Apple Hybrids Research Articles

Evaluation of the scab immune apple varieties and hybrids suitable for juice production

Based on the technological evaluation of 105 immune V f and highly resistant V m to scab apple varieties of the All-Russia Research Institute for Horticultural Plant Breeding suitable for juice production, 16 varieties perspective for raw material production are specified with the juice output from 70.4% (Orlovskoe Poles’e) to 65% (Rozhdestvenskoe), the content of the soluble dry substances not lower than 11%, and organoleptic properties higher (4.5–4.3 points) than in the control variety Antonovka obyknovennaya. A higher juice output is reliably defined in the summer varieties as compared to the winter ones. The character of appearance of some technological features of the fruits (juice output, content of soluble dry substances, organic acids, P-active catechins) is specified in the scab immune hybrid apple progeny of 28 hybrid families.

Water stress assessment at tree scale: high-resolution thermal UAV imagery acquisition and processing

Water stress assessment can be performed by analyzing thermal images taken onboard Unmanned Aerial Vehicles (UAVs). This study focuses on the acquisition and data extraction of high-resolution UAV-sensed thermal images. The datasets obtained, through computation of spectral indices and image classification, allowed to assess the response to drought of an apple hybrid population submitted to different water regimes. Studies were performed in an experimental apple orchard located in southern France. Flights were planned at solar noon on four successive dates during summer 2013 (40 m altitude, 0.10 m spatial resolution) and at five successive hours of the day, once water stress was established. The high temporal and spatial resolution of images allowed acquiring data at canopy and intra-canopy scales, with a short revisit time. As the miniaturized uncooled thermal camera carried onboard the UAV needs careful correction of radiometry, this was performed by continuous reference to ground thermal targets, while an automatized image processing was carried out. Thanks to the high resolution of the remote images obtained, and the capacity to efficiently delineate each individual tree within the whole trial, it was possible to analyze inter- and intra-canopy thermal variations. Indices extracted from thermal images showed significantly higher canopy temperatures in water restricted trees compared to well-irrigated ones. These differences were related to the severity of water deficit. However, responses also varied significantly according to the genotype. The image-based variables in apple trees constitute a basis for a further finely tuned analysis of the differential response to water stress.

Realization of the genetic potential of frost hardiness in apple hybrids of different ploidy

The results of a study of resistance to unfavorable winter conditions of new selection seedlings of apple developed in the Institute as part of priority directions of apple breeding are presented. The goal of the work is to estimate winter hardiness of apple genotypes developed by combining scab resistance in a triploid genotype (RVi6+3х). Methods of a winter hardiness study in the field and laboratory conditions were used by modelling damage factors in a “ESPEC” PSL-2 KPN deep-freezer . It was determined that by early December the genotypes gained a good hardening and displayed the resistance of vitally important tissues to early winter frosts up to 30 °C (frost resistance component I). The genotypes were revealed that under artificial freezing bore critical temperatures –38 and –40 °C as well as –42 °C with damages of vitally important tissues at the level of Antonovka Obyknovennaya (component II). The modelling of a three-day artificial thaw (+2 °C) with the following temperature lowering to –30 °C showed that in all studied apple seedlings the damages of bark, cambium and wood were reversible and did not exceed 2.0 points while in immune, triploid forms 31-2-130 and ELS 31-36-149, the damages did not exceed 1.2 points. The winter hardiness study of selection apple seedlings allowed revealing the most winter hardy and promising genotypes: scab resistant and triploid forms 31-2-15, 31-2-115, 31-2-130 (Afrodita×13-6-106) and 31-36-149 [Veniaminovskoye×25-35-144 (Wealthy tetraploid× Papirovka tetraploid)] as well as scab resistant diploids 32-35-58 (Yubiley Moskvy×Krasa Sverdlovska) and 31-15-126 [23-16-96 (seedling 814 – open pollination)×Gulliver)]. Those genotypes displayed the resistance of vitally important tissues to early winter frosts, frosts in the middle of winter up to –40 °C at the level of Antonovka Obyknovennaya as well as to the frosts after thaws and retained the ability to restore resistance during repeated hardening after thaws.

