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.     

In vitro screening of the world apple germplasm collection for resistance to Phytophthora cactorum crown rot

Five hundred and sixteen accessions from the USDA world apple germplasm collection were screened for resistance to Phytophthora cactorum, causal agent of apple crown rot. In vitro, dormant excised twigs were inoculated with P. cactorum. Lesion length was used as a measure of relative resistance. Eighty-two plant-introduction cultivars were significantly resistant compared to 162 very susceptible cultivars, including M9 moderately resistant rootstock. Of the 82 cultivars, 16 were considered to be very resistant while 66 were moderately resistant. These results indicate variation in resistance, and suggest the possibility of breeding resistant rootstocks to control the disease.     

The Phytophthora diseases of apple

The most important Phytophthora pathogens of apple are P. cactorum and P. syringae, although other species may be locally significant. P. cactorum is widespread in the apple growing regions of the world and causes girdling bark rots on the scion (collar rot) and on the rootstock (crown rot), necrosis of the fine root system (root rot) and fruit rot. P. syringae is a significant pathogen of apple only in north-western Europe, where it causes collar rot but is most damaging as a cause of rot in stored fruit. Several other species of Phytophthora have been implicated in crown rot and root rot.

Bark rots due to Phytophthora spp. have distinctive features, such as mottled green/ orange/brown coloration of necrotic tissue, but may be confused with other causes of bark death. Isolation of the pathogen is therefore essential for diagnosis, and is now made easier than formerly by the use of selective media. Phytophthora fruit rot is usually distinctive, and isolation from diseased tissue is readily achieved by conventional methods.

P. cactorum and P. syringae are homothallic, soil-borne species. The principal peren- nating structure is the oospore. Zoospores are the main infective structures and are relatively short-lived. Mycelium and sporangia have intermediate survival characteristics. The longevity of ephemeral stages is favoured by moderate soil moisture and low temperatures. Growth and reproduction is associated with the colonization of living tissues. The two species have different temperature/growth characteristics. Oospore germination and sporangium production require soil moisture near to saturation, while zoospore release and motility depend on the presence of free water. The flexible growth response of these pathogens permits them to cope with fluctuating soil conditions.

P. cactorum and P. syringae cause diseases of a range of other economic plants, woody and herbaceous. There is evidence for host adapted strains in P. cactorum.

Phytophthora pathogens may be present in the soil when apples are planted or enter with planting material, in irrigation water, on animals or on implements. Once present, they may regenerate and produce durable increases in inoculum content of soil by colonizing live, abscissed apple organs such as leaves and fruit. Other plant species in orchards may also be important in inoculum regeneration.

Infection of unthickened tissues is direct or via stomata or lenticels. Bark may be infected directly through wounds, growth cracks or lenticels, or indirectly via unthickened roots.

Growth of the pathogens in host tissues is intercellular and intracellular. Susceptibility to bark rot is related to the effectiveness of phelloderm barriers in walling-off fungal growth. Attempts to relate the biochemical constituents of bark to resistance have been inconclusive.

Disease incidence and development is affected by the availability of water above ground and in the soil, soil type, tree age, the height of the graft union, the interaction between scion and rootstock and soil management techniques. Seasonal influences on disease reflect climatic effects on pathogen activity and cyclic changes in tissue resistance. Bark diseases due to P. cactorum are associated with the growing season, while those due to P. syringae are associated with dormancy of the host.

Host resistance and the manipulation of cultural conditions are the most effective means of disease control. The early selection for resistance in breeding material is complicated by the fact that susceptibility to collar rot develops only in mature trees, and the conditions required to induce crown rot experimentally in susceptible rootstocks are not fully understood. Other methods of control are the use of chemicals protectively or cura- tively and the use of Phytophthora-iree planting material. The possibilities of biological control are at an early stage of investigation.     

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Susceptibility of Gisela 5 and Maxma 14 cherry rootstocks to Phytophthora cactorum, P. citrophthora, P. citricola and P. parasitica was evaluated. All Phytophthora species were pathogenic to both of the cherry rootstocks tested. The level of susceptibility, however, varied according to Phytophthora species. P. citrophthora and P. parasitica isolates were the most virulent. P. citricola showed moderately virulence. The least virulence was shown from the P. cactorum isolates. Both rootstocks showed similar susceptibility.     

