Cultivar-rootstock Combinations Research Articles

ТЕОРЕТИЧЕСКОЕ И ПРАКТИЧЕСКОЕ ОБОСНОВАНИЕ ВЫБОРА ПОДВОЯ ПРИ ВЕГЕТАТИВНОЙ РЕПРОДУКЦИИ ИНТРОДУЦЕНТОВ РОДА SYRINGA L. (OLEACEAE) В УСЛОВИЯХ ОРЕНБУРГСКОЙ ОБЛАСТИ

The proper selection of rootstock and graft combinations in lilac introducers, in order to take full advantage of grafting, requires a thorough understanding of the synergy of cultivar-rootstock combinations, as well as the identification of factors that may influence this process. The article analyzes the results of three grafting experiments using Syringa vulgaris L. and Syringa josikaea J. Jacq. ex Rchb. seedlings and vegetative rootstocks (rooted shoots) of Syringa vulgaris L. as rootstocks. The grafting material was the dormant buds of four highly ornamental cultivars of S. vulgaris L. – ‘Au- cubaefolia’, ‘Sensation’, ‘Marc Micheli’, ‘Congo’ and the late hybrid Syringa × prestoniae МсКelveу ‘Miss Canada’. It was found that the survival rate of cultivars on a particular rootstock may depend on the systematic affiliation of the mother plants of the cultivars. The best survival rate among all studied cultivars in the climatic conditions of the Orenburg region is achieved when using rooted vegetative shoots of S. vulgaris as a rootstock (over 90%), the worst – on the seed rootstock of S. josikea J. Jacq. ex Rchb. (up to 40%). The influence of the ambient temperature and humidity at the time of oculant fusion on the survival rate of grafts using S. vulgaris L. vegetative rootstock has been demonstrated (Wilcoxon T-test, statistical significance level p <<0.05). It is recommended to select the rootstock individually for each cultivar in order to achieve maximum survival rates of lilac cultivars in the climatic and geographical conditions of the Orenburg region and/or regions with similar conditions.

Winter hardiness of apple clonal rootstocks in Southern Cisbaikalia

The paper presents the results of a study of apple clonal rootstocks carried out in 2017-2022 in the trial plots located in the Irkutsk region. The objects of the study were clonal rootstocks from various scientific institutions. The conducted fieldwork allows us to state that the ecological conditions of the Southern Cisbaikalia are generally favorable for the use of clonal rootstocks in the regional horticulture. It was found that the most adaptive forms of all the studied clonal rootstocks are the rootstocks of the Ural selection (Ural and Ural 2) and the rootstock of the Estonian selection (E-56). The clonal rootstocks 70-6-8, Arm18, and K-2 withstood winter worst of all. According to the fieldwork results, the rest of the rootstocks showed medium winter hardiness. As a result of laboratory freezing experiments, E-56 high winter hardiness was confirmed. The study of cultivar-rootstock combinations showed good compatibility of clonal rootstocks with semi-cultivated apple trees. The variety and type of the rootstock were statistically proven to affect the degree of temperature damage to fruit trees. The clonal rootstocks with high winter hardiness and those with medium winter hardiness and high recovery ability were selected for further breeding work.

