Incompatibility and resistance to woolly apple aphid in apple

The study investigated the reported linkage of the locus for resistance to woolly apple aphid with the locus for incompatibility. Apple seedlings from the cross ‘Northern Spy’(heterozygous for resistance) בTotem’(susceptible) were scored for resistance, and for incompatibility genotype, by analysis of stylar ribonucleases, and for Got‐1, the isoenzyme marker for incompatibility. Cosegregation analysis provided no evidence that the loci for resistance and incompatibility are linked. Two rootstock cultivars,‘M9’and ‘Merton 789′, which in early work had been reported to give poor set in crosses with ‘Northern Spy’, were found to have the same incompatibility genotype as ‘Northern Spy’, namely S₁S₃.‘M4’and ‘Irish Peach’, two other cultivars that had given poor set when crossed on to ‘Northern Spy’, appeared to be homozygous at the incompatibility locus and to have the genotypes S₃S₃ and S₁S₁, respectively.     

Genotyping apricot cultivars for self-(in)compatibility by means of RNases associated with S alleles

In previous work the existence of proteins with RNase activity associated with S alleles in apricot was demonstrated. These proteins were inherited as described previously for the inheritance of self‐compatibility in this species. In this study, new cultivars have been genotyped for self‐compatibility using this method and it has been demonstrated that in all self‐compatible cultivars examined, the self‐compatibility allele is the same and is associated with an RNase with high activity. Homozygous self‐compatible individuals have been detected among established cultivars as well as among seedlings following breeding activity. This germplasm is of great value within the breeding programme because only self‐compatible seedlings will be produced. The number of S alleles in apricot appears to be low and only eight different alleles have been found in the large number of different cultivars screened. Furthermore, there are alleles present in the Spanish population that are also found in the genetic pool of North American cultivars. The screening of a progeny from the cross between the American cultivar ‘Goldrich’ and the Spanish cultivar ‘Pepito’ demonstrated the existence of the common allele S₂ (detected previously by examining RNases), which was confirmed by the segregation of self‐compatibility in the progeny.     

Stylar ribonucleases in almond: correlation with and prediction of incompatibility genotypes

To clarify incompatibility relationships among almond cultivars, 35 were analysed for stylar ribonucleases, which have previously been shown to correlate with incompatibility S alleles. Stylar proteins were extracted and separated electrophoretically and the zymograms compared with ladders of ribonucleases corresponding to the 12 S alleles previously reported. Sixteen cultivars showed a band corresponding to two of the known ribonucleases, 17 showed one known ribonuclease and one ‘new’ band, and two showed two new bands. Twelve new ribonucleases were detected; 11 were attributed to new S alleles (S₁₃ to S23) and a mutant form of S₇ was attributed to S_7A. Genotypes were proposed for nine cultivars of five incompatibility groups that had not been genotyped previously, VII, X, XI, XII and XIII. Twenty‐four cultivars of unknown incompatibility relationships were provisionally genotyped: six of these could be assigned to existing groups and two new groups were established, XIV and XV, along with group O of cultivars with unique genotypes. Test crosses confirmed that eight pairs of cultivars showing similar zymograms were indeed cross‐incompatible, including the two representatives of each of the two new groups. Virtually all self‐incompatible cultivars of known genotype are listed in a table. The data should be useful for planning cultivar combinations for orchards and for designing crosses for breeding programmes.     

