Frequency of euploids in different seed size classes of hexaploid triticale

Summary Bulk seeds of each of nine strains of hexaploid triticale were classified according to size by passing them over four round-holed sieves, 8/64, 9/64, 10/64 and 11/64-inch mesh. The actual size was different in different strains depending on the characteristic seed size of the strain (Table 2). Of the nine strains, six had low aneuploid frequency (11.8% average) and three had high aneuploid frequency (39.0% average) in the bulk populations. Chromosome numbers were counted in root-tip mitosis of germinating seeds.The frequency of euploids was highest in large-seed classes in all but one strain, UM 6608 (Group F). The euploid frequency was variable in medium- and small-seed classes. It was suggested that the screening of larger seeds would give a higher frequency of euploids, particularly in most populations with a low frequency of aneuploids.     

Variation for crossability in a reciprocal,interspecific cross involvingHordeum vulgare andH. lechleri

Summary Several crossing series including the hexaploid (2n=6x=42), South American speciesHordeum lechleri and diploid (2n=2x=14) cultivated barley (H. vulgare) were performed. Barley functioned better as the paternal than as the maternal parent in all cases. Viable offspring were only obtained from one hybrid combination when barley was used as the maternal parent. There was an environmental influence on the success of crosses. A high seed set was counteracted by a lower germination frequency. The outcome is that different crossing series give similar results. As a result of chromosome elimination and in a few cases duplication of especially the barley chromosomes, the chromosome numbers of the offspring (239 plants) varied from 2n=21 (trihaploids ofH. lechleri) to 2n=30. Fifty-five % of the plants were euploid with the number expected for a hybrid (2n=28). The frequency of hyperploids, euploids, hypoploids (2n=22–27) and trihaploids varied by year, locality, type (winter/spring) of barley,H. lechleri population, and crossing direction.     

The stabilization of chromosome numbers and the maintenance of euploidy in Brassicoraphanus

Summary To examine whether chromosome numbers of Brassicoraphanus (amphidiploids between Brassica japonica Sieb. and Raphanus sativus L.) are stable or not, the following four items were studied with some plants during the 2nd–11th generations: (1) chromosome numbers of open-pollinated progenies from eu-, hyper-, and hypoploids, (2) chromosome distribution at metaphase II in these plants, (3) frequency of euploids in relation to flower colour and generation, (4) seed fertility in eu-and aneuploids in relation to flower colour. In early generations, hyper-and hypoploids were frequently produced from euploids. In later generations, however, the chromosome number became less unstable. In euploids (2n=38), chromosome numbers at metaphase II showed some variation, and the mean frequency of the euploid chromosome number (n=19) was approximately 78%. This value was almost the same in white-and yellow-flowered plants through early and late generations. Nevertheless, yellow-flowered plants tended to produce euploids more frequently than did white-flowered ones. It is assumed that the difference in euploid productivity between yellow-and white-flowered plants is due to the difference in seed fertility between them. The progeny of each hypoploid showed higher chromosome numbers than their parents. The progeny of each hyperploid showed lower chromosome numbers than their parents: they were approaching to euploidy. This phenomenon, together with higher fertility of euploids and lower fertility of aneuploids, will favor the maintenance of euploidy of this strain.     

Induction of haploids and aneuhaploids in colchicine-induced tetraploid Solanum chacoense Bitt.

Summary The species Solanum chacoense BITT. (2n=2x=24) is a tuber-bearing, self-incompatible species which is important both for breeding and for genetic research. It crosses readily with most other tuber-bearing Solanum species including the common potato S. tuberosum (2n=4x=48). Gametophytic incompatibility hampers research in and utilization of this species. Doubling the chromosome number by colchicine makes it a self-compatible autotetraploid. By crossing selfed progeny of 4x-S. chacoense with a number of haploid-inducing diploid Solanum species a high yield of different dihaploid S. chacoense individuals (2n=24) could be obtained from one originally diploid clone: S. chacoense CPC 1153. More than 160 haploids showing a large variability were identified. The average haploid frequency was 53.7 per 100 berries. Most hybrid plants (70–100%) from four 4x × 2x crosses studied were tetraploid. The frequency of triploid hybrids was low (0–10%). Haploid-inducing capacity of fifteen male parents used in this study varied from 0–141 haploids per 100 berries. Careful examination of 156 haploids revealed 15 viable aneuhaploids (2n=25, 26, and 27), i.e. 9.4%. The potential value of these aneuhaploids is discussed.About 50% of the haploids were sufficiently male fertile to use them in crossing. A few of them set berries after selfing. Five aneuhaploids including the one with 27 chromosomes were successfully crossed as females with a diploid hybrid clone.     

