Inheritance and linkage relationships of isoenzymes in two interspecific cherry progenies

Two interspecific cherry progenies, Prunus avium ‘Napoleon’ × P. incisa E621 and ‘Napoleon’ × P. nipponica F1292, were analysed with polyacrylamide gel electrophoresis for 19 enzyme systems: alanine aminopeptidase (AAP), aldolase (ALD), alkaline phosphatase (AKP), arginine aminopeptidase (ARA), catechol oxidase (CO), diaphorase (DIA), endopeptidase (ENP), esterase (EST), formate dehydrogenase (FDH), fructose-bisphosphatase (FBP), β-galactosidase (GAL), glucose-6-phosphate dehydrogenase (G6PDH), β-glucosidase (GLU), glutamate dehydrogenase (GDH), glyceraldehyde-3-phosphate dehydrogenase (G3PDH), hexokinase (HEX), peroxidase (PRX), phosphorylase (PHO) and triose-phosphate isomerase (TPI). Activity for GAL was identical with GLU, and CO with PRX. In addition, activity for AKP was identical with some regions detected previously as acid phosphatase; and most of the PRX activity was identical with regions detected previously as superoxide dismutase. In all, 16 new segregating loci were identified, Ara-1, Dia-2, Est-1, Est-2, -6, -7 and -9, Glu-1 to -4, Hex-1, Pho-1 and -2, and Prx-8 and -9, together with 10 polymorphic putative loci. Analysis of cosegregations of the segregating loci with each other, and with loci established previously, resulted in 19 more loci being added to the cherry linkage map. Fifteen of these were new, and four had been described previously, but were hitherto unlinked. The additional linkages are: Ara-1– Dia-2– Mdh-2–Est-2; Glu-3/Prx-8–Glu-1/-2/-4–Prx-1/-9; Pgd-2–Pho-1/-2; Idh-2–Est-7–Est-6; (Amy-2)–Est-1–(Adh-4/-6); and (Acp-1/-2/-3)–Hex-1–(Gpi-2). (The bracketed loci had been mapped already). Several cherry linkages resemble linkages reported in apple. Analysis of 14 cultivars of P. avium for the same enzyme systems revealed polymorphism for just four of the 15 loci, and for an additional putative locus that was monomorphic in the interspecific material. This lack of isoenzyme polymorphism among cherry cultivars reduces the utility of these markers for linkage analysis and mapping in progenies of P. avium. This revised version was published online in July 2006 with corrections to the Cover Date.     

Comparison of isoenzymes in Prunus avium separated by two different electrophoretic techniques

Isoenzyme variation for seven systems revealed by two different electrophoretic procedures was compared in Prunus avium. Fourteen cultivars and 14 wild selections were analysed for acid phosphatase (ACP), isocitrate dehydrogenase (IDH), leucine aminopeptidase (LAP), malate dehydrogenase (MDH), phosphoglucomutase (PGM), shikimate dehydrogenase (SKD) and superoxide dismutase (SOD). Extracts were separated by isoelectric focusing (IEF) and by polyacrylamide gel electrophoresis (PAGE). For the eight loci that had been described previously in these enzyme systems on the basis of IEF analysis, we compared the variation revealed with IEF and PAGE. Similar variation was revealed for Acp‐1 and Pgm‐1, and the alleles revealed by PAGE could be identified directly with those reported for IEF. For Lap‐1, Mdh‐1 and Skd‐1, variation was seen with IEF but not with PAGE. For Mdh‐2, PAGE revealed additional variation not revealed by IEF. For Idh‐1, different patterns of variation were revealed by PAGE and IEF, and both procedures would be needed to genotype cherry accessions. We were unable to detect variation corresponding to that reported previously for Sod‐1 with either technique. The implications of these findings for allele labelling, for studies of genetic diversity and for linkage analysis are discussed.     