Identification and characterization of genomic DNA sequences of the S-ribonuclease gene associated with self-incompatibility alleles S1 to S5 in European pear

The stylar products of the S‐locus for the gametophytic self‐incompatibility (GSI) system in the Rosaceae are ribonucleases (S‐RNases). Recently, sequences for 13 pear S‐RNase alleles have been published and named following a letter–symbol nomenclature (S_a to S_d and S_h to S_p). To establish the correspondence between these sequences and the self‐incompatibility alleles we have described previously (S₁ to S₅), we have amplified genomic DNA with consensus primers from the cultivars, ‘Williams’ (S₁S₂), ‘Coscia’ (S₃S₄), ‘Butirra Precoce Morettini’ (S₁S₃), ‘Santa Maria Morettini’ (S₂S₃) and ‘Doyenne du Comice’ (S₄S₅) and identified PCR products specifically associated with each S allele. Cloning and sequencing of the amplification products has revealed that they correspond to European pear sequences already deposited in the database. This allowed us to link S‐RNase sequences with S allele phenotypes and to determine a correspondence between the symbol–letter nomenclature used to name S‐RNase sequences and the number‐based nomenclature used to name S alleles. Based on this result the prediction of new cross‐incompatibilities among pear cultivars is discussed. Finally, we propose a unified number‐based nomenclature to avoid future confusion denominating S alleles in pear.     

Development of a molecular marker for self‐compatible S4′ haplotype in sweet cherry (Prunus avium L.) using high‐resolution melting

Sweet cherry (Prunus avium L.) has stylar gametophytic self‐incompatibility, which is controlled by the multi‐allelic S‐locus and encompasses the highly polymorphic genes for the S‐ribonuclease (S‐RNase) and S‐haplotype‐specific F‐box (SFB), which are female and male determinants, respectively. The self‐compatible mutant SFB4′ corresponds to an allele variant of SFB4 and presents a frameshift mutation. Even though male‐determinant molecular markers can discriminate between SFB4 and SFB4′ alleles, the methods required are laborious, time‐consuming and expensive, and not suitable for massive analysis and integration into breeding programmes. Our aim was to develop molecular markers for the evaluation of self‐compatibility alleles in sweet cherry, that could be used as a high‐throughput screening strategy to identify SFB4 and SFB4′ alleles, based on a marker for male determinacy. Our results were consistent using primers flanking the mutation responsible for the SFB4′ allele. We designed a specific molecular marker and confirmed it in sweet cherry commercial varieties. This new molecular marker is feasible for self‐compatibility alleles in the male determinant in sweet cherry‐assisted breeding programs.     

Correlation of stylar ribonuclease zymograms with incompatibility alleles in sweet cherry

Summary Protein stylar extracts of 16 cultivars of sweet cherry (Prunus avium), from the 10 different incompatibility groups to which incompatibility alleles have been assigned, were separated on acrylamide gels using isoelectric focusing (IEF) and were stained for ribonuclease activity. When two cultivars from the same incompatibility group were analyzed they gave identical zymograms and the cultivars of the 10 different incompatibility groups gave in all eight distinct zymograms. The ribonuclease polymorphism could be correlated with the reported S allele constitutions of the cultivars. Three ribonuclease bands were identified that each consistently corresponded to one of the six known incompatibility alleles (S ₁, S₂ and S ₆), a fourth band apparently corresponded to S ₃ and to the combination of S ₄ and S ₅, and a fifth band to S ₄ and S ₅ in other combinations. Thus, it seems that S alleles of cherry have ribonuclease activity and that IEF is useful for distinguishing S allele constitutions. The ribonuclease pattern of Summit, a cultivar of unknown incompatibility group, indicated its incompatibility genotype to be S ₁S₂, and this was confirmed by controlled pollination. The same band corresponded to S ₄ and S ₄', the mutant allele in self-compatible cultivars. IEF and ribonuclease staining promise to be useful tools for exploring the incompatibility relationships of cherry cultivars and perhaps of other self-incompatible Prunus crops.     