Field and laboratory investigations of clonal rootstocks in South Cisbaikal

The study of the possibility of using low-growing clonal rootstocks in the conditions of the South Сisbaikal, the territory most suitable for horticulture in the Irkutsk region, was the goal of this work. The studies were carried out in 2017-2022 on experimental plots, which are located in the Irkutsk district of the Irkutsk region and on the territory of SIPPB SB RAS (Irkutsk). Assembled collection was included: six varieties of clonal rootstocks bred by MichGAU (62-396, 54-118, 70-20-20, 70-6-8, 64-143, 62-223), stock bred by A.P. Apoyan (Armenian RIVWFG) (Arm18), rootstock of Estonian selection (E56), eight rootstocks of Orenburg ESHV selection (Ural, Ural2, Ural5, 18-7, B-3-4, 4-12, 8-2, OB), rootstock Crimean OSH (K-2). The conducted field observations allow us to state that clonal rootstocks can be used in horticulture in the South Сisbaikal. We found out that of all the studied clonal rootstocks, the rootstocks of the Ural selection Ural and Ural 2 and the rootstock of the Estonian selection E-56 showed high winter hardiness. We attributed clonal rootstocks 70-6-8, Arm18, K-2 to low winter-hardiness. The rest of the rootstocks over the years of research showed an average winter hardiness. The results of laboratory studies confirmed the high winter hardiness of E-56. The study of cultivar-rootstock combinations showed good compatibility of clonal rootstocks with semi-cultivated apple trees: strong fusion of the rootstock with the scion, active growth, well-developed leaf apparatus, the absence of any signs of starvation and discoloration. It has been statistically proven that the variety and type of rootstock affect the degree of temperature damage to the fruit tree. Highly winter-hardy clonal rootstocks and medium-hardy clonal rootstocks with high regenerative capacity were selected as promising for breeding.

Comparative analysis of drought resistance of plum cultivar-rootstock combinations in dry steppe conditions

The adaptability of the variety to abiotic environmental factors depends on a number of factors, one of which is the rootstock on which the variety is grafted. The data on the influence of various rootstocks on the drought resistance of the grafted variety and the dependence of this influence on the prevailing meteorological conditions of the growing season are presented. Drought resistance was studied in the laboratory according to the indicators of the water regime and the the ability of leaves to retain moisture. The correlation dependence of drought resistance of cultivar-rootstock combinations on the hydrothermal coefficient of the growing season is revealed. Rootstock forms were identified that have a positive effect on increasing the drought resistance of the variety and the most drought-resistant variety-rootstock combination was selected for each variety.

Deficit irrigation differently affects aroma composition in berries of Vitis vinifera L. (cvs Sangiovese and Merlot) grafted on two rootstocks

Background and Aims Water deficit modifies the concentration of the aroma compounds of grape berries, but little information is available on the effect of deficits applied at different phenological stages. We evaluated the effect of deficit irrigation on glycosylated volatile organic compounds (VOCs) responsible for the aroma of berries of Sangiovese and Merlot cultivars grafted on 1103P or SO4 rootstocks. Methods and Results Vines were subjected to either pre- or post-veraison water stress, and berry composition compared against that of fruit of fully irrigated vines. At harvest, a higher concentration of glycosylated VOCs was measured in berries from vines stressed pre-veraison, but while it increased as water deficit increased in Sangiovese, this occurred only at a low or moderate level of stress in Merlot. Post-veraison water stress had a negative or negligible effect on the concentration of glycosylated VOCs in berries at harvest. The rootstock affected the concentration of glycosylated VOCs, particularly in vines stressed pre-veraison, with higher glycosylated VOCs observed for SO4 grafted vines than for 1103P grafted vines. Conclusions Pre-veraison water deficit enhanced the concentration of berry glycosylated VOCs, while post-veraison deficit did not. The rootstock–scion interaction might amplify the irrigation effect on berry glycosylated VOCs. Significance of the Study Modifying the timing and volume of irrigation might allow management of berry flavour for improved fruit and wine composition. Irrigation protocols should be tailored for specific cultivar–rootstock combinations.

Biological features of plum cultivar-rootstock combinations in arid conditions of the Northern Caspian sea

The results of studies of biological features of growth and fruiting of plum varieties are presented. Found that released at the yield grade the Great blue on dwarf rootstock VVA-1 and Anna Shpet on medium Eureka-99 was characterized by a statistically significant difference in comparison with control Greengage Altana (LSD05 3.5 t/ha). The Kuban early variety exceeded the control yield by 35%, while the Burbank and Great blue varieties on Eureka-99 were at its level in terms of yield. In the third year after planting, almost all varieties of rootstock combinations formed single fruits. It indicates the potential rapidity of these varieties. The size of the fruit stood out varieties Bogatyrskaya and Angelina with a fruit weight of 53.6...52.3 g, with a fruit weight of the control variety Renklod Altana-20.5 g. the Lowest percentage of the bone from the fruit weight (3.3%) was marked in Angelina variety.

