Podosphaera Leucotricha Research Articles

Breakdown of Pl2, a major gene of resistance to apple powdery mildew, in a French experimental orchard

Pl2, a major resistance gene to powdery mildew originating from Malus zumi, is mainly used in apple‐breeding programmes. In an experimental orchard in France, an increase of susceptibility to powdery mildew was observed on apple genotypes carrying Pl2. This increase of susceptibility could not be explained by an effect of the age of the trees, or by an effect of the amount of inoculum on expression of the resistance Pl2. It was demonstrated by tests of pathogenicity in controlled conditions that isolates of Podosphaera leucotricha sampled in this orchard were virulent to Pl2. The appearance of virulent isolates within 6 years after planting apple genotypes selected for the presence of Pl2 resulted in a breakdown of the resistance. Ten years after planting, the percentage of genotypes that were still resistant to powdery mildew varied between 2 and 56%, depending on the progenies. This suggested that additional quantitative resistance genes may influence the durability of the resistance Pl2.

Mapping QTL involved in powdery mildew resistance of the apple clone U 211

AbstractScab and powdery mildew, caused by Venturia inaequalis (Cke.) Wint. and Podosphaera leucotricha (Ellis et Ev.) Salm. are the most important apple diseases. The apple clone U 211 is resistant to scab and is also highly resistant to powdery mildew under field conditions. The interval mapping method was applied for the identification of genomic regions conferring U 211 resistance to powdery mildew. The genetic maps of the ‘Idared’ and U 211 genome sectors were constructed using amplified fragment lenght polymorphism and simple sequence repeat markers and 98 individuals from the progeny of the cross ‘Idared’× U 211. On the basis of the phenotypic and molecular marker data 10 powdery mildew resistance quantitative trait loci (QTL) were identified in U 211 and ‘Idared’. One of the QTL in the clone U 211 explained 48‐72% of the phenotypic variation and its effect was stable over years.

Acetic Acid Fumigation of Apple Rootstocks and Tree Fruit Scionwood to Remove External Microflora and Potential Plant Pathogens

Acetic acid (AA) fumigation of rootstocks and dormant shoots was explored as a method of eliminating plant pathogens from propagation material. Dormant shoots were tested in early winter to determine the rate of AA vapor that they could tolerate before being damaged. Apricot (Prunus armeniaca), apple (Malus ×domestica), and peach (Prunus persica) shoots collected from a single site in Dec. 1999 tolerated 30, 12, or 6 mg·L–1 AA, respectively. Vineland 3 (V3) and Malling-Merton 106 (MM.106) rootstock liners fumigated with 1 mg·L–1 AA were adequately surface-sterilized although the effect on growth was not recorded. A similar experiment with Malling 9 (M9) rootstocks showed that 12 mg·L–1 AA would eliminate most surface microorganisims from roots although it delayed shoot growth when the trees were planted. The higher 15 mg·L–1 rate delayed tree growth and appeared to kill some trees. The 12 mg·L–1 rate prevented growth of Erwinia amylovora and Pseudomonas syringae pv. syringae bacteria on shoots even when an enrichment technique was used to detect them. Finally, when 96 `Jonagold' apple shoots known to be infected by Podosphaera leucotricha were fumigated with AA in 2001, none developed powdery mildew, although 99% of the control shoots did. These promising results suggest that further research should be done toward adapting AA fumigation for use by commercial nurseries.

Evaluation of hydrophobic and hydrophilic kaolin particle films for peach crop, arthropod and disease management

