Male Sterile Clones Research Articles

Industrial chicory genome gives insights into the molecular timetable of anther development and male sterility.

Industrial chicory (Cichorium intybus var. sativum) is a biannual crop mostly cultivated for extraction of inulin, a fructose polymer used as a dietary fiber. F1 hybrid breeding is a promising breeding strategy in chicory but relies on stable male sterile lines to prevent self-pollination. Here, we report the assembly and annotation of a new industrial chicory reference genome. Additionally, we performed RNA-Seq on subsequent stages of flower bud development of a fertile line and two cytoplasmic male sterile (CMS) clones. Comparison of fertile and CMS flower bud transcriptomes combined with morphological microscopic analysis of anthers, provided a molecular understanding of anther development and identified key genes in a range of underlying processes, including tapetum development, sink establishment, pollen wall development and anther dehiscence. We also described the role of phytohormones in the regulation of these processes under normal fertile flower bud development. In parallel, we evaluated which processes are disturbed in CMS clones and could contribute to the male sterile phenotype. Taken together, this study provides a state-of-the-art industrial chicory reference genome, an annotated and curated candidate gene set related to anther development and male sterility as well as a detailed molecular timetable of flower bud development in fertile and CMS lines.

Development of cardoon male sterile clones

Development of cardoon male sterile clones

“The fad for Polygonum will fade away!”: historic aspects of the propagation and success in France of the Reynoutria complex based on archives

ABSTRACT Japanese Knotweeds were introduced by man during the 19th century in Europe, where they hybridized and formed a species complex now considered as “invasive”. On the basis of many herbarium specimens, the literature and archive documents, we describe the history of their discovery and introduction in France. The circumstances of their hybridization are given, as well as the reasons for the spread of the complex composed of both taxa and their polyploid hybrids. We show that after its discovery by Von Siebold, Reynoutria japonica was introduced as a single male-sterile clone in Lorraine during the early 1850s, whereas R. sachalinensis was discovered by both the French and Russians and subject to successive introductions. Our study reveals that at the end of the 19th century, these Asiatic Knotweeds became very popular among horticulturists and botanical gardens. Their cultivation in sympatry has led to the production of their hybrid R. x bohemica, as well as interspecific hybridizations and introgressions with parental species, leading to considerable genetic diversity, escape and naturalisation.

Temperature related instability of a naturally induced cytoplasmic male sterility in industrial chicory (Cichorium intybus L.)

AbstractNatural alloplasmic cytoplasmic male sterile (CMS) clones of industrial chicory were obtained after crossing wild chicory with selected breeding lines. We investigated the CMS stability of 10 clones in various environmental growing conditions. CMS was stable under cool growing conditions in most of them. Fertility restoration, based on pollen production scores, was observed in all clones after a period of hot temperatures. The early flower bud stage was sensitive, resulting in fertile flowers 12–17 days after exposure to high temperatures. Experiments under controlled growing conditions at 15°C demonstrated that a heat shock of 2 days at 25 or 30°C was sufficient to restore fertility. Sterile flowers were formed when plants were again grown at lower temperatures. Significant differences between individual clones were observed, indicating the potential of genetic selection to obtain stable CMS parent lines.

Flower induction, microscope-aided cross-pollination, and seed production in the duckweed Lemna gibba with discovery of a male-sterile clone

Duckweed species have a great potential to develop into fast-growing crops for water remediation and bioenergy production. Seed production and utilization of hybrid vigour are essential steps in this process. However, even in the extensively-studied duckweed species, Lemna gibba, flower primordia were often aborted prior to maturation. Salicylic acid (SA) and agar solidification of the medium promoted flower maturation and resulted in high flowering rates in L. gibba 7741 and 5504. Artificial cross-pollination between individuals of L. gibba 7741 yielded seeds at high frequencies unlike that in L. gibba 5504. In contrast to clone 7741, the anthers of 5504 did not dehisce upon maturation, its artificially released pollen grains had pineapple-like exine with tilted spines. These pollens were not stained by 2,5-diphenylmonotetrazoliumbromide (MTT) and failed to germinate. Therefore, clone 5504 is male sterile and has potential application with respect to hybrid vigour. Moreover, pollination of flowers of 5504 with 7741 pollen grains resulted in intraspecific hybrid seeds, which was confirmed by inter-simple sequence repeat (ISSR) markers. These hybrid seeds germinated at a high frequency, forming new clones.

