The Effect of ‘Latent’ Virus Infections on the Yield of Maiden Trees on 20 Apomictic Apple Seedling Rootstocks

Five years’ experiments with apomictic apple seedling rootstock selections budded with apple cultivars have shown that incompatibility in Malus sieboldii, M. sargenti, M. hupehensis and their derivatives is mainly due to high sensitivity of the species rootstocks to viruses latent in commercial apple cultivars. The yields of maiden trees from rootstocks which were budded with material that was virus-free, infected with ‘latent’ viruses and infected with ‘latent’ viruses plus rubbery wood virus were 67%, 28% and 16%, respectively. There were, however, differences in the sensitivity reaction between the rootstocks tested. Fairly good compatibility with scions infected with ‘latent’ viruses was observed in the M. sieboldii root- stock selections 4542, 4556 and 4608 and in M. hupehensis.     

The Effect of Some Latent Virus Infections on the Growth and Cropping of Apples

SUMMARY

Seedlings of Newton Wonder apple multiplied vegetatively on Malus sikkimensis rootstocks and inoculated with a mixture of chlorotic leaf spot, scaly bark and dwarf viruses showed varying degrees of sensitivity to these infections. Although none of the seedlings showed clearly recognizable virus symptoms, many showed a very significant reduction in vigour; the girth differences between the infected and control trees were still increasing three years after inoculation.

The infected trees showed signs of nitrogen deficiency, which were confirmed by foliar analysis ; leaf nitrogen as percentage of dry weight was 10% lower than that of the controls. Four years after inoculation 43% of the infected trees had cropped, compared with 58% of the controls.

The results suggest that some selection of varieties and rootstocks for virus tolerance has taken place and that the evaluation of new seedlings on their own roots may not be a true indication of their performance on infected rootstocks.     

Reaction of 25 Apomictic Apple Rootstock Selections to Inoculation with Mixtures of ’latent’ Viruses

Malus sieboldii, M. sargenti and most hybrids showed sensitivity to inoculation with mixtures of ‘latent’ viruses from apple cultivars. The main symptoms were chlorotic leaf spots and leaf distortions combined with severe stunting in many seedlings. There was no reaction in the M. hupehensis group and Bittenfelder Seedling except for stem pitting or stem grooving symptoms in two hybrids. It is suggested that the same sensitivity reaction to apple ’latent’ viruses which leads to incompatibility when apple rootstocks are budded may also cause virus symptoms in apomictic species rootstocks. This would seem to apply especially to the M. sieboldii and M. sargenti groups, but probably not to the M. hupehensis group.     

A Note on the use of Honey-Bees as Pollinating Agents in Cages

Ninety-seven trees of 25 seedling varieties of apple, propagated on Malus sikkimensis seedling rootstocks, were inoculated by bud-grafting from a tree of Emneth Early showing symptoms of bitter pit. A further 97 trees were kept as uninoculated controls. The incidence of bitter pit in the two groups of trees was 67% and 68% respectively, from which it is concluded that bitter pit is very unlikely to be a virus disease.     

Virus,Fertilizer and Rootstock Effects on the Nutrition of Young Apple Trees

The chemical analyses of leaves of young apple trees on three clonal rootstocks with four different virus infections were compared. The trees were grown on plots that had received different N, P and K treatments for 40 years.

The viruses reduced leaf-N most in the one-year-old trees, and the effect was greater than that of 63 units per acre of fertilizer-N. Interactions occurred between virus and rootstocks; the leaf-N of trees on MM. 111 was reduced more by the viruses than that of trees on the other rootstocks. The omission of fertilizer-N had little effect on the leaf-N in one-year-old trees, but as they aged the effect became significant.

Fertilizer, virus and rootstock treatments all affected the levels of leaf-P. Virus effects were greatest on the leaf-P with rootstock MM. 104 and least with MM. 111, and leaf-P with MM. 104 was generally higher than that of trees on the other rootstocks. The omission of fertilizer-N increased leaf-P more than did the application of fertilizer-P.

Rootstock and fertilizer treatments affected the level of leaf-K throughout the experiment, but virus effects were significant only in the two-year-old trees.

Magnesium and calcium levels in the leaves were affected by fertilizer, root-stock and virus treatments. The presence of viruses usually reduced both magnesium and calcium, and trees on MM. 106 were generally higher in leaf-Mg and Ca than trees on the other rootstocks. The effects of the latent viruses on nutrition as indicated by leaf analysis were less than those shown on growth and flowering.     

