Morphological variations and isoenzyme polymorphism of date palm clones from in vitro culture acclimatized and established on soil in South Morocco

Five clones of date palm (Phoenix dactylifera L.) corresponding to three reputed Moroccan cultivars (BFG, JHL and BSK) and two selected seedling genotypes (S16 and S35), derived from in vitro culture, were acclimatized and planted in Errachidia soil (South Morocco) in 1989. After 10 years of culture, clones were evaluated on the presence/absence of the two principal morphological characters (offshoots, inflorescences). Then, their leaf extracts were subjected to electrophoresis on polyacrylamide gels in order to determine their isoenzyme polymorphism. Inflorescence formation is relatively more frequent in the clones S16 and S35 than in clones JHL and BSK. Clone BFG showed an intermediate situation. High isoenzyme variations were found for the oxidoreductases (peroxidases (POX) and polyphenoloxidases (PPO)), the transferase (glutamate oxaloacetate transaminase (GOT)) and the hydrolases (esterases (EST) and endopeptidases (ENP)) enzymes. The factorial component analysis exhibited a negative correlation between the two principal morphological characters (presence of inflorescences and offshoots formation). Date palm clones typified respectively by high inflorescences and high offshoots formed two separated groups showing each one some isoenzyme characteristics. All morphological and enzyme variations were discussed in respect to the genotype effect on the micropropagation process.     

Increasing productivity in sweet almond using selected clones of bitter almond

Summary Eight controlled crosses were made between seven different sweet-kerneled almond cultivars (Prunus dulcis [Mill.] D. A. Webb), and five crosses were made between sweet x highly floriferous bitter almond clones. Sweet x bitter progenies out-yielded the sweet x sweet matings by more than three to one in the first year of production. This was attributable to greater cropping efficiency rather than to tree size or precocity. There was no pleiotropic association or association due to linkage between bitterness and yield. The selected Alnem (bitter) clones appear to be potentially useful progenitors for increasing almond yield capacity by conventional breeding methodology.     

Breeding behavior for tuber protein in Solanum tuberosum and Tuberosum-phureja hybrids

Summary True protein content among tubers within a plant of Solanum tuberosum cv. Oneida was found to be negatively correlated with tuber size. A similar study of S. phureja genotype 148-17 revealed no correlation. Tuber protein was determined for 250 genotypes in each of four hybrid potato populations in a factorial mating design with four potato cultivars as stylar parents mated to four groups of pollen parents (4x cultivars, 4x high protein selections, 2x S. phureja, 2x high protein S. phureja). The hybrid population derived from the 4x high protein selections was significantly higher in protein content than the other populations. High estimates of general combining ability for tuber protein content were found for both stylar and pollen parents. Poor photoperiodic adaptation to growing conditions in northern latitudes was a possible explanation for the variable protein phenotypes typical of S. phureja and the lack of transmission of the high protein character in phureja to 4x-2x hybrids. Although protein content was negatively correlated with total yield, high protein segregates with good yield potential were identified in all four populations.Scientific Journal Series Article 11, 616 of the Minnesota Agricultural Experiment Station.     

An extended interspecific gene pool available to peach and almond breeding as characterized using simple sequence repeat (SSR) markers

Genetic diversity, as revealed by eighteenSimple Sequence Repeat (SSR) markers inthirty almond [P. dulcis (Mill.) D.A.Webb], twenty fresh-market peach [Prunus persica (L.), Basch], fifteenprocessing clingstone peach cultivars, andten rootstocks, established the geneticrelatedness among cultivars andcharacterized the variation within andbetween species. One accession each of thewild Prunus species, P.davidiana [(Carriere) Franch] and P.webbii [(Spach.) Vieh.], was included inthe analysis. The number of presumedalleles revealed by the SSR analysis rangedfrom one to six in peach whereas almondcultivars showed a range of three to nine.Peach cultivars clustered into ten groups,which are in general agreement withdocumented origin. Most processingclingstone peach cultivars clusteredseparately from fresh-market freestonecultivars supporting a distinct origin. Twomajor clusters were observed in almond withone containing California cultivars and theother containing European cultivars and theimportant California cultivar Mission.Results establish the value of SSR markersfor distinguishing different geneticlineages and characterize an extensive andlargely unexploited inter-species gene poolavailable to peach and almond breedingprograms.     

