Apple Breeding Programs Research Articles

Fine genetic mapping of the Co locus controlling columnar growth habit in apple

Tree architecture is an important, complex and dynamic trait affected by diverse genetic, ontogenetic and environmental factors. 'Wijcik McIntosh', a columnar (reduced branching) sport of 'McIntosh' and a valuable genetic resource, has been used intensively in apple-breeding programs for genetic improvement of tree architecture. The columnar growth habit is primarily controlled by the dominant allele of gene Co (columnar) on linkage group-10. But the Co locus is not well mapped and the Co gene remains unknown. To precisely map the Co locus and to identify candidate genes of Co, a sequence-based approach using both peach and apple genomes was used to develop new markers linked more tightly to Co. Five new simple sequence repeats markers were developed (C1753-3520, C18470-25831, C6536-31519, C7223-38004 and C7629-22009). The first four markers were obtained from apple genomic sequences on chromosome-10, whereas the last (C7629-22009) was from an unanchored apple contig that contains an apple expressed sequence tag CV082943, which was identified through synteny analysis between the peach and apple genomes. Genetic mapping of these five markers in four F(1) populations of 528 genotypes and 290 diverse columnar selections/cultivars (818 genotypes in total) delimited the Co locus in a genetic interval with 0.37% recombination between markers C1753-3520 and C7629-22009. Marker C18470-25831 co-segregates with Co in the 818 genotypes studied. The Co region is estimated to be 193kb and contains 26 predicted gene in the 'Golden Delicious' genome. Among the 26 genes, three are putative LATERAL ORGAN BOUNDARIES (LOB) DOMAIN (LBD) containing transcription factor genes known of essential roles in plant lateral organ development, and are therefore considered as strong candidates of Co, designated MdLBD1, MdLBD2, and MdLBD3. Although more comprehensive studies are required to confirm the function of MdLBD1-3, the present work represents an important step forward to better understand the genetic and molecular control of tree architecture in apple.

LARGE-SCALE STANDARDIZED PHENOTYPING OF APPLE IN ROSBREED

The USDA - Specialty Crop Research Initiative-funded RosBREED project is focused on enabling marker-assisted breeding in the Rosaceae. New molecular tools for selection need to be developed before this technology will be widely accepted and applied to apple breeding programs. As well as detailed genotypic data of inter-related progenies, parents and ancestor cultivars, fully descriptive phenotypic data also need to be collected. For apple, fruit phenotyping begins at harvest, followed by 10 and 20 weeks regular storage, each followed by 7 days shelf life at room temperature. The standardized phenotyping protocols agreed by breeding teams in Washington, Minnesota and New York states will be presented in this paper.

Texture dynamics during postharvest cold storage ripening in apple (Malus × domestica Borkh.)

Texture is a principal quality factor and represents one of the main priorities in apple postharvest management and breeding programs designed for the creation of new ideotypes defined by a better fruit quality and extended storability. The apple panorama is characterized by a great variability of texture performance due to specific functional regulation and genetic control of the physiological machinery devoted to the degradation of the polysaccharide architecture of the middle lamella/cell wall structure. In this work we present an investigation of texture dynamics in apple, in terms of variation of several texture components dissected over two months of postharvest storage. Apple texture was assessed at harvest and after storage, by acquiring both mechanical and acoustic profiles in a collection of 83 apple cultivars. The general texture variability, illustrated over the reduced hyperspace defined by principal components, revealed a different variety distribution between the two stages. Time evolution plots and the novel storage index presented here highlighted that each single texture component behaves differently, as seen by some cultivars (i.e. ‘Fuji’) having a more favourable acoustic response after postharvest. The dissected fruit texture dynamics assessed in a set of reference apple cultivars are discussed.

