Morphologic,cytogenetic, and enzymatic variation in tissue culture regenerated plants of apomictic old-world bluestem grasses (Bothriochloa sp.)

Somaclonal variant plants may be of use in broadening the germplasm base of plant species and providing useful stocks for cytogenetic investigations. This study was conducted to compare morphologic, cytogenetic and enzymatic characteristics of 21 R₁ (initial regenerate) bluestem,Bothriochloa sp., plants, visibly identified in a field-grown population of 522 plants as probable variants, with their respective R₀ (explant donor) progenitor. An R₂ seedling population was grown to ascertain the transmission of the variant R₁ phenotypes. All R₁ plants differed from their respective R₀ progenitors in one or more morphological characters. Foliage colour was the most pronounced difference in most cases. Four of the plants, three of which were dwarfed, produced no inflorescences. The R₁ plants tended to be shorter than R₀ progenitors and had corresponding decreases in lengths on inflorescences and lowest racemes. All R₁ plants of accessions 8911C and 8793 had an increase in chromosome number from2n=4x=40 to2n=5x=50. Three dwarfed R₁ plants, derived from accession 8873B, were aneuploids, two having2n=48 chromosomes and the third being a probable mixoploid with 55–58 chromosomes. Other plants of accession 8873B had the R₀ chromosome number. Fertility, as estimated by pollen stainability and seed set, generally was reduced in R₁ plants relative to the R₀. This reduction was not drastic, however, with all flowering plants having 45% or higher seed set. Apomixis apparently maintained fertility in all R₁ plants, including those with a pentaploid chromosome number. All R₁ plants differed from their respective R₀ plants in peroxidase and esterase banding patterns. All R₁ plants of accessions 8911C, and 8793, respectively, had identical peroxidase and esterase bands. For both enzyme systems two banding patterns were present in R₁ plants of accession 8873B, with 12 of 13 plants exhibiting common patterns. Examination of R₂ progeny plants confirmed the genetic transmission of the variant phenotypes and, by virtue of uniformity, indicated apomictic reproduction in the R₁ plants. The results demonstrate the production of potentially useful genetic and cytogenetic variant plants via tissue culture in these apomictic species.     

<Emphasis Type="Italic">Hieracium</Emphasis> subgen. <Emphasis Type="Italic">Pilosella</Emphasis>: pollen stainability in sexual,apomictic and sterile plants

Two pollen stainability tests (Alexander’s stain and acetocarmine) were used to detect differences in pollen viability of the sexual, apomictic and sterile plants of Hieracium subgen. Pilosella. In sexual taxa (Hieracium bauhini and H. densiflorum), the average stainability was 93.7–98.4%. Similarly high stainability (92.2–97.2%) was found in the apomictic Hieracium pilosellinum and in the majority of the apomictic populations (or plants) of the pentaploid and hexaploid H. bauhini. In some apomictic plants of Hieracium bauhini the average pollen stainability was 49.0–75.4%. The lowest pollen stainability was found in the sterile plants, i.e. the triploid H. pistoriense (33.6%) and the pentaploid H. brachiatum (29.6%).     

Induced Androgenesis in vitro in Mutated Populations of Barley,Hordeum vulgare

Graduated concentrations of chemomutagens ethylmethanesulphonate (EMS), N-nitroso-N-methylurea (MNU) and N-nitroso-N-ethylurea (ENU) and one concentration of sodium azide (NaN₃) were used to treat seeds of spring barley cultivars Heris, Tolar, Granát and Novum. Androgenesis in vitro was induced in mutagenised plant populations. The significant stimulation effect of mutagenic treatment on the mean number of androgenic anthers from all 36 treated variants was registered in 17 variants, on the mean number of regenerated plants in 15 variants and on the mean number of regenerated plants per androgenic anthers in seven variants only. Genotypes with a lower androgenic response were relatively more stimulated. Evaluation was made of the frequency of chlorophyll mutations within androgenic regenerants and in seed progeny of androgenic donors. Androgenesis was also induced in vital chlorophyll mutants and in the variants where the mutagen treatment resulted in less than 50% survival of the donor plants. Ratios between frequency of haploids and spontaneous dihaploids were similar in green and in albino androgenic plants. The results confirm that in barley it is possible to enhance the frequency of in vitro pollen embryogenesis by mutagenic treatment of seeds.     