Correlation of isoenzyme polymorphism and Bayoud-disease resistance in date palm cultivars and progeny

Summary Seedlings of date palm (Phoenix dactylifera L.), obtained from seven cultivars crossed with two males, were analyzed by polyacrylamide gel electrophoresis for esterase (EST), glutamate oxaloacetate transaminase (GOT), endopeptidase (ENP) and alcohol dehydrogenase (ADH) polymorphisms. Eleven, eight, five and two phenotypes were revealed for the enzymes tested, respectively. Seedlings of F₁ populations derived from Bayoud (Fusarium)-resistant and low fruit quality cultivars were characterized by a high electrophoretic polymorphism, when compared with progenies of Bayoud-susceptible and high fruit quality cultivars. In almost all cases, the most frequent electrophoretic phenotypes scored for each enzyme in different F₁ populations, were similar to those of the corresponding parent cultivars. Heterozygous phenotypes have been found for, at least, 3 loci; Got-2, Est-1 and Enp, indicating that such loci could be used to screen for hybrid seedlings. The expected Mendelian segregation of allozymes has been observed for these 3 loci, in many F₁ populations. It seems that progenies of Bayoud-resistant cultivars are characterized by a high level of electrophoretic polymorphism. The estimation of this index and the search for genetic linkage with segregating allozymes, may be biochemical criteria useful as an aid in distinguishing date palm seedling populations derived from Bayoud-resistant cultivars and suitable for breeding programs.     

Inheritance of isozymes in peach x Prunus kansuensis and peach x Prunus davidiana hybrids

Summary Isozyme variation and inheritance were investigated with starch gel electrophoresis in peach (Prunus persica L. Batsch) x P. kansuensis Rehd. and peach x P. davidiana (Carr.) Franch. interspecific hybrids. Of five enzyme systems surveyed for polymorphism, four systems were identified as polymorphic [isocitrate dehydrogenase (IDH, EC 1.1.1.41), phosphoglucomutase (PGM, EC 2.7.5.1), aspartate aminotransferase (AAT, EC 2.6.1.1), and 6 phosphogluconate dehydrogenase (PGD, EC 1.1.1.44)] and may be useful as genetic markers in future cultivar and rootstock development. Analysis of progenies segregating for pairs of loci suggests a possible linkage between the loci coding for Aat-1 and Pgd-2. Independent assortment was observed for isozyme loci Idh/Pgm-2, Idh/Aat-1, Idh/Pgd-2, Pgm-2/Aat-1, Pgm-2/Pgd-2, and Aat-2/Aat-1. The red leaf locus, Gr, assorted independently of the isozyme loci: Idh, Pgm-2, Aat-1, and Pgd-2.     

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.     

Identification of QTLs for fruit quality traits in Japanese apples: QTLs for early ripening are tightly related to preharvest fruit drop

Many important apple (Malus × domestica Borkh.) fruit quality traits are regulated by multiple genes, and more information about quantitative trait loci (QTLs) for these traits is required for marker-assisted selection. In this study, we constructed genetic linkage maps of the Japanese apple cultivars ‘Orin’ and ‘Akane’ using F₁ seedlings derived from a cross between these cultivars. The ‘Orin’ map consisted of 251 loci covering 17 linkage groups (LGs; total length 1095.3 cM), and the ‘Akane’ map consisted of 291 loci covering 18 LGs (total length 1098.2 cM). We performed QTL analysis for 16 important traits, and found that four QTLs related to harvest time explained about 70% of genetic variation, and these will be useful for marker-assisted selection. The QTL for early harvest time in LG15 was located very close to the QTL for preharvest fruit drop. The QTL for skin color depth was located around the position of MYB1 in LG9, which suggested that alleles harbored by ‘Akane’ are regulating red color depth with different degrees of effect. We also analyzed soluble solids and sugar component contents, and found that a QTL for soluble solids content in LG16 could be explained by the amount of sorbitol and fructose.     