Heritability of Morphological Traits in Apple Early-ripening Full-sib and Half-sib Offspring and Its Potential Use for Assisted Selection

To select the superior parents for the breeding program we oriented to produce new early-ripening cultivars, we evaluated more than 60 productive and vegetative characters in 108 native and imported cultivars grown in national collection for commercial apples located in Karaj, Iran, using an apple descriptor. The germination percentage of 100,000 hybrid seeds was 7% in the first year. In the second year, only 3000 from 7000 seedlings had to pass the final screening. Use of morphological markers as an early selection technique showed high efficiency in the apple breeding program. This study was conducted to determine heritability of certain morphological traits potentially used for selection of fruit early-ripening progenies in apple (Malus ×domestica Borkh.). Morphological traits in 3- and 4-year-old seedlings from 28 half-sib and 16 full-sib families were studied in 2007 and 2008, respectively. Parent–progeny correlations were analyzed using true-to-type progenies and their relative parents, all in the juvenile phase. Significant variations were observed between parental cultivars and half-sib and full-sib progenies for most of the studied traits. Positive correlations were found between seedling height and other morphological characters. A highly significant correlation (r = 0.98) was observed between branch distance along seedling stem and number of branches. The results showed that the heritability varied among the traits, ranging from moderate to high values. A high level of heritability was found in leaf chlorophyll concentration (LCC) and seedling heights in both half-sib and full-sib families. Heritability of half-sib progenies derived from the early-ripening parents was higher than the late-ripening parents. The relatively high heritability estimates for morphological traits, particularly in early-ripening cross combinations, suggested narrow-sense heritability as a criterion for early screening. The progenies of early cultivars exhibited the maximum and minimum heritability for seedling height (0.91) and leaf length (0.56), respectively. Oppositely, in the late-ripening progenies, the maximum and minimum heritability were found in LW and TD traits (0.79 and 0.42), respectively.

The role of Schmidt ‘Antonovka’ in apple scab resistance breeding

‘Antonovka’ has long been recognised as a major source of scab (Venturia inaequalis) resistance useful for apple breeding worldwide. Both major gene resistances in the form of the Rvi10 and Rvi17 and quantitative resistance, collectively identified as VA, have been identified in different accessions of ‘Antonovka’. Most of the ‘Antonovka’ scab resistance used in apple-breeding programmes around the world can be traced back to Schmidt ‘Antonovka’ and predominantly its B VIII progenies 33,25 (PI 172623), 34,6 (PI 172633), 33,8 (PI 172612) and 34,5 (PI 172632). Using genetic profile reconstruction, we have identified “common ‘Antonovka’ ” as the progenitor of the B VIII family, which is consistent with it having been a commercial cultivar in Poland and the single source of scab resistance used by Dr. Martin Schmidt. The major ‘Antonovka’ scab resistance genes mapped to date are located either very close to Rvi6, or about 20–25 cM above it, but their identities need further elucidation. The presence of the 139 bp allele of the CH-Vf1 microsatellite marker known to be associated with Rvi17 (Va1) in most of the ‘Antonovka’ germplasm used in breeding suggests that it plays a central role in the resistance. The nature and the genetic relationships of the scab resistance in these accessions as well as a number of apple cultivars derived from ‘Antonovka’, such as, ‘Freedom’, ‘Burgundy’ and ‘Angold’, are discussed. The parentage of ‘Reglindis’ is unclear, but the cultivar commercialised as ‘Reglindis’ was confirmed to be an Rvi6 cultivar.

Mode of inheritance in fruit acidity in apple analysed with a mixed model of a major gene and polygenes using large complex pedigree

With 5 figures and 2 tablesAbstractFruit acidity is an important characteristic to determine the marketability of apple (Malus × domestica Borkh.). To reveal the mode of inheritance in fruit acidity and to estimate the genetic parameters, we performed segregation analysis using a population from an apple breeding programme. Four models (mixed, Mendelian, polygenic and environmental) were compared to find the most likely mode of the inheritance of acidity. The phenotypic variance of acidity in the population was properly explained using a mixed model of a major gene and polygenes. The genotypic values of the major gene (AA, Aa and aa) were estimated to be 0.45, 0.52 and 0.92 g/100 ml in titratable acidity, respectively. The values of the homozygote (AA) and the heterozygote (Aa) were very close and lower than that of the other homozygote (aa), indicating that an allele of the major gene appeared to have complete dominance with a function of lowering acidity. The estimate of the heritability after accounting for the major gene was moderately high, 0.43, in the mixed model. This means that even with removal of the effect of the major gene, acidity could fluctuate considerably by the effect of polygenes. The proportions of progeny with adequate acidity differed greatly, depending on which genotype was used as parents for the crossing. Therefore, it is very important to know the genotypes of parental cultivars before crossing.

Putative resistance gene markers associated with quantitative trait loci for fire blight resistance in Malus 'Robusta 5' accessions.