Sorten-Unterlagen-Kombinationen f��r den Mostapfelanbau

In a field trial 5 rootstocks (seedling, M 25, A 2, MM 106, MM 111) and 13 varieties were investigated under Northeast German climate conditions to obtain information on the optimal rootstock-variety combinations for intensive juice apple production. Further the sugar and acid content of the fruits were determined. Due to the fact that exclusively scab resistant varieties were examined, the occurrence and stability of the resistance were of special interest. The most favourable rootstocks were M 25 (highest absolute yield) and MM 106 (highest specific yield). The varieties ??Judeline??, ??Rebella??, ??Resi??, ??Angold??, ??Schwechow 3?? and ??Priam?? had the highest absolute yield (mean of all rootstocks). The suitability of these six varieties for juice apple production was described. Although fungicides were used for controlling apple scab, particularly varieties with the Vf resistance factor were infected. A strong scab resistance had the variety ??Reka?? (Vr).     

Depressing Effects of Virus Infection on Adventitious Root Production in Apple Hardwood Cuttings

Adventitious rooting in dormant hardwood cuttings of MM. 106 apple rootstock was depressed by latent infection with five viruses, viz. rubbery wood, stem pitting, epinasty and decline, chlorotic leaf spot and platycarpa scaly bark viruses.

Both the number of rooted cuttings and the number of roots per rooted cutting were reduced, and fewer unrooted cuttings remained alive, thus representing a further potential loss.

The production of shoots suitable for use as cuttings was decreased from infected hedges, as was the ability of cuttings subsequently to become established and grow in the nursery.     

Moderne Apfelz��chtung: Genetische Verarmung und Tendenzen zur Inzucht

The apple varieties used in the modern commercial apple cultivation are nearly all genetically based on six relatively disease susceptible ??ancestorvarieties??: Golden Delicious, Cox Orange, Jonathan, McIntosh, Red Delicious and James Grieve. This applies to varieties bred after 1920 until today, including the new scab resistant varieties. The following article shows the dimension of the genetical narrowing and problems concerning the vitality of modern apple varieties. The author has compared the healthiness of old and new apple varieties in his trialorchard under no fungicide-spray conditions. As a conclusion out of his observations he calls to bethink an overall??not just reduced on scab resistance??term of vitality, as well as to use also the genetical potential of old apple varieties.     

Abteilung Kern- und Steinobst

Using varieties and rootstocks of apple and cherry as examples, the development of wide-ranging experimental work on pome and stone fruits is retraced. In the case of apple varieties, directed breeding programmes have produced new varieties showing successive and step-wise improvements. In the case of apple rootstocks, the excellent performance of M9 is beyond doubt. Competitiveness of sweet cherry production in the ??Altes Land?? has been maintained by several developments such as new varieties, slower-growing and more fertile rootstocks, and transparent roof-covers in order to avoid fruit-bursting. Changing personal responsibilities, ??historical merits?? and current personnel capacities are addressed. An outlook at future challenges casts a brief flashlight on perspectives for the next 25 years?? experimental work at the Fruit Experiment Station (OVA) Jork.     

柱型苹果引种研究

在山东省的自然条件下进行了柱型苹果引种试验。结果表明,3个柱型苹果品种生长结果正常,表现出典型的柱型生长习性。柱型苹果与生产上常见品种的花期相遇,可以互为授粉树。利用M_(26)和M_9矮化中间砧可有效地控制树体高度和侧梢的产生,促进成花和结果。不同砧木或中间砧对柱型苹果果实的品质性状有一定的影响。在高度密植(0.6m×1.0m)条件下,1年生和2年生柱型苹果即可获得较高的产量。在供试的3个品种中,以特拉蒙综合表现较好。杂交试验表明,柱型性状是由单个显性基因(Co基因)控制的,利用现有的柱型苹果品种作为亲本选育新的柱型苹果品种是可行的。     

Einfluss schwach wachsender Apfelunterlagen auf Wachstum,Ertrag und Fruchtgröße verschiedener Sorten – Teil IV: Abschließende Bewertung

From 2001 to 2005 the influence of the dwarfed apple rootstocks M?9 (clone: Burgmer 984), Fleuren 56, Supporter 1, P?16, P?22, J-TE-F, J-TE-E and M?27 on growth, yield and fruit size of the apple varieties ‘Elstar, Elshof’, ‘Boskoop, Herr’ and ‘Jonagored’ was investigated on the locations Auweiler, Dresden-Pillnitz, Osnabrück and Wurzen in Germany.All rootstocks induced a less vegetative growth as the rootstock M?9. In comparison with M?9 the crown volume of the trees ranged from 92% (Supporter 1) to 52% (M?27). The highest yield potential showed the rootstock P?16. Her specific yield (kg/m³) was 17% higher than the specific yield of M?9. All rootstocks produced a lower individual fruit size as M?9. J-TE-E and J-TE-F produced the lowest specific yield.     