Genetic variation in the olive tree (Olea europaea L.) cultivated in Morocco

Summary Genetic variation was studied using enzyme polymorphism at 8 loci in ancient olive trees. These were being cultivated in 10 sites along a transect from North (Pre-Rif) to South (Anti-Atlas), involving the main ecological areas where the species is cultivated in Morocco. For the 328 trees studied, 16 alleles and 68 multilocus genotypes, of which one was present in more than half the individuals analysed, were detected. Eighty seven per cent of the total genetic diversity was attributable to within site variation and showed a high proportion of local genotypes. The highest values for both genotype number and heterozygosity were observed in the South of Morocco. Such high variation may be due to the partial domestication of olive material which may be derived from crosses between cultivars or between cultivars and feral or wild olive (oleaster) trees growing frequently in the Southern region. Genetic diversity in Moroccan olive, constitutes an important genetic resource which must be conserved for further breeding.     

Inheritance of resistance to Phytophthora fragariae Hickman in strawberry

Summary It has been found that complete resistance of the strawberry cultivars and selections Earliglow, Guardian, MdUS 2700, MdUS 2929, MdUS 3816 and Redchief to Phytophthora fragariae is inherited in a one-to-one ratio, suggesting that these genotypes have one major resistance gene effective to the races present in the test field.The high level of partial resistance of Cambridge Favourite has clearly been recovered in its progenies. However, from results presented here, no conclusions could be drawn with regard to the number of genes involved in the partial resistance of Cambridge Favourite. It is, however, suggestive that about half the susceptible selections derived from crosses with Cambridge Favourite have shown a relatively high level of partial resistance. The selections concerned were obtained by selection on horticultural characters in seedling populations planted on an uninfested field.     

A practical method for almond cultivar identification and parental analysis using simple sequence repeat markers

Early and accurate identification of almond [Prunus dulcis (Mill.) D.A. Webb] cultivars is critical to commercial growers and nurseries. Previously published simple sequence repeat loci were examined for their ability to distinguish commonly grown almond cultivars. Twelve highly polymorphic loci were selected for their ability to uniquely identify a set of 18 almond cultivars commonly grown in California, many of which are closely related. These markers also allow an accurate assessment of parent/progeny relationships among cultivars. This system can reliably identify at an early stage of development all major California almond cultivars in current production.     

Early generation selection for potato tuber quality in progenies of late blight resistant parents

Developing disease resistant cultivars is one of the major objectives for a potato (Solanum tuberosum L.) breeding program, but many resistant clones have not achieved commercial acceptance because of late maturity and non-marketable tuber characteristics. Selection for tuber quality should have greater emphasis inbreeding disease resistant cultivars. The objectives of this study were 1) to evaluate the ability of late blight (Phytophthora infestans (Mont.) de Bary) resistant parents to transmit chip-processing (tuber appearance, specificgravity, and chip-color) or tablestock (tuber appearance) quality to the offspring and 2) to compare selecting for tuber quality in single-hill versus eight-hill generations. We made crosses among eight unadapted potato cultivars (B0718-3,Bertita, Bzura, Greta, Libertas, Stobrawa, Tollocan, and Zarevo) with reported late blight resistance with adapted susceptible cultivars/breeding clones to generate 95populations (4,750 seedlings). Approximately 10% of the progeny from each cross were selected from single-hill plots based on tuber appearance, number, shape, and internal defects. These selected clones (408) were evaluated for tuber appearance, specific gravity, and chip-color. The same evaluations in the following year were made on tuber samples from eight-hill plots. Libertas and Tollocan were the best parents for transmitting chip-color; B0718-3, Zarevo, and Tollocan for transmitting tuber appearance; and Bzura, Libertas, and Zarevo for transmitting high specific gravity to the highest percentage of the offspring. Overall, 50% and 56% of the clones based on single- and eight-hill generation, respectively, were considered to possess chip-processing quality; over 90% of the clones had acceptable tablestock quality. A total of 71% of the clones possessing acceptable chip-processing and 95% of the clones possessing acceptable tablestock quality selected in both generations were identified in single-hill plots. The evaluation of tuber quality characteristics in single-hill generation not only permitted the identification of clones with acceptable chip-processing and tablestock, but also increased the amount of clonal information for the following generation of selection. In crosses between late blight resistant and susceptible clones, selection for tuber quality traits can be initiated in single-hill generation using a moderate selection intensity and precede late blight testing. This revised version was published online in August 2006 with corrections to the Cover Date.     

Morphological characterization of Mediterranean populations of Biserrula pelecinus L.