All hermaphrodite progeny are derived by self-pollinating the sunrise papaya mutant

Self‐pollination of a hermaphroditic cultivar normally gives a ratio of 2 : 1 hermaphrodite to female papayas with genotypes M₂m and mm, respectively. Much effort has been dedicated to marking the sexual types of papaya at the seedling stage to distinguish hermaphroditic from female papayas. A hermaphroditic papaya mutant (SR*) has been obtained, derived from the ‘Sunrise’ papaya cultivar mutant. Self‐pollination of the mutant resulted in all progenies being hermaphroditic. The genotype of the female was lethal, as a result of a lethal gene being linked to the mm female gene complex in this case. However, a 3 : 1 segregation ratio was obtained from the progeny of the hermaphroditic cultivar ‘Thailand’ crossed with SR*, indicating that all genotypes survived. Homozygous genotypes (M₂M₂) would be lethal according to Storey's model. Randomly selected F1 plants of the ‘Thailand’ SR* combination were self‐pollinated to obtain an F₂ generation. The F₂ segregation ratio suggested that the SR* mutant had a different form of the M₂ allele, now designated as M_@, which allowed the dominant M_@M₂ to survive in cross combinations. Genetic study has proved that SR* has the M_@ml genotype, a new mutant. It is capable of producing all hermaphroditic papaya progenies.     

Heritability of early blight resistance in a Lycopersicon esculentum×Lycopersicon hirsutum cross estimated by correlation between parent and progeny

Sixteen‐hundred BC₁ plants of a cross between an early blight (EB) susceptible tomato (Lycopersicon esculentum Mill.) breeding line (‘NC84173’ maternal and recurrent parent) and a resistant accession (‘PI126445’) of the tomato wild species Lycopersicon hirsutum Humb. and Bonpl. were grown in a field in 1998. This population was segregating (among other traits) for growth habit, self‐incompatibility and earliness in maturity. To eliminate confounding effects of these factors on disease evaluation and h² estimation, plants that were self‐incompatible, indeterminate and/or late‐maturing were eliminated. The remaining plants (146), which were self‐compatible and determinate (sp./sp.) in growth habit, with early‐ to mid‐season maturity, were evaluated for EB resistance and self‐pollinated to produce BC₁S₁ seed. The 146 BC₁S₁ progeny families, consisting of 30 plants per family, were grown in a replicated field trial in 1999 and evaluated for EB resistance and plant maturity. For each of the 146 BC₁ plants and corresponding BC₁ families, the area under the disease progress curve (AUDPC) and final disease severity (final percentage defoliation) were determined and used to measure disease resistance. The distributions of the AUDPC and final percentage defoliation values in the BC₁ and BC₁S₁ generations indicated that resistance from ‘PI126445’ was quantitative in nature. Estimates of h² for EB resistance, computed by correlation between BC₁S₁ progeny family means and BC₁ individual plant values, ranged from 0.69 to 0.70, indicating that EB resistance of ‘P1126445’ was heritable. Across BC₁S₁ families, a small, but significant, negative correlation (r = ‐0.26, P < 0.01) was observed between disease resistance and earliness in maturity. However, several BC₁S₁ families were identified with considerable EB resistance and reasonably early maturity. These families should be useful for the development of commercially acceptable EB‐resistant tomato lines.     

Characterization of an S-allele associated protein in Japanese pear

Summary This paper describes some characteristics of a stylar protein associated with the S₂ self-incompatibility allele (S₂-protein) in Japanese pear reported earlier (Hiratsuka, 1992). The term style refers to style plus stigma in this paper unless indicated otherwise.The S₂-protein, which is a relatively major component of styles with a pI of 6.5, was present only in the style, and the stigmatic zone involved the protein much higher in quantity than upper half of the style, followed by lower half. Molecular weight was assumed to be 24,000 judged from migration distance in sodium dodecyl sulfate (SDS) polyacrylamide gel. Immature styles from 8 to 4 days before anthesis also contained the protein though the amount was relatively small. Neither the heat treatment of prepollinated styles nor the pollination (compatible or incompatible) altered the pI value and staining concentration of S₂-protein in the gel. The protein did not have so strong ribonuclease (RNase) activity as reported in S-proteins of Nicotiana alata (McClure et al., 1989) and the RNase activities of extractable stylar proteins from self-incompatible strains were almost the same as those from self-compatible strains.Abbreviations CBB Coomassie Brilliant Blue - IEF-PAGE isoelectricfocusing polyacrylamide gel electrophoresis - RNase ribonuclease - SDS-PAGE sodium dodecyl sulfate polyacrylamide gel electrophoresis     