Polar transport of [3H]-IAA in apical shoot segments of different apple rootstocks

Summary

The polar transport of [³H]-indole-3-acetic acid in apical shoot segments of clonal apple rootstocks (M.27, M.9, M.26, MM.111 and MM.104) was investigated in the UK using a donor-receptor system. The month in which the experiment was undertaken had a significant influence on the uptake and transport of [³H]-indole-3-acetic acid activity; uptake and transport were greater in June and July (faster extension growth period) than in August (slower extension growth period). Shoot segments from dwarfing rootstocks (M.27 and M.9) showed smaller uptake and less transport of [³H]-indole-3-acetic acid than those from invigorating rootstocks (MM.111 and MM.104). [³H]-indole-3-acetic acid was transported to the agar receptors through shoot segments from all the rootstocks in June and July; those from dwarfing rootstocks showing lower levels of transport than those from invigorating ones. However, in August, [³H]-indole-3-acetic acid activity from the agar receptors was detected only from shoot segments of invigorating rootstocks, which continued to produce extension growth slowly, when dwarfing rootstocks had already ceased shoot extension growth. These results are discussed with reference to the effects of apple rootstocks on the size of scions.     

Varietal Reactions to Viruses Causing Star Crack and Russet Rings on Apple Fruits

English sources of viruses causing star crack and russet ring were grafted to nine apple varieties. Only Golden Delicious reacted to all virus sources. This variety differentiated most clearly between different sources of star crack inoculum. Cox’s Orange Pippin and Spartan reacted to all star crack sources; Belle de Boskoop, Weisser Winterglocken, Lord Lambourne, Laxton’s Fortune and Worcester Pearmain reacted when inoculated with some sources but not others, while Granny Smith reacted to none. Golden Delicious developed leaf and fruit symptoms when inoculated with russet ring viruses, but Cox’s Orange Pippin, Spartan, Belle de Boskoop, Weisser Winterglocken and Granny Smith did not. Mailing II rootstocks developed characteristic leaf symptoms when infected with russet ring viruses. One inoculation source caused leaf mottling and necrosis and russeted warts on the fruits of Golden Delicious and Cox’s Orange Pippin. A rough-skin condition of Belle de Boskoop was perpetuated by buds and grafts but not transmitted. Some of the English viruses caused symptoms, in certain varieties, indistinguishable from diseases reported from Germany, Switzerland, the Netherlands, and North America.     

海洋生物功能肥对苹果果实病害的影响

苹果无袋栽培模式下常见的果实病害如苦痘病、黑点病和红点病等严重影响商品果率和经济效益。试验以10年生琴富1号为材料,研究海洋生物功能肥不同施用量对其果实病害发生情况的影响,结果表明,随施肥量的增加防治效果更佳,均优于豆粕肥及常规商品有机肥的防治效果。对12年生的中早熟且抗病性不同的苹果品种琴富1号、斗南、名月和绯红验证该肥料的防效,结果表明,处理组的总病果率均显著低于对照组。     

苹果砧木枝条电阻抗参数与其抗寒性的关系

 以18株2年生苹果砧木西府海棠（Malus micromalus Makino）实生后代单株为试材,研究了不经冷冻处理的枝条的电阻抗（EIS）参数与其抗寒性（电导法测定枝条冷冻半致死温度）的关系。结果表明,3个时期（3月、7月、11月）枝条的EIS参数高频电阻率r和低频电阻率r1、胞外电阻率re、弛豫时间τ与抗寒性呈显著负相关（r =﹣0.737** ~﹣0.877**）,在11月时胞内电阻率ri与抗寒性也呈显著负相关（r =﹣0.857**）,表明在非冷冻条件下可采用枝条的电阻率r和r1、胞外电阻率re、弛豫时间τ估测苹果砧木实生后代枝条的抗寒性。通过比较3个时期各参数的最终通径系数,得出re为估测枝条抗寒性最佳的参数。     

Rootstock influences the fruit mineral,sugar and organic acid content of a very early ripening peach cultivar

Summary

The influence of rootstocks differing in genetic origin and agronomic performance on the commercial characteristics and chemical composition of the fruit was investigated on the low-chill, very early ripening (fruit development period = 100 d) cv. Maravilha (Prunus persica (L.) Batsch) trained to a Y in a high density planting (2,500 trees per ha). Of the rootstocks tested, five belonged to P. persica (Harrow Blood, Ps B2, Ps C14, Rubira and Rutgers Red Leaf), three were hybrids of P. persica x P. dulcis (GF677, Hansen 2168 and Hansen 536) and two were complex hybrids of P. cerasifera (Mr S 2/5, M x P). The more vigorous graft combinations gave significantly higher yields. Rootstocks significantly influenced mineral content (N, K, Fe and Zn), sugars (sucrose and fructose) and organic acids (succinic) of the fruit, although these differences are not so important as to affect the commercial value of the fruit and to direct the choice towards one rootstock rather than another. Neither fruit weight, skin overcolour, shape nor refractometer value (°Brix) were affected by rootstocks. The short fruit development period together with the heavy pruning required for high density plantings presumably minimized differences in fruit quality between the graft combinations.     

