Prediction infection risk on the basis of weather-related factors and Erwinia amylovora colonization in apple and pear flowers39-54.Views:149
Current infection risk prediction models utilize environmental parameters and field records, but do not take into account the estimated inoculum potential within the orchard. The object of this study was to survey the accuracy of three simple prediction methods under Hungarian climatic conditions, which could easily be used by the farmers. We also tested whether the accuracy of infection risk predictions can be improved by taking into consideration the incidence and/or rate of flower colonization by Erwinia amylovora.
After preliminary investigations in 1999-2001, data concerning the weather-related infection risk were recorded in 5 apple and 1 pear orchards in 2002, and in 12 apple and I pear orchards in 2003. The weather data were processed by the easy-to-use risk assessment models of the mean temperature prediction line (MTL), Smith's Cougarblight 98C and Billing's integrated system (BIS), and by the MaryblytTM 4.3 computer-assisted model for reference. The population size of E. amylovora in the flower samples was estimated within an order of magnitude by PCR.
For all years and orchards tested, Maryblyt indicated 35 days on which there was an acute infection risk. The same days were indicated by all 3 methods in 23 cases (66%), 8 days were indicated by 2 methods (23%) and 4 days were indicated by 1 method only. A similarly good correlation was found for prediction of the date of the first massive infection risk: in 2003, for instance, there was a perfectly consistent prediction by all 4 models in 9 of the 13 participating orchards. A coincidental forecast was provided by 3 of the 4 models in the other 4 orchards.
The results indicate that any of the risk assessment models could provide an increased accuracy of the actual infection risk prediction if combined with an estimation of the incidence of Erwinia amylovora colonization in the open flowers. We found no convincing differences in the size of the epiphytic population in flowers of cultivars possessing high or low susceptibility to Erwinia amylovora.
We conclude that the easy-to-use methods tested could be used by the fanners to recognize weather-related risks, especially when coupled with an estimation of the proportion of the pathogen-infested flowers. This local prediction would provide rapid information (faster than the regional forecast systems) specifically for a given orchard.
Water use of young apple trees related to leaf area development61-63.Views:123
Present paper describes an investigation concerning seasonal water use and foliage area development of apple trees. Sap flow velocity was measured in the trunks of five years old apple trees cv. `Florina'/M.26 by a thermal dissipation (Granier) method from 20th of May to the end of September in 1998. The development of foliage area was estimated by a method including leaf area measurements, recording of leaves and shoot length. The foliage area reached to 70% of the maximum yearly value at beginning of June. The remaining 30% developed to the end of August. The leaf area specific water use was considerable higher in June and July, than in second part of summer. The trends of ET-FAO and water use curves differed mostly in the late season: the ET-FAO curve falls quite in September compared to August, whereas the value of water use was a similar as in August. This insensitivity of ET-FAO in this period may be a great disadvantage while using the Penman-Monteith equation in irrigation scheduling of apple.
Influence of aromatic cytokinins on shoot multiplication and their after-effects on rooting of apple cv. Húsvéti rozmaring84-87.Views:180
Different aromatic cytokinins (BA, BAR, TOP and KIN) were tested alone or in combination for the shoot proliferation response of ‘Húsvéti rozmaring' apple scion. The best multiplication rate was achieved by dual cytokinin application (1 mg 1-1 BA + 1.5 mg 1-1 KIN). The rooting capacity was affected considerably by the position of shoots: transfer of the three-week-old shoots to the same or other proliferation medium in vertical position inhibited the following rooting totally. Post-effects of different cytokinins (BA and TOP) on subsequent rooting could be detected: BA increased the number of roots markedly, while TOP resulted in significantly longer roots.
Floral biological studies on pear cultivars in relation to fire blight susceptibility25-30.Views:142
Floral biological characteristics that may influence cultivar susceptibility to fire blight were studied in 10 pear cultivars in two Hungarian orchards from 1999 to 2003. The receptaculo-ovarial, automorphic nectary is usually bigger in tolerant cultivars than in susceptible ones. Nectary stomata are meso- or xeromorphic. Susceptible cultivars tend to have more xeromorphic stomata, where guard cells are located 1-3 cell rows below the epidermis. The size of nectar chambers is usually smaller in susceptible cultivars. Floral nectar, consisting mainly of glucose and fructose, is more abundant and less concentrated if the cultivar is susceptible to fire blight. The amount of chlorogenic acid was higher in the flowers of tolerant cultivars than in susceptible ones.