Studies on the possible role of micropropagation in the dissemination of the strawberry crown rot pathogen Phytophthora cactorum

Summary

Attempts to develop a method for establishing latent infection by the crown rot pathogen (P. cactorum) in strawberry stolon tips or unrooted plantlets were largely unsuccessful. One month after dipping stolon tips in suspensions of zoospores (from 10 to 10³ ml^?1) 6% had died and 6% had become severely necrotic; only 2% of stolons with no obvious necrosis yielded P. cactorum in isolation on a selective medium. When young, pre-rooted plantlets were sprayed with more concentrated zoospore suspensions (from 10³ to 10⁵ ml^?1) and grown on for only one week, 9% died, 51% became necrotic and 40% remained apparently healthy; 22% of the “healthy” plantlets yielded P. cactorum. The frequency of isolation from different parts of the plantlets indicated that most infections originated in the base of the crown, probably via root initials. When 298 stolon tips and 357 meristems were excised from symptomless plantlets one week after inoculation with a suspension of 10⁴ zoospores per ml, P. cactorum grew conspicuously into the culture medium and killed the plant tissue in 6% of stolon tip cultures and in 0.8% of meristem cultures. Of 380 micropropagation cultures successfully established from explants after inoculation not one yielded the pathogen on destructive sampling although other microorganisms were detected. It is concluded that the crown rot fungus does not become cryptically established in micropropagation cultures of strawberry and that, conversely, the technique of micropropagation is a reliable way of ensuring freedom from this pathogen in plant material.     

Rootstock influence on ‘delicious’ and ‘golden delicious’ apple fruit quality at harvest and after storage

The influence of 9 rootstocks (M2, M7, M25, M26, MM104, MM106, MM109, MM111 and seedling) on fruit quality at harvest and after storage of ‘Wellspur Delicious’ (WS) and ‘Goldspur’ (GS), and of 3 rootstocks (M7, M26 and MM106) on fruit quality of ‘Red King Delicious’ (RK) and ‘Golden Delicious’ (GD) apple (Malus domestica Borkh.) was evaluated during a 4-year period. Fruits from trees on M26 were larger, developed earlier color and soluble solids (SS), and maintained higher levels of acidity (at harvest and during storage) in comparison with other rootstocks. Fruit from trees on M2 tended to have high SS. Fruit color from trees on MM104, MM106 and MM109 tended to be comparatively poor. There were significant rootstock effects on SS, starch, acidity, color, circumference, weight and box size.     

Relationships among mineral nutrition,ethylene and post-harvest physiology in apples on six rootstocks

The relationships among several mineral elements of August-sampled leaf October-harvested fruit, maturity and post-harvest quality factors of ‘Starkspur Golden Delicious’ apple trees grown on Seedling, Malling (M) 1, Malling Merton (MM) 106, M 7, Oregon Apple Rootstock (OAR 1) or M 26 in a high-density orchard during 1980–1982 were evaluated. Positive correlations were found between leaf N, K and P and fruit N, K and P, respectively, in most rootstocks. Leaf Ca did not correlate with fruit Ca; thus leaf analysis cannot be recommended for estimates of fruit Ca. Both leaf and fruit N positively correlated with fruit green color and negatively with fruit soluble solids in all rootstocks. Fruit Ca and fruit P were both negatively correlated with fruit soluble solids at harvest and after 6 months of 0°C storage for all rootstocks. The ratio of fruit $\text{N}\text{Ca}$ was positively correlated with internal ethylene in MM 106, M 7 and OAR 1, while fruit $\text{K}\text{Ca}$ ratio was positively correlated with titratable acidity in all rootstocks. Fruit Ca showed negative correlations with bitterpit, storage rot and field internal ethylene, but positive correlation with firmness. Yield was positively correlated with leaf and fruit N, Ca and Cu but slightly negatively correlated with B of those tissues. Higher yield was associated with lower leaf K concentrations. Fruit green color was negatively correlated with soluble solids and titratable acidity. Fruit dry matter was highly positively correlated with soluble solids and titratable acidity in MM 106, OAR 1 and M 26. Soluble solids at harvest were strongly predicted by pre-harvest dry matter.     

