Showing papers in "Plant Breeding in 1994"
TL;DR: Together resistance to the three globally most important viruses PLRV, PVY and PVX has proved difficult, and new sources of broad spectrum resistance to viruses are required for potato breeding.
Abstract: The types of resistance to viruses in potato are immunity, extreme resistance coded for by the R genes and hypersensitivity coded for by the N genes. Immunity prevents the establishment of virus infection, whereas extreme resistance is expressed as an extremely low virus titre resulting from restricted virus multiplication or localization of virus infection in the plant without obvious necrotic reactions. Expression of the N genes can also lead to localization of the virus infection followed by necrosis at the infection site. Tolerance to virus infection and resistance to inoculation and virus vectors are useful components of field resistance. Virus or virus strain specific resistance genes have been identified in cultivated and wild potato species and transferred to cultivated potato. However, combining resistance to the three globally most important viruses PLRV, PVY and PVX has proved difficult, and new sources of broad spectrum resistance to viruses are required for potato breeding. New molecular techniques will enhance the isolation of the natural resistance genes and studies of gene regulation.
92 citations
TL;DR: An octoploid triticale was derived from the F 1 of a Russian wheat aphid-resistant rye and recovered five euploid Russian-wheat-aphid- resistant plants.
Abstract: An octoploid triticale was derived from the F 1 of a Russian wheat aphid-resistant rye, «Turkey 77», and «Chinese Spring» wheat. The alloploid was crossed to common wheat, and to «Imperial» rye/«Chinese Spring» disomic addition lines. F 2 progeny from these crosses were tested for Russian wheat aphid resistance and C-banded. A resistance gene(s) was found to be associated with chromosome arm 1RS of the «Turkey 77» rye genome. A monotelosomic 1RS («Turkey 77») addition plant was then crossed with the wheat cultivar «Gamtoos», which has the 1BL.1RS «Veery» translocation. Unlike the 1RS segment in «Gamtoos», the «Turkey 77»-derived 1RS telosome did not express the rust resistance genes Sr31 and Lr26, which could then be used as markers. From the F 1 a monotelosomic 1RS addition plant that was also heterozygous for the 1BL.1RS translocation was selected and testcrossed with an aphid-susceptible common wheat, «Inia 66». Meiotic pairing between the rye arms resulted in the recovery of five euploid Russian-wheat-aphid-resistant plants. One recombinant also retained Sr31 and Lr26 and was selfed to produce translocation homozygotes
92 citations
TL;DR: The results indicated that genes on all three chromosomes of group 3 can have striking effects on ear-emergence time, and a negative association between gene dosage and day-length response was found in CS 3D which was thought to carry a gene for promoting insensitivity to day- length.
Abstract: To identify homoeologous group-3 chromosomes that carry genes for vernalization, day-length responses, and earliness per se, a series of aneuploid lines (mono-somics and tetrasomics) and chromosome-substitution lines in ‘Chinese Spring’ (CS) were surveyed under different vernalization and day-length regimes in controlled environments. The results indicated that genes on all three chromosomes of group 3 can have striking effects on ear-emergence time. The replacement of CS 3B by its homologues in ‘Lutescens 62’ and ‘Cheyenne’ produced an increased insensitivity to vernalization, while 3B homologues from ‘Ceska Presivka’ gave CS a remarkable sensitivity to vernalization. This provided evidence for multiple allelism at a new Vrn locus on chromosome 3B. A negative association between gene dosage and day-length response was found in CS 3D which was thought to carry a gene for promoting insensitivity to day-length. The behaviour of CS monosomic 3A and CS (Timstein 3A), in reducing numbers of days to heading independently of environmental stimuli, suggested the presence of earliness per se genes on this chromosome.
85 citations
TL;DR: Wheat × maize and wheat × pearl millet crosses have proved efficient for haploid production using various genotypes of wheat and some doubled haploid (DH) lines (after colchicine treatment in vitro) were produced using these methods.
Abstract: Wheat × maize and wheat × pearl millet crosses have proved efficient for haploid production using various genotypes of wheat; 22 and 27 % of florets produced embryos. In favourable conditions 6—9 haploid plants per spike were produced. The following simplifications or improvements in technique are recommended: 1. Only a single treatment with an aqueous solution of dicamba or 2,4-D (50–100 ppm) for embryo stimulation in vivo; 2. Application by spraying or dipping the spikes; 3. Application time two to four days after pollination; 4. Embryo rescue 15 to 18 days after pollination; 5. Crosses without emasculation are possible if pollination occurs 1–2 days before anthesis. More than 450 haploids and some doubled haploid (DH) lines (after colchicine treatment in vitro) were produced using these methods. No hybrid plants, chromosome additions or substitutions were found.