Hydrophobic and/or hydrophilic kaolin particle film treatments to peach (Prunus persica (L) Batsch) trees were evaluated for crop and pest management capabilities in six studies from 1997 to 2000. Unsprayed control and standard treatments, the latter consisting of a commercial pesticide program, were included for comparison. Treatments in initial studies were applied via handgun, which resulted in a uniform and heavy deposit of kaolin after the first application. In contrast, treatments in subsequent studies used airblast equipment, which provided a uniform but less dense coverage, even after multiple applications. Results showed that both formulations of kaolin provided control of oriental fruit moth (Grapholita molesta (Busck)), plum curculio (Conotrachelus nenuphar (Herbst)) and Japanese beetle (Popillia japonica Newman) that was comparable with or better than the standard pesticide program. Effective management of late season catfacing insects (tarnished plant bugs Lygus lineolaris (Palisot de Beauvois) and stinkbugs Acrosternum hilare (Say), Euschistus servus (Say), and E tristigmus (Say)) and leafrollers (undetermined species) was also observed, although kaolin applications significantly increased phytophagous mite (Panonychus ulmi (Koch)) levels. In contrast to arthropod management, kaolin failed to control either peach scab (Cladosporium carpophilum (Von Thumen)) or rusty spot (Podosphaera leucotricha (Ell and Ev) ES Salmon) in any of the 4 years of the study. However, hydrophobic kaolin provided effective brown rot (Monilinia fructicola (G Winter) Honey) control when applied via handgun, and partial control when applied via airblast; hydrophilic kaolin failed to provide any control. These results suggest that hydrophobicity and deposit density may be important factors for effective disease management. The application of kaolin significantly delayed fruit maturation, increased fruit size and increased soluble solids relative to the standard. This effect, attributed to a reduction in plant stress, also resulted in increased fruit number and yield on young trees, indicating that an accentuated beneficial response from kaolin applications may be possible.

Use of PCR and DNA hybridization for identification of pear powdery mildew caused by Podosphaera leucotricha

Polymerase chain reaction (PCR) amplification of the ribosomal gene internal transcribed spacer (ITS) region has been used to classify Podosphaera leucotricha from apple but not pear. Molecular information is needed to show the relationship between apple and pear powdery mildew. DNA was successfully extracted from cleistothecia, conidia and mycelial fragments from leaves and shoots of apple, pear and six unrelated hosts with symptoms of powdery mildew. PCR amplification of the ITS regions of P. leucotricha with primers that amplify non-specific fungal DNA resulted in a 506 bp PCR product. Sequencing of the PCR products from apple and pear from different orchard blocks produced identical sequences for the ITS region that did not differ from P. leucotricha sequences in the GenBank database. The sequence data was also used to select species-specific oligonucleotides for P. leucotricha that could be used in a confirmatory hybridization assay. The hybridization reactions were positive for eight out of nine apple and pear powdery mildew samples. Six other hosts with powdery mildew symptoms were negative when tested with the assay and showed that this DNA test was specific for P. leucotricha. In conclusion the PCR and hybridization assays should prove to be useful tools in monitoring both apple and pear powdery mildew for epidemiological studies.

Pre-selection of apple seedlings for partial powdery mildew (Podosphaera leucotricha Ell. et Ev. /Salm./) resistance

Incidences of powdery mildew were repeatedly evaluated for two years on 1 420 young seedlings of 20 progenies (of different levels of mildew susceptibility) in a green house, and then for 10 years on 642 seedlings in an orchard. Part of the seedlings in the orchard were pre-selected for the characteristic and others not. Except for the first scoring done in the first year, there was no correlation between mildew incidence on individual seedlings in the green house and their mean performance in the orchard. The seedlings with scores above 6 (resistant or tolerant) at the first stage of evaluation in the green house, however, yielded four times more desirable seedlings after final selection in the orchard than the mean of the total. The progenies that had a better healthy state as a whole yielded more partially resistant genotypes than those with low mean scores. Therefore, the progenies that most rapidly develop infestation on the whole lot should be discarded, whereas those that retain a healthy state longer should be subjected to individual selection according to the previous item.

RESPONSE OF SEVERAL APPLE VARIETIES TO POWDERY MILDEW (PODOSPHAERA LEUCOTRICHA) ATTACK IN CENTRAL TRANSYLVANIA CONDITIONS

The response of apple cultivars to powdery mildew attack – Podosphaera leucotricha (Ell. et Everh.) Salm. – on leaves and shoots, for seven years (1990-1996), emphasised a large variability for this character existing within 75 apple varieties tested in an experimental field at the Fruit Research Station in Cluj-Napoca, Central Transylvania, Romania. The experimental results confirmed that the cultivars of the Jonathan group are highly susceptible to powdery mildew (e.g. Jonathan, Jonne Spur, Jonathan Smith, Black John, Jonathan Watson, Nured Jonathan, Delia, Aromat de vara, Rosu de Cluj). Cultivars Gloster, Starkrimson and Prima were registered with a low attack degree. None of the tested cultivars were included in the category “No attack”. Out of all varieties, 21 of them representing 28.0% were registered with a very high attack, both on leaves and shoots.