The Relationship Between Growth Vigour of Rootstock and Phenolic Contents in Apple (Malus × domestica)

The aim of the study is to determine the effect of different growth vigorous rootstocks on phenolic compounds in leaves of apple. For this purpose it was used the leaves of cultivar ‘Red Chief’ grafted on dwarf (M9), semi-dwarf (M26) and semi-vigorous (MM106) rootstocks. During mid-July, the leaf samples were taken from the middle part of annual shoots. Phenolics of the leaves were determined by HPLC analysis. While significant differences among the rootstocks for p-hydroxybenzoic acid, eriodictyol, ferulic acid and p-coumaric acid were detected, these differences were insignificant for gallic acid and quercetin. It was shown that semi-vigorous rootstocks (MM106) had higher phenolic contents in total than the other two dwarf rootstocks. In addition, apigenin-7-glucoside, chlorogenic acid, caffeic acid, rosmarinic acid, epicatechin, syringic acid, catechin, rutin, resveratrol, hesperidin, naringenin, luteolin, apigenin and acacetin could not to be detected. Data showed that there is the relationship between growth vigour and phenolic contents of apple leaves. Especially, p-hydroxy benzoic acid and p-coumaric acid contents were higher in semi-vigorous rootstock than in dwarf rootstock.     

Performance of ‘Discovery’ apple on M.9, M.26 and MM.106 rootstocks at two densities

Summary

The apple rootstocks M.9, M.26, and MM.106 were evaluated for their efficiency in bringing ‘Discovery’ apple trees into production. The experiment, carried out over a ten- year period compared two planting densities at 1666 and 3333 trees per ha. Tree vigour differences between rootstocks were measured in term of trunk growth, tree volume, weight of branches pruned off and final weight of the above-ground parts of the trees. Fruit production is presented both as total yield and as the weight of first class fruit. Fruit colour development is also shown. Cropping efficiency is calculated and presented in relation to the different vigour measurements. The results confirm that ‘Discovery’ is slow to come into production. M.9 was the most productive rootstock, but due to vigour differences MM.106 gave the same yields per tree, although the latter had the lower yield efficiency. M.26 performed poorly; its vigour was similar to M.9 but it produced the lowest yields.     

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.     

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.     

Apple Rootstock Studies: Fifteen Years’ Results with Malling-Merton Clones

The field performance of 27 apple rootstock clones, including M.XXV and all the Malling-Merton ones is reviewed over a fifteen-year period. Three scion varieties were used, Cox’s Orange Pippin, Jonathan and Ellison’s Orange, and the trials were planted both on loam and on sand soil types.

None of the new clones made trees as small as those on M.IX, their vigour ranging from that of M.VII to that of M.XVI. MM.106 made trees similar in size and cropping to those on M.VII on the loam soil, but on the sand they were smaller. MM.I06, unlike M.VII, was free from the suckering habit. Trees on MM.III and M.Il were similar in size but Cox on MM.III yielded 20% more fruit over the whole period of the trial and during the years 11 to 15. Trees on MM.I04 were heavy-bearing and larger than those on M.Il and MM.III. In the very vigorous group, MM.Iog cropped heavily but was poorly anchored. Trees on M.XXV were superior in this respect and cropped more heavily than those on M.XVI. Cox and Ellison were unthrifty on 829, but the Jonathan trees behaved normally. Jonathan on MM.102 showed severe interveinalleaf scorch symptoms of magnesium deficiency and cropping was poor.

Many of the new rootstocks fell into similar vigour groups. It is suggested that, in other apple-growing areas of the world, other rootstocks besides MM.104, MM.106, MM.III and M.XXV, which were selected .for English conditions, should be tried experimentally. The data presented suggest MM.1O1, MM.103, MM.110, MM.115 and MM.116 as worthy of local study in addition to the four others.     

Investigations on Chlorosis of Fruit Trees.: III.—A Chlorosis of Plums Due to Potassium Deficiency.

