Stone Fruit Plants Research Articles

Identification of phytoplasmas in stone fruit (Prunus sp.) and persimmon (Diospyros kaki L.) trees exhibiting leaf alterations and witches'‐broom in Jordan

AbstractDuring field surveys conducted in 2020 in Jordanian orchards, phytoplasma‐like symptoms (leaf yellowing/reddening and rolling, and witches'‐broom) were observed in three stone fruit species (peach, European plum, sweet cherry) and persimmon. Molecular analyses identified phytoplasma strains belonging to the species ‘Candidatus Phytoplasma solani’ (subgroup 16SrXII‐A) as largely prevalent in stone fruit and persimmon symptomatic plants. Moreover, ‘Ca. Phytoplasma omanense’ (16SrXXIX‐B) was found in few European plum symptomatic plants. In previous studies, such phytoplasma strains were identified in other important crops (almond, pomegranate, and grapevine) and in several putative insect vectors, suggesting their complex ecology in Jordan. Further studies are needed to in‐depth investigate the diffusion of phytoplasma‐associated diseases of stone fruits throughout the Country, to clarify their aetiology, and to study their epidemiological pattern(s).

Characterization of Bacillus velezensis 32a metabolites and their synergistic bioactivity against crown gall disease

Crown gall disease caused by Agrobacterium tumefaciens is considered to be the main bacterial threat of stone fruit plants in Mediterranean countries. In a previous study, Bacillus velezensis strain 32a was isolated from Tunisian rhizosphere soil and revealed high antagonistic potential against A. tumefaciens strains. In order to better characterize the antagonistic activity of this strain against this important plant pathogen, the production of secondary metabolites was analyzed using liquid chromatography coupled with mass spectrometry. The results revealed the production of different compounds identified as surfactins, fengycins, iturins and bacillibactin belonging to the lipopeptide group, three polyketides (macrolactins, oxydifficidin and bacillaenes), bacilysin and its chlorinated derivative; chlorotetaine. The involvement of lipopeptides in this antagonistic activity was ruled out by performing agar and broth dilution tests with pure molecules. Thus, the construction of B. velezensis 32a mutants defective in polyketides and bacilysin biosynthesis and their antagonistic activity was performed and compared to a set of derivative mutants of a comparable strain, B. velezensis GA1. The defective difficidin mutants (△dfnA and △dfnD) were unable to inhibit the growth of A. tumefaciens, indicating the high-level contribution of difficidin in the antagonism process. While the macrolactin deficient mutant (∆mlnA) slightly decreased the activity, suggesting a synergetic effect with difficidin. Remarkably, the mutant △dhbC only deficient in bacillibactin production showed significant reduction in its capacity to inhibit the growth of Agrobacterium.Taken collectively, our results showed the strong synergetic effect of difficidin and macrolactins and the significant implication of siderophore to manage crown gall disease.

Modern bioengineering approaches to creating resistance to the Plum pox virus in stone fruit crops

In recent years, Plum pox virus (PPV) has become a major threat to the cultivation of stone fruit plants. This virus has caused enormous economic damage and caused a significant decrease in production areas in eastern Europe and the Mediterranean. Plum pox virus has spread around the world and is classified by plant quarantine services as the most dangerous pathogen for apricots, plums and peaches Unfortunately, at present, science cannot offer any ways to treat viral plant diseases, and the destruction of infected trees remains the only way to contain the spread of viruses. Given the seriousness of the disease, the difficulty of controlling its spread, the lack of disease-resistant existing varieties, the need to create commercial varieties with increased resistance to this pathogen is obvious. Modern methods of genetic engineering make it possible to significantly accelerate the processes of creating highly productive plum varieties with increased or complete resistance to viruses, unattainable by traditional breeding methods. However, most of the work on the modification of the genomes of stone fruit crops was carried out using juvenile material of zygotic origin, which has a higher morphogenetic potential compared to varieties. The use of modern bioengineering techniques in the selection of stone fruit plants is hampered by the lack of reliable techniques that can provide a sufficiently high frequency of regeneration of shoots from somatic tissues. These and other reasons call for the development of an effective genotype-independent system for regenerating and modifying the genomes of commercial plum varieties. Given the rapid development of plant genome editing techniques, targeted mutation of host genes involved in replication and widespread PPV in infected tissues may be a promising approach for engineering resistance to viruses that exclude the introduction of foreign sequences into the plum genome.