Overwintering of Ampelomyces mycoparasites on apple trees and other plants infected with powdery mildews

Apple shoots and aerial parts of 13 other plant species infected with powdery mildews during the previous season were collected in late winter and early spring between 1998 and 2003 at a total of 34 sample sites in Hungary. Samples were examined for the presence of overwintering structures of Ampelomyces, common mycoparasites of powdery mildews. Pycnidia and resting hyphae resembling those of Ampelomyces were found on six plant species, including apple. Their viability and subsequent mycoparasitic activity of the hyphae emerging from the overwintered fungal structures were studied in vitro to determine whether they can serve as sources of primary inocula of Ampelomyces in the spring. Overwintered pycnidia of Ampelomyces collected in the spring, and produced in both the ascomata and the conidiophores of powdery mildews during the previous season, initiated the life cycle of these mycoparasites when placed close to fresh powdery mildew colonies in vitro. Similarly, thick‐walled resting hyphae, found in the dried powdery mildew mycelia which covered the overwintered aerial parts of the host plants, also germinated and gave rise to new intracellular pycnidia of Ampelomyces when powdery mildew colonies were inoculated with them in vitro. On apple trees, Ampelomyces mycoparasites overwintered as resting hyphae in the dried powdery mildew mycelia covering the shoots and in the parasitized ascomata of Podosphaera leucotricha on the bark and the scales of the buds. Approximately 31% of the field samples collected from apple trees in spring between 1998 and 2003 contained overwintered structures of Ampelomyces. Artificial bursting of apple buds in the laboratory showed that both P. leucotricha and Ampelomyces start their life cycle during or soon after bud burst, but Ampelomyces can only slowly follow the spread of its mycohost on infected leaves. Most probably, the mycoparasites did not overwinter in the dormant hyphae of P. leucotricha in the buds, but only on the bark and the bud scales, as their hyphae were not found in the young hyphae of apple powdery mildew that appeared on the leaf tissues during bud burst. This study demonstrated that Ampelomyces mycoparasites can survive the winter in the field as pycnidia and as resting hyphae in the dried mycelia of their mycohosts.

Development and ultrastructure observations of secondary hyphae of Podosphaera leucotricha on apple cultivars of varying susceptibility to powdery mildew

The development and ultrastructure feature of secondary hyphae of Podosphaera leucotricha were studied using light and electron microscopy. The percentage of development and length of secondary hyphae, differed in compatible and incompatible combinations. In compatible host-parasite combinations, hyphal cells of powdery mildew fungus contained a full complement of fungal organelles. There were differences of hyphal ultrastructure in compatible and incompatible host-parasite combinations, the main one was the appearance of dense material inside the nucleus, in the cytoplasm, and a few mitochondria.

First Report of Powdery Mildew Caused by Podosphaera leucotricha on Prunus africana in Kenya.

Prunus africana, formerly known as Pygeum africanum, is widely distributed in moist, tropical Africa and produces durable timber. Extracts from its bark are used in treatment of prostate disorders. Powdery mildew was observed on nursery-grown seedlings of P. africana in Kenya (Nyeri, Kiambu, and Kericho districts) in the dry seasons of 1998, 1999, and 2000. White ectotrophic mycelial growth was observed on leaves. The fungus caused stunting, distortion of leaves, surface necrosis of invaded tissues, and general decline in growth of seedlings that led to premature leaf fall and death. Invaded leaflets wilted and dropped, leaving behind a bare stem. The primary mycelium was hyaline, with no secondary brown mycelium. The conidial state was conspicuous, with conidia produced in chains. Appressoria were unlobed and nipple shaped. Conidiophores were straight and three-celled, measuring 75 to 112 μm. Conidiophore foot cells were topped by a longer cell and one or two shorter cells measuring 35 to 77 μm. Conidia had fibrosin bodies, were ovoid, and measured 27 to 30 × 17 to 18 μm. The fungus was identified by the International Mycological Institute IMI (W6496) as Podosphaera leucotricha (Ellis & Everh.) E. S. Salmon. Infected leaves of P. africana were deposited at the East African Herbarium, National Museums of Kenya (Accession No. KM-KEFRI/446/2001). Pathogenicity was confirmed by inoculating seedlings of P. africana by gently pressing infected leaves with abundant sporulation onto healthy leaves. The plants were then incubated under moist conditions for 48 h and thereafter maintained in a glasshouse. After 15 days, powdery mildew symptoms developed on seedlings. Examination of leaves confirmed that they were infected with Podosphaera leucotricha. Uninoculated control plants were free of powdery mildew. To our knowlege, this is the first report of Podosphaera leucotricha as a pathogen of P. africana. Reference: 1. H. J. Boesewinkel. Bot. Rev. 46:167, 1980.