Evaluation of apple cultivars and hybrids in a fruit nursery

The study was conducted in the fruit nursery of the Institute of Agriculture - Kyustendil during a two-year period (2011-2012). The main aim of this study was to check the quality of nursery trees of 24 introduced apple cultivars and hybrids, grafted on ‘MM 106’ rootstock. The rootstocks were budded at the height of 15 cm from the ground by chip budding on July 28. During the research, the following indicators were measured: percentage of developed buds, growth dynamics of the nursery trees, the number of plants with sylleptic shoots, the height and the thickness of nursery trees and at the end of the growing season. Percentage of standard and non-standard trees was recorded according to the norms of the Bulgarian State Standard. It was established that the ‘Hybrid No 6’ and ‘Rubin’ had the highest percentage of developed buds, while ‘Red General’ and ‘Pinova’ had the lowest values. ‘Remo’, ‘Free Redstar’, ‘Melfree’, ‘Gold Millennium’, ‘Reandra’, ‘Primera’, ‘Hybrid No 6’ and ‘Red General’ had a stronger growth and ‘Brina’, ‘Pacific Rose’, ‘Longlu’, ‘Honglu’, the hybrid ‘Pinova’ × ‘Fuji’, ‘Goldrush’, ‘Yanga 1’ and ‘Renora’ had weaker growth, compared to the standard (‘Granny Smith’) and the rest of cultivars. Cultivars ‘Granny Smith’, ‘Longlu’, ‘Yanga’ and the ‘Pacific Rose’ showed a tendency to form sylleptic shoots in the nursery. The highest percentage of standard planting material was obtained from ‘Hybrid No 6’, ‘Granny Smith’ and ‘Rubin’ and the lowest from ‘Brina’, ‘Pacific Rose’ and the hybrid ‘Pinova’ × ‘Fuji’.

Biological and economic qualities of some apple hybrids

Six apple hybrids created at the Institute of Agriculture, Kyustendil (Bulgaria) were tested in 2012-2014. The trees were grafted on 'MM 106' rootstock and planted in the spring of 1998 at a distance 4.5×2.5 m. The trial was established in five replications (1 tree replication-1). The flowering period, ripening time, tree growth, yield, morphometric (fruit weight and dimensions) and chemical properties (soluble solids, total sugars and titratable acids content) were determined. The earliest bloom was observed in hybrid 1/16 ('Winesap' × 'Erwin Baur') - April 10, and the latest in hybrid 1/38 ('Prima × Cooper 4') - April 16. The weakest growth (trunk cross-section area) had the trees of hybrid 1/21 ('Spartan' × 'Prima') and the strongest the trees of hybrid 1/38. Fruit ripened between September 21 and 25, respectively, for hybrid 1/20 ('Winesap' × 'Erwin Baur') and hybrid 1/36 ('Prima' × 'Cooper 4'). Hybrids 1/23 ('Spartan' × 'Prima') and 1/16 produced the highest average yields (22.8 and 22.7 kg tree-1, respectively). The fruits of hybrid 1/20 were the largest (197.3 g). Average soluble solids were between 11.7 and 13.6%, total sugars ranged from 6.7 to 7.7% and titratable acids from 0.15 to 0.76%.

Using achievements of fruit crop genetics and breeding: a contribution from the Michurinsk Department of the Vavilov Society of Geneticists and Breeders

The Michurinsk Department of the Vavilov Society of Geneticists and Breeding Scientists (VOGiS) was formed in 1966 after the constituent congress of VOGiS and nowadays includes 54 members. The scientists are engaged in 4 scientific institutions affiliated with FASO of Russia. The paper presents investigations of the individual genetics of leading fruit crops (pear, cherry, apple), identified genes, regularities of inheriting resistance to low temperatures, the most harmful diseases and several characters responsible for fruit quality. Some genes were identified for the first time. These are genes regulating Coccomyces hiemalis Higg. resistance (A), retarded growth habit in cherry (O2), astringency (Ta) and juiciness (Su) of fruit in pear. On the base of hybridological analysis and DNA marking, genotypes were identified. These genotypes carry target alleles of the following genes: columnar growth habit (Co) in apple, dwarf trait (PcDw) in pear, retardant growth (O2) in cherry. It was found that the markers C18470-25831, Mdo.chr 10.12, Co04R12 do not always show robust results for screening of young apple seedlings with columnar growth habit (Co) because they are identified as non-columnar forms. The primer pairs of 29f1 и jwi1r are the most robust ones for identification of columnar genotypes. These primers amplify specific PCR product of 586 bp (5’CR). On the basis of molecular-genetic analysis of apple initial forms and hybrid seedlings, there were identified targeted alleles of monogenic scab resistance genes including dominant homozygous genotype (Rvi6Rvi6) and also alleles of genes involved in the control of the biosynthesis of ethylene (Md-ACS1 and Md-ACO1) and expansin (Md-Exp7) controlling fruit long shelf life and pulp firmness.