Recurrent selection for increased protein content in yellow mustard (Sinapis alba L.)

Increasing protein content is an important objective in breeding high protein oilseed yellow mustard (Sinapis alba L). The objectives of this research were to increase meal protein content, study population variation during three cycles of selection for increased meal protein content, and quantify the relationships of protein with oil and 1000‐seed weight. Recurrent selection was employed with half‐sib family evaluation in replicated field trials. Meal protein content increased by an average of 1 % per cycle. The correlation between meal protein and seed oil content was negative (r= ‐0.49 to ‐0.58). The population shifts, with selection, reflected successful increase of average meal protein content, and an increased frequency of genotypes with high meal protein content. Furthermore, simultaneous selection for meal protein and seed oil content was possible. The correlation between meal protein content and seed weight was positive (r= 0.29‐0.39) and thus selecting for increased meal protein content posed no risk of decreasing seed weight in this yellow mustard germplasm.     

Cytogenetic and isozymic characterization of anther-panicle culture derived tall fescue aneuploids

Summary Chromosome associations of 44 tall fescue (Festuca arundinacea Schreb., 2n=6x=42) plants derived from anther-panicle culture of Kentucky 31 were evaluated to determine if new genetic stocks could be identified. Seventeen of the plants were euploids (21 II), two were monosomic (20II+1I), 22 were double monosomic (19II+2I) and three were triple monosomic (18II+3I). Zymograms were obtained for phosphoglucoisomerase (PGI), glutamate oxaloacetate transaminase (GOT), acid phosphatase (ACPH), malate dehydrogenase (MDH) and 6-phosphogluconate dehydrogenase (6-PGD). The zymograms were identical for GOT, ACPH, and 6-PGD but different patterns were found for MDH and PGI in some of the double monosomics and euploids from a different piece of callus than the majority of the plants.Contribution of the USDA-ARS in cooperation with the Kentucky Agricultural Experiment Station. Scientific Journal Series No. 86-3-61.     

The potential for breeding an improved lucerne-rhizobium symbiosis. 1. Assessment of genetic variation

Summary Six cultivars of lucerne (Medicago sativa L.) were grown in all possible combinations with eight strains of Rhizobium meliloti in order to assess genetic variation in symbiotic nitrogen fixation. Host genotype and Rhizobium genotype effects on nitrogen fixation were respectively 4.8% and 21.0% of total phenotypic variance. Genetic variation due to host cultivar × Rhizobium strain interactions accounted for a further 6.0% of phenotypic variance. The results indicated low heritability of general symbiotic effectiveness in the host with interaction effects being large enough to suggest that plant performance may be unpredictable with populations of R. meliloti in field soils. Joint regression analysis showed that about 50% of the interactive variation could be explained by generalized differences in the sensitivity of cultivars to alterations in the genotype of Rhizobium strains. One cultivar, Siriver, was relatively insentitive to changes in the Rhizobium genotype whilst still maintaining high average yield. The implications of the results for lucerne breeding are discussed.     

