Apple Breeding Programs Research Articles

Dynamics of total phenolic content in different apple tissues and genotypes: impacts and relevance for breeding programs

The content and quality of phenolic compounds in apple pulp, peel, and leaves constitute important nutraceutical properties of apples in the human diet and are equally important to plant ecology. Moreover, increased understanding of the dynamics of polyphenol synthesis in different apple tissues of different genotypes may assist in apple breeding programs. Thus, the present study aimed to analyze the levels of total phenolics in apple pulp, peel, and leaves from cultivars Aori27, Elstar, Fuji, and Mellow at harvest time. Significant differences in the total phenolic content were found between cultivars for all evaluated tissues, but the differences between cultivars were not consistent among tissues, indicating the potential existence of tissue-specific genetic regulation mechanisms, as well as cultivar-specific dynamics. Additionally, tissues of two cultivars, Fuji and Mellow, were analyzed in the last three months of fruit development, showing a similar overall evolution in the phenolic concentration for all tissues, but some notable cultivar-specific characteristics for apple pulp and peel. These results are relevant for apple breeding when we consider as selection criteria the nutraceutical properties of apple polyphenols, the speed and degree of pulp enzymatic browning, and the physiological and agro-ecological roles of polyphenols in different organs and tissues of apple trees.

Apple breeding programs and methods, their development and improvement

It is shown that the long-term studies of some features of apple development allowed breeding intensification and reduction of cultivar development time from 36–48 to 23–27 or even 13–17 years. It is noted that requirements for new cultivars are constantly becoming tougher. They include high fitness, early maturation, performance, large size of fruit (140–160 g), thin and firm skin without rust signs or waxing, absence of abscission, sugar content of no less than 12%, ascorbic acid content of about 30 mg/100 g, and preservation capacity of winter varieties of no less than 7–8 months (Kichina, 2011). It is hardly possible to create a perfect cultivar, because requirements for new cultivars change fast and do not cover the time required for breeding. Nevertheless, we should aspire to it.

An Investigation of U.S. Apple Producers’ Trait Prioritization—Evidence from Audience Surveys

Systematic studies of the relative importance of apple traits for U.S. apple producers to inform U.S. apple breeding programs have been lacking. To fill this gap, a series of audience surveys with instant feedback at five apple producer meetings across the United States was conducted. The traits included in this study were fruit crispness, juiciness, firmness, flavor, soluble solids concentration, sugar–acid balance, shelf life at retail, freedom from storage disorders, host plant disease resistance, and other fruit and tree traits provided by the producer. Producers rated fruit flavor and crispness as the most important traits for a successful apple cultivar. The relative importance assigned to traits was associated with growing location and producers’ years of experience in the decision-making process of managing apple orchards. This study contributes directly to a larger effort that provides breeding programs with systematic knowledge of trait preferences of supply chain members, including producers, and should result in a more targeted approach to developing and commercializing new apple cultivars.

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’.

The Effect of Ethrel Application on Length of the Juvenile Phase of Apple Seedlings

A 10 year study (1998-2007) was conducted to work out a method that would allow shortening of the juvenile phase of apple seedlings in conventional apple breeding programs. The investigation was based on two separate experiments, each conducted first in high plastic tunnel and then in the field. In both experiments in the first two years, the seedlings were grown on their own roots in plastic containers (cylinders) placed in the high plastic tunnels. At the end of the second year (December), shoot tips from the seedlings were collected and grafted onto dwarfing rootstock M.9 (winter grafting). By the end of March, the grafts were planted in plastic containers and placed in the same high plastic tunnel. They were cultivated there until mid - August and then planted out to the selection field. In the first experiment, seedlings belonging to two families, ‘Ligol’ x ‘Delbard Jubile’ and ‘Linda’ x ‘Golden Delicious’ were investigated. In the second experiment, two seedling populations, ‘Free Redstar’ x ‘Melodie” and ‘Free Redstar’ x ‘Coop 38’ were tested as well. In the first experiment, nine experimental treatments were studied. They involved two growing media (peat substrate and mixture of peat substrate with compost soil 1:1), two mineral fertilizers (Osmocote Plus and Azofoska - the Polish manufactured fertilizer) and two bioregulators (Gibrescol 10 MG containing GA3 and Ethrel). In the second experiment, additionally compost soil was included. It was found that Ethrel applied twice on young apple seedlings grown in high plastic tunnel, in the first and second year of cultivation in both experiments, shortened the juvenile stage of seedlings grafted and grown on M.9 rootstock. In the first year after planting in the selection field (fourth year after seed germination), 25% of the seedlings produced flowers, and in the second year all of them flowered and produced fruits.