In vitro shoot multiplication of apple: comparative response of three rootstocks to cytokinines and auxin36-39.Views:192
Shoot multiplication responses of rootstocks cvs. M.26, MM.106 and JTE-H to different concentration of BA, BAR and IBA in eight various combinations were tested on MS-medium. The effect of hormones depended on genotype, type of cytokinin and interaction of cytokinin and auxin. Shoot multiplication was significantly enhanced with the use of BAR as cytokinin. High multiplication rate could be achieved in cvs. M.26, MM.106 and JTE-H: 7.7, 6.9 and 9.9 shoots per explant, respectively.
Single and dual effects of different cytokinins on shoot multiplication of different apple scions76-78.Views:148
Shoot multiplication responses of three apple scions to different concentrations of BA and BAR as single source of cytokinins and in combination with two concentrations of KIN were studied. The effects of hormones depended on genotype, type and interactions of different cytokinins. Use of BAR significantly enhanced the shoot multiplication of cv. Jonagold (6.5 shoots per explant). The multiplication rate of cv. Jonagold could not be improved by using the combination of BAR and KIN. The best proliferation was achieved by 1.0 mg 1-1 BA combined with 1.0 mg 1-1 KIN of cv. Prima..(8.1) and of cv. Galaxy (10.4).The effect of 0.5 mg 1-1 BA along with 1.5 mg 1-1 KIN was similar on multiplication rate (10.9) of cv. Galaxy.
Some structural characteristics of the flowers of apple cultivars with different susceptibilty to fire blight21-23.Views:106
Several morphological characters of the hypanthium (size and form of the surface, the shape of the hypanthium) and anatomical traits (number and pattern of stomata) of apple cultivars (Malus domestica L.) with different susceptibility to fire blight were studied. The size of hypantium surface was calculated by modelling the hypanthium with a truncated cone. Three types of hypanthium surface form have been revealed: straight, convex and a complex "shouldered" one. The angle between the style and the wall of the hypanthium was narrow or wide. The stomata on the hypanthium surface can be arranged in a zone in the middle third of the hypanthium or dispersed more or less evenly. The number of stomata/flower substantially differed among the cultivars examined. The highest stomata number was detected in the flowers of the tolerant cultivar (Freedom)
No single characteristics of the hypanthium could convincingly be correlated with susceptibility to fire blight. We suggest, however, that combination of morphological properties that sustain moist environment in the hypanthium contribute to susceptibility.
Sugar composition of floral nectar in sour cherry cultivars109-113.Views:157
The composition of floral nectar in sour cherry cultivars studied in 1997 at Újfehértó was in agreement with our previous data, the three most frequent sugar components being glucose, fructose and sucrose. Nectar secreted at night is generally more diluted than nectar produced during the day. None of the nectar samples produced at night reached the threshold value (100 mg/ml) of bee visitation. In the majority of cultivars the difference in concentration between night and day nectar is not too high, but in two cultivars, 'Korai pipacs' and ‘Újfehértói fürtös’ the difference is quite significant. Most sucrose was found in the nectar of cvs. 'Érdi jubileum' and ‘Újfehértói fürtös’, but a high amount of sucrose was measured also in the flowers of 'Korai pipacs' and 'Meteor USA'. Nectar concentration varies from opening of the flower to petal fall to a smaller or greater degree, depending on the given cultivar. From the 9 sour cherry cultivars studied ‘Újfehértói fürtös’ and Tandy 48' had the most attractive nectar for bees. There was no correlation between nectar composition and free fertilisation. On the basis of nectar composition the majority of the sour cherry cultivars studied can be classified into the sucrose-rich category; only one cultivar, 'Érdi jubileum' had a sucrose-dominant secretory product. The composition of nectar in the studied sour cherry cultivars is preferred by bees.
Study of Erwinia amylovora colonization and migration on blossoms of susceptible and tolerant apple cultivars15-19.Views:125
The stigmata of detached flowers of susceptible and tolerant apple cultivars were inoculated with about 104 gfp labeled Erwinia amylovora . There were no apparent differences in the colonization, multiplication and survival of the bacteria on the stigmatic surface of the culivars. Bacteria were washed down to the hypanthium surface 24 hours after inoculation. The visual symptoms of the infection were the discoloration and shrinkage of the floral parts. The gradual browning associated with the infection appeared first on the surface of the hypanthium followed by the discoloration of the style. The color of the filaments turned into brown only 120 hours after the inoculation. Bacterial cells were not detected in the tissues of the styles and filaments. The traits of the hypanthium surface are of prominent importance in the progression of the infection. The wrinkled surface, the convex shape of the outer epidermal cell walls with thin cuticle and the sunken stomata helped to preserve a water film for a longer period providing medium for the motility of the bacteria in the susceptible cultivar. Bacteria were restricted to small water droplets on the flat and waxy surface of the hypanthium of the tolerant cultivar and only a few were able to enter the tissues.