Biological peculiarities of cherry growth and fructification on seedling and clonal rootstocks

Cherry is a stone fruit crop which is valued for early raping, yield capacity, fruit eating qualities. The drawback is growth of trees, absence of short rootstocks for cultivating in Central chernozemic region. The Faculty of Agricultural Science conducts research on the selection of compatible cultivars and rootstocks with high winterhardiness of the above-ground part and roots for their introduction into commercial orchards in the Voronezh region. Biometrical attributes of cultivar growth and development, crown parameters, weak-, medium, active plantings of the cherry on seedling and clonal rootstocks have been determined by the study. The effects of cultivar-rootstock combinations on the cherry yield have been determined. The content of sugar, organic acids, dry basis, and vitamin C have been determined. The cultivars for introduction and study have been suggested for intensive commercial orchids of the Voronezh region.

Використання сорто підщепних комбінувань – перспективний прийом підвищення продуктивності та якості помідора за вирощування способом малооб’ємної гідропоніки

Tomato grafting has a considerable scientific and practical interest, because it promotes plant resistance to illnesses, pests, stress factors, improves nourishment conditions and as a result increases crop yields and contributes to the greening of cultivation. The study of this issue is actual for the indoor ground conditions, particularly, for growing in glass greenhouses using low-volume hydroponics method. Experiments for studying three indeterminate hybrids of tomatoes Torero F1, Barteza F1 and Merlice F1 with grafting on rootstocks Maxifort F1, TD-1 F1 і Emperador F1 were conducted in the “Venlo” type on Private Joint Stock Company «Сombinat «Teplychnyy» («Комбінат «Тепличний»). The main goal of the experiments was to find out the efficiency of varietal-rootstocks combinations on the inderterminate hybrids F1 tomato. Consequently, the usage of rootstocks promotes the increase in early yield in all options. Significantly higher yield compared to the plants that were not rootstocked during all the years of research, was gotten from the Toreto F1 hybrid on the TD-1 F1 rootstock (in general during 3 years 30,4 kilograms per square meter), from Merlice F1 hybrid on Emperador F1 (31 kilogram per square meter). Mathematically significant difference in early yield between the studied cultivar-rootstock combinations was not found. The usage of the rootstocks also improves biochemical indicators, particularly, contributes to the increasing the dry matter content in the fruits of all hybrids by 0.1-0.8%. Emperador F1 rootstock causes an increase in the total sugar content in tomatoes by 0.3-0.5% and ascorbic acid by 1-4.7% for all studied rootstocks. It is recommended to use such grafting options as Torero F1 to TDß1 F1; Barteza F1 to Emperador F1; Merlice F1 to Emperador F1 with a view to increasing the share of early yield (10th July) in modern block hydroponic winter greenhouses of the “Venlo” type at the level of 30,4-31,0 kilograms per square meter with high biochemical indicators of fruits.

Growth and Feathering of Some Apple Cultivar-Rootstock Combinations in a Fruit-tree Nursery

The planting of well feathered trees are crucial in a high density orchard, than unbranched rods. Lateral bud-brake can be effectuated by several agro-technical methods in order to overcome apical dominance. Main targets of the researches were to investigate the feather induction by removing the apical leaves and to study a proper basic and foliar fertilization scheme. The highest mean height of the trees with significant differences was achieved by untreated Florina, followed by variants of Florina treated with Solfert, untreated control Idared and Florina with NPK and Fertitel. The number of feathered trees was higher in Florina than in Idared. The best results were obtained with Solfert and NPK followed by Fertitel. The growth in height was not affected by the lack of fertilizers in the control variants, but in other fertilization variants where branching was observed the height of the trees was reduced.