83 citations
TL;DR: In this paper, the authors developed a yellow seeded Brassica napus through interspecific cross with the two mustard species, B. juncea and B. carinata, respectively.
Abstract: Yellow seeded Brassica napus was developed through interspecific crosses with the two mustard species, B. juncea and B. carinata. The objective of these two interspecific crosses was the introgression of genes for yellow seed colour from the A genome of B. juncea and C genome of B. carinata into the A and C genomes of B. napus, respectively. The interspecific F1 generations were backcrossed to B. napus in an attempt to eliminate B genome chromosomes and to improve fertility. Backcross F2 plants of the (B. napus×B. juncea) ×B. napus cross were then crossed with backcross F2 plants of the (B. napus×B. carinata) ×B. napus cross. The objective of this intercrossing was to combine the A and C genome yellow seeded characteristics of the two backcross populations into one genotype. The F2 generation of the backcross F2 intercrosses was grown in the field, plants were individually harvested and visually rated for seed colour. Ninety-one yellow seeded plants were identified among the 4858 plants inspected. This result indicated that the interspecific crossing scheme was successful in developing yellow seeded B. napus.
80 citations
TL;DR: Synthetic lines derived from two wild accessions of B. rapa, and their F1 hybrids with oilseed rape cultivars, expressed high levels of resistance to L. maculans in glasshouse experiments and in field experiments in England and Australia when exposed to a genetically diverse pathogen population.
Abstract: Six accessions belonging to four subspecies of Brassica rapa, including three accessions of B. rapa subsp. sylvestris, were crossed with B. oleracea subsp. alboglabra in order to develop a series of synthetic B. napus lines with a common C genome but contrasting A genomes. Different A genomes had significant effects on the efficiency of B. napus resynthesis and the sexual compatibility of the synthetic lines with oilseed rape cultivars. The synthetic lines were used to investigate the effect of A genome substitution on the resistance of B. napus to infection by Leptosphaeria maculans, and to explore the potential for the use of wild forms of B. rapa in oilseed rape breeding programmes. Synthetic lines derived from two wild accessions of B. rapa, and their F1 hybrids with oilseed rape cultivars, expressed high levels of resistance to L. maculans in glasshouse experiments. One of these lines also expressed high levels of resistance in field experiments in England and Australia when exposed to a genetically diverse pathogen population. All other synthetic lines and cultivars were highly susceptible in both glasshouse and field experiments. F1 hybrids between oilseed rape cultivars and synthetic lines derived from B. rapa subsp. chinensis were significantly more susceptible than either parent.
76 citations
TL;DR: Considering the total number of doubled-haploid plants produced, low levels of colchicine added to the initiation media were very effective.
Abstract: Chromosome doubling is critical for obtaining doubled-haploid plants from wheat (Triticum aestivum L.) anther culture. The most common doubling method applies colchicine to the plant. However, colchicine is phytotoxic and can induce a high frequency of plant death. In this experiment, anthers from two wheat genotypes (“Pavon 76” and ‘Centurk’) were placed on nine embryoid initiation media having three sugar sources (maltose, sucrose, and maltose + glucose) with three colchicine concentrations (0.0, 0.1, and 0.2 g · l-1). Wheat starch was used as a gelling agent. After three days, the anthers were washed and moved to fresh media without colchicine. Increasing the colchicine concentration decreased the number of embryoids produced from 77.4 embryoids/100 anthers to 29.9 embryoids/100 anthers, but did not significantly affect the frequency of plant regeneration (0.49 green plants/embryoid to 0.40 green plants/embryoid), and increased the frequency of doubled-haploid plants (19.0 doubled-haploid plants/100 green plants to 72.3 doubled-haploid plants/100 green plants). Considering the total number of doubled-haploid plants produced, low levels of colchicine added to the initiation media were very effective.
70 citations
TL;DR: Three methods of chromosome doubling to produce doubled haploid plants from microspore cultures of Brassica napus were compared, and direct colchicine treatment of isolated microspores resulted in a doubling efficiency of 70% of the whole plants.