BackgroundBreeding of fire blight resistant scions and rootstocks is a goal of several international apple breeding programs, as options are limited for management of this destructive disease caused by the bacterial pathogen Erwinia amylovora. A broad, large-effect quantitative trait locus (QTL) for fire blight resistance has been reported on linkage group 3 of Malus ‘Robusta 5’. In this study we identified markers derived from putative fire blight resistance genes associated with the QTL by integrating further genetic mapping studies with bioinformatics analysis of transcript profiling data and genome sequence databases.ResultsWhen several defined E.amylovora strains were used to inoculate three progenies from international breeding programs, all with ‘Robusta 5’ as a common parent, two distinct QTLs were detected on linkage group 3, where only one had previously been mapped. In the New Zealand ‘Malling 9’ X ‘Robusta 5’ population inoculated with E. amylovora ICMP11176, the proximal QTL co-located with SNP markers derived from a leucine-rich repeat, receptor-like protein ( MxdRLP1) and a closely linked class 3 peroxidase gene. While the QTL detected in the German ‘Idared’ X ‘Robusta 5’ population inoculated with E. amylovora strains Ea222_JKI or ICMP11176 was approximately 6 cM distal to this, directly below a SNP marker derived from a heat shock 90 family protein gene ( HSP90). In the US ‘Otawa3’ X ‘Robusta5’ population inoculated with E. amylovora strains Ea273 or E2002a, the position of the LOD score peak on linkage group 3 was dependent upon the pathogen strains used for inoculation. One of the five MxdRLP1 alleles identified in fire blight resistant and susceptible cultivars was genetically associated with resistance and used to develop a high resolution melting PCR marker. A resistance QTL detected on linkage group 7 of the US population co-located with another HSP90 gene-family member and a WRKY transcription factor previously associated with fire blight resistance. However, this QTL was not observed in the New Zealand or German populations.ConclusionsThe results suggest that the upper region of ‘Robusta 5’ linkage group 3 contains multiple genes contributing to fire blight resistance and that their contributions to resistance can vary depending upon pathogen virulence and other factors. Mapping markers derived from putative fire blight resistance genes has proved a useful aid in defining these QTLs and developing markers for marker-assisted breeding of fire blight resistance.

Implementation of Bar-code Technology in a Tree Fruit Breeding Program

Inventory control of trees and fruit samples in the Washington State University apple breeding program has been simplified by the use of bar codes. Tree labels incorporate individual bar-coded identities that can be scanned in the field when taking measurements or collecting samples. Bar codes on fruit sample labels also simplify data recording as well as improve the efficiency of the program by greatly reducing the risk of errors. The interface of bar-code identities with data organization and statistical software makes data analysis more straightforward.

Variability of properties of promising apple selections of the ‘Jonathan’ group

Apple (Malus ? domestica Borkh.) is economically the most important species of genus Malus Miller. Developing new apple genotypes is carried out on a large scale in many scientific institutes throughout the world. ?Jonathan? is one of four cultivars which have been used as the most frequent progenitors in apple breeding programmes worldwide. The paper presents six promising apple selections bred at Fruit Research Institute, and ?Jonathan? as the parental cultivar. The assessed selections derived from the crosses ?Jonathan? ? ?Idared? (J/3/60 and J/2/53), [?Jonathan? ? J/54/53/59] ? J/27/127/62 (J/4/106) and ?Jonathan? ? J/54/53/59 (J/1/55, J/1/71 and J/1/15). Major phenological properties (flowering phenophase and harvest time), cropping and pomological properties (morphometrical and chemical characteristics of fruits) were assessed. The highest fruit weight (J/2/53; 188.4 g) and yield per unit area (J/3/60; 34 t ha-1) were reported in selections derived from the cross ?Jonathan? ? ?Idared?. Selections raised from a cross between ?Jonathan? and J/54/53/59 have high quality fruits. The highest soluble solids content was found in J/1/55 (15.3%), while the highest total sugars and acids content was evidenced in J/1/71 (9.61%; 1.46%, respectively).