Field Evaluation of Traditional Apple Cultivars to Induced Diseases and Pests

During the survey we studied traditional old apple cultivars in order to test disease resistance, as part of an apple breeding program. Diseases and pests assessments were made throughout the two growing season in 2008 and 2009 in traditional apple cultivars (‘Batul’, ‘Pónyik’, and ‘Sóvári’) from stray and commercial (‘Golden Delicious’ and ‘Starkrimson’) apple orchards. Our data add to a body of evidence indicating that traditional apple cultivars under natural selection and without pesticide regime are highly and/or moderately resistant to fire blight, apple powdery mildew and apple scab. High resistance was observed for green apple aphid (‘Sóvári’) and rosy leaf-curling aphid (all cultivars, except ‘Sóvári’) throughout the assessment. Susceptibility from mediate to high level was observed for fruit peel moth and pear-leaf blister moth, while resistance and/or moderate resistance for spotted tentiform leafminer and codling moth. The codling moth damages were significantly correlated with seed number in fruits throughout the whole vegetation period. We can conclude that old apple cultivars sustained in their original regions could be a significant source of genes for apple breeding programs.

Fruit Texture Phenotypes of the RosBREED U.S. Apple Reference Germplasm Set

Establishing marker-locus-trait associations to enable marker-assisted breeding depends on having an extensive, reliable database for phenotypic traits of interest in relevant germplasm. A reference germplasm set of 467 apple (Malus ×domestica Borkh.) cultivars, selections, and seedlings (referred to as individuals) was identified as part of the USDA-Specialty Crop Research Initiative (SCRI) project, RosBREED. The germplasm set provides efficient allelic representation of current parents in RosBREED demonstration apple breeding programs at Cornell University, Washington State University, and the University of Minnesota. Phenotyping at the three locations was conducted according to standardized protocols, focusing on fruit traits evaluated at harvest and after 10 and 20 weeks of refrigerated storage. Phenotypic data were collected for the sensory texture traits of firmness, crispness, and juiciness as well as for instrumental texture measures. In 2010 and 2011, fruit from 216 and 330 individuals, respectively, were harvested and a total of 369 individuals were evaluated over the two years. Correlations between sensory and instrumental texture measures were high in some instances. Moderate year-to-year repeatability of trait values was observed. Because each location had a largely unique set of individuals, as well as differing environmental conditions, means, ranges, and phenotypic variances differed greatly among locations for some traits. Loss of firmness and crispness during storage was more readily detected instrumentally than by the sensory evaluation.

Identificação de polinizadoras para a cultivar de macieira Daiane

A garantia de boas produções em pomares comerciais de macieira depende de uma polinização eficiente, que também está relacionada com a compatibilidade de pólen-estigma, com a coincidência de época de floração e com a capacidade de produção e de germinação de pólen. O objetivo deste estudo foi avaliar a eficiência de diferentes genótipos de macieira como polinizadores da cv. Daiane nas condições climáticas do meio-oeste de Santa Catarina. Plantas de 'Daiane' foram polinizadas a campo com pólen de diversas seleções e cultivares de macieira, com subsequente proteção dos cachos com sacos de papel, por 72 h. Consideraram-se a coincidência de época de floração, a adaptação climática, a taxa de germinação, a reação à mancha foliar de Glomerella, além da frutificação efetiva e do número de sementes por fruto induzido pelas polinizadoras avaliadas. Os tratamentos mais eficientes na polinização da cultivar de macieira Daiane foram as seleções 140/76 e 140/228, respectivamente, que são indicadas para utilização conjugada, visando à maior eficiência na polinização.