Evaluation Results of Finnish Apple Rootstocks in Latvia

Abstract A trial was established in 2011 with five rootstocks - MTT1, MTT4 and control B.9 (1.5 × 4 m, five replications with two trees), MTT5 and control MM.106 (2.5 × 5 m, six replications with two trees), and two cultivars - ‘Auksis’ and ‘Gita’. The evaluated parameters were: tree general condition, flowering, and yielding intensity (points), number of root suckers, average yield (kg·tree-1), yield per trunk cross section area (g·cm-2), average fruit mass (g), and amount of non-standard fruits (%). A randomised fruit sample from each cultivar-rootstock combination was put into storage, and a panel taste was performed once each season. A snowless winter occurred in 2013/2014, when soil froze to 1.5 m depth, which was critical for MM.106. Other rootstocks did not show injury. The best results were obtained for MTT4, which was similar to that of M.26 in Finland. Its vigour was similar to MM.106, and start of bearing to B.9. Rootstock MTT5 was initially grouped with medium vigour MM.106, as having 60-80 % of vigour of ‘Antonovka’ seedlings in Finland. Yet in our trial, it had vigour and start of bearing was similar to that of B.9 or slightly larger, depending on cultivar; it has a tendency to form root suckers. MTT1, ranged with B.9 in Finland, had too weak vigour. The most promising cultivar-rootstock combination was ‘Gita’ on MTT4.

Results from 13-year study of cultivar-rootstock combinations in sweet cherry

The study was carried out during the period 1999-2011 at the Institute of Agriculture - Kyustendil, Bulgaria. The growth, reproductive characteristics and fruit quality of 'Van' sweet cherry trees, grafted on clonal rootstocks: 'P-7', 'Karamy', 'Hybrid 2', 'SL-64' and seedlings from 'Vladimir' and 'Mahaleb 20-86' were studied. The trees on 'SL-64' were used as a control. The trees were planted in the spring of 1999 at distances of 5.50×5.0 m, formed in free-growing crowns and grown without irrigation. After thirteen years, the biggest trunk cross-sectional area had the trees grafted on 'Hybrid 2' and the smallest on 'Mahaleb 20-86'. The trees crown volume was reduced by 14.9% for 'Vladimir', 21.4% for 'P-7', 22.6% for 'Hybrid 2', 27.8% for 'Mahaleb 20-86', and 35.9% for 'Karamy', when compared to 'SL-64'. The row strips were not occupied by the trees, which allow optimizing planting distances. 'P-7' had the highest root-suckering ability, followed by 'Vladimir'. Trees grafted on 'Vladimir' had the best vitality, while those on 'Karamy' were with the highest mortality rate. The highest productivity had the trees on 'SL-64' and the lowest on 'Karamy'. Productivity was also good for 'P-7' and 'Vladimir', which was confirmed by the data for yield efficiency and the quantity of fruit 1 m-3 of the crown volume. No significant differences were found in the average weight and fruit size as well as in their chemical composition (dry matter, total sugars and acids) among tested rootstocks.

Investigation of responses of some apple (Mallus x domestica Borkh.) cultivars grafted on MM106 and M9 rootstocks to lime-induced chlorosis and oxidative stress