Phenological Stages of Development of Cornus L. S. Str. Species (Cornaceae) According to BBCH Scale

Under conditions of pronounced dynamic climate change, the scope of phenological data is constantly expanding and increasingly extends beyond local regions. For the international integration of phenological research, a standardized description of the stages of plant development and their identical coding is used – the BBCH scale (Biologische Bundesanstalt, Bundessortenamt und CHemische Industrie). Phenophases of seasonal development, according to BBCH, are already unified for many different in origin, nature of ecology, and economic use of plants of common and little-known species and crops, including fruit. According to the BBCH scale, we described the seasonal stages of development of 23 cultivars of Cornus mas L. selection gene pool of the M.M. Gryshko National Botanical Garden of the National Academy of Sciences of Ukraine, genotypes of C. officinalis Siebold & Zucc., nine genotypes of C. sessilis Torr. ex Durand, as well as three genotypes of the artificial hybrid from crossing C. officinalis × C. mas. Phenological monitoring was carried out in NBG (Ukraine) two or three times a week for three seasons (2018–2020) from the beginning of vegetation (bud development) to November and the beginning of winter dormancy. In the studied species of the subgenus Cornus, as in some other stone fruit plants, there are eight of the ten main stages of seasonal development. In all studied species and cultivars of dogwood at the beginning of the growing season generative buds in their development significantly ahead of vegetative and plants begin seasonal development from the development of inflorescences and flowering (principal growth stage 5 and principal growth stage 6, respectively). Different species and varieties differ in the calendar dates of onset and duration of certain major stages of development. The obtained data are important for further studies of adaptive capabilities of Cornus species and cultivars in different climatic conditions, for practical use of genetic resources of studied Cornus species and cultivars, as well as for the introduction of little-known Cornus species and their use in agricultural production, pharmacology, ornamental and landscape gardens.

Diseases Caused by Xylella fastidiosa in Prunus Genus: An Overview of the Research on an Increasingly Widespread Pathogen.

Cultivated plants belonging to the genus Prunus are globally widespread and for some countries, are economically important crops; and they play a key role in the composition of a landscape. Xylella fastidiosa is a key threat to plant health, and several Prunus species are heavily stressed by this pathogen, such as almond, peach, and plum; many strain types of different subspecies can cause severe diseases. This review highlights different approaches to managing epidemic events related to X. fastidiosa in stone fruit plants. In fact, in most new European and Asian outbreaks, almond is the main and very common host and peach, plum, apricot, and cherry are widespread and profitable crops for the involved areas. Various diseases associated with stone fruit plants show different degrees of severity in relation to cultivar, although investigations are still limited. The development and selection of tolerant and resistant cultivars and the study of resistance mechanisms activated by the plant against X. fastidiosa infections seem to be the best way to find long-term solutions aimed at making affected areas recover. In addition, observations in orchards severely affected by the disease can be essential for collecting tolerant or resistant materials within the local germplasm. In areas where the bacterium is not yet present, a qualitative-quantitative study on entomofauna is also important for the timely identification of potential vectors and for developing effective control strategies.

Development of large-fruited bird cherry cultivars on the basis of wild species for northern and eastern regions of Russia