THE APPLE BREEDING PROGRAM AT THE DEPARTMENT OF AGRICULTURE AND FOOD WESTERN AUSTRALIA

THE APPLE BREEDING PROGRAM AT THE DEPARTMENT OF AGRICULTURE AND FOOD WESTERN AUSTRALIA

Addition of a breeding database in the Genome Database for Rosaceae

Breeding programs produce large datasets that require efficient management systems to keep track of performance, pedigree, geographical and image-based data. With the development of DNA-based screening technologies, more breeding programs perform genotyping in addition to phenotyping for performance evaluation. The integration of breeding data with other genomic and genetic data is instrumental for the refinement of marker-assisted breeding tools, enhances genetic understanding of important crop traits and maximizes access and utility by crop breeders and allied scientists. Development of new infrastructure in the Genome Database for Rosaceae (GDR) was designed and implemented to enable secure and efficient storage, management and analysis of large datasets from the Washington State University apple breeding program and subsequently expanded to fit datasets from other Rosaceae breeders. The infrastructure was built using the software Chado and Drupal, making use of the Natural Diversity module to accommodate large-scale phenotypic and genotypic data. Breeders can search accessions within the GDR to identify individuals with specific trait combinations. Results from Search by Parentage lists individuals with parents in common and results from Individual Variety pages link to all data available on each chosen individual including pedigree, phenotypic and genotypic information. Genotypic data are searchable by markers and alleles; results are linked to other pages in the GDR to enable the user to access tools such as GBrowse and CMap. This breeding database provides users with the opportunity to search datasets in a fully targeted manner and retrieve and compare performance data from multiple selections, years and sites, and to output the data needed for variety release publications and patent applications. The breeding database facilitates efficient program management. Storing publicly available breeding data in a database together with genomic and genetic data will further accelerate the cross-utilization of diverse data types by researchers from various disciplines.Database URL: http://www.rosaceae.org/breeders_toolbox

Evaluation of old Carpathian apple cultivars as genetic resources of resistance to fire blight (Erwinia amylovora)

In the interests of re-diversifying cultivar use in apple, one of the most important breeding aims, apart from using local cultivars in breeding, is to improve resistance to fire blight (FB). At the Corvinus University of Budapest, the investigation of Hungarian cultivars found in the Carpathian Basin as genetic resources is a major part of the apple breeding program aimed at multiple resistance. The present study, initiated in the early 2000s, evaluates the FB resistance of 31 apple cultivars. Examination of the damage to shoots and flowers, and of the correlation between them, was carried out after artificial inoculation. Two dominant SCAR markers and one SSR marker were used for the genetic analysis of the cultivars giving the best results in phenotypic analysis, in order to detect quantitative trait locus alleles coding for FB resistance. Based on the results of several years of inoculation tests, the assayed cultivars exhibited a wide range of susceptibility levels on the basis of shoot necrosis and in terms of flower damage. A positive correlation (R = 0.058, p = 0.04) was demonstrated between the susceptibility found for the two plant organs. The cultivars Szabadkai szercsika and Sikulai, which gave outstanding results both in the flower and shoot tests and in the genetic analysis, could be suitable genetic resources for resistance breeding programmes. The present work confirmed the complex polygenic nature of FB resistance and the need to identify further markers in addition to those found on linkage group (LG) 3 and LG 7.