A successful strategy to obtain artichoke hybrids

In the last half century the world population has doubled to 7 billion, while the land under cultivation increased just by 12%, from 1.37 to 1.53 billion ha. In what manner, then, did agricultural production triple? By increasing productivity, with a combination of improved agronomical practices and improved crops. In this context the exploitation of plant heterosis has been an effective approach in crop enhancement, hybrid cultivars in major crops can show more than 20% yield advantage over the best conventional ones under the same cultivation conditions. In this attempt, trying to meet commercial and industrial needs, academy (University of Tuscia, Italy) and industry (BHS, USA) encountered over again aiming to produce artichoke commercial hybrid seed through the use of male sterility. The project started in 2007, with 3 male sterile clones and 5 stable open pollinated cultivars, since then, more than 200 male sterile clones and 20 open pollinated cultivars have been developed to produce more than 500 crosses; around 30 of them, with interesting agro-morphological traits and uniformity, have been tested in different countries of the new and old world. The selected hybrids are under evaluation to assess their reproducibility and possibility of success in the global seed market. The different market requests in term of artichoke typologies and quality characteristics, which vary between the fresh market (green, purple, spiny, ovate, round heads) and the processing industry market characterized for green ovate typologies; hence it is required to allow the production/registration of a wide range of hybrids covering the different requests. Currently, one hybrid of Romanesco type, named 'Romolo' has been registered in Italy and is been sold successfully by La Semiorto Sementi srl. and its commercial firm Top Seed. The project results show how artichokes hybrids combine advantages that contribute to more vigorous plant growth, earliness, healthier plants which require lower input in pesticides and fungicides. In addition, plants from seeds are cheaper than plants derived by meristem practices. In other words, seed planting is a viable approach that makes globe artichoke friendlier both to the grower and to the environment.

雄性不稔スギ「爽春」と精英樹の交配家系における特性と新たな雄性不稔品種開発のための育種計画

雄性不稔スギ「爽春」と精英樹の交配家系における特性と新たな雄性不稔品種開発のための育種計画

Use of single cross hybrids to measure heterosis for yield in diverse lucerne genotypes growing in a subtropical environment

Yield stagnation is a worldwide issue for lucerne breeding, and reasons for the yield plateau include emphasis on disease and pest resistance and not yield per se, and the broad-based synthetic approach to lucerne breeding which is generally used. In this study, an incomplete diallel was made between 50 lucerne clones with representatives from the 3 hypothetical heterotic groups, Medicago sativa subsp. falcata, dormant subsp. sativa, and non-dormant subsp. sativa. Male sterile clones were also included among the dormant group. The single crosses were compared in a subtropical environment at Gatton, Queensland, for yield and other relevant agronomic traits against the adapted synthetics Sequel (dormancy group 9), UQL-1 (group 7), and a highly non-dormant experimental synthetic (line B) derived by introgression of highly non-dormant Arabian germplasm into Sequel. The trial was conducted in a known low-disease-pressure site for Phytophthora root rot, and anthracnose was managed by regular application of prophylactic treatments. The best single cross outyielded Sequel and line B by 13% and 8%, respectively. In this environment, yield was very much influenced by the dormancy group of the test material, with group 9 material significantly outyielding more dormant material. General combining ability (GCA) effects were more important determinants of cumulative yields than specific combining ability (SCA) effects, with these effects being significantly greater than zero for only 4 of the 236 crosses tested over the 15-month period. Similarly, GCA effects were more important for determining autumn height and persistence. The research did identify a small number of clones with good GCA for yield per se, and it would appear that future work should focus on developing more narrow-based synthetics with 4–8 parents which have been selected on the basis of their GCA for yield per se. DNA markers would appear to have a role in selecting clones carrying multiple resistances, and in establishing marker pedigrees for high-yielding parental clones such as we have identified, which can be traced through subsequent generations of recurrent selection in cultivar improvement.

The Biology of Invasive Alien Plants in Canada. 5. Polygonum cuspidatum Sieb. & Zucc. [= Fallopia japonica (Houtt.) Ronse Decr.