Bird cherry occupies a special place among stone fruit plants. Its fruits, collected in nature, were widely used by local communities, native to regions with severe climate. Development of new bird cherry cultivars, well adapted to such environments, with stable productivity and larger fruit, is a necessity.Crossings were performed involving the most large-fruited genotypes of Prunus padusL. and P. virginianaL., selected during the study of their intraspecific variability and interspecific hybrids. A number of hybrids were identified for their considerably higher fruit weight than that of both parents. Crossing the most large-fruited hybrid cultivars ‘Pamyati Salamatova’ and ‘Cherny blesk’ with large-fruited P. padussamples from Bondarev No. 11-2-64, No. 11-2-70, No. 11-2-76, and P. virginianasamples No. 1-14-1 and No. 10-5-2, produced many hybrids with a fruit weight gain of 20–50% over the parent with the largest fruit. It can be explained by the polygenic nature of fruit weight inheritance. The samples with the largest fruits had an average fruit weight of 1.4–1.5 g and maximum weight of 1.8–1.9 g. Many of them combined large fruit size with good quality and high productivity. Brief descriptions of fruit traits are presented for several hybrids. Suppositions are made about the prospects of further breeding for the large fruit trait on the basis of the same genetic sources or with the use of other sources of large fruit size in hybridization.Thus, preliminary selection of the best genotypes in nature and in introduced populations, followed by their crossing within their own species and with other species, makes it possible to produce genotypes with larger fruits than the average fruit size for a population and considerably larger than in their parents. It would help to develop bird cherry cultivars, well adapted to local conditions, for amateur and industrial horticulture under different climate conditions of Russia.

The role of Prunus cerasifera Ehrh. in the origin, evolution and improvement of stone fruit cultivars

At Krymsk Experiment Breeding Station of VIR, as a result of collecting, studying, and selective use of myrobalan plum genetic diversity, the intraspecific taxonomy of the species Prunus cerasifera Ehrh. was clarified. Donors of traits significant for breeding were identified and, with their use, adaptable cultivars of myrobalan plum, Russian plum and clonal rootstocks of stone fruit plants were developed.Intraspecific classification of P. cerasifera is proposed, with the identified subspecies:subsp. cerasifera (typical myrobalan plum);subsp. orientalis (M. Pop.) Erem. et Garcov. (Oriental myrobalan plum);and subsp. macrocarpa Erem. et Garcov. (large-fruited myrobalan plum).Within subsp. P. cerasifera subsp. macrocarpa, varieties were identified:var. macrocarpa (typical, or Krymsk);var. georgica Erem. et Garcov. (Georgian);var. iranica (Koval.) Erem. et Garcov. (Iranian);var. nairica (Koval.) Erem. et Garcov. (Armenian);var. pissardii Carr. (Pissard);and var. taurica (Kost.) Erem. et Garcov. (Taurida).The participation of myrobalan plum in the origin of spp. P. brigantiaca Vill., P. cocomilia Tem., and P. spinosa L. was traced. Involvement of large-fruited myrobalan plum in hybridization with blackthorn contributed to the manifestation of an exceptional polymorphism among the varieties of the hybridogenic species P. domestica L. (P. cerasifera × P. spinosa). As a result of hybridization between myrobalan plum and Chinese plum varieties, a new cultigen species emerged – Russian plum (× P. rossica Erem.). By now, 127 cultivars of this species and 7 clonal rootstocks for stone fruit crops have been developed. These cultivars and clonal rootstocks are zoned for Russia and a number of other countries.

Prospects for the gene pool use of stone fruit plants in the distant hybridization of cherries

18 species of cherries are collected for the preservation and study in the gene pool of the station. The following species P. sachalinensis, P. kurilensis, P. pensylvanica, P. incisa, P. serrullata, P. lannesiana, P. fruticosa separated by economically valuable traits, were involved in distant hybridization as a female parent. Cherry varieties, donors of large – fruited fruit, performed as a male parent. The article shows the yielding results of interspecies crossing, the patterns of inheritance of hybrid traits of early and late emergence from the condition of a deep dormant period and winter hardiness. According to the results of our research, we recommended the following species – P. lannesiana, P. serrullata, P. sachalinensis as donors of short onset, and as for late and long-lasting – P. pensylvanica, P. incisa, P. fruticosa. Species which transmit the sign of winter hardiness to their progeny – P. fruticosa, P. incisa and P. kurilensis.