Chromosomal and genic structure of Brassicoraphanus related to seed fertility and the presentation of an instance of improvement of its fertility

Summary In order to elucidate the mechanism of low fertility of Brassicoraphanus, i.e., amphidiploids between Brassica japonica Sieb. and Raphanus sativus L., the chromosome number of 253 plants was studied during the 3rd–9th generations for their seed fertility. Meiotic irregularity showed no connection with degree of sterility. Brassicoraphanus consisted of euploids (2n=38), hyperploids (2n=39–43) and hypoploids (2n=34–37) with white or yellow flowers. The number of plants was highest in euploids and became lower as the chromosome number diverged from the euploid number. Further, seed fertility was highest and the range of its variation widest in euploids. The seed fertility of aneuploids became lower and its variation narrower in proportion to the number of chromosomes additional to or missing from the euploid number. Yellow-flowered plants were superior in seed fertility to white-flowered plants. Seed fertility of plants is primarily affected by their chromosome numbers and secondarily modified by genic effects. As a whole, seed fertility of Brassicoraphanus increased gradually and its variation widened with the advance of generations. This was explained mainly by the increase of balanced combinations of genes.     

Origin and variation of gliadin proteins associated with pasta quality in durum wheat

Summary Studies were made of the presence and frequency of occurrence of gliadin bands 42 and 45 in three samples of Aegilops sharonensis Eig and 59 samples of wild tetraploid wheat (Triticum dicoccoides Korn.) from natural distributions of these species in Israel.Two samples of Ae. sharonensis possessed a band in position 45 and one possessed no bands corresponding to either band 45 or band 42. In T. dicoccoides, band 45 was either present or not and 42 was always absent. In its grassy and intermediate growth habit forms, (believed to be more primitieve than the cercal forms) band 45 appeared to be more frequent than in the cereal form.The presence of band 45 in the Ae. sharonensis, and its relatively high frequency in T. dicoccoides, populations from Mt. Hermon (likely to be relatively free from introgression from cultivated tetraploid wheat) indicate the likelihood of a primary origin of the allele coding for band 45. The absence of band 42 from all Ae. sharonensis and T. dicoccoides populations in this study, indicates a more recent evolutionary origin of the allele coding for this band, possibly arising as a mutation during the domestication of tetraploid wheat.The results have implications for breeding programmes in tetraploid wheat.     

Identification of sugarcane microsatellites associated to sugar content in sugarcane and transferability to other cereal genomes

Microsatellites or simple sequence repeats (SSRs) markers are very informative for various applications in genetics and breeding. Information obtained with these markers has contributed to a better understanding of evolution and the complexity of the sugarcane genome. With the objective of identifying a large set of polymorphic microsatellite markers designated as Unigene derived Sugarcane Microsatellite (UGSM) and Sugarcane Enriched Genomic Microsatellite (SEGMS), 351 UGSM and 36 SEGMS were tested to find out informative SSRs marker for sugar content. These markers were screened and validated for their use in genetic diversity, cross transferability and comparative linkage potential in high and low sugar bulk of two segregating progenies and twenty each, cultivated high and low sugar cultivars. 158 (40.83%) of the microsatellite markers (144-UGSM: 14-SEGMS) were found to be highly robust and polymorphic. Cross amplification was estimated among nineteen accessions of six sugarcane cultivars, one inter specific hybrids, five related species, four related genera, and three divergent genera by using 27 UGSM primers. Analysis of 388 alleles, amplified by these markers, indicated the high number of observed allele ranged from 2 to 26, with an average of 14.37 alleles detected per locus. High level of polymorphism detected by these markers among sugarcane species, genera and cultivars was 96.3%, while cross-transferability rate was 98.0% within Saccharum complex and 88.27% to cereals. Wide range of genetic diversity (0.33–0.79 with an average of 0.56) assayed with UGSM markers suggested their importance in various genotypic applications in sugarcane.     

Orientation and integration of the classical and molecular genetic maps of chromosome 11 in rice

Summary The classical genetic map and molecular map of rice chromosome 11 were oriented to facilitate the use of these maps for genetic studies and rice improvement. Three morphological markers (d-27, z-2, and la) were crossed to a rice breeding line, IRBB21, which has the Xa-21 gene for bacterial blight resistance. Three F₂ populations were analyzed with RFLP markers known to be located on chromosome 11. Segregation analysis of molecular markers and morphological markers was used to construct an RFLP map for each population. The recombination frequency between markers varied from population to population although the marker order on the maps was the same for all three populations. Based on a common set of markers mapped in the three populations, an integrated map was generated consisting of both RFLP and morphological markers. The genetic distance between markers on this map was determined by taking a weighted average of the data from the three populations. The oriented map serves as a bridge to understand the relationship between the classical and molecular linkage maps. Based on this information, the location of several genes on the classical map can be approximated with respect to RFLP markers without having to map them directly.     