Fertile progeny of a hybridization between soybean [Glycine max (L.) Merr.] and G. tomentella Hayata

Summary A colchicine-doubled F₁ hybrid (2n=118) of a cross between PI 360841 (Glycine max) (2n=40) x PI 378708 (G. tomentella) (2n=78), propagated by shoot cuttings since January 1984, produced approximately 100 F₂ seed during October 1988. One-fourth of the F₂ plants or their F₃ progeny have been analyzed for chromosome number, pollen viability, pubescence tip morphology, seed coat color, and isoenzyme variation. Without exception, all plants evaluated possessed the chromosome number of the G. max parent (2n=40). Most F₂ plants demonstrated a high level of fertility, although 2 of 24 plants had low pollen viability and had large numbers of fleshy pods. One F₂ plant possessed sharp pubescence tip morphology, whereas all others were blunt-tipped. All evaluated F₂ and F₃ plants expressed the malate dehydrogenase and diaphorase isoenzyme patterns of the G. max parent and the endopeptidase isoenzyme pattern of the G. tomentella parent. Mobility variants were observed among progeny for the isoenzymes phosphoglucomutase, aconitase, and phosphoglucoisomerase. This study suggests that the G. Tomentella chromosome complement has been eliminated after genetic exchange and/or modification has taken place between the genomes.Journal Paper No. J-13776 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA, USA, Project 2763     

Introduction of a gene from fertility restored radish (Raphanus sativus) into Brassica napus by fusion of X-irradiated protoplasts from a radish restorer line and iodacetoamide-treated protoplasts from a cytoplasmic male-sterile cybrid of B. napus

To establish a cytoplasmic male-sterile/restored fertility (cms-Rf) system for F₁ seed production in Brassica napus, we transferred a gene from fertillity restored radish to B. napus by protoplast fusion. X-irradiated protoplasts, isolated from shoots of Raphanus sativus cv Kosena (Rf line), were fused with iodoacetamide-treated protoplasts of a B. napus cms cybrid. Among 300 regenerated plants, six were male-fertile. The fertile plants were characterized for petal color, chromosome number and the percentage of viable pollen grains. Three fertile plants had aneuploid chromosome numbers and white or cream petals, which is a dominant marker in radish. Of these three plants, one which had 2n = 47 chromosomes and white petals was used for further backcrosses. After two backcrosses, chromosome number and petal color became identical to that of B. napus. No female sterility was observed in the BC₃ generations.     

Evidence for the existence of 2n gametes in Lotus tenuis Wald. et Kit. (2n=2x=12): their relevance in evolution and breeding of Lotus corniculatus L. (2n=4x=24)

Summary Crosses between male sterile L. corniculatus (2n=4x=24) and L. tenuis (2n=2x=12) plants were performed in order to verify the presence of 2n gametes in L. tenuis. All but one of the plants from these crosses had 2n=4x=24 and the L. corniculatus phenotype; this plant had 2n=2x=12 and the L. tenuis phenotype. The plants also showed good quantity of pollen at tripping, good pollen fertility and good percentage of seed setting in the backcross to L. corniculatus. On the whole, both cytological and morphological observations, showing that all but one of the plants from L. corniculatus x L. tenuis were normal tetraploids, suggest the existence of diploandrous gametes in L. tenuis. On the other hand, haploid parthenogenesis probably gave origin to the dihaploid plant 2n=2x=12.     