The response of dwarf (M9) and semi dwarf (MM106) clonal apple rootstocks and 5 apple cultivars [Granny Smith (GS), Fuji (F), Royal Gala (RG), Mondial Gala (MG) and Red Chief (RC)] grafted on these rootstocks to lime induced iron chlorosis and iron deficiency induced oxidative stress were investigated. Both rootstocks and cultivars were divided into two groups. One of the group were kept as control group. To the second group, to ensure the lime-induced chlorosis, bicarbonate (HCO3−) was applied. Both groups were grown for two years in a pot experiment. The soil used in the experiment was a clay loam calcareous soil containing 70.9gkg−1 lime. To evaluate the lime-induced chlorosis effects on both rootstocks and cultivars, accumulation of H2O2 and membrane damage (MDA, lipid peroxidation), activities of catalase (CAT, EC 1.11.1.6), superoxide dismutase (SOD, EC 1.15.1.1) and ascorbate peroxidase (APX, EC 1.11.1.11) determined. Bicarbonate treatment reduced active and total Fe and total chlorophyll concentrations, and FCR (leaf ferric chelate reductase) activity while increased the MDA, H2O2, SOD and APX activity of cultivars and rootstocks in both years. These changes and the statistical significances of individual and combined effects of treatment and cultivar or rootstocks showed great differences among the cultivars and rootstocks. So B/C rates helped us to evaluate the tolerance to lime induced chlorosis of the cultivars and rootstocks. B/C referring Fe efficiency ratio calculated as the value for the bicarbonate treatment divided by that for the control for each parameter studied used for tolerance state of cultivars and rootstocks. According to B/C ratios calculated for active and total Fe, FCR, the MG and RG grafted on both rootstocks regarded as tolerant cultivars. In addition to this, the MM106 rootstock was more tolerant than the M9 rootstock under bicarbonate applied condition giving higher B/C ratio for active and total Fe, total chlorophyll, FCR and APX but lower MDA concentrations. It can be concluded that suitable cultivar-rootstock combinations is a good strategy to overcome Fe chlorosis in apple plants grown in calcareous soils.

Incidence of grape anthracnose on different VITIS labrusca and hibrid cultivars and rootstocks combination under humid subtropical climate

Anthracnose is a severe disease present in several grape production areas; it is considered a tropical disease. In South Brazil, high relative humidity and other conditions favor the occurrence of fungal disease in vineyards. The objective of this study was to evaluate the anthracnose incidence progress in grape leaves in three scion cultivars (Concord, Bordo and BRS Carmem) in combination with three rootstock (1103 Paulsen, VR 043–43 and IAC 766), in regional climatic conditions favorable for disease development. The experiments were carried out on ridges with semi-trellis system. The experimental design was randomized blocks, with split plots, with 4 replications and 4 plants per plot. The plots were represented by 9 different combinations. Disease incidence was assessed at two week-interval from September to March (2010/2011, 2011/2012, and 2012/2013). At each sampling, disease was assessed 10 leaves of a same shoot of 6 plants for each cultivar/rootstock combination, for a total of 54 plants. All cultivar-rootstock combinations showed disease symptoms with highest disease incidence coinciding with the greatest amount of precipitation. Based on the relative area under the disease progress curve (AUDPC), the anthracnose incidence showed differences between seasons. Differences between rootstocks and rootstock/cultivar combinations were observed during the first and third season, but there was no consistency between the seasons, indicating that the variation in disease progress could be due to other factors, including as weather conditions, age of the vineyard and inoculum pressure.

New Training Systems for High-density Planting of Sweet Cherry

We assessed the vegetative growth and fruit production behavior of different sweet cherry cultivars grown using multiple new ultra-high-density planting (HDP) and training systems. An experimental orchard established in 2007 in the Ferrara province of Italy was used for this trial. The sweet cherry cultivars under evaluation were ‘Giorgia’ and ‘Grace Star®’ grafted on Gisela® 6; and ‘Black Star®’, ‘Early Bigi®’, ‘Early Star®’, ‘Ferrovia’, ‘Grace Star®’, ‘Kordia’, ‘Regina’, ‘Summit’, ‘Sweet Early®’, and ‘Sylvia’ grafted on Gisela® 5 rootstock. Each cultivar–rootstock combination was trained to spindle, V-system, or Super Spindle Axis (SSA). Planting densities ranged from 1905 trees/ha for spindle with Gisela® 6 to 5714 trees/ha for V-system and SSA with Gisela® 5. Vegetative growth, yield productivity, and fruit quality were evaluated. Among the three systems grafted on Gisela® 5, trees trained to the spindle system had the highest trunk cross-sectional area (26.2 cm2), followed by V-system (21.8 cm2) and SSA (20.2 cm2). Seven years after planting, ‘Ferrovia’ had the highest cumulative yield per hectare among cultivars on Gisela® 5, especially with V-system (50.5 t·ha–1) and SSA (52.2 t·ha–1) training systems. For cultivars on Gisela® 6, ‘Giorgia’ on had the highest cumulative yield per hectare after 7 years, but ‘Grace Star®’ on had higher production (≈14.0 t·ha–1 with V-system and SSA and 12.8 t·ha–1 with spindle) than ‘Giorgia’ in 2013.