‘Artemisz’, ‘Cordelia’, ‘Hesztia’, and ‘Rosmerta’: New Hungarian Multiresistant Apple Cultivars

‘Artemisz’, ‘Cordelia’, ‘Hesztia’, and ‘Rosmerta’ are the first four Malus 3domestica (Borkh.) cultivars developed in the apple breeding program of the Corvinus University of Budapest and their registration was accepted by the state in 2011 and 2012. They are mid–early to late-ripening cultivars with the following ripening dates: from the fourth week of August to the first week of September (‘Hesztia’), the second week of September (‘Artemisz’), the third week of September (‘Rosmerta’), and the first 10 d of October (‘Cordelia’) in the growing region between the rivers Danube and Tisza, the central part of Hungary. All four cultivars are resistant to apple scab and also have good resistance to the apple powdery mildew. Their shoots have resistance or moderate resistance to fire blight. The flowers of ‘Hesztia’ exhibited moderate resistance to fire blight. The medium to large fruits (averaging 147 g in weight) of ‘Artemisz’ can be used for both fresh consumption and making into apple chips. ‘Cordelia’ has very large fruit, averaging 269 g, with great flesh firmness (8.3 kg·cm on average) and high pectin concentration (0.87%). This cultivar has good storage ability. It is recommended to be used for fresh consumption; however, it can be used for processing purposes based on its physical and chemical properties, e.g., for processing into concentrates, applesauce, and apple chips. The fruit size of ‘Hesztia’ is large, averaging 246 g. On average, the concentrations of gallic acid polyphenols were 392 mg·L. It has the highest antioxidant capacity [ferric-reducing ability of plasma (FRAP) 1.34] among the new cultivars. It is suitable for both fresh consumption and processing into apple chips and concentrates. ‘Rosmerta’ (155 g/fruit) is ideal for fresh consumption. However, this cultivar can be potentially used for processing purpose. It is a potential alternative cultivar for ‘Jonathan’; the latter is highly susceptible to various diseases.

The mQTL hotspot on linkage group 16 for phenolic compounds in apple fruits is probably the result of a leucoanthocyanidin reductase gene at that locus

BackgroundOur previous study on ripe apples from a progeny of a cross between the apple cultivars ‘Prima’ and ‘Fiesta’ showed a hotspot of mQTLs for phenolic compounds at the top of LG16, both in peel and in flesh tissues. In order to find the underlying gene(s) of this mQTL hotspot, we investigated the expression profiles of structural and putative transcription factor genes of the phenylpropanoid and flavonoid pathways during different stages of fruit development in progeny genotypes.ResultsOnly the structural gene leucoanthocyanidin reductase (MdLAR1) showed a significant correlation between transcript abundance and content of metabolites that mapped on the mQTL hotspot. This gene is located on LG16 in the mQTL hotspot. Progeny that had inherited one or two copies of the dominant MdLAR1 alleles (Mm, MM) showed a 4.4- and 11.8-fold higher expression level of MdLAR1 respectively, compared to the progeny that had inherited the recessive alleles (mm). This higher expression was associated with a four-fold increase of procyanidin dimer II as one representative metabolite that mapped in the mQTL hotspot. Although expression level of several structural genes were correlated with expression of other structural genes and with some MYB and bHLH transcription factor genes, only expression of MdLAR1 was correlated with metabolites that mapped at the mQTL hotspot. MdLAR1 is the only candidate gene that can explain the mQTL for procyanidins and flavan-3-ols. However, mQTLs for other phenylpropanoids such as phenolic esters, dihydrochalcones and flavonols, that appear to map at the same locus, have so far not been considered to be dependent on LAR, as their biosynthesis does not involve LAR activity. An explanation for this phenomenon is discussed.ConclusionsTranscript abundances and genomic positions indicate that the mQTL hotspot for phenolic compounds at the top of LG16 is controlled by the MdLAR1 gene. The dominant allele of the MdLAR1 gene, causing increased content of metabolites that are potentially health beneficial, could be used in marker assisted selection of current apple breeding programs and for cisgenesis.