Summary

Grafting is a suitable method to control soil-borne diseases in melon (Cucumis melo L.) crops. To date, several Cucurbita species and their inter-specific hybrids have been tested as rootstocks. However, graft-scion incompatibility and lower fruit quality have prevented their commercial use. The wild accession ‘Pat 81’ ssp. agrestis of C. melo is highly resistant to Monosporascus cannonballus Pollack et Uecker root rot, and develops a root system that is more suitable to withstand infested soils than that of cultivated melon. The potential of ‘Pat 81’ as a rootstock for melons (e.g., ‘Piel de Sapo’ type, C. melo ssp. melo) compared with the popular rootstock ‘RS 841’ (Cucurbita maxima Cucurbita moschata) has been evaluated here. The response of grafted plants to Monosporascus root rot disease, and rootstock effects on plant performance and fruit quality have been investigated using both classical methods and modern technologies (e.g., root image analysis and real-time PCR). The results indicate that, during infection, the root system of ‘Pat 81’ adapts to the needs of the aerial part of the ‘Piel de Sapo’ scion, displays a high level of resistance to M. cannonballus (similar to ‘RS 841’), and provides the plant with more healthy roots, with a higher root/vine biomass ratio compared with non-grafted ‘Piel de Sapo’. In addition, ‘Pat 81’ rootstock retains its favourable root structure (i.e., larger total length and root area) to withstand soil stress. In healthy soils, ‘Pat 81’ rootstocks had less effect on fruit quality than ‘RS 841’, leading to a lower percentage of non-marketable products. The high resistance of ‘Pat 81’, and its reduced effect on fruit quality, point to it as a good rootstock for the grafting of melons to resist M. Cannonballus infested soils.     

Influence of rootstock on orchard productivity and fruit quality in peach cv. ‘Redhaven’

Summary

We have evaluated the influence of four different peach rootstocks (Prunus pumila,‘GF 655/2’ ,‘Missour’ and ‘GF 677’ as a standard) planted in medium-heavy to heavy soil on phenological events (flowering and harvest date), growth, yield, fruit quality and mortality of peach (P. persica L.) scions of cv. ‘Redhaven’. At the end of flowering, there were no significant differences between the different rootstocks in the years 1999, 2000, 2003 and 2004. In 2001, trees grafted on P. pumila reached the end of flowering 2 d before trees grafted on the other rootstocks. ‘Redhaven’ fruits ripened on the same day on trees grafted on the different rootstocks. The differences were only between years. The results showed that significantly less vigorous trees, according to their trunk cross-sectional area (TCSA) and canopy volume, with the lowest yield, were observed on P. pumila rootstock. The rootstock P. pumila had a significant negative influence on fruit dimensions and mortality was 50%. Trees grafted on ‘GF 655/2’ rootstock produced significantly lower yields than those grafted on ‘GF 677’ or ‘Missour’ rootstocks. Only the ‘GF 655/2’ rootstock had root suckers. Trees grafted on ‘GF 677’ rootstock were significantly more vigorous than on the other rootstocks, and produced the highest yield with good fruit quality. The final canopy volumes of peach trees grafted on the different rootstocks were very different. The most vigorous trees were those grafted on ‘GF 677’ rootstock, where the final tree volume was 12.8 m³. Trees grafted on P. pumila and ‘GF 655/2’ had significantly lower TCSA values than on the other rootstocks.     

The relative effects of rootstocks and calcium sprays on the appearance of internal breakdown and superficial scald of ‘Red Delicious’ apples during storage

The 2-year investigation involved storing fruit samples from each tree in a trial of 8 rootstocks with the locally selected ‘Lalla Red Delicious’ to see how the storage characteristics were modified by rootstock and/or calcium sprays.The 6 spray applications of calcium made a significant reduction in the incidence of internal breakdown in both years, although the magnitude of the response varied from rootstock to rootstock in 1976. There were no significant rootstock effects in 1975, and in 1976 they were eliminated where calcium sprays were used. In the absence of calcium sprays in 1976, apples from ‘M. 16’ produced significantly more internal breakdown than those from any of the other stocks, with ‘MM. 107’ producing the second highest level. At the other end of the scale, apples from ‘MM. 110’ had the lowest incidence, closely followed by ‘M. 1.’ The remaining 4 stocks (‘11 immune’, ‘M.13’, ‘M.25’ and ‘Seedling’) gave intermediate readings and were not significantly different from each other.The calcium spray treatments also significantly reduced the incidence of superficial scald with all rootstocks. The main rootstock effect observed was that apples from ‘MM. 110’ and ‘M. 1’ had significantly less scald than from 5 of the other 6 rootstocks.     