Towards genomic selection in apple (Malus × domestica Borkh.) breeding programmes: Prospects, challenges and strategies

The apple genome sequence and the availability of high-throughput genotyping technologies have initiated a new era where SNP markers are abundant across the whole genome. Genomic selection (GS) is a statistical approach that utilizes all available genome-wide markers simultaneously to estimate breeding values or total genetic values. For breeding programmes, GS is a promising alternative to the traditional marker-assisted selection for manipulating complex polygenic traits often controlled by many small-effect genes. Various factors, such as genetic architecture of selection traits, population size and structure, genetic evaluation systems, density of SNP markers and extent of linkage disequilibrium, have been shown to be the key drivers of the accuracy of GS. In this paper, we provide an overview of the status of these aspects in current apple-breeding programmes. Strategies for GS for fruit quality and disease resistance are discussed, and an update on an empirical genomic selection study in a New Zealand apple-breeding programme is provided, along with a foresight of expected accuracy from such selection.

THE HISTORY OF APPLE BREEDING IN PEOPLE'S REPUBLIC OF CHINA

China has more than 50 years of history in apple breeding. There have been 260 apple breeders from 40 universities or institutes all over the country, including the provinces of Liaoning, Hebei, Shaanxi, Shandong and Shanxi. In the past 50 years China released 270 apple varieties obtained by crossing, using ‘Fuji’, ‘Ralls’, ‘Delicious’, ‘Golden Delicious’, ‘Jonathan’, and ‘Toko’ as parents. Among them, ‘Qinguan’ and ‘Yanfeng’ bred in Shaanxi, ‘Huaguan’ and ‘Huashuai’ in Henan, ‘Liaofu’, ‘Yueshuai’, ‘Hanfu’, ‘Qiujin’, and ‘Huahong’ in Liaoning, ‘Guohong’ and ‘Yanshanhong’ in Hebei, ‘Danxia’ in Shanxi, and ‘Dailv’ in Shandong have a significant planted area. China has also initiated a program for breeding red flesh and juice apples with high acid content. Traditional crossing, sport selection, and open-pollinated seedling selection combined with marker-assisted selection, anther culture, transgenic engineering, are the approaches used for breeding new apple varieties. Research on inheritance of important traits, pre-selection and early evaluation of seedlings, methods to shorten the juvenility, resistance to apple canker and apple ring rot, and genetic engineering was also conducted in the apple breeding programs. China began apple rootstock breeding program thirty years ago. Traits of dwarfing, high disease resistance, drought tolerance, and cold hardiness, are the primary consideration in the apple rootstock breeding programs. China has released several apple rootstocks as S19, S20, SH15, 63-2-19, 77-34, Liaozhen No. 2, GM2 56, CX3, 75-9-5, and 75-7-1. A National Apple Breeding Association in China has been formed to coordinate the breeding groups across the country.

Application of a high-speed breeding technology to apple (Malus × domestica) based on transgenic early flowering plants and marker-assisted selection

Breeding of apple (Malus × domestica) remains a slow process because of protracted generation cycles. Shortening the juvenile phase to achieve the introgression of traits from wild species into prebreeding material within a reasonable time frame is a great challenge. In this study, we evaluated early flowering transgenic apple lines overexpressing the BpMADS4 gene of silver birch with regard to tree morphology in glasshouse conditions. Based on the results obtained, line T1190 was selected for further analysis and application to fast breeding. The DNA sequences flanking the T-DNA were isolated and the T-DNA integration site was mapped on linkage group 4. The inheritance and correctness of the T-DNA integration were confirmed after meiosis. A crossbred breeding programme was initiated by crossing T1190 with the fire blight-resistant wild species Malus fusca. Transgenic early flowering F(1) seedlings were selected and backcrossed with 'Regia' and 98/6-10 in order to introgress the apple scab Rvi2, Rvi4 and powdery mildew Pl-1, Pl-2 resistance genes and the fire blight resistance quantitative trait locus FB-F7 present in 'Regia'. Three transgenic BC'1 seedlings pyramiding Rvi2, Rvi4 and FB-F7, as well as three other BC'1 seedlings combining Pl-1 and Pl-2, were identified. Thus, the first transgenic early flowering-based apple breeding programme combined with marker-assisted selection was established.