Resistência parcial de cultivares antigas de macieira a Venturia inaequalis

Among the practices recommended for apple scab (Venturia inaequalis) control, the use of genetically resistant cultivars is of great importance in integrated management programs, in which restrictions to fungicide use are common. In this study we used multivariate analysis techniques to identify variables useful in apple breeding programs for detecting partial resistance to V. inaequalis and to rank cultivars for this resistance type. A collection of ten old apple cultivars from propagative material 35 to 50 years old was evaluated for partial resistance to the pathogen. CNPUV-09 and CNPUV-04 had levels of resistance similar to that of cultivar Prima, the standard resistant cultivar. The stroma and apressorium (ST + AP) formation and sporulation (ESP) of the pathogen after a foliar inoculation by conidial suspension were the largest eigenvectors of the first and second principal components, and contributed with 23.9% and 28.5% of the total variance, respectively. ST + AP and ESP were highly correlated with first and second axes. These variables could be useful in apple breeding programs to select cultivars with partial resistance to V. inaequalis.

‘WA 38’ Apple

‘WA 38’ (‘Enterprise’ · ‘Honeycrisp’) is a new apple selection from the Washington State University apple breeding program with commercial potential based on its exceptional eating quality, its large fruit size, attractive appearance, and its productivity. It is very attractive with 90% of the skin surface covered by dark red–purple blush over a green–yellow background. It is significantly more crisp and juicy eaten both fresh and out of storage when compared with commercial cultivars. Unlike many existing cultivars, it has little reduction in quality, particularly firmness, after several months in regular cold storage. It ripens in late September in Wenatchee, WA, and its vigor and productivity fall within the range of existing commercial cultivars. Its cut flesh shows very low enzymatic browning, making it suitable for fresh-cutslice packaging and for use in salads. It is suited to the fresh market both directly off the tree and out of mediumand long-term storage.

Relationships of morphological traits and ripening time during juvenile phase in apple

Young progenies were appraised with relative bearing parents for values of specific morphological traits related to earliness trait in order to defeat the juvenile period in breeding program. 38 Iranian local and imported apple cultivars with different times of ripening, from very early to very late, selected as parents to produce high yielding early descendents were formerly propagated on MM111 clonal rootstocks, grown in the identical pedo-climatic conditions. So, all the parents were classified in 3 distinct classes of earliness including very early–early ripening, mid ripening and late–very late ripening. The 3-year-old True-to-Type plants of the same parents were exploited for comparative biennial studies of 10 definite vegetative traits, defined as morphological markers, with their parents to estimate probable correlations with earliness character as the target of the current apple breeding program. Stepwise regression analysis revealed leaf length as the first trait entered to the model explaining approximately 45% of variations. Maximum and minimum direct effects obtained from path analyses for ripening time were deduced 8.71 and −7.47 for leaf length and leaf width, respectively. Maximum indirect effect belonged to leaf width through leaf length (8.17). Cluster analysis according to UPGMA procedure and principal component analysis (PCA) was used for classifying cultivars and assessment of the traits. According to the results of cluster analysis, high variability among the groups of cultivar was determined by ripening time and origin or geographic distribution. As a result, the early ripening cultivars were placed in opposite side of cluster related to the late cultivars. Furthermore, four efficient factors (traits) including total leaf chlorophyll content, leaf length, leaf width and pedicle length justified 87% of existing diversity based on factor analysis.

Fine mapping of Co, a gene controlling columnar growth habit located on apple (Malus×domestica Borkh.) linkage group 10

With 2 figures and 3 tablesAbstractTree architecture and shoot morphology are important factors in apple production systems. Because a columnar growth habit facilitates high‐density planting and labour‐saving fruit production methods, columnar apple breeding programmes are spreading worldwide. Columnar growth habit is controlled by a single dominant gene, Co, on linkage group 10. Fine mapping of Co was conducted using 1000 F1 progeny plants from 31 populations. Novel simple sequence‐repeat (SSR) markers were developed based on the genome sequence of apple ‘Golden Delicious’ and analysed for linkage to Co. Graphical genotyping of 22 progeny with recombination event in the vicinity of Co identified three SSR markers (Mdo.chr10.12, Mdo.chr10.13 and Mdo.chr10.14) that co‐segregated with Co. Mdo.chr10.12 and Mdo.chr10.14 are well suited for marker‐assisted selection because the sizes of the alleles linked to Co are different from those found in common ancestors of current apple breeding germplasm. The Co region was delimited to a 196‐kb region of the apple genome, between markers Mdo.chr10.11 and Mdo.chr10.15.