Polygonum cuspidatum (Japanese knotweed) is an introduced perennial geophyte in the buckwheat family (Polygonaceae). The phytogeographic distribution of P. cuspidatum in North America suggests a large number of intentional introductions via ornamental plantings from 1870 to 2000, followed by secondary spread from these foci. This species is most pernicious along riparian corridors and road and railroad rights-of-way, reducing visibility, displacing native species, negatively affecting native wildlife, and causing alterations in natural hydrologic processes. Although non-hybrid seed recruitment has not been observed in Europe because of the presence of male-sterile clones only, dispersal of seeds and stem and rhizome fragments by flowing water does occur in North America and populations are readily established from these sources. The primary means of local and regional range expansion is human-mediated transport of rhizome-infested soil. Hybridization is common with the congener P. sachalinense in the introduced ranges of North America and Europe resulting in the equally noxious P. × bohemicum. Key words: Japanese knotweed, Mexican bamboo, Polygonum, Fallopia, Reynoutria, POLCU, invasive plant, weed biology

Analysis of somatic hybrids between two sterile dihaploid Solanum tuberosum L. breeding lines. Restoration of fertility and complementation of G. pallida Pa2 and Pa3 resistance

Fourteen somatic hybrids generated by electrofusion of mesophyll protoplasts from a non-flowering dihaploid S. tuberosum clone, DHAK-11, and a male-sterile dihaploid clone S. tuberosum, DHAK-33, were grown in the greenhouse and subjected to morphological assessments and tests for fertility and resistance to the white potato cyst nematode Globodera pallida pathotypes Pa2 and Pa3. The ploidy level of the hybrids ranged from 38 to 63 chromosomes. All hybrids developed flowers with violet petals except for one, hy-56, that possessed red petals. The colour of the tuber skin was purple in all hybrids except in hy-56 where the tuber skin was red. All of the hybrids were female fertile and generated viable seeds. Near-tetraploid hybrids produced the highest number of seeds per fruit and these seeds had a normal size. Hybrids with 58 or more chromosomes produced smaller seeds and less seeds per fruit. The germination frequency of the seeds was not influenced by the chromosome number of the hybrids. Pollen viability was determined and the male fertility of three hybrids was tested. Pollination with these three hybrids gave rise to fruit development, but only one produced viable seeds. The hybrids were tested for resistance to G. pallida pathotypes Pa2 and Pa3. A high level of resistance to Pa3, inherited from one parental clone, DHAK-11, and a high level of resistance to Pa2, inherited from the other parental clone, DHAK-33, was combined in four hybrids. These results demonstrate, that protoplast fusion is an efficient method for restoring the fertility of somatic hybrids generated from sterile parent clones, and is a powerful procedure for the complementation of multigenetic disease resistance traits in potato breeding lines.

A comparative study of the tapetal behaviour in male fertile and male sterileIris pallidaLam. during microsporogenesis

SUMMARY- Two different clones of Iris pallida Lam., male-fertile and male-sterile, are present in Tuscany. In the male-sterile clone, the degeneration of the fertile tissue takes place at the dyad or tetrad stage. Comparative analysis of the anthers, during microsporogenesis, revealed that the tapetal cells of the two clones behaved different­ ly. In the male-fertile line the tapetum presents developmental stages ending in its final degeneration and disappearance. On the contrary, in the male-sterile line the tapetum maintains its initial aspect until necrosis takes place at the dyad or tetrad stage. The persistence of the inner tangential wall of the cells seems to hinder the orbicules from reaching the locular cavity.

Production of somatic hybrids between frost-tolerant Solanum commersonii and S. tuberosum: characterization of hybrid plants

Somatic fusion of mesophyll protoplasts was used to produce hybrids between the frost-tolerant species Solanum commersonii (2n=2x=24) and dihaploid S. tuberosum (2n=2x=24). This is a sexually incompatible combination due to the difference in EBN (Endosperm Balance Number, Johnston et al. 1980). Species with different EBNs as a rule are sexually incompatible. Fifty-seven hybrids were analysed for variation in chromosome number, morphological traits, fertility and frost tolerance. About 70% of the hybrids were tetraploid, and 30% hexaploid. Chloroplast counts in stomatal guard cells revealed a low frequency of cytochimeras. The frequency of aneuploids was relatively higher at the hexaploid level (hypohexaploids) than at the tetraploid level (hypotetraploids). The somatic hybrids were much more vigorous than the parents, and showed an intermediate phenotype for several morphological traits and moderate to profuse flowering. Hexaploid hybrid clones were less vigorous and had a lower degree of flowering than the tetraploid hybrid clones. All of the hybrids were female fertile but male sterile except for one, which was fully fertile and self-compatible. Many seeds were produced on the latter clone by selfing and on the male-sterile clones by crossing. The somatic hybrid plants showed an introgression of genes for frost tolerance and an adaptability to cold from S. commersonii. Therefore, the use of these somatic hybrids in breeding for and in genetic esearch on frost tolerance and cold-hardening is suggested.