Functional allelic diversity of the apple alcohol acyl-transferase gene MdAAT1 associated with fruit ester volatile contents in apple cultivars

Flavour is an important key factor of apple (Malus × domestica Borkh.) fruit quality, and its improvement is an important but complex breeding goal. Acetate esters are quantitatively the most important volatile compounds in apple fruit, and only a few of them dominate the typical aroma of a cultivar. Alcohol acyl-transferase (AAT) is a key enzyme involved in the last step of ester biosynthesis. The aim of this study was to target single nucleotide polymorphisms (SNPs) in an AAT candidate gene genetically associated with ester quantitative trait loci (QTL), to enable functional marker development for marker-assisted apple breeding programs. The AAT gene inventory of apple was characterized by in-silico mining of the assembled Golden Delicious genome, and 17 putative AAT genes in total were defined. MdAAT1 located on chromosome 2 was selected as the main candidate gene associated with QTL for different acetate esters, and its allelic diversity was assessed by direct amplicon sequencing in a collection of 102 apple cultivars characterized for ester volatile profiles. Sequencing a 468 bp nucleotide sequence of the MdAAT1 coding region resulted in the detection of four SNPs. In total, 18 different SNP haplotypes/heterozygous patterns were generated from the four SNPs identified within the apple collection. Association analyses resulted in highly significant associations of both individual SNPs and distinct haplotypes with the content of four acetate esters, including hexyl acetate, butyl acetate and 2-methyl-butyl acetate. About a third (31) of the 102 apple cultivars possessed the specific MdAAT1 haplotype H1 (C-A-C-A) and were characterized by strongly decreased ester concentrations. The contrasting H8 haplotype (T-G-T-G) was found in 28 varieties but was associated with normal to elevated ester concentrations. The observed association suggests a putative causal functional relationship between MdAAT1 and production of key apple esters.

The self-incompatible RNase S-alleles of Brazilian apple cultivars

Apple plants are self-incompatible because a genetic mechanism allows the female reproductive organ to recognize and reject self-pollen or pollen from genetic related individuals and allows non-self pollen to effect fertilization. Thus, there are implications to both breeding strategies and orchard management for fruit production. The purpose of this study was to identify and to characterize the S-RNase alleles of the gametophytic incompatibility among apple cultivars developed in Brazil, seeking to give support for choosing right combinations of parent in the apple breeding programs. It also sought to identify correct combinations of scion/pollinator cultivars of commercial apple orchards. A total of 16 specific S-RNase alleles primers were tested against DNA extracted from 12 Brazilian cultivars and their parents. The molecular analysis confronted to the reference cultivars, showed that the cultivars Daiane, Imperatriz and Princesa have the same incompatibility S3 and S5 alleles, while ‘Lisgala’ showed the alleles S2 and S5; ‘Suprema’, S1 and S9; ‘Catarina’, S1 and S19; ‘Joaquina’ and ‘Fred Hough’, S5 and S19; ‘Baronesa’, S3 and S9; ‘Duquesa’, S2 and S3. For ‘Primicia’ and ‘Condessa’ it was only possible to identify one of the S-alleles, namely S24 and S2, respectively, with the second allele remaining to be identified. Progeny test indicated the Mendelian inheritance for RNase alleles. Results of this study will be helpful to judiciously choose parents in apple breeding programs to improve compatibility.

Identification of wild apple germplasm (Malus spp.) accessions with resistance to the postharvest decay pathogens Penicillium expansum and Colletotrichum acutatum

With 3 figures and 4 tables Abstract Penicillium expansum and Colletotrichum acutatum cause blue mould and bitter rot of apples during storage which results in significant economic losses. Resistance to these pathogens in commercial apple cultivars has not been documented in the literature. An apple germplasm collection, from the centre of origin in Kazakhstan, is maintained in Geneva, New York. This collection represents a more diverse apple gene pool than commercial cultivars and was evaluated for resistance to the pathogens that cause blue mould and bitter rot. Resistance reactions were skewed towards susceptibility for both fungi and comprised the majority of accessions examined. However, resistance to P. expansum was confirmed in select accessions over multiple years. Maturation patterns and quality indices for soluble solids and acidity, which may also affect susceptibility, were highly variable and represent the genetic diversity of the germplasm collection. Resistance in four accessions to C. acutatum and two accessions resistant to both P. expansum and C. acutatum are reported here for the first time. Data from this study will serve as a foundation for conventional apple breeding programmes and molecular genetics investigations to provide resistance against blue mould and bitter rot in commercial apple varieties.