DNA sequence polymorphisms and their application to bread wheat quality

Single-nucleotide polymorphisms (SNPs) constitute an abundant source of DNA polymorphisms, which have been successfully used to identify loci that are associated with a particular phenotype. Additionally, such markers could be efficiently used in combination with doubled haploid technology to improve the efficiency of breeding programmes. Information on such markers in plants is still scarce. For bread wheat, SNP data are restricted to a few genes. This can be explained by the hexaploidy of Triticum aestivum which makes SNP discovery difficult. We developed a novel method for SNP discovery in bread wheat. The strategy is based on the development of highly specific PCR-primers, which were used to sequence 27 lines. SNPs were discovered from sequence alignment data. Some SNPs were identified by mass spectrometry in a collection of 113 lines, which were both evaluated for agronomic traits and genotyped at 42 neutral microsatellite loci. Traits investigated include: protein content, the quantity of high-molecular-weight glutenins and that of the GluBx subunit. The 42 markers were used to infer population structure, which was included in linear models for association studies. The results of this preliminary study showed 89 SNPs in approximately 20 kbp, i.e., one SNP every 223 bp on average. Six SNPs were genotyped: three were located along the sequence of Glu-B1-1, while three non-synonymous SNPs were located along the sequence of the B homoeologous gene coding for SPA (Storage Protein Activator). The SNPs from Glu-B1-1 had a significant effect on the studied variables, whereas those of SPA had no effect. Such results might indicate that some haplotypes for Glu-B1-1 are linked to higher protein content, through an increased amount of high-molecular-weight glutenins, especially the GluBx subunit.     

Nuclear DNA content and in vitro induced somatic polyploidization cassava (Manihot esculenta Crantz) breeding

Summary The diploid (2C) amount of DNA in cassava (Manihot esculenta Crantz) is 1.67 picograms (pg) per cell nucleus. This value corresponds to 772 mega-base pairs in the haploid genome. The size of the nuclear genome in cassava is very small in comparison with other Angiosperms. Flow cytometry techniques were used to screen ploidy levels in a large population of in vitro plantlets treated with colchicine and oryzalin (3,5-dinitro-N⁴,N-dipropylsulphate). Culture of axillary node cuttings for 48 hours in liquid medium supplemented with 2.5 to 5.0 mM colchicine in combination with 2% dimethyl sulfoxide (DMSO) resulted in a high frequency (23 to 42%) of non-chimeric tetraploids in the V₃ generation. Although mixoploidy may persist in as many as four cycles of vegetative propagation of node cuttings, solid (non-chimeric) tetraploids can be identified by flow cytometry among in vitro plantlets and then rapidly propagated for field testing. A somatic polyploidization system is proposed for implementation in cassava breeding programmes.Dedicated to the memory of the late Dr. Novak. Correspondence to M. van Duren     

Variations in pathogenicity patterns ofMycosphaerella graminicola withinTriticum spp. in Israel

Summary Pathogenicity patterns of 42Mycosphaerella graminicola (Septoria tritici) isolates secured from the major wheat growing regions in Israel, were assessed on seedlings of 16 bread and durum wheats. The spring bread wheat cultivar Titan (CI12615), the winter bread wheats Bezostaya 1, Kavkaz, NE7060 and the durum wheats Nursit 163 and Zenati Bouteille, all exhibited a high level of resistance. Significant cultivar × isolate interactions were recorded for isolates from the different regions in relation to the response of the 16 cultivars organized in 6 reponse classes to the test isolate ISR8036. Number of genes for resistance in the 16 cultivars was estimated, based on the assumption of a gene-for-gene relationship. Twelve complementary genes were hypothesized in the 42M. graminicola isolates × 16 wheat cultivars matrix. There was considerable variation in virulence frequencies between regions and between locations within the same region. The overall frequency of Bezostaya-Kavkaz virulence was low throughout the country (5–7%). The frequency of designated hypothesized virulence genes VST OLAF, VST COLOTANA, VST IAS 20 in Israel, was high in most locations. The reported analytical approach enables the identification of virulence hot-spots and assists in designing breeding for resistance strategies.     