Efficiency of the breeding use of the genus Prunus L. biodiversity

Preservation and search of the source material of the Prunus L. gene pool for breeding, especially in contrasting weather conditions, it becomes particularly relevant. Breeding collection of representatives of the genus Prunus L. NCFSCHVW: sweet cherry (Prunus avium L.), common cherry (Prunus сerаsus L.), plum (Prunus domestica L.), has more than 500 samples and is the basis for improving the genotypes of stone fruit plants. The purpose of the research is to evaluate the breeding potential of stone crops and to identify unique variety forms for new varieties creation. The paper presents donors and sources of important traits: early fruitfulness, winter hardiness, drought resistance, resistance to Coccomyces hiemalis Higg., Monilia cinerea, large fruitfulness and productivity, and substantiates their importance in ensuring the further breeding process and updating the gene pool of stone crops. The best varieties, primarily of domestic breeding, with specific characteristics for integration into new breeding programs are selected: sweet cherry – Madonna, Kavkazskaya Uluchshennaya, Volshebnitsa, Cherniye Glaza, Alaya and Mak; cherry – Krasnodarskaya Sladkaya, Kazachka, Kirina Kubanochka, Alexa; plum – Prikubanskaya, Krasnodarskaya, Milena, Podruga, Charodeyka, Krasotka, Gertsog.

Chemical composition of bird cherry fruits in the Northwestern region of Russia

Background. Among stone fruit plants, a special place belongs to bird cherry (Padus Mill.). As a food plant, it has found use in areas with harsh climate conditions. Since the breeding of bird cherry cultivars for food purposes continues to develop, there is a need to know the chemical composition of its fruits. The aim of this research was to study bird cherry in the environments of the Russian Northwest and isolate genotypes with an optimal biochemical composition for subsequent use.Materials and methods. Fruit composition in 21 accessions from the bird cherry collection was analyzed in 2009 and 2011–2013 at the Biochemistry and Molecular Biology Laboratory of the N.I. Vavilov All-Russian Institute of Plant Genetic Resources (VIR). Biochemical studies were performed using the methods adopted at VIR. Statistical processing of the data obtained was made using the Microsoft Excel software package.Results. The best genotypes were selected for each chemical component: for increased soluble solid content (SSC), accessions of Group I ‘Nevesta’ (29.63%), 1-1-8 (30.35), ‘Carpaty 5’ (30.87), ‘Chaika’ (33.9); for accumulation of sugars, ‘Granatovaya grozd’ (Group III; 12.13%), 1-1-8 (Gr. I; 12.5), ‘Pamyati Salamatova’ (Gr. IV; 12.8); for low acid content, ‘Sibirskaya krasavitsa’ (Gr. II; 1.03%), 1-1-8 (Gr. I; 1.14) ‘Granatovaya grozd’ (Gr. III; 1.17), ‘Zelenoplodnaya’ (Gr. I; 1.21), ‘Pozdnyaya radost’ (Gr. III; 1.25); for high content of ascorbic acid, 1-1-8 (Gr. I; 19.1 mg/100 g), ‘Sakhalinskaya chernaya’ (Gr. I; 19.35) ‘Rannyaya kruglaya’ (Gr. IV; 20.65), ‘Krasny shater’ (Gr. II; 21.23); for triterpene (ursolic, oleanolic) acids, ‘Cherny blesk’ (Gr. IV; 0.045%) and ‘Atica’ (Gr. I; 0.056).Conclusion. Significant differences were found in SSC between accessions of Groups I (P. avium) and II (P. avium × P. virginiana); and in the sugar/acid ratio (SAR), between I (P. avium) and IV (seedlings of cv. ‘Pamyati Salamatova’); II (P. avium × P. virginiana) and III (P. virginiana × P. avium); III (P. virginiana × P. avium) and IV (seedlings of cv. ‘Pamyati Sala matova’).

Genetic basis of selection of stone fruit and other agricultural plants

Methods of creation, identification on marker signs and maintenance of the valuable genotypes used at creation of new grades, pure lines, interlinear hybrids of stone fruit plants are considered. The maintenance of valuable genotypes used in the creation of new cultivars, clean lines, interline hybrids of stone fruit plants. The laying of plantations of nectarine and peach by sowing seeds directly into the garden with subsequent budding in the form of reducing the cycle of cultivation of eyepieces, the entry into the period of full fruiting of trees, as well as accelerating the introduction into production of new breeding cultivars grown by non-transplanting method. This makes it possible to create for two years of vegetation productive mother-cuttings gardens up to 500 trees of each new cultivar. Significant importance is given to modem molecular genetic and biotechnological methods, as well as classical-hybridization, individual selection, acceleration of the breeding process (use of greenhouses for growing hybrid seedlings, as well as grafting seedlings of fruit plants). In nectarine, as well as endemic to China the peach of David and the peach of the world when self-pollinating interspecific hybrids F1 in inbred offspring sometimes there are sterile individuals of plants.