Dissemination of Phytophthora cactorum, cause of crown rot in strawberry,in open and closed soilless growing systems and the potential for control using slow sand filtration

Closed (recirculating) growing systems provide a greater potential for the dispersal of water-borne plant pathogens and disease expression compared to open (run-to-waste) systems. Here we studied the effects of three soilless growing systems (open, closed, and closed with slow sand filtration) on the dispersion of Phytophthora cactorum propagules and the severity of the crown rot disease in strawberry (Fragaria × ananassa Duch.). The plant-growth medium used was coir fiber. The three growing systems showed the same density of P. cactorum propagules in the water drained from the growing media. However, propagules of this pathogen were not detected by the baits in the filtered solution recovered from slow sand filtration. In all systems Phytophthora propagules dispersed from the inoculated plant to adjacent uninoculated plants. At the end of the first crop no differences in the severity of crown rot were found between the different systems of crop culture. However, at the end of the second crop cycle, crown rot in the closed soilless system without slow sand filtration was more severe than in the other two systems. These results demonstrated that the commercial potential of slow sand filtration to prevent propagule dispersal and hence suppress crown rot in strawberry crops grown in a closed culture system.     

Auxin transport capacity in relation to the dwarfing effect of apple rootstocks

SUMMARY

Basipetal auxin transport in shoots obtained from dwarfing (M.9) and less-dwarfing (MM.Ill) apple rootstocks was compared by measuring the distribution of ¹⁴C-[carboxy]-labelled indole 3-acetic acid supplied to the ends of shoot segments. Auxin was transported at a greater velocity in MM.111 than in M.9 in both woody and non-woody segments, and was effectively blocked by 2,3,5-triiodobenzoic acid. The velocities of transport were approximately 8 mmh-¹ in M.9,and 13 mmh-¹ MM.111. There was relatively little transport in the acropetal direction, and there were no significant differences between the two rootstocks in total auxin uptake. Chromatographic analysis suggested that the metabolismof the auxin supplied followed similar patterns in both rootstocks. It is proposed that the slower auxin transport in M.9 results from a lower capacity for auxin efflux from transporting cells. A limiting auxin transport capacity could explain the reduced cambial activity and subsequent xylem formation in the dwarfing M.9 rootstock, and thus make an important contribution to the dwarfing effect.     

Einfluss verschiedener Unterlagen auf vegetative und generative Parameter bei der Apfelsorte ‘Topaz’ unter biologischen Anbaubedingungen in Ostösterreich

In autumn 2008, in the research orchard of the University of Natural Resources and Life Sciences in Vienna, the apple cultivar ‘Topaz’ was planted on the rootstocks M9 (clone T337) with and without ‘Rubinola’ as interstem, M26, M7 grafted at 25?cm and at 55?cm respectively, M111 and ‘Bittenfelder seedling’, trained as spindles and tested for eight years according to organic production rules. The trees on seeding grew very vigorously, followed by MM111 and M7 normally grafted; the M7 highly grafted trees showed less vigor, comparable with M26, while the trees on M9 with and without interstem grew very weakly. Tree losses were only observed on M9 without interstem. The highest yields per hectare were found on M7 normally grafted, followed by M26, M7 highly grafted and M9 without interstem. M7 highly grafted showed the highest single fruit weights, followed by MM111, at the other end were M9 with and without interstem, and M26. The rootstock M7 grafted at 55?cm combines a medium growth with high yield and good fruit quality and therefore can be recommended for dry areas like our site. M9 without interstem showed a higher specific yield and fruit firmness after storage compared to the variant with interstem. Whether these advantages for ‘Topaz’ on M9 can be combined with a higher grafting height as effective preventive method to control Phytophthora cactorum, has to be examined in further research.     

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.     

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.