Location of the self-incompatibility gene on the almond linkage map

A progeny obtained from the almond cross ‘Ferragnès’בTuono’ (Prunus amygdalus Batsch) was used to study the self-incompatibility trait in three different ways: fruit set, pollen tube growth and stylar ribonuclease activity. As expected from the genotypes of the parents, all progeny appeared phenotypically as self-compatible. However, the progeny could be scored for the segregation of stylar ribonuclease isozymes and thus allowed the incompatibility locus to be placed on the almond linkage map.     

Hybrid performance and heterosis in strawberry (Fragaria × ananassa Duchesne), regarding acidity,soluble solids and dry matter content in fruits

A top‐cross‐mating design among 29 S₄ inbred lines and tester (cultivar ‘Dukat’) was carried out to study their breeding value in terms of general combining ability (GCA). The objectives of this study were to evaluate the acidity, soluble solids and dry matter contents in fruits of progeny F₁ in comparison with S₄ inbred lines as well as the cultivars (S₀); identify strawberry genotypes with high value of GCA for use in cultivar development; and determine mid‐parent heterosis regarding S₄ inbred lines and cultivated strawberry. The 2‐year observations showed statistically significant differences between tested genotypes in terms of the studied traits. The highest breeding value based on GCA was estimated for Chandler 123‐5 for soluble solids and dry matter content, and Kent 7‐6 for acidity. Estimated mid‐parent heterosis had positive and negative values. The highest heterosis in terms of extract and dry matter content (26.71% and 17.50%, respectively) occurred in the offspring Chandler 123‐5 × ‘Dukat’, but as regards acidity in hybrid Chandler 123‐22 with cv. ‘Dukat’. The study of genetic divergence by dendrograms may help to identify parents suitable for obtaining hybrids with higher heterosis effects.     

Comparison of two fertility restoration systems against photoperiod-sensitive cytoplasmic male sterility in wheat

A ‘two‐line system’ using photoperiod‐sensitive cytoplasmic male sterility (PCMS) caused by Aegilops crassa cytoplasm under a long‐day photoperiod ( 15 h) has been proposed as a new means of producing hybrid varieties in common wheat. The PCMS line is maintained by self‐pollination under short‐day conditions, and hybrid seeds can be produced through outcrossing of the PCMS line with a pollinator under long‐day conditions. Two kinds of fertility restoration systems against the PCMS are known. One is involved with a set of multiple fertility‐restoring (Rf) genes in the wheat cultivar ‘Norin 61’ located on (at least) chromosomes 4A, 1D, 3D and 5D. The other is controlled by a single dominant major Rf gene, Rfd1, located on the long arm of chromosome 7B in the wheat cultivar ‘Chinese Spring’. To examine the degree of fertility restoration by these two systems, nine PCMS lines were crossed with ‘Norin 61’ and ‘Chinese Spring’ as the restorer lines, and the F₁ hybrids were investigated. The degree of fertility restoration was estimated by comparing the seed set rates in the F₁ hybrids having the Ae. crassa cytoplasm and those with normal cytoplasm. The results revealed that the fertility restoration ability of a set of multiple Rf genes in ‘Norin 61’ was higher than that of the Rfd1 gene in ‘Chinese Spring’.     

Self-pollination vs. cross-pollination in almond: pollen tube growth, fruit set and fruit characteristics

Pollen tubes reaching the ovary, fruit set and the main fruit characteristics of six self‐compatible genotypes (‘Marta’, ‘Antoñeta’, ‘Guara’, ‘Lauranne’, ‘S2332’ and ‘S4017’) of almond were studied after self‐ or cross‐pollination. No significant differences after self‐ or cross‐pollination were found in the number of pollen tubes reaching the ovary, the percentage of ovaries finally penetrated, fruit set and fruit characteristics. The results showed the possibility of obtaining suitable fertilization, yields and quality of fruits by self‐pollination of self‐compatible almond cultivars in a single cultivar orchard.     