Variable karyotype with B-chromosomes in Bellevalia saviczii (Liliaceae)

Bellevalia saviczii (Liliaceae), a hexaploid (2n = 6x = 24), was collected from mountain slopes in the Shiraz valley, southern Iran. The basic karyotype consists of one long metacentric chromosome, a slightly shorter acrocentric, and two shorter submetacentrics. In 32% of the plants, one and sometimes two of the acrocentrics (IIa) appeared with a pericentric inversion that changed it into a metacentric (IIm). This metacentric IIm was present in a Hardy--Weinberg ratio throughout the collection range of more than 300 km. A number of aneuploids were found, pentasomics [2n – 1 = 23 (4.9%)], heptasomics [2n + 1 = 25 (2.5%)], and one octasomic [2n + 2 = 26 (0.3%)]. Re-assorted karyotypes with 2n = 24, but with odd numbers of two of the chromosomes, were also present (6.6%). B-chromosomes were found in root meristems and in pedicels in a number (19.1%) of the plants that grew around a 30 km marsh. Their numbers ranged from 1B to 8Bs per plant peaking in the 2B mode. The B-chromosomes (two polymorphs with terminal and near-terminal sticking points) were telocentric with a few metacentric iso-Bs. No B-carrying plants were found in the drier regions away from the marsh. The B-frequency distribution for aneuploids and pericentric inversions was much different than for the standard euploid. Dr Mark Gettner died on November 2nd, 2002. He is fondly remembered by his family, his many students and friends for his kindness and generosity, and for his dedication to his scientific work. Dr Broun is the son-in-law of Dr Gettner and he will be the corresponding author for this article (pb22@york.ac.uk).     

Distyly and incompatibility inVillarsia congestiflora (Menyanthaceae), with comparative remarks onV. capitata

The Western Australian annual of restricted distribution,Villarsia congestiflora, has distylous flowers and pollen-size heteromorphism. Results of a crossing program indicate that this species is strongly self-incompatible, that crosses among individuals of the same morph produce little or no seed, and that intermorph crosses produce copious seed. The species shares a number of morphological and ecological traits withV. capitata, another distylous, self-incompatible annual species of Western Australia with a greater area of distribution. Artificial hybrids between the two, however, showed reduced pollen stainability. Both species combine a number of specialized morphological features with a breeding system that is primitive for the familyMenyanthaceae.     

A new biological function of Shiitake mushroom,Lentinula edodes, in a myco-heterotrophic orchid,Erythrorchis ochobiensis

The biological function ofLentinula edodes in a myco-heterotrophic orchid,Erythrorchis ochobiensis was examined, using one local variant each from Japan (JPN), Papua New Guinea (PNG) and New Zealand (NZ). All variants induced seed germination: PNG and NZ isolates were effective at 25°C and JPN isolate showed the highest germination rate at 30°C. Germinated seeds developed into plants and formed normal endomycorrhizas. Hence, it is concluded thatL. edodes has a perfect symbiotic potential withE. ochobiensis, though it has not been observed in the root of the orchid in the field.     

Intergeneric hybridization between Brassica napus and Sinapis pubescens,and the cytology and crossability of their progenies

The cytological possibility of gene transfer from Sinapis pubescens to Brassica napus was investigated. Intergeneric hybrids between Brassica napus (2n = 38) and Sinapis pubescens (2n = 18) were produced through ovary culture. The F₁ hybrids were dihaploid and the chromosome configurations were (0–1) _III + (2–11) _II + (5–24) _I . One F₂ plant with 38 chromosomes was obtained from open pollination of the F₁ hybrid. Thirty-one seeds were obtained from the backcross of the F₂ plant with B. napus. Five out of seven plants had 38 chromosomes, and the pollen stainability ranged from 0% to 81.4%. In the B₂ plants obtained from the backcross of B₁ plants with B. napus, 66.7% of the plants examined had 38 chromosomes. S. pubescens may become a gene source for the improvement of B. napus.     