A genetic map of macadamia based on randomly amplified DNA fingerprinting (RAF) markers

The first genetic linkage map of macadamia (Macadamia integrifolia and M. tetraphylla) is presented. The map is based on 56 F₁ progeny of cultivars ‘Keauhou’ and ‘A16’. Eighty-four percent of the 382 markers analysed segregated as Mendelian loci. The two-way pseudo-testcross mapping strategy allowed construction of separate parental cultivar maps. Ninety bridging loci enabled merging of these maps to produce a detailed genetic map of macadamia, 1100 cm in length and spanning 70–80% of the genome. The combined map comprised 24 linkage groups with 265 framework markers: 259 markers from randomly amplified DNA fingerprinting (RAF), five random amplified polymorphic DNA (RAPD), and one sequence-tagged microsatellite site (STMS). The RAF marker system unexpectedly revealed 16 codominant markers, one of them a putative microsatellite locus and exhibiting four distinct alleles in the cross. This molecular study is the most comprehensive examination to date of genetic loci of macadamia, and is a major step towards developing marker-assisted selection for this crop. This revised version was published online in July 2006 with corrections to the Cover Date.     

Development of cultivar-specific DNA markers based on retrotransposon-based insertional polymorphism in Japanese pear

We developed retrotransposon-based insertional polymorphism (RBIP) markers based on the long terminal repeat (LTR) sequences of copia-like retrotransposon Ppcrt4 and flanking genome sequences, which were derived from 454 sequencing data from Japanese pear (Pyrus pyrifolia) ‘Hosui’. Out of 40 sequences including both LTR and flanking genome regions, we developed 22 RBIP markers and used them for DNA profiling of 80 pear cultivars: 64 Japanese, 10 Chinese (Pyrus ussuriensis) and 6 European (Pyrus communis). Three RBIP markers were enough to differentiate ‘Hosui’ from the other Japanese pear cultivars. The 22 RBIP markers could also distinguish 61 of the 64 Japanese pear cultivars. European pears showed almost no amplification of the 22 RBIP markers, which might suggest that retrotransposons had transposed during Asian pear evolution or reflect the genetic relationship between Asian and European pears. Sixteen of the RBIP markers could be positioned on a genetic linkage map of ‘Hosui’. The RBIP loci were distributed in 10 linkage groups, and some loci were very closely located within the same linkage group. The information obtained will be applicable to developing cultivar-specific RBIP marker sets in plants.     

Genetic control of isozymes in eggplant and its wild relatives

Summary This study was conducted to elucidate the inheritance and linkage relationships of isozymes in aspartate aminotransferase (AAT, EC 2.6.1.1), alcohol dehydrogenase (ADH, EC 1.1.1.1), phosphogluconate dehydrogenase (PGD, EC 1.1.1.43), phosphoglucomutase (PGM, EC 2.7.5.1) and shikimate dehydrogenase (SKDH, EC 1.1.1.25) in eggplant and its wild relatives. Segregating populations were generated by backcrossing of hybrids among the species. Evidence of Mendelian inheritance was obtained for seven loci: Aat-1, Adh-1, Adh-2, Pgd-1, Pgm-1, Pgm-2 and Skdh-1. Twenty-one pairs of loci were tested for independent assortment, suggesting three linked pairs, Aat-2 with Pgd-2 (R=0.35±0.07), Adh-2 with Pgm-1 (R=0.33±0.07) and Pgd-2 with Pgm-2 (R=0.32±0.06).Abbreviations AAT aspartate aminotransferase - ADH alcohol dehydrogenase - PGD phosphogluconate dehydrogenase - PGM phosphoglucomutase - SKDH shikimate dehydrogenase     

Identification of QTLs controlling harvest time and fruit skin color in Japanese pear (Pyrus pyrifolia Nakai)