Identification and characterization of new S‐alleles associated with self‐incompatibility in almond

Almond is a highly heterozygous species with a high number of S‐alleles controlling its gametophytic self‐incompatibility system (GSI). In this work, we have analysed 14 Spanish local almond cultivars for S‐RNase allele diversity. Five new S‐RNase alleles were identified by cloning and sequencing, S₃₁ (804 bp) in ‘Pou de Felanitx’ and ‘Totsol’, S₃₂ (855 bp) in ‘Taiatona’, S₃₃ (1165 bp) in ‘Pou d’Establiments’ and ‘Muel’, S₃₄ (1663 bp) in ‘Pané‐Barquets’ and S₃₅ (1658 bp) in ‘Planeta de les Garrigues’. Additionally, seven already known almond alleles could be recognized in the local cultivars studied. The high number of new alleles identified reveals the wide diversity of almond germplasm still existing and requiring characterization, and points to the possibility of new findings by a wider study focusing on other provenances. The almond S‐RNases have been compared to those of other Prunus species, showing a high identity and confirming that the S‐RNase gene in this genus presents a probable common ancestor.     

Determination of incompatibility genotypes in almond using first and second intron consensus primers: detection of new S alleles and correction of reported S genotypes

The work aimed to develop a reliable and convenient PCR approach for determining incompatibility S genotypes in almond. Initially, genomic DNAs of 24 accessions of known S genotype were amplified with novel consensus primers flanking the first and second introns of the S‐RNase gene. The PCR products separated on agarose showed length polymorphisms and correlated well with the reference alleles S1‐S₂3 and Sf. In addition, to improve discrimination between alleles of similar sizes, the same sets of primers but fluorescently labelled were used, and the products sized on an automated sequencer. These fluorescent primers were particularly informative in the case of the first intron, variation in the length of which has not been used previously for S genotyping in almond. Some reference alleles showed the same patterns with first and second intron primers, and others showed a microsatellite‐like trace. Subsequently, the S genotypes of 26 cultivars not genotyped previously and of four of uncertain genotype were determined. An allele described in Australian work as putative S₁₀ was shown to be a ‘new’ allele and ascribed to S₂₄ and evidence of five more ‘new’S alleles was found, for which the labels S₂₅‐S₂₉ are proposed. This PCR approach should be useful for genotyping in other Prunus crops.     

self-(in)compatibility almond genotypes: A review

To compile self-(in)compatibility almond genotypes, a review of 133 commercial cultivars of wide geographical origin was made. The information gathered from own and mainly published work will be useful for both grower's cultivar choice when planting and for breeder's cross design when planning. The almond S genotypes compiled were identified using five different methods: biological (pollination tests in the field and in the laboratory) and molecular (RNases, PCR and sequencing). In most cases, genotypes were assigned after combining more than one technique. Cultivars were classified into three categories: self-incompatible (99), self-compatible (16) and doubtful self-incompatible (18). The database is divided in 9 fields (name, origin, parentage, obtention year (crossing, selection or release), S genotype, technique used, reference, consensus genotype, and cross incompatibility group). A study of the 27 S alleles already identified and their geographical distribution within the cultivated almond is also presented. The study was divided into cultivars of known and unknown parentage and the distribution of S alleles frequencies was uneven among the 133 cultivars. S allele frequencies are related to geographical origin. Some alleles (S ₁, S ₅, S ₇ and S ₈) are more frequently observed than the others among cultivars of both known and unknown parentage. In the cultivated almond, the S f allele is only found in the Puglia region, Italy. The S _f frequency is three times higher in cultivars released from breeding programmes than in cultivars selected by growers. From the 351 resulting possible genotypes by combination of the 27 S alleles identified only 20 CIG (0-XIX) have been established, which represents a small fraction of the whole genetic diversity of this polymorphic gene in almond.     

