Plum Plants Research Articles

Determination of Some Antioxidant Enzyme Activities in Plum (Prunus domestica), Black Mulberry (Morus Nigra) and Carob (Ceratoniasiliqua L.) Fruits

Objective: Antioxidants prevent and/or slow down many adverse effects on the body, especially oxidative stress caused by free radicals. Phenolic compounds in fruits and vegetables have beneficial effects by neutralizing free radicals. Since most phenolic compounds have antioxidant effects, they help to protect cells against oxidative damage caused by free radicals. In our study, we aimed to determine some enzyme activities thought to be present in black plum, carob and black mulberry plants. Material and Methods: In this study, antioxidant enzyme activities were determined using the spectrophotometric method. The extracts of the fruits used in the study were measured manually by preparing reagent solutions. Statistical significance level was taken as 5%, and SPSS 26 statistical package program was used for calculations. Results: Plum (prunus domestica), black mulberry (morusnigra) and carob (ceratoniasiliqua) fruits were found to have higher Superoxide Dismutase (SOD) and Catalase (CAT) values. SOD and CAT values were much higher in black mulberry than in white mulberry. CAT activity was low in black plum and high in green plum. Similarly, SOD activity was low in black plum and high in green plum. Green plum was significantly higher than black plum in terms of both CAT and SOD activity. SOD activity measured in carob was almost twice as high as CAT activity. Conclusion: Antioxidants, which are known to be effective against diabetes, the disease of our age, and many various diseases, protect the body against diseases. Due to the high amounts of antioxidants found in black mulberry, carob and plum, adding extracts to the treatment of chronic patients can stop and/or slow the progression of diseases.

Cold Atmospheric Plasma (CAP) Treatment of In Vitro Cultivated Plum Plantlets—A Possible Way to Improve Growth and Inactivate Plum Pox Virus (PPV)

Plasma technology, relatively new in the fields of biomedicine, agriculture, and ecology, is the subject of intensive research as a prospective means of decontamination of various microorganisms (bacteria, viruses, and fungi). The objectives of the present study were to follow the effect of cold atmospheric plasma (CAP) treatment on in vitro grown plum plants (Prunus domestica L. ‘Kyustendilska sinya’ cv.) and the possibility of eradicating or inactivating plum pox virus (PPV) causing Sharka disease by CAP. The source tree is naturally co-infected by PPV (both M and D strains). In the experiments, two different plasma sources were used. First, a surface-wave-sustained Argon plasma torch and second, an underwater diaphragm discharge. For the treatments, nodal segments (10 mm in length) from in vitro cultured plum plants with or without one leaf were prepared. Apical shoots from treated plants (PPV-positive and negative clones as well non-treated controls) were cultivated in vitro for four passages. Then they were rooted and acclimatized to ex vitro conditions, and their virus status was observed periodically for more than 3 years after treatment for the appearance of Sharka symptoms. All plants, acclimatized to ex vitro conditions, were tested for PPV by immune capture–reverse transcription–polymerase chain reaction (IC-RT-PCR). As a first step in understanding the plasma treatment of living plants, a plasma treatment variant causing no damage must be established; this has been done in our previous works. Treatment of plants by plasma with parameters that have been carefully selected leads to better development than the non-treated plants. In the treated in vitro plants, no significant differences were found in the number and length of shoots compared to the control plantlets. In ex vitro acclimated plants, greater stem length was reported, but no differences in leaf number were observed. No significant differences in growth were recorded between the control and plants that were treated twice or three times. At this stage, 3 years after ex vitro cultivation in a greenhouse, Sharka symptoms were not registered on treated in vitro negative PPV plants, and the virus was not detected by IC-RT-PCR. Very mild symptoms were showing in CAP-treated PPV-positive plants. Development of typical Sharka symptoms on non-treated controls were observed.

The influence of the Reglalg biostimulator and micro elements on the photosynthetic productivity of native and foreign plum varieties

The research carried out with plum plants under controlled conditions (lysimeters, Institute of Genetics, Physiology and Plant Protection) with varieties of local and foreign selection in 2023 revealed the stimulatory effect as a result of treatments with solutions containing Reglalg and a mixture of trace elements - B, Zn, Mn, Mo regarding the formation and activity of the photosynthetic apparatus that contributed to the realization of the production potential of plants. The work in this direction with plum plants for six years aims to highlight the most informative indicators of the pigment background and photosynthetic activity of different plum varieties under the exogenous influence of biologically active substances and microelements.