RESULTS OF EXPEDITIONS CARRIED OUT BY KRYMSK EXPERIMENT BREEDING STATION OF VIR TO COLLECT WILD AND RUN-WILD FRUIT AND BERRY PLANTS IN SOUTHERN REGIONS OF RUSSIA

Since the beginning of the 2000s, the ecological and climatic situation in southern regions of Russia has deteriorated sig­nificantly due to the increased anthropogenic impact. In particular, the Republic of Crimea, especially its steppe zone, has been experiencing a real ecological disaster since 2016 because of water deficiency due to the drying up of the North-Crimean Canal after it has been blocked by Ukraine. All this makes it urgent to search for and collect wild and run-wild plant species in their natural habitats, and con­serve them in controlled conditions at VIR’s branches. Krymsk Experiment Breeding Station has developed a long-term plan for conducting expeditions to collect stone fruit and berry genetic resources for augmenting VIR’s collec­tions. This plan is being implemented on a regular basis. The goal of this work is to explore natural habitats, collect fruit and berry plant diversity, further maintain it in field collections at Krymsk Experiment Breeding Station, and comprehensively study it with the aim of identifying sources of economically important traits for creating new highly adaptive and technologically advanced varieties and root­stocks. Expeditions were conducted in 2016–2018 in southern areas of the steppe zone and northern steppe regions of Krasno­dar Territory, Volgograd Province, in southeastern regions of Rostov Province, and in the Republic of Crimea. It was es­tablished by field surveys that wild stone fruit plants are found everywhere much less frequently than it was ob­served in previous years, when similar expeditions were launched to these areas. All in all, this work resulted in col­lecting 222 samples of typical representatives of the studied fruit and berry species from the areas of their natural oc­currence. All of them were placed in the nursery of Krymsk Experiment Breeding Station, got established well, and thus augmented the VIR collection of fruit and berry crops. In view of the observed tendency of the natural distribution areas being reduced for a number of wild stone fruit species due to global climatic changes and recent increase of the an­thropogenic impact, it is necessary to continue conducting expeditions to collect genotypes, especially of such species as ground cherry and Russian almond. In the near future, it is planned to explore the mountainous and Caspian regions in the Republic of Dagestan.

Intraspecific, interspecific and intergeneric hybridization of stone fruit plants

Aim. The aim to identify valuable source material from the number of intraspecific, interspecific and intergeneric hybrids of stone fruit plants to improve and expand the varietal composition of peach that meets the needs of industrial and amateur gardening. Methods. Program and methods of varietal study of fruit, berry and nut crops / Ed. G. A. Lobanov. Michurinsk, 1973. 492 p. Program and methods of selection of fruit, berry and nut crops / Ed. G. A. Lobanov. Michurinsk, 1980. 529 p. Program and methods of selection of fruit, berry and nut crops / Ed. Sedova and T. P. Ogoltsova. Orel: VNIISPK, 1999. 608 p. Results. New genotypes of peach, which are sources of cytoplasmic male sterility (CMS), were selected; large-fruited peach I4 970-89 was isolated, as a pollinator for genotypes with male sterility; in the population of hybrid seedlings F2 (peach of the world x David peach) we identified new genotypes of plants with absent characters in their original species; with resistance to powdery mildew and leaf curl, dwarf plant growth, forms with decorative double flowers, white, pink and purple-red color of the petals of the corolla, bell-shaped and rosy flower types, male sterility, pollen fertility and honey taste of the fruit inherited from his wild ancestor - David peach. Summary. Selected maternal genotypes of the original parental forms of apricot, with a character of CMS - 189-88, 249-81, 498-86. They are of breeding value for the development of new peach cultivars. Peach I4 970-89 of the Nikitsky Botanical Gardens’ breeding is a pollinator for hybrids of peach with common almond, characterized by male sterility. Valuable characters of David peach could be transferred to common peach and its cultivars as a result of natural hybridization due to their joint growth in the primary Chinese-Japanese genetic center. From wild ancestor, David peach common peach cultivars inherited such valuable characteristics as resistance to powdery mildew and leaf curl, dwarf growth of plants, shapes with decorative double flowers, white, pink and purple-red petals of the corolla campanulate and rose-like types of flower, male sterility, pollen fertility and the honey taste of the fruit.