Previous data on the relationship between the intensity of pruning and the degree of damage in integrated and organic applegrowing systems

In Hungary, fruit growers are increasingly interested in environmentally friendly growing methods, such as organic and integrated systems. Vital is the establishment of a strengthened system of cultivar-pruning-plant protection in production technology. Consequently, our aim was to examine the susceptibility of apple cultivars to diseases and pests and the effect of pruning technique on diseases and pests in organic and integrated growing systems.Two pathogens (Venturia inaequalis, Podosphaera leucotricha) and two pests (Leucoptera malifoliella, Pannonychus ulmi) were observed in organic and integrated systems under „strong” and „weak” pruning techniques. Our results on six cultivars showed that the pathogens and pests infested the trees more in the organic system, as compared to that of integrated production. The pruning technique affected mainly the susceptiblecultivars to diseases and pests. The „weak” pruning technique caused a higher level of diseases and pests infestations than the „strong” pruning technique, especially in the organic growing system. The likely reason is that the shoots grow fast and powerfully under “strong” pruning technique. This supports better preservation of the trees supported by susceptibility of plant tissues to diseases and pests.

A novel technique for evaluation of apple (Malus × domestica Borkh.) cultivars for susceptibility to powdery mildew

A technique for the evaluation of apple cultivars for susceptibility to powdery mildew caused by Podosphaera leucotricha (Ell. & Ev.) E. S. Salmon (anamorph Oidium farinosum Cooke) was tested at the Pacific Agri-Food research Centre (PARC), Summerland, BC. Shoots of test cultivars [Braeburn, Creston, Elstar, Empire, Fuji strain BC2, Gala strain Royal, Jonagold, McIntosh, Delicious red strain Bisbee, Shamrock, Silken, Sunrise, and one breeding selection (11w-17-85)], approximately 6 cm in length, were grafted on to branches of mature Jonagold trees in the spring and evaluated in the summer of the same year and in subsequent years after growth on the host tree. Incidence and severity of powdery mildew were evaluated in 1994, 1995, 1997, and 1998. They were not evaluated in 1996 because approximately half the grafts from the previous year did not grow and had to be replaced. The highest incidence of powdery mildew averaged 84% for Gala, compared with only 15% for Bisbee Delicious with the lowest incidence. Gala had the highest number of P. leucotricha conidia per cm2 of leaf area (4.9 × 104) compared to Bisbee Delicious (1.2 × 104). Some of the grafted cultivars were also evaluated for primary powdery mildew and fruit russetting in 1998 after the growth for three seasons. Jonagold had the highest numbers of primary infections and russetted fruit. Key words: Podosphaera leucotricha, breeding, cultivar resistance, pest management

Pruning and incidences of diseases and pests in environmentally oriented apple growing systems: some aspects

In Hungary, fruit growers are increasingly interested in environmentally oriented growing methods, such as organic and integrated systems. The main factor in creating such systems is the establishment of a system of cultivar-pruning-plant protection based on production technology. Therefore, our aim was to examine the susceptibility of apple cultivars to diseases and pests and the effect of pruning technique on diseases and pests in organic and integrated growing systems.
 Two pathogens (Venturia inaequalis, Podosphaera leucotricha) and two pests (Leueoptera malifoliella, Pannonychus ulmi) were observed in organic and integrated systems under "strong" and "weak" pruning techniques. Our results showed that, compared to integrated production, the pathogens and pests infected the trees more in the organic system. The pruning technique affected mainly the cultivars susceptible to diseases and pests. In general, the "weak" pruning technique correlated with a higher level of damage caused by diseases and pests than the "strong" pruning technique, especially in the organic growing system. The reason that techniques should be carefully chosen is that shoots grow faster and more vigorously after employing the "strong" pruning technique. This supports a better preservation of the trees, as a result of reduced susceptibility of plant tissues to diseases and pests.