The effect of non-root fertilizing on the yield and quality of plum fruits of the Velikaya sinyaya variety in arid conditions of the Northern Precaspian Sea

The research was carried out in order to study the effect of non-root fertilizing using complex fertilizers on the yield and quality of plum fruits of the Velikaya sinyaya variety in the Astrakhan region. The following treatment variants with complex fertilizers were used in the experiment: Master; Aquarin; Ultramag Boron + Ultramag Calcium; Aquarin + Ultramag Boron + Ultramag Calcium. Non-root fertilizing of plum plants was carried out before flowering, after flowering and during fruit development. On average for 2021-2023 non-root treatments contributed to an increase in the number of plum ovaries compared with the control (water treatment) by 3.3...26.7 %, the best result was obtained in the variant Ultramag Boron + Ultramag Calcium. In all variants of the experiment, foliar fertilization increased the yield of plum of the Velikaya sinyaya variety by 3.1...4.2 t/ha (LSD05 = 0.1 t/ha). The highest yield of plum fruits was formed in the variant Aquarin + Ultramag Boron + Ultramag Calcium – 12.9 t/ha (in the control – 8.7 t/ha). The maximum values of the average fruit weight were obtained in the variants Ultramag Boron + Ultramag Calcium and Aquarin + Ultramag Boron + Ultramag Calcium – 45.1 and 45.6 g, respectively (in the control – 43.3 g, LSD05 = 1.2 g). Foliar fertilizing with Ultramag Boron fertilizers together with Ultramag Calcium provided a higher sugar content (14.2 %) and the value of the sugar acid index (17.7) in the fruits of the Velikaya sinyaya plum variety (at the control – 13.2 % and 16.5 respectively).

The effect of Reglalg in combination with microelements on the pigment fund of pear and plum plants

The effect of Reglalg in combination with microelements on the pigment fund of pear and plum plants

Edaphic growth conditions of Prunus cerasifera Ehrh. in Nikitsky Botanical Garden

A soil survey was carried out under the collection plantings of Prunus cerasifera Ehrh., growing on the experimental site of the Nikitsky Botanical Garden. During the research, the morphological structure, granulometric composition, pH, content of carbonates, humus, exchangeable potassium, oxalate-soluble (amorphous) iron were studied using generally accepted methods of soil analysis. The content of mobile forms of micronutrients and heavy metals (Zn, Cu, Mn, Pb, Cd) was determined in ammonium acetate extract at pH=4.8. It was revealed that the soils of the experimental site are characterized by favorable physical, chemical properties and agrochemical parameters for cherry plum plants, including uniform distribution of humus along the profile, slightly alkaline reaction, low content of carbonates, high content of available potassium. Among the mobile forms of trace elements and heavy metals, exceeding of the maximum permissible concentration was found only for copper, the source of which is copper-containing fungicides. The slightly alkaline reaction of the soil contributes to a decrease in the mobility of micronutrients and heavy metals, therefore, even with their excessive content in the soil, there was no excess of maximum permissible concentration in cherry plum fruits.

Trans-grafting plum pox virus resistance from transgenic plum rootstocks to apricot scions.

Trans-grafting could be a strategy to transfer virus resistance from a transgenic rootstock to a wild type scion. However contradictory results have been obtained in herbaceous and woody plants. This work was intended to determine if the resistance to sharka could be transferred from transgenic plum rootstocks to wild-type apricot scions grafted onto them. To this end, we conducted grafting experiments of wild- type apricots onto plum plants transformed with a construction codifying a hairpin RNA designed to silence the PPV virus and studied if the resistance was transmitted from the rootstock to the scion. Our data support that the RNA-silencing-based PPV resistance can be transmitted from PPV-resistant plum rootstocks to non-transgenic apricot scions and that its efficiency is augmented after successive growth cycles. PPV resistance conferred by the rootstocks was robust, already occurring within the same growing cycle and maintained in successive evaluation cycles. The RNA silencing mechanism reduces the relative accumulation of the virus progressively eliminating the virus from the wild type scions grafted on the transgenic resistant PPV plants. There was a preferential accumulation of the 24nt siRNAs in the scions grafted onto resistant rootstocks that was not found in the scions grafted on the susceptible rootstock. This matched with a significantly lower relative accumulation of hpRNA in the resistant rootstocks compared with the susceptible or the tolerant ones. Using transgenic rootstocks should mitigate public concerns about transgenes dispersion and eating transgenic food and allow conferring virus resistance to recalcitrant to transformation cultivars or species.

Bacterial Leaf Spot of Plum Caused by Sphingomonas spermidinifaciens in Guangxi, China.