Within- and between-population variation in ramet behaviour in the gynodioecious clonal herb, Glechoma hederacea (Labiatae)

Clones of the gynodioecious herb Glechoma hederacea L. produce ramets which flower and bear seed, ramets which flower but fail to bear seed, and sterile ramets. Performance and survivorship of these subsets of ramets were compared for hermaphrodite and male sterile clones in contrasting grassland and woodland habitats for 2 consecutive years. For all clones, ramet densities on given dates were comparable between years. Winter survival of ramets exceeded 95% and mortality during the growing season was exponential. No genet recruitment was recorded throughout the study. For all clones, flowering ramets were larger than nonflowering ramets. Both flowering and nonflowering ramets of hermaphrodite clones, from grassland and woodland, were significantly larger than corresponding types of ramets from male sterile clones. A higher proportion of ramets of hermaphrodite clones flowered and set seed than ramets of male sterile clones. Flowering ramets of hermaphrodite clones produced more flowers than flowering ramets of male sterile clones. For all clones, half-lives of subsets of ramets declined in the order: seed-bearing > flowering but not seed-bearing > nonflowering. Within the grassland habitat, ramet subsets from hermaphrodite clones had longer half-lives than corresponding subsets from the male sterile clones. In the absence of greater flowering and seed set by male sterile clones, self-incompatibility of hermaphrodite flowers, which has been reported previously for G. hederacea, is crucial for the maintenance of clones of both sexes in populations.

Comparison of Genes Controlling Race 1 Anthracnose Resistance in Arc and Saranac AR Alfalfa

Resistance in ‘Arc’ alfalfa, Medicago sativa L., to anthracnose caused by race 1 of Colletotrichum trifolii Bain is conditioned by a single dominant gene, An1. A single gene with gene action like An1 conditions resistance to race 1 anthracnose in ‘Saranac AR’. This tudy was conducted to determine whether or not the gene in Saranac AR coding for resistance to race 1 of C. trifolii is the same An1 gene operating in Arc. Crosses between three simplex race 1 C. trifolii‐resistant clones each of Arc and Saranac AR were made, progeny were evaluated for resistance to race 1 of C. trifolii, and susceptible progeny discarded. Resistant progeny were testcrossed to a susceptible male sterile clone. Those progeny whose testcross lines segregated 1:1 were discarded and those that appeared to segregate as a 3:1 or 5:1 were evaluated further. Ultimately the actual segregation ratio was determined to be 5:1, thus indicating the gene in Saranac AR coding for resistance to race 1 of C. trifolii to be the same An1 gene occurring in Arc.

Single cross alfalfa (Medicago sativa L.) hybrids produced via 2n gametes and somatic chromosome doubling: experimental and theoretical comparisons

The potential breeding value of 2n gametes from diploid alfalfa (2n = 2x = 16) was tested by comparing single cross alfalfa hybrids produced via 2n = 2x gametes from diploids versus n = 2x gametes from somatic-chromosome-doubled, tetraploid counterparts. Three diploid clones, designated 2x-(rprp), homozygous for the gene rp (conditions 2n gamete formation by a first division restitution mechanism) were colchicine-doubled to produce their tetraploid counterparts, designated 4x-(SCD). These six clones were crossed as males to the same cytoplasmic male sterile clone. Yield comparisons of progeny from the six clones demonstrated a significant yield increase of the hybrid progeny from 2n = 2x gametes from the diploids over the hybrid progeny from n = 2x gametes from the chromosome doubled tetraploid counterparts. The yield gain ranged from a 12% increase to a 32% increase. Theoretical comparisons indicated the 2n = 2x gametes from diploids would have 12.5 to 50% more heterozygous loci, on average, than the n = 2x gametes derived from somatic doubling. These results confirm the importance of heterozygosity on alfalfa yield, and the results demonstrate that 2n gametes formed by first division restitution offer a unique method for producing highly heterotic alfalfa hybrids.