THE MODELS FOR ESTIMATION OF A COMBINING ABILITY OF VARIETIES AND ROOTSTOCKS TO FORECAST YIELDING IN APPLE TREES

Vegetative reproduction of the best varieties of fruit crops by grafting on clonal rootstocks provides uniform trees, early onset of fruiting, it allows to create dense plantings. In order to identify rootstock, which gives maximum crop yield of the grafted varieties, a large number of expensive tests of cultivar-rootstock combinations, lasting dozens of years, are carried out, and the results of such empirical selection were reported in numerous publications. Therefore, so far there is no theory or methods of forecasting yields for trees grafted on indicators of variety and rootstocks. To increase efficiency of such searches and to lower expenses and time for their carrying out, there is the only possible way based on theoretical researches targeted to development of the principles of prediction of signs of grafted trees according to characteristics of varieties and rootstocks. Our researches summarized herein, are curried out to clarify the features of use of the principles and mathematical models of biometrical genetics for knowledge of communications in a system «grafted components—grafted plant». The implementation of this program started with studying possible applications of the formulas for calculation of the combinational ability of varieties and rootstocks as measures of their influence on the quantitative signs of the resulting combinations. The data on yielding in 28 such combinations (4 grades of apple, namely Jonathan, Golden Delicious, Idared, and Korah, and 7 rootstock, 1-48-1, 1-47-55, 1-48-46, M2, M3, M4 and M7), averaged up for 21 years fruiting, were used as the experimental material. It is established that the genotypes of varieties differ on both the productivity averaged for all rootstocks and the degree of dependence of this sign from the rootstocks. Besides, the rootstocks unequally differentiate varieties according to phenotypic manifestation of productivity. The widely used method and mathematical models for an assessment of combining ability of the parental lines of F1 hybrids can be successfully applied to estimate the influence of common and specific combining ability of the varieties and rootstocks on crop yield in grafted trees. It is based on the fact that in variation of the total combining ability of grafting components the general combining ability (GCA) as a function of additive genes, similar to that observed in the parental forms of hybrids, is relatively prevalent. When formulas of biometrical genetics are used, the calculations show that the general combining ability (GCA) of grafting components is 6.4 times more than their specific combining ability (SCA). It caused high efficiency of the forecasts on productivity of grafted trees based on the GCA of varieties and rootstocks. The high coefficient of correlation between the actual and predicted estimates of productivity has been noted (r = 0.930). Close correlation between the predicted on the GCA and actual estimates of productivity of the variety—rootstock combinations shows the high degree of integration of grafting components in the manifestation of quantitative sings of a grafted tree. The preliminary analysis revealed the possibility for further improving accuracy of such forecasts due to separating the linear component from the dispersions of the specific combinational ability (SCA) estimates.