Plum (Prunus salicina L.) is a traditional fruit in Southern China and is ubiquitous throughout the world. In August 2021, leaves of plum trees showed water-soaking spots and light yellow-green halos with incidence exceeding 50% in Babu district in Hezhou, Guangxi (N23°49'-24°48', E111°12'-112°03'). To isolate the causal agent, three diseased leaves collected from three different trees growing in different orchards were cut into 5 mm × 5 mm pieces, disinfected with 75% ethanol for 10 sec, 2% sodium hypochlorite for 1 min and rinsed three times in sterile water. The diseased pieces were ground in sterile water and then kept static for about 10 min. Ten-fold serial dilutions in water were prepared and 100 µL of each dilution from 10-1 to 10-6 were plated on Luria-Bertani (LB) Agar. After incubation at 28℃ for 48 h, the proportion of isolates with similar morphology was 73%. Three representative isolates (GY11-1, GY12-1 and GY15-1) were selected for further study. The colonies were non-spore-forming, yellow, round, opaque, rod shaped, convex with smooth and bright neat edges. Biochemical test results showed that the colonies were strictly aerobic and gram-negative. The isolates were able to grow on LB agar containing 0-2% (w/v) NaCl and could utilize glucose, lactose, galactose, mannose, sucrose, maltose and rhamnose as a carbon source. They displayed a positive reaction for H2S production, oxidase, catalase and gelatin, but negative for starch. Genomic DNA of the three isolates was extracted for amplification of the 16S rDNA with primers 27F and 1492R. The resulting amplicons were sequenced. Additionally, five housekeeping genes atpD, dnaK, gap, recA, and rpoB of the three isolates were amplified using the corresponding primer pairs and sequenced. The sequences were deposited in GenBank (16S rDNA, OP861004-OP861006; atpD, OQ703328-OQ703330; dnaK, OQ703331-OQ703333; gap, OQ703334-OQ703336; recA, OQ703337-OQ703339; and rpoB, OQ703340-OQ703342). The isolates were identified as Sphingomonas spermidinifaciens based on the phylogenetic tree inferred by maximum-likelihood using MegaX 7.0 of the concatenated six sequences (multilocus sequence analysis, MLSA) compared with sequences from different Sphingomonas type strains . Pathogenicity of the isolates was tested on healthy leaves of the two-year-old plum plants in a greenhouse. The leaves were wounded by a sterilized needle and sprayed with bacterial suspensions prepared in PBS (Phosphate buffer saline) at OD600=0.5. PBS buffer solution was used as negative control. Each isolate was used to inoculate on 20 leaves per plum tree. The plants were covered with plastic bags to maintain high humidity. Dark brown-to-black lesions were observed on leaves 3 days post incubation at 28℃ with constant light. The average diameter of lesions was 1 cm after seven days, but the negative controls were symptomless. Bacteria reisolated from the diseased leaves were the same as the ones used for inoculation on the basis of morphological and molecular identification, fulfilling Koch's postulates. Plant disease caused by a Sphingomonas species has been reported on mango, pomeand Spanish melon. However, this is the first report of S. spermidinifaciens causing leaf spot disease of plum in China. This report will help to develop effective disease control strategies in the future.

In Vitro Multiplication and Rooting of Plum Rootstock 'Saint Julien' (Prunus domestica subsp. insititia) under Fluorescent Light and Different LED Spectra.

In recent years, light emitting diodes (LEDs), due to their low energy consumption, low heat emission and specific wavelength irradiation, have become an alternative to fluorescent lamps (FLs) in plant tissue culture. The aim of this study was to investigate the effects of various LED light sources on the in vitro growth and rooting of plum rootstock Saint Julien (Prunus domestica subsp. insititia). The test plantlets were cultivated under a Philips GreenPower LEDs research module illumination system with four spectral regions: white (W), red (R), blue (B) and mixed (W:R:B:far-red = 1:1:1:1). The control plantlets were cultivated under fluorescent lamps (FL) and the photosynthetic photon flux density (PPFD) of all treatments was set at 87 ± 7.5 μmol m-2 s-1. The effect of light source on the selected physiological, biochemical and growth parameters of plantlets was monitored. Additionally, microscopic observations of leaf anatomy, leaf morphometric parameters and stomata characteristics were carried out. The results showed that the multiplication index (MI) varied from 8.3 (B) to 16.3 (R). The MI of plantlets grown under mixed light (WBR) was 9, lower compared to the control (FL) and white light (W), being 12.7 and 10.7, respectively. In addition, a mixed light (WBR) favored plantlets' stem growth and biomass accumulation at the multiplication stage. Considering these three indicators, we could conclude that under the mixed light, the microplants were of better quality and therefore mixed light (WBR) was more suitable during the multiplication phase. A reduction in both net photosynthesis rate and stomatal conductance in the leaves of plants grown under B were observed. The quantum yield (Yield = FV/FM), which represents the potential photochemical activity of PS II, ranged from 0.805 to 0.831 and corresponded to the typical photochemical activity (0.750-0.830) in the leaves of unstressed healthy plants. The red light had a beneficial effect on the rooting of plum plants; the rooting was over 98%, significantly higher than for the control (FL, 68%) and the mixed light (WBR, 19%). In conclusion, the mixed light (WBR) turned out to be the best choice during the multiplication phase and the red LED light was more suitable during the rooting stage.