Abstract: Three methods of chromosome doubling to produce doubled haploid plants from microspore cultures of Brassica napus were compared: colchicine treatment of microspore-derived plants, microspore-derived embryos, and isolated microspores. In the whole plant treatment, 53% of the treated plants set seed, but the treatment delayed plant growth and reduced seed set. When microspore-derived embryos were treated with colchicine, the doubling frequency was 32% (compared to 15% for spontaneous doubling). Direct colchicine treatment of isolated microspores resulted in a doubling efficiency of 70% of the whole plants. This treatment also stimulated embryogenesis in microspore culture, leading to increased plant regeneration
69 citations
TL;DR: A high degree of genetic diversity was found among both different apple cultivars and wild species of the genus Malus, and the results gave additional evidence for the hypothesis that M. pumila and M. sylvestris were involved in the origin of the cultivated apples.
Abstract: The potential use of RAPD markers for taxonomic studies in Malus was investigated using 18 accessions of wild species and 27 apple cultivars. 29 preselected random decamer primers were applied to three sets of Malus genotypes. Random amplified polymorphic DNA (RAPD) ‘fingerprints’ were analysed for polymorphic amplification fragments, and coefficients estimating genetic similarity were calculated on the basis of about 50 polymorphic RAPD loci in each set of genotypes. Cluster analysis by an unweighted pair-group method with arithmetic averages (UPGMA) revealed that, in the cultivars, the molecular classification was in good agreement with the known lineage. A dendrogram generated for the wild species gave relationships that were, in principle, in accordance with the known phylogenetic information. Closely related species from section I were clearly distinguishable from those of sections III and IV. On the molecular level, a high degree of genetic diversity was found among both different apple cultivars and wild species of the genus Malus. The results gave additional evidence for the hypothesis that M. pumila and M. sylvestris were involved in the origin of the cultivated apples.
64 citations
TL;DR: This experiment cultured anthers from three wheat genotypes on a modified Liang's 85D12 initiation medium with seven sugar combinations, finding that maltose was the best sugar, followed by glucose and maltose + glucose, and these three sugar combinations were superior to the standard medium sugar.
Abstract: Sugars are critical components in bread wheat (Triticum aestivum L.) anther culture media for successful somatic embryo initiation and plant regeneration. In this experiment, anthers from three wheat genotypes were cultured on a modified Liang's 85D12 initiation medium with seven sugar combinations (I-sugars: galactose, mannose, maltose, fructose, sucrose, glucose, maltose + glucose) at 0.26 M, and 2,4-dichlorophenoxyacetic acid (2 mg/L), 1-naphthalene acetic acid (1 mg/L), and glutamine (254 mg/L). Wheat starch (5 % W/V), a potential source of sugars, was used as the medium gelling agent. No previous research has studied the effect of different sugars with wheat starch. A split-plot experimental design with 42 replications was used with genotypes as whole plots and sugar combinations as subplots. Galactose and mannose did not support embryoid initiation and were dropped from the analysis. Averaged over the three genotypes, maltose was the best sugar (105 embryoids/100 anthers), followed by glucose (47 embryoids/100 anthers) and maltose + glucose (37 embryoids/100 anthers). These three sugar combinations were superior to the standard medium sugar, sucrose (24 embryoids/100 anthers), and to fructose (12 embryoids/100 anthers). The embryoids were divided into two groups for plant regeneration. The first group was transferred to regeneration medium (Liang 85D12 salts, sugars at 0.06 M, and wheat starch at 7 % w/v as gelling agent) with the same sugar (R-sugar) used as in initiation. The second group was transferred to regeneration media with sucrose. I+R-maltose (0.55)
64 citations
TL;DR: The presence of chromosome 4V in the addition line and its homo eology to chromosome 4 in wheat were confrmed by Southernysis of genomic DNA using chromosome group,l-speci6c clones, and this teneric locus is not homoeologous wirh other known genes for resistance to P. tilosam, and thus represents a new source of resisrance to rhis pathogen.