Pollen tube expression of pseudo-self-compatibility (PSC) inPetunia hybrida

Summary AnS _1.1 self-incompatible (SI) petunia plant which showed atypical seed set was found in an I₇ population. This plant showed a strong SI reaction when selfed but produced varying amounts of seed when used as the seed parent in crosses with unrelated individuals homozygous for the sameS allele. Reciprocal crosses yielded no seed indicating that the reaction was a stylar response. Self seed obtained by high temperature treatments produced 18 plants, all of which exhibited the parental characteristics, the ability to reject self pollen but accept, to varying degrees, pollen bearing the sameS allele from unrelated plants. Several petunias homozygous forS ₁, and exhibiting various levels of PSC as determined by self seed set, progeny tests and temperature treatments, were used as pollen parents. The mean seed set of these crosses produced a ranking of the pollen parents which reflected the PSC levels obtained by other methods. The behavior of the F₁ and F₂ populations suggests that the pollen discriminating ability may be a simply inherited, dominant character in these plants. The styles of these unusual petunias illustrate the participation of the pollen tube in determining PSC.Scientific Journal Series Paper Number 10.479 of the Minnesota Agricultural Experiment Station     

濒危植物大别山五针松母树林花粉传播规律

大别山五针松是典型的风媒传粉植物,花粉流是种群基因流的重要形式。用重力玻片法研究大别山五针松母树林的花粉飞散特征,分析了时间和空间对花粉飞散的影响,结合林分密度和气象因子探讨花粉飞散的特点。结果表明:大别山五针松从5月中旬开始传粉,散粉期为14d,盛粉期为3d,种植密度低的下坡花粉密度比密度大的上坡的要高。日散粉最大值出现在10:00～14:00,植株中上部花粉密度较高,距花粉源50m处花粉密度最高。建议对种植密度大的区域移栽以促进花芽生成,以保证结实率与提高种子品质。     

Isolation affects reproductive success in low-density but not high-density populations of two wind-pollinated <Emphasis Type="Italic">Thalictrum</Emphasis> species

Since pollen usually travels limited distances in wind-pollinated plant species, plants growing at low density may become pollen limited. We examined how local pollen availability and population density affect reproductive success in two wind-pollinated, dioecious species, Thalictrum fendleri and Thalictrum dioicum. Distance to the nearest flowering male, the number of flowering males within 2 m, and flower number on those males served as measures of local pollen availability. Increased distance from pollen donors reduced seed set in the lowest-density population of each species, but seed set in high-density populations was not correlated with local pollen availability. For plants in high- and low-density populations at similar distances from pollen donors, this distance only affected seed set in low-density populations. To ensure that differences in resource availability were not causing spurious correlations between seed set and plant density, we constructed low-density artificial arrays in populations of T. dioicum. In these, seed set decreased rapidly with increases in distance from pollen donors. Despite these effects, the density of males in a population was not correlated with average seed set in T. dioicum, and hand pollination in the T. dioicum populations also failed to increase seed set over natural levels. These results suggest that pollen receipt only limits seed set on isolated plants within low- density populations of T. dioicum and T. fendleri.     

The effects of pollen diversity on plant reproduction: insights from apple

For many plants, the number of pollen genotypes deposited on a flower’s stigma is positively related to fruit maturation and seed number; however, the mechanisms underlying this effect are less understood. Here we examined whether diversity of pollen (1, 3, or 5 donors) affects reproductive success in self-incompatible apple (Malus × domestica). Using paternity analysis, we then assessed the siring rate of individual donors to test whether diversity effects are related to the presence of a superior pollen donor or to donor × donor interactions. Increasing the diversity of compatible pollen enhanced seed number and reduced seed abortion in some but not all recipient genotypes. This effect was associated with an increased number of sires per fruit and non-random siring success among pollen donors. Two donors had consistently high siring rates, regardless of recipient genotype; however, the siring success of pollen donors was not correlated with their siring success in single-donor pollinations. Rather, siring success was affected by the identity of other pollen genotypes present on the stigma. Our results therefore suggest that the effects of pollen diversity are variable but may enhance fecundity by fostering interactions between pollen donors.     