Resistance of domestic plum tree rootstocks against periodic overwatering of floodplain soils

This work investigates the effect of domestic plum rootstocks on the stability and productivity of Stanley plum plants. The main factor limiting the productivity of fruit crops in the floodplain soils of the foothill horticultural area of Krasnodar Oblast was found to be an unfavorable water-air regime of these soils in wet periods. The main geogenic factors that negatively affect the state and productivity of plum plants include the following: the presence of layers of low fertility and medium-clay granulometric composition in the soil profile. Depression and death of trees is promoted by prolonged overwatering of the upper part of the soil profile, caused by low filtration capacity of soil layers in combination with heavy granulometric composition and conditions of laying on the terrain (absence of horizontal surface runoff). A different degree of plum trees resistance to these unfavorable geogenic conditions depending on the type of rootstock was revealed. The lowest degree of depression under prolonged overwatering of the root-containing soil layer was observed in plum trees on the PK SK2 rootstock, which demonstrated the highest vegetative mass growth under the smallest number of dead plants. Stanley plum trees on rootstock AP1 were subjected to the greatest depression. The different degree of plum tree stability on different rootstocks is mainly related to the location of potentially active roots in the soil. The root system of plum trees on rootstock PK SK2 is characterized by the concentration of the main part (about 65 %) of potentially active roots in the upper soil layer of 0–40 cm. In plum trees on AP1 rootstock, potentially active roots penetrate to greater depths, with about 60% of the roots located in the soil layer of 40-80 cm. During wet periods and after abundant precipitation, when the soil below the 40 cm level is saturated with moisture, more than half of potentially active roots of plum trees on AP1 rootstock have to survive in unfavorable conditions.

First Report of Anthracnose of Sanhua Plum Caused by Colletotrichum aeschynomenes in Guangxi, China.