Using an F₁ population from a cross between Japanese pear (Pyrus pyrifolia Nakai) cultivars ‘Akiakari’ and ‘Taihaku’, we performed quantitative trait locus (QTL) analysis of seven fruit traits (harvest time, fruit skin color, flesh firmness, fruit weight, acid content, total soluble solids content, and preharvest fruit drop). The constructed simple sequence repeat-based genetic linkage map of ‘Akiakari’ consisted of 208 loci and spanned 799 cM; that of ‘Taihaku’ consisted of 275 loci and spanned 1039 cM. Out of significant QTLs, two QTLs for harvest time, one for fruit skin color, and one for flesh firmness were stably detected in two successive years. The QTLs for harvest time were located at the bottom of linkage group (LG) Tai3 (nearest marker: BGA35) and at the top of LG Tai15 (nearest markers: PPACS2 and MEST050), in good accordance with results of genome-wide association study. The PPACS2 gene, a member of the ACC synthase gene family, may control harvest time, preharvest fruit drop, and fruit storage potential. One major QTL associated with fruit skin color was identified at the top of LG 8. QTLs identified in this study would be useful for marker-assisted selection in Japanese pear breeding programs.     

Linkage groups of isozymes,RFLP and RAPD markers in carrot (Daucus carota L. sativus)

Summary Genetic and linkage analysis of marker loci were performed with 4 selfed progenies, derived from single plant (I_0/1 lines) of carrot (Daucus carota L. sativus). The analysis of 58 markers included 1 morphological marker, 10 isozyme loci, 14 RFLPs, 28 RAPD markers, and 6 isolated PCR fragments used as RFLP probes. Linkage analysis was carried out with the MAPMAKER program and resulted in the construction of 8 linkage groups containing 55 markers with an average distance of 13.1 cM, 3 marker loci remained unlinked. 24% of the markers deviated significantly from the expected Mendelian ratios (1:2:1 or 3:1) due to gametic or zygotic selection. It was shown that isolated PCR amplification products can be used as RFLP probes to detect polymorphisms for a certain locus in progenies where the corresponding RAPD pattern is monomorphic or no amplification product is observed. Since carrot has a relative small genome the probability of amplifying repetitive DNA sequences is comparatively low. Thus PCR amplification products represent an additional useful source of RFLP probes.     

Mapping wound-response genes involved in post-harvest physiological deterioration (PPD) of cassava (Manihot esculenta Crantz)

The genome locations of the wound-response genes that were expressedduring the post-harvest physiological deterioration (PPD) of cassava, suchas phenylalanine ammonia lyase, -1.3 glucanase, hydroxyprolinerich glycoprotein, catalase, 1-aminocyclopropane 1-carboxylate, cysteineprotease inhibitor, aspartic protease, a partial cDNA for serine/threonineprotein kinase and peroxidase, have been identified on the frameworkmolecular genetic map of cassava. Also, molecular markers linked toputative quantitative trait loci (QTLs) influencing PPD of cassava weremapped using an F₁mapping population derived from elite parentallines (TMS 30572 × cm 2177-2). A molecular linkage map previouslyconstructed based on the segregation of 240 RFLP, 100 RAPD, 85microsatellite and five isoenzyme markers on 144 F₁ individuals wasused for the QTL mapping.A set of 10 molecular markers with a significant association with putativeQTLs for PPD were identified based on probability values < 0.005in order to minimize the detection of false positives. Based on single-markerregression, eight putative QTLs located on the linkage groups G, P, L, U,and X of the female-derived framework map were found to explain between 5–12% of the phenotypic variance of the PPD. In the male-derived frameworkmap, two putative QTLs on linkage groups C and L explained 13% and11% of this variance, respectively. This study thus identified the majorgenome regions of cassava related to physiological post-harvestdeterioration, thereby providing tools for the identification of gene(s)controlling this trait.     