Unreduced gametes in diploid Medicago and their importance in alfalfa breeding

Summary In the genus Medicago, it is known that 2n gametes have been important in the evolution and breeding of cultivated alfalfa, which is a natural polysomic polyploid (2n=4x=32), however little is known on the frequency of male and female 2n gametes in diploid relatives of alfalfa. To obtain data on the frequency of 2n gametes, more than 12,000 2x–4x and 4x–2x crosses were made in 1982 at Madison (USA). Diploid parents in crosses were from four populations of M. coerulea, two of M. falcata and one diploid population of cultivated M. sativa which was derived by haploidy. The tetraploid seed parent in the crosses was a male-sterile M. sativa clone and vigorous tetraploid M. sativa plants were used as pollen parents. Each of 274 diploid plants was utilized both as male and as female. Of the 548 cross combinations, 266 crosses produced variable quantities of seeds which were sown in 1983 in a greenhouse at Perugia (Italy); the plants were subsequently space transplanted in the field in 1984. The identification of ploidy level of these genotypes was made on the basis of morphological characters, plant fertility, pollen stainability and chromosome counts.Of the 515 plants analyzed, the majority behaved as normal tetraploids indicating that many diploid plants produced 2n gametes. Diplogynous and diplandrous gamete production was not correlated with each other, which indicated a different genetic control of 2n sporogenesis in the 2 sexes. Only 4 F₁ triploid plants confirmed the presence of a very effective triploid block in alfalfa. In consequence, bilateral sexual polyploidization is a more likely alternative for the origin of tetraploid alfalfa than triploid bridges. The present study showed that it is possible to efficiently identify genotypes able to produce high frequencies of 2n gametes within natural populations of diploids Medicago that are useful in alfalfa breeding.Part of this study was conducted at the Agronomy Department, University of Wisconsin, Madison, Wis, USA, while one of us (F. Veronesi) was in receipt of financial assistance provided by the National Research Council of Italy; part was conducted at Centro di Studio per il Miglioramento Genetico delie Piante Foraggere, C.N.R., Perugia, Italy. The paper was presented at the Eucarpia Fodder Crops Section Meeting, Svalöv, Sweden, 16–19th September 1985     

APOMIXIS IN THE POA SECUNDA COMPLEX

Observation of cleared ovules of Poa secunda Presl showed that plants produce aposporous embryo sacs, and emasculation studies showed that they do not set seed without pollen. The ratio of sexual to asexual embryo sacs on a given plant does not correlate with percent stainable pollen, nor does pollen stainability correlate with meiotic regularity or with chromosome number. Percent apomictic ovules, percent pollen stainability, and regularity of meiosis all vary within a given population; they also vary if the same plant is moved from one site to another. Although there is morphological variation in the species, none of the reproductive features correlates with morphology. Pollen from any morph will stimulate seed set in any other morph, and hybrids have been produced in low frequency. Plants will also set seed using their own pollen. In its reproductive biology, P. secunda exhibits many similarities with P. pratensis L.     

Production,morphology, and cytogenetic analysis of Elymus caninus (Agropyron caninum) x Triticum aestivum F1 hybrids and backcross-1 derivatives

Summary Intergeneric hybrids were produced between common wheat, Triticum aestivum (2n=6x=42, AABBDD) and wheatgrass, Etymus caninus (Agropyron caninum) (2n=4x=28, SSHH) — the first successful report of this cross. Reciprocal crosses and genotypes differed for percent seed set, seed development and F₁ hybrid plant production. With E. caninus as the pollen parent, there was no hybrid seed set. In the reciprocal cross, seed set was 23.1–25.4% depending upon wheat genotype used. Hybrid plants were produced only by rescuing embryos 12–13 days post pollination with cv Chinese Spring as the wheat parent. Kinetin in the medium facilitated embryo germination but inhibited root development and seedling growth. The hybrids were vigorous, self sterile, and intermediate between parents. These had expected chromosome number (2n=5x=35, ABDSH), very little chromosome pairing (0.51 II, 0.04 III) and some secondary associations. The hybrids were successfully backcrossed with wheat. Chromosome number in the BC₁ derivatives varied 54–58 with 56 as the modal class. The BC₁ derivatives showed unusually high number of rod bivalents or reduced pairing of wheat homologues. These were sterile and BC₂ seed was produced using wheat pollen.     