Abstract: Resissnce ro AenlocercoEorella herpotnchodes in 6ve wheat culdvars, rcc essionV 6 7281 of Daqprrrm ztllosam, and'Chinese Spnng' disomic addition lines of the D. ollosum chromosomes lV, 2V, 4V, 5V, 6V and 7V, was evaluated in seedlings by rneasunng disease progress 6 weeks afer inoculation wirh a lglucuronrdase-transformed strain o{ the parhogen and by visualestimates o[ disease severity. D. v losam and the disomic addition line ofchromosome 4V were as resistant as wheat culdvars 'VPM-l' and 'Cappelle Desprez', but less resisrant rhan 'Rendezvous'. Resist ance of the chromosome 4V disomic addition line was equivalent to that ol D. vllosum. 'Chinese Sprrng' and drsomrc addidon lines of lV,2V, 5V, 6V and ry wcre allsusceprible. These resuhs con6rm Spn,c(;ut_'s (1936) report of resistance in D. tilosam to P. ber potnchotdes and estallish rhe chromosomal location for the genes controlling resistance. The presence of chromosome 4V in the addition line and its homo eology to chromosome 4 in wheat were confrmed by Southern anJysis of genomic DNA using chromosome group ,l-speci6c clones. This teneric locus is not homoeologous wirh other known genes for resistance to P. berpotnchotdes located on chromosome troup 7, and thus represents a new source of resisrance to rhis pathogen.
TL;DR: Following estimates of broad-sense heritability, breeding for specific adaptation may be envisaged for northern and central Italy on the one hand, and southern Italy onThe other, as well as defining macro-environments for the selection and recommendation of genotypes in the region.
Abstract: Eighteen common-wheat varieties grown for three seasons at 31 locations in Italy were used to study the relationships between cultivar adaptation patterns, climatic factors and morphophysiological traits of genotypes, as well as defining macro-environments for the selection and recommendation of genotypes in the region. The variances of both the genotype-location and genotype–season interactions were significant, the former being almost 80% greater than the latter. Some 10.4% of genotype-location interaction was accounted for by heterogeneity of genotype regressions on site mean, 38.0% by the first two axes of a principal components analysis and 32.0% by definition of four macro-environments. Occurrence of genotype-location interaction was related to the level of late frosts, winter cold, and late drought and heat stress at each location, and to heading date and tolerance of frost, Septoria blotch and lodging in each genotype. Following estimates of broad-sense heritability, breeding for specific adaptation may be envisaged for northern and central Italy on the one hand, and southern Italy on the other. Morphophysiological traits contributing to better performance in each of these macro-environments were indicated.
TL;DR: Major genetic progress for resistance can be expected among progeny from crosses with resistant parents, however, selection would be most effective if delayed to later generations because of dominance, and choice of the specific female parent may produce a higher level of resistance.
Abstract: Septoria tritici blotch constitutes a major disease problem of wheat world-wide. To efficiently breed wheat for resistance to this disease, an understanding is required of the inheritance of resistance. Our objective was to study the quantitative inheritance of resistance under field conditions. A nine-parent diallel and a generation mean experiments were conducted at Toluca, Mexico in 1986 and 1987, respectively, to investigate gene effects. General combining ability effects accounted for most of the variation although specific combining ability effects were detected in some crosses. Ias20*5/H567.71, Thornbird, and RPB709.71/Coc contributed the most to reduced disease severity. Reciprocal effects were detected in two of 36 crosses, where RPB709.71/Coc contributed additional reduced disease severity when used as female. The analysis of generation means confirmed results obtained from the diallel. Additive effects were also most important. Dominance effects and epistasis, mostly of the additive × additive type, were found in some crosses. Hence, substantial genetic progress for resistance can be expected among progeny from crosses with resistant parents. However, selection would be most effective if delayed to later generations because of dominance, and choice of the specific female parent may produce a higher level of resistance.
TL;DR: A new cytoplasmic male-sterility system was developed in an oilseed Brassica, viz.
Abstract: A new cytoplasmic male-sterility system was developed in an oilseed Brassica, viz. B. juncea var. 'Pusa Bold' with the cytoplasmic background of a wild species, Diplotaxis siifolia, obtained through wide hybridization. The synthetic alloploid (D. siifolia×B. juncea: 2n=56, D 3 D 3 AABB) was repeatedly backcrossed to B. juncea to achieve cytoplasmic substitution. The CMS plants resembled the cultivar in growth and morphology. The flowers had narrow sepals and petals and short, shrivelled anthers which failed to dehisce. The meiotic process appeared to be normal. The microspores degenerated at an early stage after tetrad formation. Female fertility in the CMS plants was as good as in the cultivar. Female transmission of sterility confirmed it to be cytoplasmically encoded.
TL;DR: It is demonstrated that oryzalin could be a better choice than colchicine for chromosome doubling on haploid apple shoots in vitro.