Potential and limitations of isozymes for chromosomal localization of resistance genes against barley mild mosaic virus (BaMMV)

Summary To assess the possibilities offered by isozymes to locate resistance genes against barley mild mosaic virus (BaMMV), the isozyme patterns of 19 barley (Hordeum vulgare L.) genotypes carrying genes different from ym4 were determined. Of the 15 isozyme systems tested, only three were polymorphic, namely aconitate hydratase, esterase, phosphogluconate dehydrogenase, providing markers on four of the seven barley chromosomes. Studies of F₂ progenies derived from three crosses between resistant genotypes and susceptible varieties failed to reveal linkage between resistance genes and isozymes. Another goal of the experiment was to study the linkage relationships between ym4 and the esterase locus (Est1-Est2-Est4). Our estimates of the recombination rate between these two loci (3.41 and 8.32%) were in the range of those reported between these esterases and one of the resistance genes of the Chinese variety Mokusekko 3.     

Comparison of QTLs mapped in RILs and their test-cross progenies of tropical maize for insect resistance and agronomic traits

Quantitative trait loci (QTL) affecting resistance to south-western corn borer Diatraea grandiosella (SWCB) and sugarcane borer Diatraea saccharalis (SCB) have been identified previously in F_2:3 lines and recombinant inbred lines (RILs) of tropical maize using restriction fragment length polymorphism (RFLP) analyses. Our objective was to determine whether QTLs identified in these generations are also expressed in test crosses (TC) of RILs. A population of 166 TC progenies was developed by crossing RILs from the cross CML131 (susceptible) × CML67 (resistant) with the unrelated, susceptible tester line CML216. Resistance to first-generation SWCB, measured as leaf-feeding damage (LFD) under artificial infestation, and other agronomic traits were evaluated in two environments for the TC progenies and three environments for 183 RILs. The correlation between line per se and TC performance was low for LFD and intermediate for most agronomic traits. Estimates of the genotypic variance and heritabilities were smaller in the TC progenies than in the RILs for all traits. Quantitative trait loci were identified using an RFLP linkage map with 136 loci. For LFD, four QTLs were detected in the TC progenies, of which two were in common with nine QTLs previously mapped in the RILs. Few QTLs for agronomic traits were common to the two types of progeny, because of the low consistency of QTL positions for all traits in RIL and TC progenies, the use of TC progenies should be considered in QTL mapping studies as the first step for marker-assisted selection in hybrid breeding.     

The European Prunus mapping project Progress in the almond linkage map

Summary Six European research groups are collaborating to develop genetic markers and linkage maps for use inPrunus breeding programmes. A basic map with 200 RFLPs and 50 more markers including isozymes and RAPDs will be constructed using two highly segregating populations: an interspecific peach × almond F₂ and a cherry F₂. Then, the parents of eleven almond, cherry, peach or plum breeding progenies segregating for target characters will be screened for polymorphisms at the marker loci, and a set of reduced maps, one per progeny, will be constructed with markers spaced 20–30 cM and covering the whole genome. Cosegregation analysis of markers and characters of interest will allow us to find linkages between markers and major genes or quantitative trait loci responsible for the expression of these traits. A map with 72 markers, 7 isozymes and 65 RFLPs, has been developed at the IRTA-Cabrils laboratory using an intraspecific almond progeny, ‘Ferragnes’ × ‘Mono’. Probes for the analysis of RFLPs were obtained from almond genomic and cDNA libraries. The level of polymorphism for RFLPs and the distribution of markers in the chromosomes of almond are discussed.     

Inheritance of nut and kernel traits in almond (Prunus amygdalus Batsch)

Summary An almond breeding program was initiated in 1966 to develop improved cultivars for arid conditions with irrigation. Nut and kernel traits were evaluated for almond parents and progenies. Highly significant parent/progeny correlation coefficients (0.7–0.9) were found for shell hardness, percentage of kernel, in-shell (nut) and kernel weight, kernel length and width, as well as kernel color and outer shell retention.Double kernels and kernel thickness had low parent/progeny correlation coefficients. Shell hardness and percent kernel were highly correlated, as were shell hardness and outer shell retention, percent kernel and outer shell retention, and kernel width and nut weight.All but two of the evaluated traits (kernel thickness and percent doubles) appear to be highly heritable with mostly additive gene action, although some degree of dominance appeared to be involved in percent kernel, shell hardness and percent doubles.Contribution No. 185-E from Agricultural Research Organization, Israel.     