Association between Herbivore Resistance and Fruit Quality in Apple

Enhanced fruit quality, plant health, and productivity are major objectives in apple breeding. The undesirable fruit quality traits frequently associated with pest- and disease-resistant cultivars may be related to resource allocation tradeoffs. The objective of the present study was to evaluate the association between insect resistance and fruit quality in apple. The studied ‘Fiesta’ × ‘Discovery’ apple progeny was characterized by reasonable fruit firmness and optimal sugar content and acidity but small fruit size. There was a positive correlation between codling moth (Cydia pomonella) fruit infestation and fruit firmness. Additionally, a positive correlation was detected between shoot infestation by green apple aphid (Aphis pomi), fruit number as well as sugar content. Infestation by the apple leaf miner moth (Lyonetia clerkella), the rosy apple aphid (Dysaphis plantaginea), the leaf-curling aphid (Dysaphis cf. devecta), and the apple rust mite (Aculus schlechtendali) was not significantly related to fruit quality traits. The positive relationship of increased infestation by some pest insects and quality-determining fruit characteristics such as firmness or sugar content points to a possibly increased necessity for plant protection measures in apple cultivars producing high-quality fruits. One possible explanation of higher pest infestation in cultivars producing fruits with high quality is a tradeoff between resource allocation to defensive secondary metabolites or to fruit quality. By identifying a relationship between pest infestation and fruit quality, the present study highlights the need to consider pest resistance when breeding for high-quality apple cultivars. The use of genetic markers for fruit quality and pest resistance in marker-assisted breeding may facilitate the combined consideration of fruit quality and pest resistance in apple breeding programs.

New Products against Apple Scab and Powdery Mildew Attack in Organic Apple Production

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.

Correlation of Sensory Analysis with Physical Textural Data from a Computerized Penetrometer in the Washington State University Apple Breeding Program

Selecting for crispness instrumentally in fruit from apple (Malus ×domestica) breeding programs is notoriously difficult. Most breeders rely on sensory assessment for this important characteristic. Following the 2009 harvest, we used a computerized penetrometer to assess firmness and texture of apple selections from the Washington State University's apple breeding program and 16 standard reference varieties. Data were compared with sensory data from the apple breeding team. In addition to the expected high correlations between the various firmness measures of the computerized penetrometer and the sensory firmness values, our data also show a significant correlation between the computerized penetrometer crispness value and the sensory crispness value, thus demonstrating the benefit from using this equipment rather than the industry standard Magness–Taylor penetrometer.

Correlation of Sensory Analysis with Physical Textural Data from a Computerized Penetrometer in the Washington State University Apple Breeding Program

Selecting for crispness instrumentally in fruit from apple (Malus ×domestica) breeding programs is notoriously difficult. Most breeders rely on sensory assessment for this important characteristic. Following the 2009 harvest, we used a computerized penetrometer to assess firmness and texture of apple selections from the Washington State University's apple breeding program and 16 standard reference varieties. Data were compared with sensory data from the apple breeding team. In addition to the expected high correlations between the various firmness measures of the computerized penetrometer and the sensory firmness values, our data also show a significant correlation between the computerized penetrometer crispness value and the sensory crispness value, thus demonstrating the benefit from using this equipment rather than the industry standard Magness–Taylor penetrometer.

THE SELF-INCOMPATIBLITY S-ALLELES OF BRAZILIAN APPLE CULTIVARS

The purpose of this study was to identify and characterize the S-alleles of gametophytic incompatibility among apple cultivars developed in Brazil, to give support to correctly choose the combinations of parents in the apple breeding programs. It also seeks to identify correct combinations of scion/pollinator cultivars of commercial apples. For the molecular characterization, 16 specific S-alleles primers were tested. The molecular analysis confronted to the reference cultivars, showed that the cultivars 'Daiane', 'Imperatriz' and 'Princesa' have the same incompatibility alleles S3 and S5, while 'Lisgala' showed the alleles S2 and S5; 'Suprema', S1 and S9; 'Catarina', S1 and S19; 'Joaquina' and 'Fred Hough', S5 and S19; 'Baronesa', S3 and S9; 'Duquesa', S2 and S3; and for 'Primicia' and 'Condessa' it was only possible to identify one of the S-alleles, namely S24 and S2, respectively, the second allele remaining to be identified.