Genomic structure of androgenic progeny of pentaploid hybrids, Festuca arundinacea × Lolium multiflorum

To assess the usefulness of the doubled haploid (DH) method in the breeding of forage grasses, a sample of anther-derived progeny of pentaploid F₁ hybrids of Festuca arundinacea × Lolium multifiorum was karyotyped using genomic in situ hybridization (GISH). The technique allowed scoring of the total number of chromosomes, the number of chromosomes contributed by each parent, and the number and positions of the Festuca-Lolium translocation breakpoints. Among 27 plants analysed, 13 belonged to three clones, effectively reducing the number of different progeny karyotyped to 17. These included 10 haploids, five doubled haploids and two plants for which the origins could not be explained. In all plants analysed, a mixture of chromosomes of both parents was present, including an average of 1.88 intergeneric translocations per plant. The translocation breakpoints were distributed along almost the entire length of the chromosome arms. Chromosome variation among androgenic progeny appeared much wider than that in the conventional backcross but low vigour and high mortality suggest that this additional variation may be difficult to exploit directly in breeding. However, a change in the pattern of recombination makes the entire genome accessible to manipulation.     

Patterns of RFLP-based genetic diversity in germplasm pools of common wheat with different geographical or breeding program origins

A set of 292 accessions of common wheat (Triticum aestivum L.) representing 21 germplasm pools based on geographical or breeding program origins was assayed for RFLP diversity. Thirty cDNA and genomic DNA probes and the HindIII restriction enzyme were employed for RFLP analysis. About 61% of all 233 scored bands were present in 75% or more of the accessions. All but one of the 30 probes revealed polymorphism, and the average number of distinct patterns per probe over all accessions was 9.5.Polymorphic Information Content (PIC) values within a pool varied from 0 to 0.9 and depended on the identities of both the germplasm pool and the probe. Rare banding patterns with a relative frequency of ≤0.2 within a pool were detected. These rare patterns were more likely to occur in pools exhibiting high levels of heterogeneity. The highest level of polymorphism was observed in the Turkish landraces from Southwest Asia. The Eastern U.S. soft red winter wheat germplasm pool was more genetically diverse than the other advanced germplasm pools, and nearly as diverse as the Turkish landrace pool. RFLP-based genetic relationships between germplasm pools generally tracked expectations based on common geographical origin, breeding history and/or shared parentages. The Chinese wheat landraces from Sichuan, Tibet, and Yunnan provinces were distinct from other pools. Similarity matrices for among-pool genetic distance estimates based on either band frequencies or banding pattern frequencies showed good correlation with matrices derived from Nei and Li's mean genetic similarity estimates (r=−0.82^** and r=−0.73^**, respectively. This revised version was published online in July 2006 with corrections to the Cover Date.     

Prediction of breeding values for average fruit weight in mango using a multivariate individual mixed model

Mango is an important horticultural fruit crop and breeding is a key strategy to improve ongoing sustainability. Knowledge of breeding values of potential parents is important for maximising progress from breeding. This study successfully employed a mixed linear model methods incorporating a pedigree to predict breeding values for average fruit weight from highly unbalanced data for genotypes planted over three field trials and assessed over several harvest seasons. Average fruit weight was found to be under strong additive genetic control. There was high correlation between hybrids propagated as seedlings and hybrids propagated as scions grafted onto rootstocks. Estimates of additive genetic correlation among trials ranged from 0.69 to 0.88 with correlations among harvest seasons within trials greater than 0.96. These results suggest that progress from selection for broad adaptation can be achieved, particularly as no repeatable environmental factor that could be used to predict G × E could be identified. Predicted breeding values for 35 known cultivars are presented for use in ongoing breeding programs.     