A collection of 24 populations of Biserrula pelecinus L. (biserrula)from Italy (Sardinia), Spain. France (Corsica). Morocco and Greece was evaluated in nursery rows at Perth, Western Australia. Fifteen morphological traits were recorded and chromosome numbers of representative populations were counted: The quantitative characters were analysed using principal component analysis and k-means clustering. The chromosome number of all accessions was 2n= 2x= 16. In other respects there was substantial variation in biserrula collected from the Mediterranean basin, the Moroccan populations in particular being distinct, some with strongly curved pods and others with long linear pods. All Greek populations had while flowers and large seeds. Populations from Italy. France and Spain were similar, with linear pods, blue flowers and smaller seeds. Most populations from Morocco were early flowering, had larger leaves, longer pods and produced more seeds per plant than other populations. All populations were extremely hard seeded (>98% hard-seeded after a one-summer exposure on the soil surface). It wits concluded that there is sufficient variation in Mediterranean populations of biserrula lo initiate a selection programme for southern Australia, and other areas with Mediterranean-type climates, especially for areas where serradella ((Ornithopus compressus L.) is adapted. Seed production is far easier than for serradella, and this advantage alone offers potential for its use in duplex soils where the deep rooting habit of serradella gives it an ecological advantage over conventional pasture legumes.     

Protein yield of oats as determined by protein percentage and grain yield

Summary Relationships among the traits protein percentage, grain yield, and protein yield of oats were studied with F₂-derived lines in F₃ and F₄ from 27 matings obtained by crossing high-protein with high-yield oat lines. High-protein parents were (a) selections from an Avena sativa bulk, (b) selections from three-way matings in which an initial parent was A. sterilss, and (c) cultivars. High-yield parents were derived from backcross populations involving A. sterilis accessions as donor parents.Significnnt genetic variation existed among F₂-derived lines for grain and protein yield in all matings and for protein percentage in all but one mating.Protein percentage had a highly significant negative correlation with grain yield (r=–0.33^**) when pooled over all matings, but in five, these two traits were not correlated. Overall, protein percentage showed a small negative correlation with protein yield (r=–0.09^*), and protein and grain yields had a high positive association (r=0.98^**). F₂-derived lines with both high protein percentage and high grain yield were obtained.High transgressive segregates for protein percentage occurred in two matings, for grain yield in nine, and for protein yield in 14. Most high transgressive segregates for protein yield were high because of high grain yield only, but in four matings, lines were found where protein yield was increased by concurrent increases in both protein percentage and grain yield.Only a few specific parental combinations between high-protein and high-yield parents produced segregates in which increased protein percentage contributed materially to high-protein yields.Journal Paper No. J-11264 of the Iowa Agriculture and Home Economics Experiment Stn., Ames, Iowa 50011. Project 2447.     

Breeding for resistance to Phialophora cinerescens (Wr.) van Beyma in glasshouse carnations (Dianthus caryophyllus L.)

Summary A breeding programme is described, aimed at introducing resistance to Phialophora cinerescens in glasshouse carnations of both the standard and the spray type. Four resistant clones, selected from seed-grown garden cultivars, served as resistant parents; the susceptible parents included the major glasshouse cultivar William Sim and some of its mutants and a few other American, French and Italian cultivars.In three generations of breeding, with extensive screening of young seedling populations, an adequate level of resistance had been reached. Selection procedure was henceforth changed to allow for primary selection on quality and productivity, followed by clonal resistance tests.Inheritance of resistance appears to be mainly additive; at least two gene pairs are likely to be involved. Under prolonged high infection pressure a significant non-additive variance can be demonstrated.     

AFLP analysis of genetic diversity within and between populations of perennial ryegrass (Lolium perenne L.)

Amplified fragment length polymorphism (AFLP) analysis has been used to measure genetic diversity in perennial ryegrass (Lolium perenne L.) and to relate intra- and interpopulation variation to breeding history. Cluster analysis of AFLP data from contrasting populations showed features consistent with the origins of these varieties. Significant differences in intrapopulation diversity were detected and partial separation of different cultivars was observed. Restricted base cultivars, derived from small numbers of foundation clones, were suitable for this type of study, allowing near complete discrimination of closely related cultivars. Analysis of bulked samples was based on the pooling of genomic DNA from 20 individuals from 6 selected populations. Cluster analysis of AFLP data from bulked samples produced a phenogram showing relationships consistent with the results of individual analysis. AFLP profiling provides an important tool for the detection and quantification of genetic variation in perennial ryegrass. This revised version was published online in August 2006 with corrections to the Cover Date.     

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.     