Abstract: In an outbreeding species such as apple, haploid plants may be especially useful in breeding programmes for the production of homozygous material. However, methods must be available to induce chromosome doubling in the haploid plants. Two antimitotic agents, colchicine and oryzalin, were compared as regards their efficiency in inducing chromosome doubling of in vitro haploid apple shoots. Three colchicine levels (0.025, 0.25 and 1.25 mM) and three oryzalin levels (5, 15 and 30 μM) were evaluated. Three techniques were also used and compared. Survival rate and chromosome counts were determined. Differences were observed between the two antimitotic agents and between the three techniques. This study demonstrates that oryzalin could be a better choice than colchicine for chromosome doubling on haploid apple shoots in vitro.
TL;DR: The nucleotype of a maize plant can be modified by selection such as early flowering time and selection for earliness resulted in selection against plants with large genome sizes.
Abstract: Several studies have indicated a possible link between genome size and earliness in maize. In this study, an original maize population, South African photo-period insensitive maize composite II (C0) and several selected generations were analyzed for days to flowering, plant height, ear height, and yield. The selection criterion was earliness. Over six cycles of selection a 14-day decrease in days to flowering was obtained with no significant reduction in grain yield. In the initial population (C0) and the most advanced selection (C6) 101 plants were analyzed for nuclear DNA content. A significant decrease in the mean nuclear DNA content of the C0 population (102 AU) was observed with respect to the C0 population (105 AU). This reduction was the result of a decrease in frequency of plants in the C6 population with large genome sizes. Therefore it was concluded that selection for earliness resulted in selection against plants with large genome sizes. Hence, the nucleotype of a maize plant can be modified by selection such as early flowering time.
TL;DR: In this paper, the authors focused on the identification of RAPD (random amplified polymorphic DNA) markers linked to the Vf gene from Malus floribunda into commercial varieties.
Abstract: Apple scab, caused byVenturia inaequalis (Cke.) Wint., is the most serious disease of apple trees in many areas of the world. Resistance toV. inaequalis, derived from the small fruited speciesMalusfloribunda 821, is determined by a major dominant geneVf. Our objective was focused on the identification of RAPD (random amplified polymorphic DNA) markers linked to theVf gene. The approach in this paper is based on the introgression of theVf gene fromM. floribunda into commercial varieties. Comparing RAPD patterns of a genomic DNA sample ofM. floribunda with a pooled DNA sample of resistant individuals and that of 10 susceptible commercial apple varieties, we identified fragments which are derived fromM. floribunda. One of them,OPD20/600, proved to be linked to theVf gene by cosegregation analysis with two backcross progenies. It is the first DNA marker so far for the scab resistance.
TL;DR: Findings indicate that TYLCV introduced by means of agroinoculation leads to the breakdown of natural resistance mechanisms which prevent the replication, spread and expression of symptoms in resistant tomato genotypes.
Abstract: Accessions of the wild tomato species Lycopersicon chilense LA 1969 and L. htrsutum LA 1777 which are resistant to tomato yellow leaf curl virus (TYLCV) in field- and in whitefly-medi ated transmission tests were agroinoculated with a tandem repeat of the TYLCV genome. Large amounts of viral DNA started to accumulate in the agroinoculated L. chilense and L. hirsutum plants about 10 days after the agroinoculation. Yellowing and narrowing of the upper leaves were observed in the L. chilense plants but no curling as in susceptible L. esculentum cultivars. The agroinoculated L. hirsutum plants showed typical yellowing and curling of young leaves. These findings indicate that TYLCV introduced by means of agroinoculation leads to the breakdown of natural resistance mechanisms which prevent the replication, spread and expression of symptoms in resistant tomato genotypes.
TL;DR: Highly resistant expressions characterized the SH which appeared to be influenced by the resistance of their T. turgidum and/or T.T. tauschii parents.
Abstract: Synthetic hexaploids (SH) developed at the International Maize and Wheat Improvement Center (CIMMYT), involving four Triticum turgidum and nine T. tauschii parents, were evaluated for resistance to Karnal bunt (KB) (Tilletia indica Mitra) during three crop seasons over three years at Ciudad Obregon, Sonora, Mexico. Ten tillers of each SH at boot stage, taken at random, were injected with a suspension of sporidia in water (10,000 spores/ml of water). At maturity the inoculated spikes were threshed individually and evaluated for the percentage KB-infected grains. Based on the mean KB score of each entry for three seasons, 49 % of the SH were immune (0 % infection) to KB. Highly resistant expressions characterized the SH which appeared to be influenced by the resistance of their T. turgidum and/or T. tauschii parents. The overall mean infection of the SH wheats was 0.24 % compared to 56.14 % in the susceptible bread wheat check cultivat ‘WL711’. Transfer of KB resistance genes from SH wheats into bread wheat is currently underway at CIMMYT.