GENETIC ANALYSIS OF A POLISH APPLE SELECTION U 211 AS A NEW SOURCE OF HIGH RESISTANCE TO APPLE POWDERY MILDEW

Breeding apple plants with multiple, durable resistances is an alternative way to control fungal pathogens and reduce any environmental impact due to pesticides use. The breeding of apple cultivars resistant to Podosphaera leucotricha could be much improved by marker-assisted selection. This investigation focuses on the identification of random amplified polymorphic DNA (RAPD) markers linked to the major genes for mildew resistance in a selection U 211 ('Primula' open pollinated). The analysis was carried out on 107 plants from progeny 'Idared'×U211 and parental plants. The cultivar Primula was also analysed. The selection U211 was found to be highly resistant to mildew in field conditions and transmitted a high level of resistance to the majority of its progeny. Moreover the V f gene from Malus floribunda, conferring resistance to scab, is present in this selection. As the RAPD marker for the Pl 1 gene from M. robusta (Markussen et al., 1995) is not present in the DNA of U 211, it is probable that a selection U 211 is a new source of mildew resistance. The RAPD marker technique was combined with a bulked segregant analysis (BSA). About 270 random decamer primers were tested by PCR analysis on the basis of resistant and susceptible DNA pools. Many polymorphisms between two pools were identified. Some of them seem to be useful for marker-assisted selection in apple breeding.

Efficacy of Kaolin-Based Particle Films to Control Apple Diseases

Studies were conducted from 1997 to 1999 to evaluate the effect of processed kaolin-based particle film applications on the incidence and severity of apple (Malus domestica Borkh.) diseases. Greenhouse and field studies demonstrated that pre-emptive application of hydrophobic and hydrophilic particles reduced the incidence of fire blight (Erwinia amylovora (Burrill) Winslow et al.) in blossoms and injured shoots. Hydrophobic and hydrophilic particles suppressed sooty blotch (Gloeodes pomigena (Schwein.)) and flyspeck (Schizothyrium pomi (Mont. & Fr.) Arx: anamorph Zygophiala jamaicensis Mason) to levels equivalent to conventional fungicides. In field studies, apple scab (Venturia inaequalis (Cooke) Wint.: anamorph Spilocaea pomi Fr.) was not suppressed by hydrophilic particles. Hydrophilic particles did not interfere with the action of conventional fungicides or the activity of calcium hydroxide to suppress apple scab. Hydrophilic particles did reduce powdery mildew (Podosphaera leucotricha (Ell. & Ev.) E.S. Salmon (anamorph Oidium farinosum Cooke)) russetting on fruit, but leaf infection was extensive. Accepted for publication 27 July 2001. Published 23 August 2001.

Polar — a potent Polyoxin B compound for controlling powdery mildews in apple and nectarine trees, and grapevines

The efficacy of Polar, a polyoxin B compound, in controlling powdery mildews was evaluated in commercial orchards and a vineyard in 1997–1999 in the Golan region of Israel. Foliar sprays of 0.0125–0.05% (v/v) suspensions of Polar [1-{5-N-(5-O-carbomonyl-2-amino-2-deoxy- l-xylonyl)-5-amino-5-deoxy-β- d-allofur anosyl uronic acid}-5-hydroxymethyluracil], sulfur, the new strobilurin fungicide Kresoxim-methyl, and sterol inhibitor (SI) fungicides inhibited the development of the powdery mildew fungi on leaves, fruits and leaves, and fruit clusters of field-grown apple trees, nectarine trees, and grapevines, respectively. The effectiveness of polyoxin B in controlling powdery mildews on apple trees and grapevines was similar to that of the standard treatment with the SI fungicides or sulfur. Applications of polyoxin B on nectarine trees provided better control of Sphaerotheca pannosa (Wallr.) Lev. than did the SI fungicides. Alternating treatment of polyoxin B with the SI fungicide, myclobutanil enhanced the inhibitory effect against Podosphaera leucotricha on apples and provided the best control of powdery mildew. These results indicate that the use of polyoxin B enables the number of SI fungicide treatments against powdery mildew to be reduced by up to 50%. Application of polyoxin B was not phytotoxic to plant tissue, and was more effective against mycelial growth and sporulation of powdery mildew fungi than against germination of conidia. At concentrations of 1, 10 and 100 mg/l polyoxin B inhibited germination of Uncinula necator conidia, by 52.5, 76.6 and 100%, respectively. A foliar spray (100 mg/l) suspension of Polar on greenhouse-grown grapevine leaves before inoculation with U. necator provided >90% protection against powdery mildew development, while spraying on mildewed leaves bearing sporulating colonies of U. necator suppressed the fungus. The inhibitory effectiveness of polyoxin B makes it a good candidate for the control of powdery mildews on grapevines, apple, and especially on nectarine trees.