МОДЕЛИ ОЦЕНКИ КОМБИНАЦИОННОЙ СПОСОБНОСТИ ПРИВОЕВ И ПОДВОЕВ ДЛЯ ПРОГНОЗА УРОЖАЙНОСТИ У ПРИВИТЫХ ДЕРЕВЬЕВ ЯБЛОНИ

Vegetative reproduction of the best varieties of fruit crops by grafting on clonal rootstocks provides uniform trees, early onset of fruiting, it allows to create dense plantings. In order to identify rootstock, which gives maximum crop yield of the grafted varieties, a large number of expensive tests of cultivar-rootstock combinations, lasting dozens of years, are carried out, and the results of such empirical selection were reported in numerous publications. Therefore, so far there is no theory or methods of forecasting yields for trees grafted on indicators of variety and rootstocks. To increase efficiency of such searches and to lower expenses and time for their carrying out, there is the only possible way based on theoretical researches targeted to development of the principles of prediction of signs of grafted trees according to characteristics of varieties and rootstocks. Our researches summarized herein, are curried out to clarify the features of use of the principles and mathematical models of biometric genetics for knowledge of communications in a system «grafted components-grafted plant». The implementation of this program started with studying possible applications of the formulas for calculation of the combinational ability of varieties and rootstocks as measures of their influence on the quantitative signs of the resulting combinations. The data on yielding in 28 such combinations (4 grades of apple, namely Jonathan, Golden Delicious, Idared, and Korah, and 7 rootstock, 1-48-1, 1-47-55, 1-48-46, M2, M3, M4 and M7), averaged up for 21 years fruiting, were used as the experimental material. It is established that the genotypes of varieties differ on both the productivity averaged for all rootstocks and the degree of dependence of this sign from the rootstocks. Besides, the rootstocks unequally differentiate varieties according to phenotypic manifestation of productivity. The widely used method and mathematical models for an assessment of combining ability of the parental lines of F 1 hybrids can be successfully applied to estimate the influence of common and specific combining ability of the varieties and rootstocks on crop yield in grafted trees. It is based on the fact that in variation of the total combining ability of grafting components the general combining ability (GCA) as a function of additive genes, similar to that observed in the parental forms of hybrids, is relatively prevalent. When formulas of biometric genetics are used, the calculations show that the general combining ability (GCA) of grafting components is 6.4 times more than their specific combining ability (SCA). It caused high efficiency of the forecasts on productivity of grafted trees based on the GCA of varieties and rootstocks. The high coefficient of correlation between the actual and predicted estimates of productivity has been noted ( r = 0,930). Close correlation between the predicted on the GCA and actual estimates of productivity of the variety-rootstock combinations shows the high degree of integration of grafting components in the manifestation of quantitative sings of a grafted tree. The preliminary analysis revealed the possibility for further improving accuracy of such forecasts due to separating the linear component from the dispersions of the specific combinational ability (SCA) estimates.

Rootstock-Mediated Effects on Watermelon Field Performance and Fruit Quality Characteristics

Most information on effects of rootstocks on watermelon [Citrullus lanatus (Thunb.) Matsum and Nakai] quality is derived from studies on disease resistance. The current study was undertaken to determine effects on yield and fruit morphometric and physicochemical characteristics of large-fruited, diploid and small-fruited, triploid watermelon cultivars grafted to interspecific hybrid rootstocks. Two yearly field experiments were conducted between April and July at the Zygi Experimental Station in Cyprus. Grafting increased marketable yield by 43% on average over nongrafted controls. No cultivar–rootstock combination resulted in commercially unacceptable (<10%) soluble solids content (SSC); only triploid cv. Extazy exhibited a rootstock-dependent decrease in SSC. Flesh firmness was increased by grafting on all rootstocks by an average of 36% over the nongrafted control. Variability in rind thickness was derived mainly from the scion. Rootstocks did not affect lycopene content and their effect on flesh color was minimal. Though grafting enhanced yield and fruit quality, choice of rootstock may adversely affect SSC of certain cultivars.