A YA-type cytoplasmic male-sterile source in common wheat

A new cytoplasmic male‐sterile (CMS) system for hybrid wheat breeding, YA‐type CMS line with the cytoplasmic mutant from the common wheat variety ‘CA8057’, was developed by the Institute of Genetics and Developmental Biology, Chinese Academy of Sciences. The pollen sterility of YA‐type CMS line was easily maintained but difficult to restore. Some sterile lines with desirable agronomic performance, such as msYA‐‘CA8057’ (BC₁₇), msYA‐‘Yuandong 6’ (BC₉), msYA‐‘Jin 411’ (BC₉), msYA‐‘WL1’ (BC₁₀), msYA‐‘Yanshi 9’ (BC₁₀), msYA‐‘BPm16’ (BC₉), msYA‐‘Jindong 8’ (BC₉) and msYA‐‘Jinmai 33’ (BC₉), were bred and a restorer line GR1 was screened with 26 new restorer lines being developed by transferring restorer genes from GR1. It was found that abnormal phenomena occurred at the uninucleate‐pollen stage and the abortive pollen was poor in starch content and other components. The variance analysis of agronomic traits in eight sterile lines indicated that there was no general negative effect of cytoplasm. The genetic analysis for fertility restoration showed that two pairs of independent major genes (designated YARf₁YARf₁YArf₂YArf₂) and some minor genes could be involved in the fertility restoration in restorer line GR1, and YARf₁ was epistatic over YARf₂ for the genetic effect of fertility restoration. As a new CMS system, the YA‐type CMS line was of potential value for hybrid wheat breeding and should be further studied.     

S-allele identification by PCR analysis in sweet cherry cultivars

Gametophytic self‐incompatibility, governed by the S‐locus, operates in sweet cherry. The knowledge of the S‐genotype of sweet cherry cultivars is therefore essential to establish productive orchards by defining compatible combinations. The isolation of sweet cherry S‐R Nases has allowed the use of different molecular techniques to characterize the S‐genotypes of sweet cherry cultivars. Previously, incompatibility group assignment could only be carried out on mature trees through pollination tests. In this work, PCR analysis with primers designed on the conserved sequences of sweet cherry S‐R Nases has been used to characterize the S‐genotype of 71 sweet cherry cultivars, including 26 cultivars whose S‐allele constitution had not been previously described. This approach has allowed the detection of alleles that had not been amplified by PCR before, to identify six putative new S‐alleles, to define three new self‐incompatibility groups and to compile the standards for a PCR‐based S‐allele typing method in sweet cherry.     

Inheritance of stylar ribonucleases in cherry progenies, and reassignment of incompatibility alleles to two incompatibility groups

Stylar proteins were extracted from parents and seedlings of six progenies of cherry (Prunus avium), separated using isoelectric focusing, and the gels stained for ribonuclease activity. The zymogram of each plant showed two main ribonuclease bands in the region pI 8.3 to 9.6. Progenies from crosses of parents with one band in common segregated into just two classes, whereas progenies from crosses of parents with no common bands segregated into four classes, the two types of segregation corresponding to those expected from semi-compatible and fully-compatible crosses respectively. This behaviour was consistent either with the ribonuclease locus being tightly linked with the self-incompatibility, S, locus, or else with the S locus coding for the ribonuclease variants. Evidence favouring the latter hypothesis is discussed. An apparently anomalous segregation led us to assign to ‘Bradbourne Black’ a genotype different from that previously reported, and analysis of some other cultivars in the same incompatibility group, Group VII, led us to conclude the genotype of this group is S₃S₅, and not S₄S₅ as previously reported. Correspondingly, we suggest the genotype of Group V is S₄S₅, and not S₃S₅. Five new S alleles, S₇, S₈, S₉, S₁₀ and S₁₁ were proposed in parental cultivars and selections that had not previously been assigned a genotype. This revised version was published online in July 2006 with corrections to the Cover Date.