TL;DR: The frequency of homoeologous recombination between chromosomes 1A and 1D was within the range observed for pairs of homologues in wheat, supporting earlier observations that homoeological recombination in triticale is frequent.
Abstract: To complement previously developed recombinant chromosomes 1R.1D, two series of translocations involving the Glu-D1 gene from chromosome ID to chromosome 1A were produced in hexaploid triticale. These series involve seven independent transfers of allele d encoding for high molecular weight glutenin subunits 5+10 and ten independent transfers involving allele a encoding for HMW glutenin subunits 2 + 12. The frequency of homoeologous recombination between chromosomes 1A and 1D was within the range observed for pairs of homologues in wheat, supporting earlier observations that homoeologous recombination in triticale is frequent. Recombined chromosomes 1A.1D can be used to introduce the Glu-D1 gene to durum wheats, and to manipulate the dosage of Glu-D1 in hexaploid triticale and bread wheat.
TL;DR: Stability parameters revealed that yield stability of the different population structures was improved by increasing heterozygosity as well as heterogeneity, but the impact of both factors of diversity on yield stability varied between the different data sets.
Abstract: In order to evaluate the effects of heterogeneity and heterozygosity on yield stability in faba beans, genotypes were generated with contrasting population structures, differing only in their levels of heterogeneity and heterozygosity. All entries were based on either eight or 36 inbred lines, respectively. The population structures tested consisted of pure stands of the inbred lines (1) and of their F1,-hybrids (2), blends of the inbred lines (3) and of their F1 hybrids (4), four-component synthetics in different Syngenerations (5), the open-pollinated source varieties (6) and 36 polycross progenies (7). Five different entry sets (= data sets), each covering several of the seven population structures listed, were grown during 1986 to 1991 in at least four different environments in Western Germany and tested for yield.
Stability parameters, i.e., the regression coefficient and deviation from regression (EBERHART and RUSSELL 1966), and the ecovalence (WRICKE 1962), revealed that yield stability of the different population structures was improved by increasing heterozygosity as well as heterogeneity. But the impact of both factors of diversity on yield stability varied between the different data sets. Positive effects of both factors on yield stability seemed to be additively combined in the hybrid blends (data set I). The same proved to be partly true for the four different Syn-generations of the nine synthetics tested. Yield advantage of the different heterozygous variety structures over the homozygous ones in creased with increasing yield level at test sites, as indicated by regression coefficients larger than 1.
TL;DR: Four morphologically different clones of Miscanthus sinensis‘Giganteus’, presently grown in Austria, one ornamental, M. sinensis, and two cultivars of M. sacchariflorus, were studied to determine their chromosome number, chromosome morphology and meiotic behaviour.
Abstract: Four morphologically different clones of Miscanthus sinensis‘Giganteus’, presently grown in Austria, one ornamental, M. sinensis, and two cultivars of M. sacchariflorus, were studied to determine their chromosome number, chromosome morphology and meiotic behaviour. The clones of M. sinensis‘Giganteus’ uniformly showed a somatic chromosome number of 57. The ornamental M. sinensis, and one M. sacchariflorus cultivar had 38 and the second M. sacchariflorus genotype had 76 chromosomes. While the ornamental M. sinensis exhibited a regular meiosis with predominantly ring bivalents, M. sinensis‘Giganteus’ displayed a highly irregular meiosis with stickiness, frequent occurrence of trivalents and a large number of laggards in both the first and second anaphases. The presence of two satellited chromosomes suggests an allotriploid genome constitution; the trivalents indicate the involvement of closely related species in the amphiploid. Triploidy of the plants is supposed to be the major cause of their sterility. Suggestions are made for further cytogenetic studies including genome analysis and an attempt to resynthesize M. sinensis‘Giganteus’ to provide an insight into the genetic architecture of the plant and to generate new genetic variations for breeding purposes.
TL;DR: Analysis of near-isogenic lines in a number of genetic backgrounds showed that Rht12 reduces height without altering ear size and significantly increases spikelet fertility, however its successful utilization in breeding programmes will require careful selection since in some backgrounds the gene reduces grain numbers and grain size.