There is nearly 5,800 ha of Sanhua plum (Prunus salicina Linn) planted in Babu district in Hezhou, Guangxi, with over 67,000 tons of annual output. In August 2021, anthracnose symptoms were observed on Sanhua plum leaves in three different cultivated towns in Babu district in Hezhou, Guangxi (N23°49' - 24°48', E111°12' - 112°03'). The plant disease incidence was over 50% with approximately 20 to 30% of leaves on a plant being symptomatic. The disease outbreak occurred in the warm and damp climate (June to August) in Hezhou. Initially, small chlorotic spots developed on the leaves which gradually enlarged to larger irregular dark brown sunken lesions with yellowish halos, necrotic lesions abscised and formed holes at a later stage. In severe cases, the whole leaf withered and defoliated. Three symptomatic leaf samples were collected from three different cultivated towns in Hezhou. Margins of infected tissues were cut into 3×3 mm pieces, surface disinfected with 75% alcohol for 10 s, 2% NaOCl for 2 min followed by three washes in sterile distilled water and transferred to potato dextrose agar (PDA) plates. In total, forty-one isolates were obtained after 4 days of incubation at 25℃ on PDA, and thirty-one of them were Colletotrichum (average isolation frequency 76%). Three representative isolates (HZ18-1, HZ22-3, and HZ46-3) were selected for further study. After 7 days on PDA at 25℃, isolates had white to light grey cottony aerial mycelium on the obverse and revealed dark grey on the reverse. Conidia were hyaline, cylindroid, tapering slightly near both ends, measuring 16.3 ± 1.2 μm × 5.6 ± 0.4 μm, 16.1 ± 1.4 μm × 6.4 ± 0.7 μm, 16.2 ± 1.1 μm × 6.0 ± 0.4 μm (n=90) for HZ18-1, HZ22-3, and HZ46-3, respectively. Appressoria were brown, elliptic or fusoid, deeply lobed, measuring 10.2 ± 1.6 μm × 6.8 ± 1.0 μm, 10.7 ± 1.3 μm × 6.6 ± 0.8 μm, 9.3± 1.3 μm × 6.9 ± 0.9 μm (n=90) for HZ18-1, HZ22-3, and HZ46-3, respectively. These characteristics were consistent with the descriptions of Colletotrichum aeschynomenes B. Weir & P. R. Johnst (Weir et al. 2012). The internal transcribed spacer (ITS) region and the intergenic region and flanking regions of Apn2 and MAT1-2-1 (ApMAT) were amplified using ITS1/ITS4 and AM-F/AM-R primers, respectively (White et al. 1990; Silva et al. 2012). BLASTn analysis of the sequences showed over 99% identity with the corresponding loci from the culture collection C. aeschynomenes ICMP 17673 (ex-type). Sequences from the three isolates were deposited in GenBank (Accession Nos.: ITS, OM838335, OM838339, OM838370; ApMAT, OM816771, OM816775, OM816806). Phylogenetic maximum likelihood analysis with RAxML version 8.2.10 based on the concatenated sequences of ITS and ApMAT showed that the three isolates clustered with the ex-type specimen of C. aeschynomenes ICMP 17673. Pathogenicity was confirmed on leaves with and without wounds of 24 two-year-old Sanhua plum plants in a greenhouse. The wound was made with a sterilized toothpick. Wounded and unwounded leaves were inoculated with 20 μL of conidial suspension (106 conidia/mL) of the three isolates and control plants were inoculated with sterile distilled water (20 leaves/plant, 3 plants/treatment). All plants were covered with plastic bags to maintain high humidity. After 8 days of incubation at 25℃ with constant light, necrotic lesions were observed on inoculated leaves, whereas control plants showed no symptoms. To fulfill Koch's postulates, all fungi were successfully reisolated from symptomatic leaves. This species has been reported on Aeschynomene virginica in the United States (Weir et al. 2012), Manihot esculenta in Thailand (Sangpueak et al. 2018), Theobroma cacao (Nascimento et al. 2019) and Myrciaria dubia (Matos et al. 2020) in Brazil. To our knowledge, this is the first report of C. aeschynomenes causing Sanhua plum leaf anthracnose in China. The results will provide valuable information for management of anthracnose associated with Sanhua plum.

Genetic diversity and phylogenetic relationships of apple chlorotic leaf spot virus isolates from Malus, Pyrus and Prunus hosts in Latvia

AbstractThe prevalence of apple chlorotic leaf spot virus (ACLSV) in different Rosaceae species, mainly from cultivated apple (Malus domestica), pear (Pyrus communis), plum (Prunus domestica), apricot (Prunus armeniaca) and wild plants of genus Amelanchier, Cotoneaster, Crataegus, Malus, Prunus and Sorbus were studied. ACLSV was found in cultivated M. domestica, P. communis, P. domestica and wild‐growing Malus, including M. sylvestris. Thirty‐four sequences of the ACLSV coat protein gene were obtained and compared with 372 homologous sequences from GenBank to evaluate the genetic diversity of the virus in Latvia and worldwide. The sequence identities varied from 79.6% to 98.4% at the nucleotide level and 84.5% to 100% at the amino acid level. Phylogenetic analyses clustered ACLSV pome fruit isolates into three genetic types but isolates from stone fruits into four phylogenetic groups. Three genetic types of ACLSV pome and stone fruit isolates were identified in Latvia. Two of them were previously characterized as type B6 and P205. The third genetic type was newly recognized among the stone fruit isolates and distinguished from other virus isolates by amino acid substitutions in three positions, Ser14, Asn23 and Leu72. Two natural recombinants, LV27 and NZ5, were detected among ACLSV isolates from Latvia, and recombination events were identified for the first time in wild‐growing Malus, confirming that recombination is a common process in the ACLSV population.