Utilizing Arachis cardenasii as a source of Cercospora leafspot resistance for peanut improvement

Summary Advanced generation 40-chromosome hybrids between A. hypogaea (2n=4x=40) and a wild diploid species. A. cardenasii were evaluated for early leafspot, Cercospora arachidicola resistance and agronomic potential. The objective of this investigation was to determine if early leafspot resistance derived from a wild species could be incorporated into the A. hypogaea genome. Interspecific hybrid selections were made and then compared in the field and greenhouse to susceptible cultivars and to A. hypogaea lines which are reported to be resistant to early leafspot. Significantly higher levels of resistance were found in five hybrid selections than in cultivated lines based on numbers of lesions per leaf. In a greenhouse study, several hybrid selections also had greatly reduced sporulation from lesions as compared to A. hypogaea. Several mechanisms of resistance are believed to be present. Although hybrid selections had small seeds and low yields as compared to A. hypogaea, a new and valuable source of early leafspot resistance derived from the species A. cardenasii is present.Paper no. 8814 of the journal series of the North Carolina Agricultural Research Service, Raleigh, NC 27695. This research was partially funded by AID-Peanut CRSP grant DAN-4048-G-SS-2065-00.     

The inheritance of stem rust and leaf rust resistance in some Ethiopian wheat collections

Summary Common and durum wheat populations obtained from Sweden and originally collected in Ethiopia were screened for resistance to steum rust and leaf rust. Resistant selections of common wheat were crossed and backcrossed with either stem rust susceptible RL6071, or leaf rust susceptible Thatcher. Genetic studies, based largely on tests of backcross F₂ families, showed that four of the selections had in common a recessive gene SrA. Plants with this gene were resistant (1⁺ infection type) to all stem rust races tested. This gene was neither Sr26 nor Sr29. The resistance of other selections, based on tests with an array of rust isolates, was due to various combinations of Sr6, 8a, 9a, 9d, 9c, 11, 13, 30, and 36. One of the selections had linked genes, Lr19/Sr25. Another selection had a dominant gene for resistance (;1 infection type) to all the races of leaf rust. With the possible exception of this gene for leaf rust resistance and SrA, no obviously new resistance was found.     

Comparative genetic analysis of field resistance to downy mildew in the lettuce cultivars ‘Grand Rapids’ and ‘Iceberg’

Downy mildew on lettuce is currently controlled using host resistance genes (Dm genes) that confer race-specific resistance in seedlings. Field resistance (FR) that is active in adult plants but not seedlings was identified in the cvs. Grand Rapids and Iceberg. The goal of our study was to evaluate the utility of Grand Rapids as a source of novel Bremia resistance alleles, particularly in comparison with Iceberg. To measure FR, downy mildew symptoms were evaluated following natural infection in field experiments. The responses of Grand Rapids and Iceberg were similar in many respects. Although both cultivars had a small percentage of plants exhibiting disease symptoms, the average disease ratings were as low as for cultivars with effective Dm genes. We observed no evidence for race specificity. FR was effective over 3 years of our study, despite documented variation within pathogen populations. Both cultivars lacked all known seedling resistance genes except Dm13, which was not responsible for the resistance observed in field experiments. Similar segregation of FR was observed in F₂ populations for both Grand Rapids and Iceberg. The presence of highly susceptible families within Grand Rapids × Iceberg populations suggested the presence of at least one unique resistance allele in each cultivar. Preliminary genetic analysis of FR from Grand Rapids revealed a high estimate of narrow-sense heritability that suggested simple inheritance, but single gene models did not fit the observed data. Our results suggest that Grand Rapids may represent an underutilized resource for controlling downy mildew in lettuce.     

Amplified fragment length polymorphism as a tool for molecular characterization of almond germplasm: genetic diversity among cultivated genotypes and related wild species of almond,and its relationships with agronomic traits

Amplified fragment length polymorphism (AFLP) analysis is a rapid and efficient method for producing DNA fingerprints and molecular characterization. Our objectives were to: estimate genetic similarities (GS), marker indices, and polymorphic information contents (PICs) for AFLP markers in almond cultivars; assess the genetic diversity of almond cultivars and wild species, using GS estimated from AFLP fingerprints and molecular characterization; and facilitate the use of markers in inter-specific introgression and cultivar improvement. The genetic diversity of 45 almond cultivars from Iran, Europe, and America, were studied assaying 19 primer combinations. In addition, several agronomic traits were evaluated, including flowering and maturity times, self-incompatibility, and kernel and fruit properties. Out of the 813 polymerase chain reaction fragments that were scored, 781 (96.23%) were polymorphic. GS ranged from 0.5 to 0.96, marker indices ranged from 51.37 to 78.79, and PICs ranged from 0.56 to 0.86. Results allowed the unique molecular identification of all assayed genotypes. However, the correlation between genetic similarity clustering as based on AFLP and clustering for agronomic traits was low. Cluster analysis based on AFLP data clearly differentiated the genotypes and wild species according to their origin and pedigree, whereas, cluster analysis based on agronomic data differentiated according the pomological characterization. Our results showed the great genetic diversity of the almond cultivars and their interest for almond breeding.     