Correction to: Using multilocus sequence analysis to distinguish pathogenic from saprotrophic strains of Pseudomonas from stone fruit and kiwifruit

A variety of pseudomonads are associated with diseases of Actinidia and Prunus plants. A recently emerged virulent haplotype of Pseudomonas syringae pv. actinidiae (biovar 3) causes severe stem cankers on kiwifruit associated with dieback of canes. Pseudomonas syringae also causes one of the most important bacterial diseases affecting cherry orchards worldwide. Bacterial canker of cherry limits production in orchards in New Zealand. Less virulent and non-pathogenic pseudomonads also exist on both hosts, providing an opportunity to investigate the diversity of pseudomonads on these hosts, to find identifiers for new emerging highly pathogenic strains that could be used at the border to prevent incursions. In this study, genetic typing was used to explore the diversity of Pseudomonas on kiwifruit and a variety of Prunus plants. Multilocus sequence analysis (MLSA) of four house-keeping genes separated pseudomonads from kiwifruit and stone fruit plants into two major groups: one corresponding to P. syringae sensu lato and one corresponding to other Pseudomonas species. Within P. syringae sensu lato, strains were assigned to six of the nine previously described genomospecies or five of the seven previously described phylogroups. In the other major group, strains from both hosts clustered with a variety of well characterised non-pathogenic pseudomonads. The classification of strains into the two major groups is of practical diagnostic value since the most common pathogens of fruit trees belong to the P. syringae species complex. Furthermore, our analysis suggests that molecular diagnostics might be possible for the classification of strains into these two groups as a first tool to screen for exotic pathogenic pseudomonads on germplasm imports of both commodities.

Using multilocus sequence analysis to distinguish pathogenic from saprotrophic strains of Pseudomonas from stone fruit and kiwifruit

A variety of pseudomonads are associated with diseases of Actinidia and Prunus plants. A recently emerged virulent haplotype of Pseudomonas syringae pv. actinidiae (biovar 3) causes severe stem cankers on kiwifruit associated with dieback of canes. Pseudomonas syringae also causes one of the most important bacterial diseases affecting cherry orchards worldwide. Bacterial canker of cherry limits production in orchards in New Zealand. Less virulent and non-pathogenic pseudomonads also exist on both hosts, providing an opportunity to investigate the diversity of pseudomonads on these hosts, to find identifiers for new emerging highly pathogenic strains that could be used at the border to prevent incursions. In this study, genetic typing was used to explore the diversity of Pseudomonas on kiwifruit and a variety of Prunus plants. Multilocus sequence analysis (MLSA) of four house-keeping genes separated pseudomonads from kiwifruit and stone fruit plants into two major groups: one corresponding to P. syringae sensu lato and one corresponding to other Pseudomonas species. Within P. syringae sensu lato, strains were assigned to six of the nine previously described genomospecies or five of the seven previously described phylogroups. In the other major group, strains from both hosts clustered with a variety of well characterised non-pathogenic pseudomonads. The classification of strains into the two major groups is of practical diagnostic value since the most common pathogens of fruit trees belong to the P. syringae species complex. Furthermore, our analysis suggests that molecular diagnostics might be possible for the classification of strains into these two groups as a first tool to screen for exotic pathogenic pseudomonads on germplasm imports of both commodities.