Modelling and forecasting epidemics of apple powdery mildew (Podosphaera leucotricha)

A model developed to simulate epidemics of powdery mildew on vegetative shoots of apple generates two types of output. Firstly, it forecasts disease severity (percentage of host tissue infected) by incorporating effects on disease development of the amount of healthy susceptible tissue and current infectious (sporulating) disease, the level of initial inoculum (overwintered ‘primary’ mildew) and weather conditions. The effects of weather variables are considered on only two aspects of the fungal life cycle: initial spore germination and the subsequent development during the incubation period. Secondly, the model generates indices of the relative favourability of weather conditions on disease development by incorporating effects of weather on conidial production/dispersal and germination. On each day, forecasts of the (relative) severity of new infection and total current infectious disease are given for both types of output. The model was evaluated by comparing its predictions with the mildew epidemics observed in two unsprayed orchards over four years. In all the years, the temporal patterns of the predicted and the observed disease were generally similar. The pattern of the disease severity forecasts was marginally closer to the observed than that derived from two weather indices. Potential roles of the model in practical management of apple powdery mildew are discussed.

Evaluation of Malus species and cultivars at the Fruit Genebank Dresden-Pillnitz and its use for apple resistance breeding

Using the results of evaluation of Malus accessions during the last 20 years more than 15 new resistant apple cultivars were selected. The breeding aim was the combination of different kinds of resistance with good fruit quality. The best of these cultivars enclose resistance against Venturia inaequalis, Podosphaera leucotricha, Erwinia amylovora, Pseudomonas syringae, Panonychus ulmi and winterfrost. Different scab resistance sources (Vf, Vr, VA) found among the Malus species are combined in the most recent breeding lines.

Integrated control of powdery mildew on apple trees by foliar sprays of mono-potassium phosphate fertilizer and sterol inhibiting fungicides

Foliar sprays of 0.5–1% solutions of KH 2PO 4 (plus Triton X-100), commercial systemic fungicides, and an alternating treatment of phosphate fertilizer and systemic fungicides inhibited development of the powdery mildew fungus, Podosphaera leucotricha (Ell. & Ev.) E. S. Salmon, on shoots and leaves of apple trees. The effectiveness of alternating an appropriate systemic fungicide with a 1% solution of mono-potassium phosphate (MKP) was similar to that of the commercial treatment with the systemic fungicides. However, application of the systemic fungicides only, omitting the phosphate treatments when they were scheduled, was significantly less effective than either the phosphate or the alternation treatments. These results indicate that the use of phosphate fertilizer has a significant role in disease control, enabling reduced numbers of fungicide treatments against powdery mildew by up to 50%. These results were confirmed in large-scale demonstration trials conducted in commercial orchards in 1996 and 1997. In these trials, the tank-mix of 1% mono-potassium phosphate solution with a half rate of an appropriate fungicide was as effective or superior to that obtained by the standard fungicide treatment. Phosphate solutions were not phytotoxic to plant tissue. The inhibitory effectiveness of mono-potassium phosphate fertilizer makes it a potential major component of an integrated pest management program.

DEVELOPMENT OF APPLE FRUIT QUALITY WITHIN THE RESISTANCE BREEDING PROGRAM

In the Pillnitz apple resistance breeding program a number of desirable cultivars with resistance against economically important diseases were produced. The most important aim is the improvement of fruit quality in new resistant cultivars, combined with resistance to scab (Venturia inaequalis), mildew (Podosphaera leucotricha), fire blight (Erwinia amylovora) and other fungal and bacterial diseases. The cultivars with high fruit quality as 'Alkmene', 'Clivia', 'Elstar', 'Golden Delicious', 'Pinova', 'Piros' and others inherited a high fruit quality and regular yields in their progenies. New multiple resistant Re-cultivars were selected in different crossing populations, e.g. 'Resi', 'Renora', 'Releika', 'Rebella', 'Regia', 'Regine'.