SELECTION FOR IMPROVED FRUIT TEXTURE AND STORABILITY IN APPLE

Several different genes have been reported to affect fruit texture in apple. We have analysed 158 cultivars for their allelic composition in the expansin gene MdExp7. Most of these cultivars had already been analysed for their allelic composition in the ethylene production-affecting gene Md-ACS1 but 29 additional cultivars were analysed also for this gene. Finally, we harvested fruit from 114 cultivars and measured firmness with a penetrometer directly at harvest and after 6 weeks (earlyripening) or 12 weeks (late-ripening cultivars) of cold storage. For the Md-Exp7 locus, an SSR allele with 198 bp has previously been suggested as a marker for the ability to retain fruit firmness during storage. However, we found that another marker with 202 bp was over-represented in (1) cultivars that also carry the favourable allele 2 in the Md-ACS1 locus, and in (2) more recently developed cultivars, both of which suggest that recent selection in several apple breeding programs around the world has favoured allele 202 more than allele 198. In addition, preliminary data from the firmness evaluations also suggest that allele 202 is more closely associated with higher initial firmness and better firmness retention during storage. Firmness was retained during storage to a very high degree by two ‘Antonovka’ types in spite of their unfavourable alleles in the Md-ACS1 and Md-Exp7 loci. These cultivars could thus be valuable in the search for additional fruit texture genes.

Genomic Selection for Fruit Quality Traits in Apple (Malus×domestica Borkh.)

The genome sequence of apple (Malus×domestica Borkh.) was published more than a year ago, which helped develop an 8K SNP chip to assist in implementing genomic selection (GS). In apple breeding programmes, GS can be used to obtain genomic breeding values (GEBV) for choosing next-generation parents or selections for further testing as potential commercial cultivars at a very early stage. Thus GS has the potential to accelerate breeding efficiency significantly because of decreased generation interval or increased selection intensity. We evaluated the accuracy of GS in a population of 1120 seedlings generated from a factorial mating design of four females and two male parents. All seedlings were genotyped using an Illumina Infinium chip comprising 8,000 single nucleotide polymorphisms (SNPs), and were phenotyped for various fruit quality traits. Random-regression best liner unbiased prediction (RR-BLUP) and the Bayesian LASSO method were used to obtain GEBV, and compared using a cross-validation approach for their accuracy to predict unobserved BLUP-BV. Accuracies were very similar for both methods, varying from 0.70 to 0.90 for various fruit quality traits. The selection response per unit time using GS compared with the traditional BLUP-based selection were very high (>100%) especially for low-heritability traits. Genome-wide average estimated linkage disequilibrium (LD) between adjacent SNPs was 0.32, with a relatively slow decay of LD in the long range (r 2 = 0.33 and 0.19 at 100 kb and 1,000 kb respectively), contributing to the higher accuracy of GS. Distribution of estimated SNP effects revealed involvement of large effect genes with likely pleiotropic effects. These results demonstrated that genomic selection is a credible alternative to conventional selection for fruit quality traits.

Investigation of dietary important components in selected red fleshed apples by GC–MS and LC–MS

Three red-fleshed apple cultivars (Malus ‘Geneva’: GFV-03, Hungarian hybrid: GFV-04, Malus pumila Niedwetzkyana: GFV-05) were investigated for their chemical composition by sHS–SPME–GC–MS and HPLC–DAD–MS/MS analytical techniques.In cultivars GFV-03 and GFV-05 sesquiterpene α-farnesene were dominant while the alphatic esters were present mostly in traces. In GFV-04 – the new disease resistant advanced selection of the Hungarian apple breeding program – hexanol and hexyl 2-methylbutanoate were present in larger amounts while the amount of α-farnesene was lower than the other two cultivars.Using HPLC–DAD–MS/MS four phenolic acid derivatives, four anthocyanins, six flavonoids of quercetin derivatives and two dihydrochalcone phloretin glycosides were identified or characterized among the detected sixteen phenolic compounds.