Construction of a Genetic Linkage Map and QTL Analysis of Fruit-related Traits in an F1 Red Fuji x Hongrou Apple Hybrid

AbstractA genetic linkage map of the apple, composed of 175 SSR and 105 SRAP markers, has been constructed using 110 F1 individuals obtained from a cross between the ‘Red Fuji’ Malus domestica and ‘Hongrou’ Malus sieversii cultivars, which have relatively high levels of DNA marker polymorphism and differ remarkably in fruit-related traits. The linkage map comprised 17 linkage groups, covering 1299.67 cM with an average marker distance of 4.6 cM between adjacent markers, or approximately 91% of Malus genome. Linkage groups were well populated and, although marker density ranged from 2.1 to 9.5 cM, just 10 gaps of more than 15 cM were observed. Moreover, just 12.5% of markers displayed segregation distortion. The present genetic linkage map was used to identify quantitative trait loci (QTLs) affecting fruit-related traits. 23 QTLs for ten fruit traits were detected by multiple interval mapping: 3 QTLs for Vc content, One QTL for single fruit weight, 2 QTLs for peel-phenols content, 2 QTLs for flesh-hardness, 2 QTLs for diameter, 6 QTLs for acid content, 1 QTL for sugar content, 2 QTLs for soluble solids content, 2 QTLs for flesh-phenols and 2 QTLs for brittleness. These QTLs were located on linkage groups C1, C2, C3, C5, C6, C7, C9, C10, C14 and C17, respectively. The phenotypic variations exhibited by each QTL ranged from 2% to 72%, and their LOD values varied from 2.03 to 8.93, of which five QTLs were major effect genes (R2 ≥ 10%). The tight linkage markers (*me2em7-460f, *MS01a03-180m, *me1em6-307m, *CH05c06-102f, *me1em8-423f) would be helpful to elucidate the molecular mechanisms of apple domestication and breeding in the future.

ИЗУЧЕНИЕ ГЕНЕТИЧЕСКОГО РАЗНООБРАЗИЯ СОВРЕМЕННЫХ СОРТОВ ЯБЛОНИ (Malus* domestica Borkh.) ОТЕЧЕСТВЕННОЙ СЕЛЕКЦИИ С ИСПОЛЬЗОВАНИЕМ МИКРОСАТЕЛЛИТНЫХ ЛОКУСОВ

SSRs are one of the most suitable DNA-markers for assessment of genetic diversity of plant genetic resources. Microsatellites were used for development of saturated genetic maps of apple ( Malus * domestica Borkh.) as well as for wide range of genetic diversity studies. Our study was aimed on the investigation of the genetic relationship within subcollection of modern Russian apple cultivars. Polymorphism of 12 microsatellite loci was estimated for 31 apple cultivars from the SKZNIISiV collection of genetic resources. These cultivars have been bred in North Caucasian Regional Research Institute of Horticulture and Viticulture (SKZNIISiV) and All-Russian Research Institute of Fruit Crop Breeding (VNIISPK). SSR-markers CH01f03b, CH01h01, CH01h10, CH02c06, CH02d08, CH04e05, CH05f06, CH01f02, CH02c11, Hi02c07, CH02c09 and CH03d07, which are recommended by Fruitbreedomics, the European consortium, were used in the study. According to the data of SSR-analysis from 5 to 10 alleles per locus were detected, with an average value of 7.75 alleles per locus. A total of 93 alleles were detected for all 12 loci. All apple cultivars showed individual, distinct SSR-profiles. Comparison with the data on the genetic diversity of the world apple tree gene pool suggests that the SSR-loci polymorphism in studied set of the apple cultivars is relatively high. Expected (H e) and observed (H o) heterozygosity varied within the ranges of 0.548-0.897 and 0.602-0.827 for H o and H e, respectively. The average values of these indexes are H o = 0.786 and H e = 0.755. PIC value ranged from 0.571 to 0.806, and 9 loci showed PIC value higher than 0.712. Results of UPGMA-analysis are consistent with the level of genetic heterogeneity of the studied cultivar set. Five clusters were determined. Distribution of cultivars into clusters in most cases is consistent with their genealogy. For example, Svezhest’ cultivar, formed a distinct cluster № 1, as well as cultivars Imrus and Zimnee utro which formed cluster № 5 are originated from the cultivars, which are not presented as the parental forms of any studied cultivars. Cultivars of VNIISPK breeding such as Solnishko, Stroevskoe, Yubilei Moskvy, Afrodita and Start, which formed distinct cluster № 3 have one common parental cultivar. The structure of dendrite obtained when performing clustering on the results of SSR-analysis may be due to large number of unique alleles studied in genotypes that in turn is due to the high genetic diversity within the studied set of cultivars. At the same time, the fact of incorporation of cultivars with the same genealogy in the same clusters confirms the high significant genetic similarity within groups of such varieties. Results of the study allows to assess the level of the genetic diversity within the set of modern apple cultivars as well as can be used for confirmation of genealogy of apple cultivars and hybrids in the case of disputes, as well as for identification of varieties.