A survey of soybean germplasm for resistance to <Emphasis Type="Italic">Phytophthora sojae</Emphasis>

Phytophthora root and stem rot of soybean caused by Phytophthora sojae is a destructive disease affecting soybean production regions throughout the world. The utilization of resistant cultivars is the most economical and environmentally safe method for controlling this disease. This work aims to screen the effective sources of special and partial resistance for the development of resistant cultivars. A total of 611 soybean germplasm lines from three ecological regions were evaluated for their responses to three P. sojae strains, namely, PNJ1, PNJ3, and PNJ4, using the hypocotyl inoculation technique. The soybean germplasm lines elicited eight different reaction types with three strains. Among these, 106 were resistant and 253 were susceptible to the three strains. A total of 123 soybean germplasm lines identified as susceptible to the three strains by the hypocotyl inoculation method were evaluated for partial resistance to PNJ1 using the slant board assay. Thirty-nine cultivars displayed high levels of partial resistance to PNJ1. The results of this study can be utilized to plant appropriately resistant cultivars in infected fields and to provide good breeding materials.     

Cross‐genera amplification of informative microsatellite markers from common bean and scarlet runner bean for assessment of genetic diversity in mungbean (Vigna radiata)

Mungbean (V. radiata) is an important Asiatic legume supplying inexpensive protein to a vast majority of vegetarian masses. To increase markers repertoire in mungbean, a study was conducted to analyse 384 microsatellite markers derived from common bean, scarlet runner bean and adzuki bean for their transferability and polymorphism. The results showed that 87 (24.71%) primer pairs could amplify DNA loci of 20 mungbean genotypes including one accession of V. trilobata, while 52 showed reliable banding and polymorphism. These showed different degrees of variability at each locus producing 250 alleles with the number of alleles varying from 2 to 9. The major allele frequency varied from 0.17 to 0.95, while the polymorphic information content of SSRs ranged between 0.09 and 0.86 with an average of 0.60 ± 0.16. UPGMA revealed three major clusters accommodating ~95% of the accessions while one accession of V. trilobata (‘NSB‐007’) did not group with any other genotype describing the discriminating power of informative microsatellites. This study identified a set of useful microsatellite markers to accelerate the genetic studies and breeding programme of mungbean.     

Evaluation of soybean cultivars for resistance to phomopsis seed decay in Korea

Phomopsis seed decay (PSD), primarily caused by Phomopsis longicolla, is one of the most important seed-borne diseases and causes serious seed yield loss in soybean. This study was performed to evaluate reactions to P. longicolla in Korean soybean major elite cultivars, which were mainly used for parents of genetic mapping populations. The natural incidence of P. longicolla and other seed-borne fungi was determined in the fields at three different locations in South Korea during 2009–2010. The significant differences in sensitivity to seed-borne diseases were shown among cultivars. Taekwangkong exhibited the greatest resistance to P. longicolla with average incidence of 0.33% and other seed-borne fungi with average incidence of 6.17%. Moreover, Taekwangkong was free of P. longicolla infection both in Milyang and in Daegu. To confirm the effective resistance source, the Korean virulent strain of P. longicolla, SSLP-3, was inoculated artificially on soybean of R4–R7 growth stage in the greenhouse. Taekwangkong exhibited a higher level of resistance to P. longicolla with significantly lower incidence (8.67%) than any other Korean elite cultivars (78.0–99.33%) and the previously reported resistant PI genotypes (35.0–55.67%). Further verification of resistance in Taekwangkong to P. longicolla by testing germination vigor of healthy seeds in vitro showed a higher germination rate than those of the susceptible cultivars. It could be suggested that Taekwangkong is a newly identified resistance source and the better source of resistance to P. longicolla to develop breeding populations for exploiting resistance gene(s) in further studies.