Large bacterium aggregations were detected in the intercellular spaces of the parenchyma of the susceptible cultivar 48 hours after the inoculation. In the next period the Erwinia amylovora cells gradually invaded the intercellulars of the hypanthium wall, the wall of the ovary and the pedicel. Low level of bacterium aggregation was found in the intercellulars of the tolerant cultivars. It is suggested that the progression of the infection was inhibited also by physiological factors.
Contributions to the resumption of growth in ecodormant buds of apple35-40.Views:110
The resumption of development in ecodormant buds in terms of establishing a functional vascular connection between the inflorescence primordia and spur tissues in apple trees was investigated. Differentiation of the xylem elements could be observed first in the pedicel of the flower primordium, in the middle of January. Much later (at the beginning of April) there were mature xylem vessels in the wall of the receptacle and, merely a procambial strand for the ovule primordium which was at this time an undifferentiated protrusion of meristematic cells, only. As for phenological development of buds incubated at a temperature of 20 °C, it was the slowest in buds sampled in January, faster in buds sampled in the middle of February and, buds from the middle of March responded very quickly. The function of temperatures needed both for xylem differentiation and for the flower primordium to achieve maturity is pointed out. The nature of frost damage in vessel elements, as well the relationship between chilling requirement and growth features of apple cultivars will be discussed.
Floral biological investigations of apple cultivars in relation to fire blight9-14.Views:140
Floral activity was studied in two apple cultivars: an Erwinia-tolerant (Treedorn') and a sensitive one (`Sampion'). Since more types of protogyny occur in apples, the period of stigma activity is different. Papillae of the exposed stigma in flowers of 'Freedom' function longer (usually more than a week) than in the delayed homogamous `Sampion'. Despite of this, cv. 'Freedom' is tolerant to Erwinia amylovora (Burr.) Winslow et al., suggesting no relationship between the floral biological type (including the exposure and longevity of stigma) and the infection by E. amylovora. According to SEM micrographs, nectary stomata in `Freedom' are already open in the flower bud, where nectar secretion starts and continues until the senescence of the stigma. However, the long period of nectar secretion does not create optimal conditions for bacterial growth, since nectar production is scant in the flowers of 'Freedom'. The surface of the nectary, its nectar-retaining capacity, and the amount and concentration of nectar may influence the susceptibility of apple cultivars. It is manifested well by the smooth nectary surface with nectary stomata rising slightly above the epidermis in flowers of cv. 'Freedom', contrasting the wrinkled, striate nectary surface with slightly sunken stomata in the flowers of 'Sampion'.
The effect of Regalis® (prohexadione calcium) on the reduction of fire blight (Erwinia amylovora) severity in apple trees61-66.Views:154
Due to the lack of effective and non-phytotoxic materials for control of the blossom and shoot blight phase of fire blight in pome fruit trees, two novel control strategies have emerged: shoot growth retardation by bioregulators and applying resistance inducer compounds. Prohexadione calcium (ProCa) is the active ingredient of the bioregulator Regalis® registered in several European countries. The reduction of shoot growth elongation is the most obvious effect of ProCa. Furthermore, it causes significant changes in the spectrum of flavonoids and their phenolic precursors, leading to the considerable reduction of susceptibility to fire blight.
In Poland, potted one-year-old apple trees of cvs. Gala Must grafted on M.26 and Sampion on M.9 (in 2001) as well as Gala Must on P.60 (in 2002) were treated with Regalis® at a range of concentration of 250, 150 or 150 + 100 ppm, respectively. The inoculation of shoots was made with the strain No.691 of E. amylovora (107 cfu/ml), on the 7th and 21st'day after treatments with Regalis. In Hungary, during the years of 2002 and 2003 one-year-old container grown apple trees of the cvs. Idared/M.9 and Freedom/M.9 were treated with the prohexadione-Ca, the active ingredient of Regalis® 100, 150 or 200 ppm, two weeks before inoculation with the Ea 1 strain of E. amylovora (107 cfu/m1).
In Poland, the suppression of fire blight in shoots reached up to 80%, depending on concentration and application time of Regalis®. In Hungary, the effect of prohexadione-Ca treatments, determined by the length of necrotic lesion developed, proved to be better than that of streptomycin used for comparison.
Phyl-Gold: a product to diminish russeting of 'Golden Delicious' apples131-133.Views:123
Producing high quality apples in mature trees of the cv. 'Golden Delicious' is rather difficult because of the russeting of it's fruits, especially in seasons of high relative humidity and/or wetness.
Earlier experiments proved the possibility to decrease russeting by treatments of GA4.7 during a period after petal fall.
