سامانه های کشت نیمه متراکم و تقاضای تولیدکنندگان برای استفاده از ارقام و پایه های جدید، به پتانسیل های موجود برای بهبود و گزینش ارقام این محصول پرداخته شده است.

a review on germplasm of common pear (pyrus communis l.) and its utilization in breeding program and selection of new cultivars in iran

pear is classified in the fifth place in importance in the world and its production is carried out in three groups as; i) common pears, ii) asian pears, and iii) chinese pears. also, the genus pyrus has at least 36 accepted species and the interspecific hybrids that are distributed in four centers of genetic diversities, including, east asia, central asia and iran, europe and the mediterranean basin. iran is one of the important centers of genetic diversity of the genus pyrus and this, resulted in existing of eight accepted species in various region of iranian plateau. also as a wide range of the native cultivars and varities are distributed in the northern and western regions of iran. the wide diversity of this species can be considered as one of the main sources of selection of superior native pear cultivars such as shah miveh, sebri, natanzi, domkaj, shahak and dar gazi, as well as, khoj, in the past centuries. this extensive genetic diversity and in parallel, the introduction of commercial pear germplasm over the past few decades have prepared an abundant breeding potentials with various objectives such resistance to the fire blight disease, selection for tolerance to the pear psylla, appropriate bearing habit and dwarf growth, early ripening and high fruit quality. in this review article, considering the extension of pear orchards in iran over the past two decades, establishment of modern semi-dwarf cultivation systems and also the demand of pear producers for the new cultivars and rootstocks, the potentials for breeding and selection of this fruit has been discussed in detail. keywords: selection, morphological markers, molecular markers, genetic diversity, introduced cultivars introductionamong various fruits, pear is classified as the fifth most important fruit in the world (fao, 2024). pear cultivars belong to different species including common pears (pyrus communis l.), asian pears (p. serotina rehd.), and chinese or ya pears (p.×bretschneideri rehd.). the common pear has wide climatic adaptation potential, from very cold regions to the relatively warm regions in southern latitudes (abdollahi, 2010). according to the fao estimates, the area under cultivation of various types of pear trees, including three species of common pears, chinese pears, and asian pears, is about 1.5 million hectares in the world and from this area 40 million tons of pears are harvested annually, which indicates an average yield of 27 tons/hec. iran ranks as the 15th pear producing country in the world with an average of 180 thousand tons of pears per year (fao, 2024). in recent years, the development of semi-intensive pear orchards, extension of fire blight resistant cultivars, the improvement and updating the new training systems, as well as the improvement of orchard management methods, including the development of drip irrigation and new nutrition methods, led to a considerable increase in the yield of modern orchards. considering this wide genetic diversity of genus pyrus in iran (khorshidi et al., 2017), there is a considerable potential in terms of developing cultivation and use of this diversity for breeding the new cultivars and rootstocks.during the bronze age (3400 to 3300 bc), that was the period of transition from the stone age and life without civilization to the iron age, early cities began to expand in the central plateau of iran. according to the historic documents, the formation of early civilizations in different parts of the iranian plateau also could be considered as the starting point for the selection and cultivation of early pear varieties for food consumption. the main point in this regard is the correspondence of the geographical extent of a number of these early civilizations, especially the early civilizations of kurdistan, with the areas of genetic diversity of the common pear species, p. communis l. in the western regions of iran. according to janick (2005), the domestication of the pear tree took place after ancient trees, including olives, pomegranates, and figs, in western asia, which could have been at the same time as the achaemenian kingdom in the iranian plateau. according to a clay tablet inscription found near the persepolis palace, the cultivation of pear trees in this region began in 500 bc (curtis and tallis, 2005). this indicates that the initial selection of superior pear tree cultivars in iran refers to the achaemenid period (550–330 bc) and the cultivation of this tree had spread from southern areas to the northern temperate regions. the historic miniatures of the ancient persia show valuable evidences for development of pear cultivars and orchards during ilkhanid (1256-1335 ad), timurid (1370-1507 ad) and safavid (1501-1736 ad) dynasties and even later. following this historic progresses in selection of early native pear cultivars, first modern selection programs were started around 1950. it can be said that until the beginning of the 14th century ah and even until the first few decades of this century, pear cultivation was limited to old native cultivars in traditional orchards. the first introduction of new pear cultivars took place from france during this period and the new european cultivars such as louise bonne, spadona, duchess, coscia, williams duchess, beurre hardy, beurre bosc, williams, beurre diel, and giffard were selected for extensions of pear orchards (abdollahi, 2010). in addition to importing the new pears, native cultivars also were collected and cultivated in the collections of the seed and plant improvement institute, and the superior cultivars were selected, grafted and extended in various temperate regions of pear cultivation in iran (atefi, 1989).a new era of pear selection and breeding was started in iran by the year 2005, that a hybridization program started aimed at obtaining fire blight (erwinia amylovora) resistant cultivars, also new successes gained for slecting new varieties tolerant to the pear psylla (cacopsylla pyricola foerster), selection of native and introduced cultivars for dwarf growth habit, early bearing and adaptability for new dwarfing rootstocks such as quince ema, quince ba29, pyrodwarf and oh×h series, tolerance to the high summer temperatures and heat shocks, escape and tolerance to the late chilling damages on the blooms that significantly reduces bearing of pear orchards in some years, tolerance to the calcareous soils and prevention of chlorosis appearance due to fe deficiency or fe stabilization in the leaves, selection for coverage of bloom period for using as pollinzer trees and also determination of self-incompatibility alleles for selecting the best pollinizer in the commercial pear orchards, selection for early ripening cultivars, and the suitable cultivars for cultivation in greenhouse, and finally selection long term cold storage cultivars such as dar gazi. according to these progresses, the yield in modern semi-intensive pear orchards of iran could be more than 50 tons/hec, and more recently, a new system for early ripening of pears has been developed for greenhouse production of this fruit.despite the progresses and the evolution of new pear orchards over the past decades, there are still broad horizons ahead for research on this fruit. among these, release of new high bearing cultivars with more fire blight resistance, new early-ripening cultivars with more commercial value and quality of the fruits, release of new cultivars with higher potential for use as pollinzers, in term of coverage and overlapping of bloom period and pollen compatibility, could be the main further programs for pear breeding and selection in iran. also starting a new breeding for fruit quality by using the cultivars with high heritability of fruit quality trait is essential for pear cultivation industry in the future. referencesabdollahi, h. 2010. pear: botany, cultivars and rootstocks. ministry of agriculture, tehran, iran. 210 pp. (in persian).atefi, j. 1989. primary evaluation of pear cultivars in iran. seed and plant improvement research institute, karaj, iran. 110 pp. (in persian).curtis, j. and tallis, n. 2005. forgotten empire: the world of ancient persia. the british museum press, london, uk. 272 pp.fao. 2024. world food and agriculture-statistical yearbook. food and agriculture organization publication. rome, italy.khorshidi, s., davarynejad, g., samiei, l. and moghaddam m. 2017. study of genetic diversity of pear genotypes and cultivars (pyrus communis l.) using inter-simple sequence repeat markers (issr). erwerbs-obstbau, 59, pp.301–308. doi: 10.1007/s10341-017-0325-y