ЗАЩИТА СЛИВЫ ОТ ТЛИ В РЕСПУБЛИКЕ ТАТАРСТАН

The research was carried out for the purpose of a comparative assessment of the use of plums in plant protection against aphids by biological and chemical means in the conditions of the Republic of Tatarstan. The experiments were performed in 2020-2021. The objects of the study were varieties and forms of domestic plum (Prunus domestica L.): early fruit ripening - blue-eyed; medium term - Kazan; mid-late period - selective hybrid 8-4-52. The scheme of the experiment included the following options: control (without treatment), biological preparation Lepidocide, chemical insecticide Iskra M. In 2020-2021. in the control, in Sineokoy and Kazanskaya, average damage to leaves and shoots (25%) of plum aphids was noted, in the hybrid 8-4-52 - severe (31.7%). Four times treatment of trees of the Sineokaya variety with a biological preparation reduced damage by aphids, compared with the control, by 15%, Kazanskaya - by 2.5 ... 15%, hybrid 8-4-52 - by 5.8 ... 6.7%. Double spraying of Sineokaya and Kazanskaya varieties with Iskra M reduced damage by 5.8...15% compared to the control, hybrid 8-4-52 - by 5.8...6.7%. In 2020, on average for varieties, treatment of plants with Lepidocid was slightly (by 1.9%) more effective than treatment with Iskra M. In 2021, biological and chemical preparations showed the same effectiveness in protecting against aphids. The share of influence of factor A (preparations) on the damage of aphids was 40.6%, factor B (varieties) - 3.3%, interactions of factors A and B - 1.8%, factor C (years) - 0.2%, interactions factors A and C - 2.1%, interactions of factors B and C - 34.2%, interactions of factors A, B and C - 9.6%. The use of the biological preparation Lepidocide in the protection of plum plants from aphids will allow the production of biologically safe fruits of the crop in the Republic of Tatarstan.

ЗАЩИТА СЛИВЫ ОТ ТЛИ В РЕСПУБЛИКЕ ТАТАРСТАН

The research was carried out for the purpose of a comparative assessment of the use of plums in plant protection against aphids by biological and chemical means in the conditions of the Republic of Tatarstan. The experiments were performed in 2020-2021. The objects of the study were varieties and forms of domestic plum (Prunus domestica L.): early fruit ripening - blue-eyed; medium term - Kazan; mid-late period - selective hybrid 8-4-52. The scheme of the experiment included the following options: control (without treatment), biological preparation Lepidocide, chemical insecticide Iskra M. In 2020-2021. in the control, in Sineokoy and Kazanskaya, average damage to leaves and shoots (25%) of plum aphids was noted, in the hybrid 8-4-52 - severe (31.7%). Four times treatment of trees of the Sineokaya variety with a biological preparation reduced damage by aphids, compared with the control, by 15%, Kazanskaya - by 2.5 ... 15%, hybrid 8-4-52 - by 5.8 ... 6.7%. Double spraying of Sineokaya and Kazanskaya varieties with Iskra M reduced damage by 5.8...15% compared to the control, hybrid 8-4-52 - by 5.8...6.7%. In 2020, on average for varieties, treatment of plants with Lepidocid was slightly (by 1.9%) more effective than treatment with Iskra M. In 2021, biological and chemical preparations showed the same effectiveness in protecting against aphids. The share of influence of factor A (preparations) on the damage of aphids was 40.6%, factor B (varieties) - 3.3%, interactions of factors A and B - 1.8%, factor C (years) - 0.2%, interactions factors A and C - 2.1%, interactions of factors B and C - 34.2%, interactions of factors A, B and C - 9.6%. The use of the biological preparation Lepidocide in the protection of plum plants from aphids will allow the production of biologically safe fruits of the crop in the Republic of Tatarstan.

Xylella fastidiosa Outbreak in Israel: Population Genetics, Host Range, and Temporal and Spatial Distribution Analysis.

Diseases caused by the insect-transmitted bacterium Xylella fastidiosa have been reported in the Americas since the 19th century, causing diseases such as Pierce's disease of grapevine, almond leaf scorch (ALS), and citrus variegated chlorosis. In the last decade X. fastidiosa was reported from different parts of the world, most notably from southern Italy, infecting olives. In 2017, X. fastidiosa was reported to be associated with ALS symptoms in Israel. Here, we investigated the causal agent of ALS in Israel, its genetic diversity, and host range, and we characterized the temporal and spatial distribution of the disease. X. fastidiosa subsp. fastidiosa sequence type 1 was isolated from symptomatic almond trees and was used to infect almond and grapevine by mechanical inoculation. The pathogen, however, did not infect olive, peach, cherry, plum, nectarine, clementine, and grapefruit plants. Genomic analysis of local isolates revealed that the local population is derived from a single introduction and that they are closely related to X. fastidiosa strains from grapevines in California. Distribution analyses revealed that ALS did not expand from 2017 to 2019; however, since 2020, newly symptomatic trees appeared in the tested orchards. Symptomatic trees were located primarily in clusters, and symptoms tended to spread within rows. Our study confirms that X. fastidiosa is the causal agent of ALS in Israel and describes its genetic and host range characteristics. Although there is no clear evidence yet for the identity of the vectors in Israel, ALS spread continues to threat the almond and grapevine industries in Israel.