Abstract: Rht12, a dominant dwarfing gene of wheat, was shown to be located distally on the long arm of chromosome 5A. Lack of recombination with the awn inhibitor B1 suggested that Rht12 is cither tightly linked to this gene or is, in this material, a pleiotropic expression of the gene. Linkage to β-Amy-A1 was also very tight, indicating that Rht12 is present on the segment of chromosome SAL ancestrally translocated from 4AL. The close linkage to β-Amy-A1 also suggests that Rht12 is not a homoeoallele of the commercially important GA-insensitive dwarfing genes.
Analysis of near-isogenic lines in a number of genetic backgrounds showed that Rht12 reduces height without altering ear size and significantly increases spikelet fertility. However its successful utilization in breeding programmes will require careful selection since in some backgrounds the gene reduces grain numbers and grain size. In all backgrounds, Rht12 delayed ear emergence time by around 6 days. A delay of this magnitude could, in many environments, adversely affect yield if it is not neutralized by altering the balance of other genes determining ear emergence time.
TL;DR: Orychophragmus violaceus, a member of the Cruciferae family, has been found to have a high oil quality with high contents of palmitic and oleic acids, and lower contents of linolenic and erucic acids.
Abstract: Orychophragmus violaceus, a member of the Cruciferae family, has been found to have a high oil quality with high contents of palmitic (14.3 %) and oleic (20.3 %) acids, and lower contents of linolenic (4.8 %) and erucic (0.9 %) acids. Plants of O. violaceus exhibit a high number of branches, pods per plant, and seeds per pod, which contributes to the high yield potential of this plant. Individual selection was made in the original population of O. violaceus, and a few early, disease-tolerant and high-yielding lines were obtained. Intergeneric hybridization was performed between B. napus and O. violaceus and several hybrid plants (F1) were obtained. After treatment with colchicine, amphidiploid plants developed. O. violaceus shows great potential for becoming an edible oil crop or being used as genetic material in a rapeseed breeding programme.
TL;DR: The low frequency of sterile lines from the fusion experiments and the inheritance of the cms in segregating progenies are both discussed.
Abstract: Fusion experiments between B. napus and X-ray-treated B. tournefortii protoplasts were carried out to develop cytoplasmic male sterility (ems) in B. napus. From the regenerants, six lines containing male sterile plants were selected; five lines segregated for male sterility, but one line (25–143) was completely male-sterile from the beginning. Molecular analyses of mitochondrial (mt) and chloroplast (cp) DNA of B. napus, B. tournefortii, B. juncea and cms juncea indicated that the original cytoplasmic donor of the cms juncea-system in B. napus was a B. tournefortii form, while the B. napus genotype used for the fusion experiments had a B. campestris cytoplasm. By analysis (it regenerated plants, line 25–143 was identified as possessing mt-DNA recombined between B. campestris and B. tournefortii. with the major part derived from B. campestris. No differences were detected between epDNAs from H. campestris and from line 25—143. The other five lines were similar to B. campestris with all the probes used. The low frequency of sterile lines from the fusion experiments and the inheritance of the cms in segregating progenies are both discussed.
TL;DR: Genetic analyses were carried out with B. napus lines that differed in total content of individual glucosinolates (GSLs), as well as in their profile.
Abstract: Genetic analyses were carried out with B. napus lines that differed in total content of individual glucosinolates (GSLs), as well as in their profile. Inheritance of total GSL content was studied with a complete F1 diallel mating of eight doubled haploid (DH) lines (5–120/μmol GSL/g dry seed) as well as with the segregating populations of two crosses between DH lines. Most of the genetic variability was caused by gca effects; heterosis was not important; heritability of GSL content was high (h2b, = 0.95, h2n= 0.87). For GSL contents below 20/μmol/g seed, heritability values reached h2b, = 0.69 and h2n, = 0.66. Low total GSL content was found to be controlled by 4–5 recessive genes with additive gene action. Alkenyl GSL profiles studied in F2 from resynthesized rapeseed lines were determined by four loci, two that are responsible for the elongation of the butenyl to pentenyl GSLs and two that are responsible for hydroxylation of alkenyl GSLs. Initial genetic studies of indolyl GSL contents from 0.1–4.5/μmol/g show that two or three genes may be involved. The frequency distribution of F2 phenotypes was virtually continuous due to both segregational and environmental variation. Genotypes with low alkenyl and low indolyl GSL contents were selected after crossing parents with low alkenyl/high indolyl and high alkenyl/low indolyl GSL content. The alkenyl GSL profiles are discussed with regard to the parental diploid species B. oleracea and B. campestris.