Genetic and linkage analysis of isozyme loci in Daucus carota L.

Summary Electrophoretic polymorphisms of eight enzyme systems were studied in leaves of Daucus carota ssp. sativus in order to identify additional isozyme loci and generate first linkage groups of genetic markers. The genetic analysis of aconitase (ACO), leucin aminopeptidase (LAP), menadione reductase (MDR), phosphoglucomutase (PGM), 6-phosphogluconic dehydrogenase (6-PGD), shikimate dehydrogenase (SKD), and triose phosphate isomerase (TPI) zymograms resulted in the identification of 8 isozyme marker loci, designated as Aco-1, Lap-1, Pgm-1, Pgm-3, 6-Pgd-2, Skd-1, Tpi-1, and Tpi-2. All loci segregated with codominant alleles and encoded for monomers (ACO, LAP, PGM, SKD), and dimers (6-PGD, TPI), respectively. MDR enzymes of the variable region MDR-2 appeared to be identical with Dia-2 isozymes. Tests of joint segregation for pairwise comparisons of all 14 isozyme marker loci now available in carrots indicate that 12 loci are linked in 4 linkage groups (marked K1 to K4) in the following order: Aco-1, Pgi-1, and Dia-3 (K1), Tpi-2, Got-2, and Lap-1 (K2), Got-3 and Tpi-1 (K3) and Pgm-1, Pgm-3, 6-Pgd-2 and Skd-1 (K4). Dia-2 and Got-1 remained unlinked. The possible duplication of a PGM locus and a 6-PGD locus is discussed.     

Effectiveness of genes for leaf rust resistance in international wheat rust nurseries, 1970–1975

Monogenic lines resistant to leaf rust of spring and winter wheats were grown in the world wheat-producing areas from 1970 through 1975. Lines containing the alleles Lr9 (Wi), Lr9 (Tc), and Lr19 (Tc) were more resistant to the leaf rust pathogen than those containing Lr1 (Tc), –1 (Wi), –1,3 (Wi), –2A (Tc), –2A (Wi), –2D (Tc), –3 (Tc), –3 (Wi), –10 (Tc), –16 (Tc), –17 (Tc), –18 (Tc), or –2D (Pld). Monogenic line Lr1 (Wi) possibly has more than one gene for resistance and resistance properties similar to cultivars with field resistance. A computer data base was created to produce the information used in this paper.Formerly Research Agronomist, Field Crops Laboratory, now Supervisoty Computer Specialist, DSAD; and Research Plant Pathologist, Germplasm Resources Laboratory, ARS, BARC-West, Beltsville, Maryland 20705.     

Two microsatellite markers flanking a dominant gene for resistance to soybean cust nematode race 3

The purpose of this work was to identifymicrosatellite markers linked to a gene forresistance to Heterodera glycinesIchinohe (Soybean Cyst Nematode – SCN) insoybean cultivar Hartwig. ABC₁F₂ mapping population derivedfrom a cross between Hartwig (resistant)and the Brazilian soybean line Y23(susceptible) was used. About 200microsatellite or simple sequence repeat(SSR) primer pairs were tested in a bulkedsegregant analysis (BSA). Those thatshowed clear polymorphisms were amplifiedin the BC₁F₂ population, whichhad been previously inoculated andevaluated for resistance/susceptibility toSCN Race 3. Three SSR markers linked toSCN resistance were detected in thepopulation. Two of them, Satt 038 and Satt163, flanking a dominant resistant gene(d/a = –0.90), explained 37% of thephenotypic variance. This gene was mappedat the edge of molecular linkage group G. Broad and narrow sense heritabilities wereestimated to be 50.54% and 37.73%,respectively. A selection efficiency of91.18% was obtained with the simultaneoususe of the two markers. The identified SSRmarkers will be useful tools for assistingthe selection of homozygous genotypes andfor expediting the introgression of the SCNresistance locus from cv. Hartwig tosoybean elite cultivars.