ВЫЯВЛЕНИЕ ГЕНЕТИЧЕСКИХ СВЯЗЕЙ МЕЖДУ ВИДАМИ РОДА PRUNUS L. ПРИ ИХ ИСПОЛЬЗОВАНИИ В СЕЛЕКЦИИ КОСТОЧКОВЫХ КУЛЬТУР

Research conducted at Krymsk Experiment Breeding Station of VIR on the gene pools of stone fruit plants and genomic analysis of the genetic collection of interspecific hybrids within the genus Prunus L. disclosed differences in the degree of incompatibility among the studied species. There are four levels in the manifestation of this indicator in hybrid F 1 families: - the first level: some hybrids are normally prolific. This is characteristic of hybrids produced by the species of one section at the same level of ploidy; - the second level: fertility of hybrids is reduced, but some of them produce fruits and partially fertile pollen. This level is typical for hybrids from crosses between species at the intersection level within one subgenus; - the third level: F 1 hybrids are infertile, but in some of them partial viability of pollen is observed. This effect is manifested by hybrids between the species of the subgenus Prunophora, and the species of the subgenus Amygdalus; - the fourth level: no hybrids are produced. Genomic morphological markers were also used in genomic analysis. Based on the information obtained in the process of genomic analysis, a number of changes are proposed in the system of the genus Prunus . It is proposed to transfer the species of the sections Microcerasus (subgenus Cerasus) and Amygdalopsis (subgenus Amygdalus) to the subgenus Prunophora, since they manifest the first level of incompatibility with the species of other sections in the subgenus Prunophora. The species P. maackii should be included in the Cerasus section of the subgenus Cerasus together with two other tetraploid species of cherry: P. vulgaris (P. cerasus) and P. fruticosa, as it is crossed with latter two showing the first level of incompatibility, and all these species have a common diploid ancestor: P. canescens. The species P. microcarpa which has marker traits typical for the species in the Spiraeopsis subsection of the Microcerasus section should be relocated from the subsection Microcerasus (Amygdalocerasus) to the subsection Spiraeopsis.

ОБРАЗЦЫ ЯГОДНЫХ И ПЛОДОВЫХ КУЛЬТУР И ИХ ДИКОРАСТУЩИХ РОДИЧЕЙ В КОЛЛЕКЦИИ IN VITRO ВИР

Background. The problem of ex situ conservation of plant genetic resources (PGR) is particularly relevant due to the decreasing of their genetic diversity. Accessions of vegetatively propagated crops are usually preserved in field genebanks. In vitro collections for medium-term storage and cryo collections for long-term storage are established as duplicate collections. Safe ex situ conservation of PGR is ensured by the existence of all three types of collections. The strategy of building up an in vitro collection of berry and fruit crops at VIR is based on the need to preserve domestic cultivars, local varieties and, primarily, landraces as well as accessions of crop wild relatives collected mainly in the Russian Federation and adjacent countries. Such genetic material is sparse or completely absent in the genebanks of other countries. Materials and methods. Accessions from the field genebanks maintained at VIR’s experiment stations in Pavlovsk and Maikop, samples obtained by collecting teams launched by VIR and other institutions were used to initiate in vitro culture. All procedures to preserve various fruit and berry germplasm in vitro at VIR in the state of active growth and under medium-term storage conditions have been carried out according to the protocols presented in the Methodological Guidelines of VIR’s Department of Biotechnology. Results and conclusion. Currently, the in vitro collection of berry and fruit crops at VIR holds 330 accessions of raspberry, blackberry, honeysuckle, strawberry, stone fruit plants (cherry, plum), mountain ash, and black currant, including 236 cultivars, 14 hybrids and 80 accessions of crop wild relatives, 68 of which were collected in the Russian Federation and neighboring countries. At present, VIR’s in vitro collection is one of the largest in the network of European and Asian genebanks that preserve accessions of berry and fruit plants cultivated under temperate climate conditions. Germplasm from the in vitro collection is used for various purposes: to develop virus eradication techniques; for genotyping; to study physiological and biochemical processes occurring in micro-plants under medium term storage; for the development of cryopreservation methods and for establishment of cryo collections; in morphobiological studies of ex vitro plants, etc.