Phyl-Gold, a product of Phylaxia Co. (ai. 10 g1-1 GA4.7) was applied to inhibit russet formation in fruit skin of 'Golden Delicious' apples. Four consecutive sprays were carried out (with 10 ppm a.i.) in weekly intervals, starting at petal fall and tank-mixed with the current pesticides of the plant protection program.
Due to the GA4.7 application the russet formation decreased at a rate of economical importance. As for the side-effects of treatments, fruit set was reduced slightly in trees treated, however, there was no consequent influence on return bloom.
Effects of crop load on tree water use in apple (Malus x domestica Borkh.)29-31.Views:108
Sap flow rate measurements were carried out during two consecutive ('on' and 'off') years in an apple orchard cv. 'Florina' M.26 to analyse the effects of various crop load on tree water use. Sap flow rate was measured by thermal dissipation method in trunks of nine trees from June to the harvest. Crop load was between 0.2-9.0 fruits • cm -2 of trunk cross section area (equal to 0.5-35.0 fruits•m-2 of leaf area), trunk diameter varied between 4.7-8.7 cm.
Total leaf area was estimated by leaf counting or using shoot girth and leaf area relationship. In both years, fruit growth rate was determined by measuring diameter of 280 marked fruits with 7 days frequency. Fruit volume calculated as a function of fruit diameter based on a previously determined relationship.
Total leaf area of trees ranged from 4.4 to 19.5 m2 and it was closely related to trunk cross section area. At high crop load the fruit growth rate peaked in August with 0.51.tree-l.day-1 and the leaf area specific total fruit volume reached 61 m2 before the harvest.
There was a linear relationship between total leaf area and daily water use, while the leaf area specific water use was influenced by crop load rate. The relationship was described by piecewise linear regression with the breakpoint at crop load rate of 12 fruits•m2 of leaf area. At low crop load the slope of the fitted regression line was less than at high crop load rate.
Field trials with non-bactericide products to control fire blight in apple orchards55-60.Views:125
Recently, novel strategies and chemical agents for prophylactic protection against the bacterial (Erwinia amylovora) disease fire blight are being sought. Resistance-inducing compounds, such as prohexadione-Ca represent promising alternatives. Prohexadione-Ca is the active ingredient of the bioregulator Regalis, currently being introduced in several European countries and overseas. Another product used in this study was Biomit Plussz, a leaf fertiliser providing harmonic supply of nutrient elements, the complete supply is assumed to improve the tolerance against diseases.
Treatments' effects of both of these products were compared to the effectiveness of treatments with antibiotics repeated twice, three or four times a season.
In the years of 2001 and 2002, the effectiveness of both Regalis and Biomit Plussz in reduction of incidence of shoot blight was similar, or proved to be superior to the check treatments consisting of repeated sprayings of antibiotics. Last year (2003) treatments of streptomycin resulted — although within the same magnitude — in a somewhat better control of shoot blight than sprayings with the other compounds.
As regards severity of blossom blight, inconsistent results were recorded concerning both Regalis and Biomit Plussz.
In general, prohexadione-Ca is less efficient for controlling flower infection by E. amylovora as compared to shoot infections, since successful prophylactic treatments are difficult to carry out early in the season. The highest effectiveness in fire blight management can, therefore, be achieved by using prohexadione-Ca (as preventive protection) in combination with streptomycin or other suitable antibiotics (as curative protection).
Floral attractivity of pear cultivar 'Cinderi'102-109.Views:121
The regularities of primary attractivity have been studied at the pear cultivar `Cinderi' for two years. Nectar quickly evaporates from the totally open nectary surface of pear flowers exposed to environmental effects, and the rhythmicity of nectar secretion can be determined with difficulty. Flowers do not function according to a unified endogenous rhythm, the whole tree becomes continuously attractive for insects, since it attracts insects on more occasions during the day with some of its flowers. During the warm afternoon hours there is usually no measurable nectar production. Pollen shedding is most intensive in the afternoon hours. Pear flowers produce little and diluted nectar, which often does not come up to apicultural expectations. The age of the flower does not significantly affect the quantity and refraction of nectar. The flowers of pear cv. ‘Cinderi' are delayed homogamous.
Post-effects of cytokinins and auxin levels of proliferation media on rooting ability of in vitro apple shoots (Malus domestica Borkh.) 'Red Fuji'26-29.Views:189
Rooting ability of in vitro apple shoots of 'Red Fuji' grown on proliferation media with different hormone content were tested at three IBA levels in root induction media. Rooting percentage could be slightly increased with an increase in IBA concentration in proliferation media. The highest IBA concentration (3.0 mg 1-1) in root induction media showed strong inhibitory effect on rooting capacity of in vitro shoots. The highest rooting percentage (95%) could be achieved by shoots grown on proliferation media containing TOP or BA+KIN as cytokinins before rooting.