Wide hybridization in Brassica

Summary Crosses were made to obtain interspecific hybrids between B. fruticulosa (wild species , 2n = 16) × B. campestris (cultivar , 2n = 20). Although many pollen grains germinated and their tubes entered the style, only about 30% of the ovules received pollen tubes. Fertilized ovules aborted at various stages of development. A few hybrid seeds resulted from hand pollinations in the field, and they showed poor germination and seedling establishment. The in vitro culture of ovaries, ovules, and seeds increased the frequency of obtaining hybrid seeds and plants: the most effective method was ovary culture followed by ovule culture. The hybrid nature of the plants was confirmed through morphological, cytological, and electrophoretic studies. A meiotic analysis of F₁ hybrids (2n = 18) showed that they had 0–5 bivalents and were completely pollen sterile. Electrophoretic analysis of leaf esterases and acid phosphatases of F₁ hybrids revealed bands derived from each parent. Induced amphidiploids of F₁ hybrids contained mostly bivalents, and had about 50% fertile pollen.     

Effects of Biological Soil Crusts on Seed Bank, Germination and Establishment of Two Annual Plant Species in the Tengger Desert (N China)

The presence of biological soil crusts can affect the germination and survival of vascular plants, but the reasons are not well investigated. We have conducted a field investigation and greenhouse experiments to test the effect of crusts on two desert annual plants, which occur on the stabilized dunes of the Tengger Desert in N China. The results showed that biological soil crusts negatively influenced the seed bank of Eragrostis poaeoides and Bassia dasyphylla. The important effect of biological soil crusts on seed germination and establishment were performed indirectly through reducing the amount of germinating seeds. Field investigation and experimental results with regard to the seed bank indicated that higher seedling density was found in disturbed crust soil and bare soil surface than in intact crust soils. Greenhouse experiments showed that the effects of biological soil crusts on germination and establishment of the two plants are not obvious in moist condition, while disturbed crusts are more favorable to seed germination in dry treatment. Significant differences in biomass were found between disturbed crust soil and bare soil. Survival and growth of the two annual plants were enhanced in both algal and moss crusts during the season of rainfall or in moist environment, but crusts did not affect seedling survival in the dry period. The small seeded E. poaeoides has higher germination than larger-seeded B. dasyphylla in crust soils, but B. dasyphylla has a relatively higher survival rate than E. poaeoides in crust soils.     

The effect of B-chromosomes of rye on the chromosome association in F1 hybrids Triticum aestivum x Secale cereale in the absence of chromosomes 5B or 5D

Summary T. aestivum var. Chinese Spring (monosomic 5B and 5D, respectively) was crossed with S. cereale (with and without B-chromosomes). The resulting nullisomic 5B hybrids exhibited a high degree of chromosome association both at 20°C and 10°C. The presence of B-chromosomes reduced association slightly whether 5B was present or not.In nullisomic 5D hybrids B-chromosomes of rye raise chromosome association at 20°C when compared to hybrids with 5D, with as well as without, B's. At 10°C, due to the absence of the Ltp gene on 5D, chromosome association in nullisomic 5D hybrids is low, and no effects of rye B-chromosomes is detectable.The hypothesis that B-chromosomes of rye carry (an) asynaptic gene(s) decreasing effective pairing, and (an) independent post-synaptic gene(s) increasing chiasma frequency on effective pairing sites, is presented.The work was supported by a fellowship of the Gulbenkian Foundation and partly carried out while the author was at the Department of Genetics, Agricultural University, Wageningen, the Netherlands