Influence of Rootstock on Plum Flowering Intensity in Different Growing Regions

The aim of the investigation is to evaluate the influence of different rootstocks on the flowering intensity of two plum cultivars: a hybrid `Kubanskaya Kometa` and European plum ‘Victoria’ in diverse locations. Sixteen well known European rootstocks were used, of which eight were clonal (St. Julien A, Brompton, Ackermann, Pixy, GF8/1, G5/22, GF655/2, Hamyra) and eight were seedlings (St. Julien INRA2, St. Julien d Orleans, St. Julien Noir, Brompton, Wangenheims Zwetche, St. Julien Wädenswil, Myrobalan, P. cerasifera var. divaricata). The evaluation was conducted in experimental orchards which were established in spring 2001 in Latvia, Estonia and Belarus. Trees were planted at a spacing of 5 × 3 m in four replications, three trees per plot. The obtained data from the years 2008-2012 are presented. The flowering intensity of plum trees depended on the cultivar rootstock combination. The influence of rootstock on flowering intensity differed between the years and growing region, and was closely correlates with meteorological conditions during the wintering period. Cv. ‘Kometa Kubanskaya’ had the highest blooming intensity in Pûre on rootstocks GF 655/2 and Wangenheims Zwetche; in Brest on Brompton seedlings, Julien d’ Orleans G5/22 and Ackermann; and in Polli on GF 8/1 and Brompton seedlings. ‘Victoria’ plum trees had the highest intensity of flowering on rootstocks Pixy and Wangenheims Zwetche in Pūre; on St. Julien INRA 2 and Ackermann in Brest; and on GF 655/2 and Ackermann in Polli.

OPTIMIZATION OF THE EVALUATION OF RESISTANCE TO SHARKA (PLUM POX VIRUS, PPV) IN CONTROLLED GREENHOUSE CONDITIONS IN THE APRICOT BREEDING PROGRAMME OF CEBAS-CSIC IN MURCIA (SPAIN)

In some countries like Spain or France, quarantine rules force researchers to evaluate the resistance to Sharka (Plum pox virus, PPV) in controlled isolated conditions. This method shows important limitations related to the management of plants in these controlled conditions with artificial cycles of growth in greenhouse and cold chamber alternatively. The objective of this study is to optimize the method of evaluation of PPV resistance in controlled greenhouse conditions. The steps of the method studied were the inoculation method (inoculation of rootstock or cultivar), the success in the grafting (depending on inoculation method, cultivar-rootstock combination, grafting in spring or autumn) and the efficiency of the process in each cycle of growth. Results showed that the inoculation onto the rootstock was much more efficient. As apricot rootstock, the 'GF305' and the 'Real Fino' seedlings had a similar behaviour. Differences observed in the grafting at different time periods were not related to the season (spring or autumn). Finally, the efficiency of the evaluation process was higher with the inoculation of the rootstock, mainly during the first cycle.

Bacterial Canker of Sweet Cherry in Oregon-Infection of Horticultural and Natural Wounds, and Resistance of Cultivar and Rootstock Combinations.

This study was done to (i) compare seven types of natural or horticultural injuries and wounds for incidence, severity, and mortality of infection of sweet cherry (Prunus avium) by Pseudomonas syringae pv. syringae; (ii) determine the relative resistance to bacterial canker of 14 cultivar-rootstock combinations; (iii) determine if P. syringae pv. syringae is transmitted by contaminated pruning tools; and (iv) determine if summer and winter pruning cuts become resistant to infection. Infection occurred at all of the seven types of injury and wound sites on both cvs. Sunset Bing and Golden Heart. Infection of inoculated wounds made in spring and summer (heading cuts when trees were planted, scoring cuts, and summer pruning) resulted in the greatest canker incidence and severity. Inoculation of heading cuts resulted in the highest tree mortality (86%). 'Bing' and 'Sweetheart' were the most susceptible cultivars while 'Regina' and 'Rainier' appeared to be more resistant. Bing trees had the highest mortality of any cultivar with 70% dead at the end of the 3-year study. Canker severity of the three rootstocks varied considerably but mortality was greatest for trees on Gisela 6 (77%). Bacterial canker was not transmitted in summer or winter by cutting through active cankers, then immediately using the same pruning tool to make heading cuts on healthy trees. Heading cuts became resistant to infection after about 1 week in summer and 3 weeks in winter. Results are discussed as part of an integrated management program for bacterial canker of sweet cherry.