First Report of Leaf Blight Caused by Fusarium pernambucanum and Fusarium sulawesiense on Plum in Sichuan, China.

Plum (Prunus salicina Lindl.) is widely cultivated for its rich nutrients and flavor in China. In August 2020, leaf blight symptoms were observed on plum in Meishan, Sichuan, China (N29°24', E104°30'). Irregular brown spots initially appeared on the edge or tip of the leaf, then extended to larger taupe lesions that were surrounded by a chlorotic halo. In the late stage, grey-brown blighted tissue covered the entire leaf causing leaves to wither, curl and abscise. The leaves with blight were collected from three different towns in Meishan where the disease incidence was found on 15-30% of plum plants. The margin of diseased leaves was cut into small pieces (3×3 mm), surface disinfected with 75% ethanol solution for 10 s, 2% NaOCl for 1 min, and rinsed in sterile distilled water three times. Tissue pieces were plated on potato dextrose agar (PDA) and incubated at 25°C. Forty-nine morphologically similar colonies were observed on PDA plates after 3-5 days and three of these (TEY9-1, TEY12-1, TEY15A-1) were selected for intensive study. The colonies produced abundant whitish to yellowish aerial mycelium after 7 days incubation at 25°C in the dark. Macroconidia on carnation leaf agar (CLA) were falcate, hyaline, straight to slightly curved, smooth to slightly rough with 3 to 6 septa, the apical cell was blunt or hooked, and the basal cell was barely notched, 31.6 ± 2.4 μm × 4.7 ± 0.4 μm, 28.9 ± 3.0 μm × 4.5 ± 0.5 μm, 32.5 ± 3.4 μm × 4.5 ± 0.5 for TEY9-1, TEY12-1, TEY15A-1, respectively. Microconidia were hyaline, fusoid or ovoid, nonseptate or one-septate, 14.4 ± 3.9 μm × 4.3 ± 0.6 μm, 13.0 ± 3.0 μm × 4.0 ± 0.4 μm, 11.0 ± 2.4 μm × 3.7 ± 0.5 for TEY9-1, TEY12-1, TEY15A-1, respectively. Genomic DNA was extracted from 7-day-old aerial mycelia of these isolates. The internal transcribed spacer (ITS), translation elongation factor (TEF1), calmodulin (CAM) and partial RNA polymerase second largest subunit (RPB2) were amplified using primers ITS4/ITS1, EF1/EF2, CL1/CL2A, and 5f2/7cr, respectively (White et al. 1990; O'Donnell et al. 2000, 2010). Sequences were deposited in GenBank (ITS: OK315638-OK315640; TEF1: OK338756-OK338758; CAM: OK338759-OK338761; RPB2: OK338762-OK338764). A maximum Likelihood (ML) phylogenetic tree was constructed with RAxML version 8.2.10 based on the concatenated sequences (ITS, TEF1, CAM, RPB2). According to morphology and phylogenetic analysis, TEY9-1 and TEY15A-1 were identified as Fusarium pernambucanum, and TEY12-1 was identified as Fusarium sulawesiense. Pathogenicity tests were conducted on young healthy leaves of 12 two-year-old plum plants in a 28°C greenhouse in Nanning, Guangxi, China. The epidermis of tested leaves was slightly scratched with sterile toothpick-tips forming a 3-mm-diameter cross-shaped wound, followed by inoculation with a 10 μl conidial suspension (106 spores /ml in 0.1% sterile Tween 20). Control leaves were wounded in the same way and treated with 0.1% sterile Tween 20. Plants were covered with polythene bags to maintain high humidity for 5 days. Inoculated leaves showed light brown to dark brown lesions, whereas control leaves were symptomless. Both species were re-isolated from symptomatic leaves, completing Koch's postulates. To our knowledge, this is the first report of F. pernambucanum and F. sulawesiense causing leaf blight on plum trees in China. These results will provide valuable information for prevention and management of leaf blight on plum trees.