Evidence of gene introgression in apple using RAPD markers

Summary A genomic remnant of Malus floribunda clone 821 introgressed into the cultivated apple M. x domestica Borkh. was identified using randomly amplified polymorphic DNA (RAPD) markers obtained by the polymerase chain reaction (PCR). Using a set of 59 oligonucleotide decamer primers, polymorphic DNA markers were identified among three pooled DNA samples. Based on the presence or absence of bands among bulked apple scab-resistant selections and cultivars, bulked scab-susceptible cultivars, and a M. floribunda clone 821 sample, one primer, A 15, identified amplified fragments in the scab-resistant bulked sample that was also unique to the M. floribunda clone 821. The unique band from M. floribunda clone 821 was amplified in four out of 17 scab-resistant selections/cultivars. This RAPD, designated OA15₉₀₀, identifies an introgressed fragment that has as yet no known function.     

Genetic relatedness among eastern North American blackberry cultivars based on pedigree analysis

Blackberry genetic relationships (Rubus subgenus Rubus Watson) have not been thoroughly studied. The University of Arkansas maintains one of the largest blackberry-breeding programs in the world and thus, in-depth knowledge of the cultivars released from the program and others instrumental in their lineages can aid in breeding endeavors. Pedigrees of 32 cultivars were traced to their founding clones. Genetic contribution (GC), maximum potential similarity (MPS), inbreeding coefficient, and coefficients of relationship (CR) were calculated for all genotypes. Nineteen founding clones contributed to the 32 cultivars, ranging from <1% to 19%. The top three founding clones for mean GC conferred nearly 50% to the 32 cultivars in this study, suggesting a somewhat narrow genetic base. Calculations for MPS ranged from complete similarity (1.00) to 0.00. Individual inbreeding coefficients ranged from 0.00 to 0.25. The coefficient of relationship was used as a method of determining genetic relatedness and ranged from 0.00 to 0.74. University of Arkansas cultivars had the highest MPS and CR in the study. This may be attributed to more generations of hybridization than the other cultivars. The MPS provided some comparable results to those of RFLP and RAPD molecular studies, but CR did not. The rather narrow genetic base of eastern North American blackberry cultivars does not create an imminent, significant concern for loss of diversity. However, more diverse germplasm should be infused for continuation of heterogeneity.     

Development of a seedling screening test for predicting relative grain protein content in oats

Summary Growth room experiments were conducted to study associations of grain protein content with properties of seedling leaf sections of oats (Avena sativa L.) using (1) 10 cultivars differing genetically in grain % protein, and (2) 10 populations of a single high protien cultivar (Hinoat) differing phenotypically in grain % protein. These populations, which were derived from a nitrogen fertilizer experiment, had grain protein concentrations which varied over the whole range displayed by the high and low protein cultivars when the latter were tested in a conventional field trial.Seedling leaf % protein was closely associated with grain % protein in both (1) and (2). Chlorophyll content per unit leaf area and leaf dry weight per unit leaf area were significantly higher in the high than in the low protein cultivars, and were significantly higher in all the Hinoat populations than in the low protein cultivars.Excised seedling leaf sections were placed on filter paper moistened with 1 ppm kinetin solution and kept in the dark at 25°C. After 96 h chlorophyll content per unit leaf area was again significantly higher in the high protein cultivars and in all the Hinoat populations than in the low protein cultivars, and the consequent differences in leaf colour were then readily visible. Absolute amounts of chlorophyll lost per unit leaf area were similar in all cultivars and populations, but the low protein cultivars showed a greater proportional loss (as % of initial content). A colour scale was used to visually rate the senesced leaf sections. The visual rating allowed the rapid separation of the high and low protein cultivars, and there was no significant variation in the ratings of the Hinoat populations.It is suggested that this procedure may be useful in the early selection phases of protein breeding programs for screening large populations rapidly at the seedling stage to detect genetic differences in potential grain protein content.Contribution No. 438 from Ottawa Research Station.