TL;DR: This study shows that RAPD markers can help in the protection of breeders’ rights to strawberry cultivars.
Abstract: Accurate and rapid cultivar identification is important for breeders'-rights protection, especially for vegetatively propagated plants The objective of this study was to test the feasibility of developing cultivar-specific RAPD markers in commercial strawberries (Fragaria ananassa Dutch) Efforts were focused on distinguishing between two newly developed Volcani cultivars, ‘Ofra’ and ‘Dorit’, and six other cultivars, ‘Douglas’, ‘Chandler’, ‘Oso Grande’, ‘Dover’, ‘Nurit’ and ‘Parker’ Reproducible RAPD fingerprints were generated, each containing at least one polymorphic DNA product A combination of 10 polymorphic DNA products exhibited cultivar-specific patterns enabling the distinction between closely related varieties, such as ‘Ofra’ (which is the progeny of ‘Dorit’ and ‘Parker’) and ‘Dorit’ (which is the progeny of ‘Nurit’ and ‘Dover’) This study shows that RAPD markers can help in the protection of breeders’ rights to strawberry cultivars
TL;DR: In the present study, hardening abilities of 13 winter wheat, 10 rye, 3 triticale and 6 winter barley cultivars were determined in field samples collected during the autumns of 1990 and 1991 by measuring the amount of ion leakage from frost-treated leaf segments.
Abstract: Profound hardening is the prerequisite for survival of a cultivar over winter. In the present study, hardening abilities of 13 winter wheat, 10 rye, 3 triticale and 6 winter barley cultivars were determined in field samples collected during the autumns of 1990 and 1991 by measuring the amount of ion leakage from frost-treated leaf segments. The cultivars tested were selected from the Inter-Nordic Winterhardiness Project, in which Field Survival Indices were determined for a total of 23 winter wheat, 13 rye, 5 triticale and 11 winter barley cultivars in order to estimate winter survival potentials under Finnish conditions. The winter survival of the materials studied correlated well with their hardening ability assessed by using the electrolyte leakage method.
TL;DR: The number of embryos able to develop was four times higher in summer than in spring and the length of the stems, leaves and guard cells was smaller than those of diploids.
Abstract: This report gives the first detailed analysis of cucumber haploid plants and the first evaluation of genotype and season effects on haploid embryo development. Female flowers of four F1 varieties and two inbred lines were pollinated with 300 Gy-treated pollen and three-week old embryos were cultured in vitro on E20A medium. The variety ‘Polan’ produced the greatest number of embryos (1.34 per 100 seeds), 51 % of which were capable of further development. The number of embryos able to develop was four times higher in summer than in spring. All the plants obtained, except one, were haploids or aneuhaploids. Haploid plants grew slowly and were sterile, although they occasionally set seedless fruits. The length of the stems, leaves and guard cells was smaller than those of diploids.
TL;DR: The results indicate the need for controlled self-pollination for purity maintenance in sesame, and contamination due to NCP can be reduced by sampling seeds from the lower capsules of early and medium-flowering genotypes and from the upper capsules of late-maturing genotypes when pollination control is not practised.
Abstract: Three sesame genotypes with contrasting characters were grown in alternate rows to estimate the degree of natural cross-pollination (NCP) at two locations. Capsules from the lower (first-formed five capsules), upper (last five fully-developed capsules) and middle portions were harvested separately and the frequency of appearance of progenies with dominant markers was used as the criterion for NCP. The degree of inter-genotypic NCP was similar in the three genotypes and at the two locations (4.02—5.10 % NCP) when the total number of hybrid seeds per plant was considered. The lower portion of the early (1.03—1.31 % NCP) and medium (1.51—2.08%) flowering genotypes and the upper portion of the late-flowering genotype (2.27—2.49 % NCP) recorded less NCP than the total plant. The NCP in the lower portion of the early-flowering genotype due to pollen from the late-flowering genotype was negligible (0—0.7 %). The results indicate the need for controlled self-pollination for purity maintenance in sesame. However, contamination due to NCP can be reduced by sampling seeds from the lower capsules of early and medium-flowering genotypes and from the upper capsules of late-maturing genotypes when pollination control is not practised.