Use of the phosphomannose isomerase (PMI) gene for agrobacteriummediated transformation of <i>Prunus domestica</i> L. leaf explants without the use of selective antibiotic resistance genes

We developed an efficient system for agro-bacterial transformation of plum (Prunus domestica L.) leaf explants using the PMI/mannose and GFP selection system. Th e variety `Startovaya` was transformed using Agrobacterium tumefaciens strain CBE21 carrying the vector pNOV35SGFP. Leaf explants were placed onto a nutrient medium containing various concentrations and combinations of mannose and sucrose to develop an efficient selection system. Nine independent transgenic lines of plum plants were obtained on a regeneration medium containing 20 g/L sucrose and 15 g/L mannose. The highest transformation frequency (1.40 %) was produced using a delayed selection strategy. Starting from the 1st days after transformation and ending by regeneration of shoots from the transgenic callus, selection of transgenic cells was monitored by GFP fluorescence that allowed avoid ing formation of escapes. Integration of the manA and gfp transgenes was confi rmed by PCR and Southern blotting. On the whole, no direct correlation between the fluorescence level and the copy numbers of the transgenes was found in the present study, though the most intensive fluorescence was observed in line #9 with a single-copy insert. The difference of GFP expression level may have been caused by the integration site or by other factors such as DNA methylation and varying copy number. The described transformation protocol using a positive PMI/mannose system is an alternative selection system for production of transgenic plum plants without genes of antibiotic and herbicide resistance, and the use of leaf explants enables retention of variety traits of plum plants.

Harmful viruses on stone fruit crops and sanitation methods

Relevance. Viral diseases can significantly reduce the yield of stone fruit crops. More than 30 viruses have been characterized on stone fruits crops, among which the most harmful are Plum pox virus (PPV), Prunus dwarf virus (PDV), Prunus necrotic ringspot virus (PNRSV), Cherry leaf roll spot virus (CLRV), Apple chlorotic leaf spot virus (ACLSV). Viral diseases monitoring is essential for controlling the viruses prevalence and choosing a control strategy. In the absence of healthy plants of a certain variety, health improvement is carried out using laboratory methods, including thermotherapy. Sanitation methods need to be improved in relation to the culture characteristics and the virus type. Of considerable interest is the development of techniques that reduce the viruses concentration when growing stone fruit trees in the field.Methods. During 2016–2020 using the ELISA (“Loewe” diagnostic kits) diagnostics of viruses on varieties and clonal rootstocks of cherry, sweet cherry and plum (660 plants) was carried out in the conditions of the Moscow region. For plant health in 2019–2021 used thermotherapy for 3 months. To study the effect of Pharmayod (“Farmbiomed”) on viruses in open ground, 24 plum plants of 5 varieties were treated with this drug at a concentration of 0.3 ml/l.Results. The total prevalence of viruses on cherries varieties was 44%, sweet cherries — 40%, plums — 59%, on clonal rootstocks — 46, 55 and 56% respectively. The highest incidence of PNRSV and PDV viruses has been established. Cherry plants of 11 varieties, free from the main harmful viruses, 4 varieties of sweet cherries, 12 varieties of plums and 9 forms of clonal rootstocks were revealed. The use of the Pharmayod on plum trees in the open field contributed to a decrease in the infection index of the studied viruses. Plum plants in a heat chamber were characterized by a higher survival rate and growth parameters in comparison with cherry and sweet cherry. After the completion of thermotherapy, a significant decrease in the index of infection in plants was noted.

Gibellulopsis nigrescens as a causal agentof plum plants wilting obtained by clonal micropropagation

Gibellulopsis nigrescens as a causal agentof plum plants wilting obtained by clonal micropropagation

Silverleaf (Chondrostereum purpureum) Effects on Japanese Plum (Prunus salicina).

Silverleaf is an important fungal trunk disease of fruit crops, such as Japanese plum (Prunus salicina). It is known that infection by Chondrostereum purpureum results in discolored wood, “silvered” foliage, and tree decline. However, effects on fruit yield and quality have not been assessed. Therefore, the objectives of this study were to determine C. purpureum pathogenicity on P. salicina and the effects on physiology, fruit yield, and quality, in Chile, in 2019 and 2020. Wood samples from affected plum trees were collected in the Chilean plum productive area. Fungi were isolated by plating wood sections from the necrosis margin on culture media. Morphological and molecular characteristics of the isolates corresponded to C. purpureum (98%). Representative isolates were inoculated from healthy plum plants and after 65-d incubation, wood necrotic lesions and silver leaves were visible. Fungi were reisolated, fulfilling Koch’s postulates. To determine Silverleaf effects, xylem water potential and fruit yield and quality were measured in healthy and Silverleaf-diseased plum trees ‘Angeleno’. Water potential was altered in diseased trees, and fruit yield was reduced by 51% (2019) and by 41% (2020) compared to fruit from healthy trees. Moreover, cover-colour, equatorial-diameter, and weight were reduced, and fruit were softer, failing to meet the criteria to be properly commercialized and exported to demanding markets.