Predicting apple tree (Malus × domestica Borkh.) canopy architecture: phytohormone balance in juvenile hybrids

Apple tree (Malus × domestica Borkh.) is one of the most widespread and economically important fruit trees. Productivity and economic effect of apple orchards depend on many strongly related factors, one of them being tree canopy architecture, which determines fruit bearing and demand for pruning. Main apple canopy architecture topics are related to application of growth regulators, fertilizers, studies of shoot development and pruning, and environmental influence while physiologic aspects are studied less. Phytohormones play a major role in controlling many physiological processes of plant growth and development. Different amounts of phytohormones are found in the shoots of apple trees depending on their canopy architecture. However, information about phytohormones and their ratio in juvenile orchard plants is insufficient. Our goal was to identify phytohormones related to apple canopy architecture and to evaluate their usage as biochemical markers in predicting future canopy ideotype of apple seedlings in the first year of growth. It was established that large amount of auxin and high auxin to zeatin ratio are specific to columnar apple trees and they can be used as biochemical markers in juvenile phase. These amounts and ratios are similar in juvenile and cropping columnar apple trees, so phytohormone amount and ratio is independent of tree development stage. It is possible to select columnar apple hybrids in the first year of growth, thus reducing breeding expenses.

Stress indicators based on airborne thermal imagery for field phenotyping a heterogeneous tree population for response to water constraints.

As field phenotyping of plant response to water constraints constitutes a bottleneck for breeding programmes, airborne thermal imagery can contribute to assessing the water status of a wide range of individuals simultaneously. However, the presence of mixed soil-plant pixels in heterogeneous plant cover complicates the interpretation of canopy temperature. Moran's Water Deficit Index (WDI = 1-ETact/ETmax), which was designed to overcome this difficulty, was compared with surface minus air temperature (T s-T a) as a water stress indicator. As parameterization of the theoretical equations for WDI computation is difficult, particularly when applied to genotypes with large architectural variability, a simplified procedure based on quantile regression was proposed to delineate the Vegetation Index-Temperature (VIT) scatterplot. The sensitivity of WDI to variations in wet and dry references was assessed by applying more or less stringent quantile levels. The different stress indicators tested on a series of airborne multispectral images (RGB, near-infrared, and thermal infrared) of a population of 122 apple hybrids, under two irrigation regimes, significantly discriminated the tree water statuses. For each acquisition date, the statistical method efficiently delineated the VIT scatterplot, while the limits obtained using the theoretical approach overlapped it, leading to inconsistent WDI values. Once water constraint was established, the different stress indicators were linearly correlated to the stem water potential among a tree subset. T s-T a showed a strong sensitivity to evaporative demand, which limited its relevancy for temporal comparisons. Finally, the statistical approach of WDI appeared the most suitable for high-throughput phenotyping.

Additional Amphivasal Bundles in Pedicel Pith Exacerbate Central Fruit Dominance and Induce Self-Thinning of Lateral Fruitlets in Apple