Protocol for Isolation and Identification of Agrobacterium Isolates from Stone Fruit Plants and Sensitivity of Native A. tumefaciens Isolates against Agrocin Produced by A. radiobacter Strain K84

Agrobacteria from rhizosphere soil and galls developed on stone fruit plants, were isolated on D1 medium. Agrobacterium isolates, belonging to biovar-1, developed glistening, transparent, convex colonies with cherry red centre at maturity on medium 1A and biovar-2 developed typical transparent to red coloured colonies on 2E. Single cell colonies of Agrobacterium took red colour when streaked on yeast extract mannitol agar supplemented with Congo red. Pathogenic Agrobacterium isolates (A. tumefaciens) developed galls whereas non-pathogenic isolates (A. radiobacter) failed to develop galls on stems of artificially inoculated 4-week old potted tomato plants. Agrocin production was detected in A. radiobacter isolates without and after exposure to chloroform. The results on number of flagella and their arrangement confirmed by scanning electron microscopy revealed that individual cells of all the native isolates possess single flagellum at their sub-polar ends. The isolate showed luxurious growth on Hofer’s alkaline, produced ketolactose and showed no acid production with bromothymol blue. All the native A. tumefaciens isolates were sensitive to agrocin produced by strain K84 which indicated their nopaline utilizing behaviour. All native Agrobacterium isolates showed 97–100 % sequence homology with A. radiobacter and A. tumefaciens.

Silencing of Plum pox virus 5′UTR/P1 sequence confers resistance to a wide range of PPV strains

An effective disease-control strategy should protect the host from the major economically important and geographically widespread variants of a pathogen. Plum pox virus (PPV) is the causal agent of sharka, the most devastating viral disease of Prunus species. We have shown previously that the hairpin RNA expression driven by h-UTR/P1, h-P1/HCPro, h-HCPro and h-HCPro/P3 constructs, derived from the PPV-M ISPaVe44 isolate, confers resistance to the homologous virus in Nicotiana benthamiana plants. Since the production of transgenic stone fruits and their evaluation for PPV resistance would take several years, the ISPaVe44-resistant plant lines were used to evaluate which construct would be the best candidate to be transferred to Prunus elite cultivars. To do that, nine PPV isolates of the D, M, Rec, EA and C strains originally collected from five Prunus species in different geographical areas, were typed by sequencing and used to challenge the transgenic N. benthamiana lines; 464 out of 464 virus-inoculated plants of lines h-UTR/P1, h-HCPro and h-HCPro/P3 showed complete and long-lasting resistance to the seven PPV isolates of D, M and Rec strains. Moreover, the h-UTR/P1 plants were also fully resistant to PPV-C and -EA isolates. Our data suggest that the h-UTR/P1 construct is of particular practical interest to obtain stone fruit plants resistant to the sharka disease.

Biological Control of Crown Gall on Peach and Cherry Rootstock Colt by Native Agrobacterium radiobacter Isolates~!2009-05-11~!2009-08-25~!2010-02-11~!

Crown gall caused by Agrobacterium tumefaciens is the major limiting factor in raising healthy stone fruit plants in nurseries. The incidence of crown gall varies from 4 to 97.5 per cent at different locations resulting in out right rejection of an average of 30 per cent stone fruit plants in nurseries. Agrobacterium radiobacter strain K-84 has been re- ported to provide nearly complete control of this disease, however this strain is not available in India. Therefore, the pre- sent work was aimed to evaluate the antagonistic activity of twelve native A. radiobacter isolates from peach cv. Redhaven, July Elberta and cherry cv. Stella rhizosphere soil against A. tumefaciens. Agrocin production was detected in three isolates of A. radiobacter UHFBA-8, UHFBA-11 and UHFBA-12, and in cross inoculation test against A. tumefa- ciens, all the three isolates completely inhibited gall formation into tomato stems, whereas inoculation of pAg - variants of UHFBA-8 and UHFBA-11 resulted in 87.6 per cent less number of galls per wound and 96 per cent reduced gall size into inoculated tomato stems. Root dip treatment of peach plants with isolate UHFBA-11 resulted in 5.37 per cent incidence of crown gall in contrast to more than 54 per cent galled plants that had not received the treatment. In cherry rootstock Colt, isolate UHFBA-8 as root dip minimized crown gall incidence to 22.22 per cent as compared to 71.11 per cent incidence in untreated plants. Rifampicin resistant mutants of A. radiobacter isolate viz., UHFBA-8 and 11 efficiently colonized the root system of peach and Colt and their populations remained in the tissues of treated plants throughout the growing sea- son. The data suggest that other mechanisms such as efficient colonization of root system, binding and physical blockage of infection sites are involved in biological control by A. radiobacter in addition to production of agrocin.