Asynapsis in cassava.

A completely male sterile clone was identified in the germplasm and detailed meiosis showed it to be asynaptic. At pachytene all the chromosomes remained as univalents without any semblance to pairing. MI aslo showed 36 univalents in 97% of pollen mother cells. The bivalent like association in MI was as low as 0.03 per cell but the absence of pairing at pachytene and the lack of well defined x'mata suggested that they were only univalents lying closely together due to factors other than true pairing. The later stages were not well defined and univalents were noticed to divide. The scattering of chromosomes and irregular groupings resulted in polyads consequently all the pollen were sterile. The type of asynapsis noticed was ‘complete’. The presence of pollen sterility in all the plants of Ce-258 throughout the season ruled out environmental factors and suggested it was of genic nature.

Differences in Alfalfa Flower Volatiles Among Parent and F1 Plants1

Nonrandom pollination of alfalfa (Medicago sativa L.) by honey bees (Apis mellifera L.) may be based on the ability of honey bees to detect differences in flower aroma among the plants in the field. When the bees associate these aroma differences with nectar or pollen availability a strong basis for ethological isolation exists. The purpose of this work was to gather quantitative data on flower volatile emanation from seven alfalfa clones and on F1 plants from these clones using one male sterile clone as a common parent. This information would assist alfalfa breeders as they consider factors involved in seed yield potential of new varieties. A gas liquid chromatography technique was used to measure the quantity of flower volatiles emanating from cut flowers from greenhouse plants. There was a six‐fold difference in total volatiles and a 19‐fold difference in ocimene (the major terpene of alfalfa flower volatiles) between the extremes of the parent clones. Among the F1 plants tested, there was only a 2.5‐fold difference in total volatiles and a 6‐fold difference in ocimene between the extremes. The F1 of one cross averaged nearly twice the ocimene level of either parent, which also raised total volatiles above that of either parent. Increased emanation of individual aroma compounds from flowers of some F1 plants suggests that total flower aroma and floral aroma character can be genetically influenced. Thus it may be possible to alter the floral character of alfalfa to increase its attractiveness to honey bees for pollination.

PERFORMANCE OF HYBRIDS IN ORCHARD GRASS

Single-cross hybrids of orchard grass (Dactylis glomerata L.) were evaluated for yield, in vitro digestibility (IVD), and relative maturity in three trials. All trials were planted broadcast, using seed produced on male-sterile clones. All trials were harvested for 2 yr. The average yield of the 48 hybrids tested was 98% of that for the cultivar Frode in the first cut each year, and 103% over the season. The most productive hybrid produced 28% more forage than Frode in the first cut, and 15% more over the season. For IVD, there was no evidence of hybrid superiority. The results indicate that the use of hybrids can result in an increase in forage yield.

Intra‐Plant Variation for Pollen Production in Male‐sterile and Fertile Alfalfa1

In Medicago saliva L. intra‐plant variation in pollen production occurred in partially male‐sterile clones, but it was not associated with either flower position on the plant or sampling date. The variation occurred at random throughout the plant. Anthers within the same flower varied for both number of pollen grains and percentage of normal pollen grains.The average number of pollen grains per anther varied among clones from about 440 to 850. The free anther had only about two‐thirds as many pollen grains as each of the remaining nine anthers. The number of normal pollen grains correlated with visual estimates of the amount of dehisced pollen, r = .854**, 11 d.f. Pollen abortion in male‐sterile plants apparently reduced internal pressure sufficiently to prevent rupture of the anther wall and extrusion of pollen.

Vacuum‐Dried Pollen of Alfalfa (Medicago Sativa L.) Viable after Eleven Years1

After 11 years in storage, the vitality of vacuum‐dried pollen of alfalfa (Medicago saliva L.) was determined by placing the pollen on stigmas of blossoms of a malesterile clone, 20 DRC. Percent pod set of blossoms so pollinated ranged from 36 to 57; the number of seeds per pod ranged from 2.5 to 3.4. The data showed that pollen for breeding studies can be stored successfully for 11 years under the conditions used in this experiment, although some deterioration in viability occurred.