Apple (Malus × domestica) trees naturally produce an excess of fruitlets that negatively affect the commercial value of fruits brought to maturity and impact their capacity to develop flower buds the following season. Therefore, chemical thinning has become an important cultural practice, allowing the selective removal of unwanted fruitlets. As the public pressure to limit the use of chemical agents increases, the control of thinning becomes a major issue. Here, we characterized the self-thinning capacity of an apple hybrid genotype from the tree scale to the molecular level. Additional amphivasal vascular bundles were identified in the pith of pedicels supporting the fruitlets with the lowest abscission potential (central fruitlet), indicating that these bundles might have a role in the acquisition of dominance over lateral fruitlets. Sugar content analysis revealed that central fruitlets were better supplied in sorbitol than lateral fruitlets. Transcriptomic profiles allowed us to identify genes potentially involved in the overproduction of vascular tissues in central pedicels. In addition, histological and transcriptomic data permitted a detailed characterization of abscission zone development and the identification of key genes involved in this process. Our data confirm the major role of ethylene, auxin, and cell wall-remodeling enzymes in abscission zone formation. The shedding process in this hybrid appears to be triggered by a naturally exacerbated dominance of central fruitlets over lateral ones, brought about by an increased supply of sugars, possibly through additional amphivasal vascular bundles. The characterization of this genotype opens new perspectives for the selection of elite apple cultivars.

Different Materials of Substrates in the Production of Chili Apple Seedlings (Capsicumpubescens R. and P.) Grajales ST

ABSTRACTThis study aimed to evaluate the effect of 12 substrates in the seedling growth of chili apple (Capsicum pubescens R. & P.) hybrid Grajales ST. The substrates were prepared with different proportions of five materials: perlite, coconut fiber, loam, Sunshine3 ® and wood dust. The seeds were sown in trays of 50 cavities. For the substrates were determined physical and chemical properties. Significant differences in growth parameters of seedlings are the effect of the substrate. Based on the remarkable accumulation of dry matter of each of the organs of the seedling, and their relative distribution, one can surmise a seedling quality with 47.70 % dry matter in leaves, 35.34 % in stem and 16.95 % in root. The substrate with better features for the production of chile apple seedlings was prepared with 25 % loam and 75 % perlite (v/v), which showed retention of 85.5 % moisture, electrical conductivity of 0.03 dS·m-1 and total porosity of 62.5 %.

Evaluation of some scab resistant apple hybrids as early season genotypes

Five scab-resistant hybrids [ASPE-99 (Sunhari x Prima), ASPE-36 (Lal Ambri x Prima), ALPE-99 (Sunhari x Prima), ASPE-22 (Sunhari x Prima) and ALPE-57 (Lal Ambri x Prima)] developed by SKUAST-Kashmir, were evaluated for phenological, pomological and storage characteristics in 2009 and 2010. The days taken to full bloom ranged between 80.5 to 86.5 in hybrids and 76.5 to 83.0 in check cultivars. ASPE-36 and ASPE-99 matured earlier (82 days for fruit development) while ALPE-57, ASPE-22 and ALPE-99 matured 6.0–16.5 days later. Fruit shape in hybrids was oblate and slight to moderately lopsided with smooth surface. Fruits were crisp, juicy, moderately flavoured and red coloured with yellowish background and creamy flesh. Fruit firmness was maximum in ALPE-57 followed by ALPE-99 and ASPE-36. Hybrids significantly varied in fruit size and weight with high values in ALPE99, ALPE-57 and ASPE-22. Hybrids had higher TSS and total sugars and were less acidic than checks. Total sugar was maximum and titrable acidity minimum in ASPE-22. The storage life of hybrids was higher than control with maximum storage life of 156–172 days under CA storage, 73–88 days under refrigeration and 34–45 days under normal storage conditions. Hybrids ASPE-99, ASPE-22 and ALPE-57 were identified as prospective genotypes for release as improved early season scab-resistant cultivars.