Decline and Death of Pear on Quince rootstocks Caused by Virus Infection

Clonal quince rootstocks D, E, F and G were either stunted or killed by three viruses prevalent in pears, viz. sooty ringspot, stunt and chlorotic leaf spot. Conference pear trees grew normally on healthy and virus-infected Quince A and Quince C rootstocks, and on healthy Quince F and G rootstocks, but they grew poorly, and died during the second year, on Quince F and G rootstocks infected with a severe strain of sooty ringstock virus. The previously reported “incompatibility” of pear on Quinces D, E, F and G was probably caused by viruses, latent in pear scionwood, affecting these sensitive quince roots tocks.     

Crown rot (Phytophthora cactorum) of apple in Britain: Observations on natural outbreaks,and experiments on artificially inducing the disease in the field

Crown rot (Phytophthora cactorum) of apple came to prominence in Britain in the 1960s following the introduction of certain new types of clonal rootstock. Observations on crown rot outbreaks over the period 1976 to 1984 were as follows: only rootstocks MM.104 and MM.106 were affected; infection occurred in the bark of the rootstock axis below soil level; lesions caused girdling, and sometimes appeared above soil level and spread down the main roots to a limited extent; infection occurred during the growing season but disease development ceased with the onset of winter and did not resume the following year; trees on MM. 104 were susceptible throughout the life of the orchard while trees on MM. 106 were susceptible only during the establishment years; disease outbreaks occurred sporadically. Crown rot was induced experimentally on trees grafted on MM. 104 and on M.25 in field trials by irrigating for four to six weeks through inoculum applied to the base of the trees. No crown rot occurred on grafted MM.106 or on other grafted rootstocks in the same trials, although lesions developed above soil level on a few trees. The limited experimental data indicated that MM.104 was liable to attack throughout the growing season. The importance of environmental influences on the susceptibility of rootstocks to crown rot is discussed.     

High multiplication frequency and genetic stability for commercialization of the three varieties of micropropagated tea plants (Camellia spp.)

RAPD and microsatellite markers were used to determine the genetic fidelity of micropropagated plants from the three varieties of tea plant derived from explants of field grown mother bush as well as in vitro germinated seedlings. Rate of shoot multiplication was better from nodal explants than from shoot tips. A maximum of 32–33 shoots was observed in cotyledonary node in 1/2 MS medium with BAP (6 mg/l), GA₃ (1 mg/l) and IBA (0.5 mg/l). 90% of the in vitro derived microshoots were micrografted into rootstocks. The micropropagated plantlets showed both cytological and genetical stability. SSR primers showed complete stability among the regenerants. The results convinced that plants derived from axillary as well as adventitious mode of propagation can be genetically true to type. This cost effective technique would help in fast clonal propagation at a commercial scale.     

Evaluation of new rootstocks for resistance to soil-borne pathogens and productive behaviour of pepper (Capsicum annuum L.)

Summary

An evaluation of five rootstocks for pepper (Capsicum annuum L.) was carried out over a 3-year period on three farms in Campania (Italy). Pepper is very susceptible to soil-borne pathogens, especially Phytophthora capsici, Verticillium dahliae and Meloidogyne spp. (root-knot nematode). The lack of resistant hybrids and of crop rotation, and the longterm survival of propagules of the pathogen, have increased the risk of damage that so far has been controlled by pre-planting soil treatment with methyl bromide. The use of pepper grafted onto rootstocks resistant to the main soil-borne pathogens is not undertaken commercially in Italy because the available rootstocks are unsatisfactory. P. capsici, V. dahliae, Fusarium oxysporum, F. solani and M. incognita have been detected on farms where the new rootstocks were tested. Trials were performed on the same sites for 2 or 3 years in order to provide favourable conditions for parasites. Two rootstocks, ‘Graffito’ and ‘Gc 1002’, were found to be resistant to P. capsici. In the presence of an early, high population density of M. incognita, ‘Graffito’ showed good tolerance, while ‘Gc 1002’ was susceptible to the root-knot nematode. In addition, both rootstocks showed good compatibility with the different scions tested and did not decrease vegetative growth, fruit yield or the size of the scions. In contrast, in the presence of V. dahliae, F. oxysporum and F. solani, none of the rootstocks tested was sufficiently resistant to vascular or crown and root rot damage.