МОЛЕКУЛЯРНЫЕ МЕТОДЫ В СЕЛЕКЦИИ ЯБЛОНИ НА УСТОЙЧИВОСТЬ К КРАСНОГАЛЛОВОЙ ЯБЛОННОЙ ТЛЕ

The rosy leaf-curling aphid ( Dysaphis devecta Walk) is a widespread pest insect on apple-trees ( Malus × domestica Borkh.). The aphid damages both young trees and old trees. The aphid forms the colonies on the rind, leaves and shoots and it is nourished by apple tree juice. Some cultivars exhibit resistance to this insect owing to appropriate genes in genome. The current methods permit to identify the genes of such resistance and to transfer of them purposefully to created varieties. In presented article the molecular marker technology was used for detecting resistance Sd -locus to rosy leaf-curling aphid, basing on PCR with SdSSR-F/SdSSR-R primers. The Discovery и Fiesta cultivars were used as a control, the first one as a parent to create the plant mapping populations, and the second one as a carrier of Sd1 gene and the corresponding marker. The allele linked with Sd -locus has a size of 183 bp. The collection of 132 apple cultivars and hybrids was tested for Sd -locus, and the Sd -locus identified in genomes of 31 apple accessions from different countries. Sd -locus is presented in ancient cultivars, known as long ago as ХIХ century (Belyi Naliv, Papirovka, Pepin Litovskii, Chulanovka, Cox's Orange Pippin) and cultivars of modern breeding (Sinap Belorusskii, Belorusskoe Malinovoe, Slava Pobeditelyam, Charavnitsa). The molecular marker technology was applied for developing promising apple hybrid seedling resistant to rosy leaf-curling aphid.

Breeding of new Apple Cultivars in Belarus

The article presented the results of 20 years of the Belarusian apple breeding programmne. Apple breeding has old traditions at the Institute for Fruit Growing in Belarus. Special attention is paid to new adaptive dessert apple cultivars. As a result of the second stage of the durable resistant apple breeding programme, conducted in 1994-2010, six Belarusian apple cultivars were submitted to State Testing of the Republic of Belarus. The cultivars were selected from the apple hybrid fund obtained in 1994-2000. In total, 252 progenies with more than 22 300 seedlings were assessed for their susceptibility to scab after artificial inoculation in the nursery, and almost 5000 seedlings were further evaluated for spontaneous infections after natural inoculation in orchards, where they had grown without any chemical spraying against the disease. After evaluation of three cropping seasons, 120 selections were propagated on rootstocks B.62-396 and PB 4. The best selections with combined resistance to fungal diseases and winter frost, high crop yield and attractive fruits were the new cultivars ‘Belana’, ‘Diyament’, ‘Krasavita’, ‘Navavita’, ‘Sakavita’ and ‘Zorka’.

Apple cultivars resistant to scab (Venturia inaequalis (Cke.) Aderh.) Part II. Winterhardiness of apple cultivars

The severe winter which occurred in Poland in 1986-1987 damaged the most part of scab resistant apple cultivars and selected apple hybrids. Cold hardiness studied in 1987 and 1988 showed significant differences in degree of frost injury on stem, branches, twigs and buds of apple trees. Two scab-resistance cultivars, namely Florina and Sir Prize, as well as two check culuvars, Idared and Golden Delicious, were killed by frost. Strong damages were noted in cultivars: Prima, Primula, and Priam. Lower susceptibility showed: Jonafree, Gavin, Liberty Sister and three hybrids selected from crosses of Bankroft with scab-resistant Primula. Relatively frost resistant was Novamac and three hybrids of U-breeding line: U-1101 and U-50, originated from crosses of polish culrivar Fantazja (McIntosh x Linda) with Primula, Highest resistance to frost showed cultivars: Freedom. Liberty. new polish cultivar Witos (Fantazja x Primula) and three hybrids: U-337, U-237 and U-1098. During the 1987 and 1988 seasons severe infection of apple trees by numerous fungi was noted. Twelve species of isolated fungi were identified as pathogens of apple trees bark and wood.

Morphological traits of phytomers and shoots in the first year of growth as markers for predicting apple tree canopy architecture

With 1 figure and 7 tablesAbstractApple tree canopy architecture is very important for productivity, fruit quality and ripening. Our objective was to evaluate inheritance traits of an apple tree canopy and to identify morphological phytomer or shoot parameters, which could be used as a marker for selection of apple trees with desired canopy architecture. Crosses between apple trees with different canopy architecture using top‐cross scheme were performed. Combining ability of parental cultivars and clones was evaluated. Progeny of columnar and spur ideotype apple trees will have the shortest internodes according to general combining ability effects. Offspring of standard and weeping apple trees will have moderate and long internodes. Data show that apple phytomer parameters, such as internode length and lamina angle to shoot, are inherited and related to future plant canopy architecture. These phytomer traits are easily detected in the first year of growth of apple hybrid. It was shown that short internode is directly related to columnar tree canopy, and high lamina angle to shoot in the juvenile phase is a morphological marker of weeping apple tree canopy.

Inheritance of and Molecular Markers for Susceptibility of Malus domestica to Fruit Ring Rot (Botryosphaeria dothidea)

AbstractTo analyse the inheritance of fruit ring rot (FRR) resistance and to screen for microsatellite markers linked to resistance/susceptibility, 875 apple hybrid seedlings (Malus domestica, Jonathan × Golden Delicious) were inoculated with five isolates of Botryosphaeria dothidea in 2 years (2008 and 2009). The results indicated that incidence and non‐incidence were qualitatively segregated, and incidence was dominant to non‐incidence. The variation in susceptibility within this population was attributed to the segregation of three major genes. For the phenotype of incidence, the severity of lesion development was a quantitative trait. From 230 published microsatellite primer pairs, six markers were identified that were linked to the susceptibility to FRR. CH04d02‐120 and Hi08g12‐190, located in LG12 and LG2, respectively, were linked to susceptibility to the pathogen isolate Mx1, and their map distances to the susceptibility loci were 8.2 and 5.1 centimorgan (cM), respectively. CH01e01‐120 and CH02c02b‐100, which were linked to susceptibility to Ls1, were located in LG14 and LG4, and the map distances to the susceptibility loci were 16.9 and 8.4 cM, respectively. CH05d11‐150 and CH03a03‐230, linked to susceptibility to Lw048, were located in LG12 and LG14; for both of them, the map distance was 13.4 cM.

Heritability and Genetic Parameters Estimated for Fruits Size in F1 Interspecific Apple Hybrids

Interspecific hybridization is a frequently used b reeding method to create a wide genetic diversity useful to broaden selection base and creating new cultivars of apple. The aim of the present study was to determine the heritability of fruit size in F 1 apple hybrids belonging to interspecific apple pollenization between different cultivars and wild species (rustic apple crabs) li ke Malus coronaria, M. floribunda, M. niedzwetzkyana, M. zumi, and M. prunifolia . A wide variability of fruits sizes has been identified, in all families b eing identified a broad fruit size variability (e.g . CV = 47.1% in M. zumi ◊ 'Golden Delicious', CV = 42.2% in M. coronaria ◊ 'Jonathan' and 'Rosu de Cluj' ◊ M. prunifolia ). Between the five cyclic hybridizations, the mean of notes for fruit size was quite close, with limits ranging from 2.70, from hybridis ation where the species M. floribunda and M. prunifolia participated as paternal testers, and 2.93, in the cyclic where specie M. niedzwetzkyana was hybridization as paternal tester (less than 3, wh ich express small fruits, by 1-9 scale). Even if the trait studied showed a strong genetic determinism ( H 2 : 0.611-0.700), analysis of the heritability coefficients in narrow sense (h 2 between 0.074 when M. prunifolia was used as paternal tester and 0.154 when M. floribunda was used as paternal tester) revealed that not add itive effects played the most important role, but non-additive effects, of d ominance and epistatic. Genetic gain and expected selection response had similar values, which have s hown that the chances of obtaining by selection a population of hybrids that have the desired fruit s ize are greater when in interspecific hybridization are involved as genitors M. zumi and M. floribunda , compared to M. niedzwetzkyana and M. prunifolia .

The variability of juvenile period, fruits size and response to diseases attack on F1 interspecific apple hybrids and the efficiency of selection.

Interspecific hybridizations represent one of the apple breeding methods by which a wide variability can be achieved, useful for creating new cultivars. The study of 2190 interspecific hybrids, obtained from 25 combinations among crab apple species (Malus coronaria, M. floribunda, M. niedzwetzkyana, M. zumi, M. prunifolia) and different apple cultivars, points out a large variability of the F1 seedlings for several traits, with significant importance in apple breeding programs. The first year of fructification, as mean per hybrid combination, varied from 6 (M. zumi x 'Jonathan') to 9.3 years; the average hybrid's age for fructification was 7.4 years. The size of fruits among families varied from 1.5 ('Starkrimson' x M. prunifolia) to 4.0 ('Reinette Baumann' x M. zumi), the mean being settled at 2.8 (therefore below mark 3, meaning 'small fruits'). The lowest infection rate both for apple scab and powdery mildew attack was noticed at hybrids from M. coronaria x 'Reinette Baumann'. On the whole, the hybrids with genitors of 'species x cultivars' type have had an early fruiting and a better resistance to scab and powdery mildew, compared to the ones from 'cultivars x species' combinations. The large variability of the studied traits gave the possibility to identify offsprings with desirable characteristics on nine hybrid combinations. Among these, 53 elite plants were selected, with a strength of selection of 2.42%, therefore a relative low value, correlated with the peculiarities of the interspecific population and the selection criteria for dessert apple.