Cytology of Phleum sp. affin. P. montanum C. Koch

Diploid, tetraploid, and hexaploid plants occurred in foreign plant introductions of P. sp. affin. P. montanum from Turkey and Iran. Within-progeny variations in polyploid levels indicate that divergent races occurred as interspersed but natural populations. One to six B-chromosomes of varying sizes in addition to the normal chromosome complement were present in some plants. Their behaviours appeared essentially similar to those recorded for other species. Certain of the plants examined exhibited cytological features similar to those observed in known hybrids. These included prophase pycnosis, stickiness, split metaphase I plates, unoriented chromosomes at M-1, and low levels of pollen stainability. These features were absent in microsporocytes of other plants. Low open-pollination seed set characterized all plants examined. This may be due to hybridity or possibly to response to ecological conditions of the new environment.Results of co-operative work of the Crops Research Division, A.R.S., U.S. Department of Agriculture, and the Wisconsin Agricultural Experiment Station, Madison, Wisconsin.Former Graduate Student, Department of Agronomy, Wisconsin Agricultural Experiment Station, and Geneticist, Crops Research Division, Agricultural Research Service, U.S. Department of Agriculture.     

Intergeneric hybrids and an amphiploid between Elymus canadensis and Psathyrostachys juncea

Summary Fifty four hybrid plants between Elymus canadensis and Psathyrostachys juncea were obtained by handpollination and embryo culture. The average cross compatibility between both species was 31.2 percent. One amphiploid plant was induced by colchicine treatment. The hybrid and amphiploid plants resembled P. juncea in appearance but showed a higher plant height and dry matter yield than the parents. The hybrids showed extremely low pollen stainability and were completely sterile. With the exception of one plant (2n=3x+1=22), all hybrid plants were allotriploids (SHN, 2n=3x=21). The amphiploid plant (SSHHNN, 2n=6x=42) showed 58.9% pollen stainability and 11.6% seed fertility.Mean chromosome associations of the hybrids and amphiploid at metaphase I were 0.02IV+0.06III+2.03II+16.91I and 0.07III+18.00II+5.85I, respectively. Lagging chromosomes, chromosome bridges, abnormal cytokinesis, and micronuclei were occasionally observed at the anaphase, telophase, or tetrad stage.     

Production of interspecific hybrids between Alstroemeria pelegrina L. var. rosea and A. magenta Bayer by ovule culture

Interspecific hybrids were efficiently produced in the cross-incompatible combination between Alstroemeria pelegrina L. var. rosea and A. magenta Bayer by culturing immature ovules with placenta 7–14 days after pollination on 2 g/l Gelrite-solidified MS medium containing 3% (w/v)sucrose. The plants showed intermediate characteristics between the parents and their hybridity was confirmed by karyotype and DNA analyses. The mean number of chromosome association per PMC at metaphase I was 2.60I+6.70II, pollen stainability was20.8%, and they produced viable seeds after self-pollination. Furthermore, mature plants were obtained when the hybrids were backcrossed as male parents with both the parents. The backcross-progeny from A. pelegrina var. rosea × hybrids exhibited 3.8 to 79.7% pollen stainability and that from A. magenta × hybrids 78.8 to 98.3%. Almost all of these plants produced viable seeds after self-pollination, which implies that they can beutilized for breeding of novel cultivars of Alstroemeria. This revised version was published online in July 2006 with corrections to the Cover Date.     

Meiosis in triploid Solanum tuberosum L.

Summary Meiosis in triploid Solanum tuberosum was studied in plants that originated from crosses between tetraploids and diploids, the latter being mainly dihaploids.Association of chromosomes in first metaphase was regular, being as expected for autotriploid material. In first anaphase lagging chromosomes occurred that mostly divided precociously into their chromatids, the amount of lagging chromosomes being more or less proportional to the average number of univalents at M I. The A I distribution of chromosomes over the poles fitted a normal distribution.In the second meiotic division also lagging chromosomes were observed. During this division disturbances occurred resulting in cells with more or less the somatic chromosome number. The origin of this aberration is discussed, together with the relation between meiotic behaviour and pollen stainability.     

Fertility,plant morphology,and transmission rates of the extra chromosome in single and double trisomics of Solanum tuberosum L. Group Tuberosum

Summary Initial single and double trisomics of S. tuberosum Group Tuberosum cv. Gineke were successfully crossed with and backcrossed to clones obtained through inbreeding of self-compatible dihaploids of the same variety. Some trisomics showed reduced flowering or flower abnormalities and contributed therefore only to a small extent. Berry-set and seed-set varied considerably. There was no relation between these phenomena, nor was there any relation between either berry-or seed-set and the identity of the extra chromosome in the female parent. Seed-set seemed to be influenced by the male parent. When a more inbred male parent was used in the crosses with trisomics this often resulted in less seed per cross. There was no clear relation between seed-set and stainability of the pollen grains, but both the strong selection for good pollen and the high level of self-compatibility, have apparently contributed to the success of the crosses. The double trisomic plants yielded less seed than most single trisomics. Only three of the single trisomics produced stainable pollen and two of them yielded progeny when used as male parent in crosses or selfings.In the progenies several of the trisomic types could be distinguished on the basis of plant morphology in the young seedling stage. For ten different trisomics the morphotype is being described. The average rate of female transmission of the extra chromosome was about twenty per cent, but there was a wide variation, both between and within the various trisomic types. The results indicated that for chromosomes 3 and 8 the rate of transmission was higher than the average value. In one out of two trisomic types male transmission of the extra chromosome occurred, with a rate of 4.7%. The possible causes for the observed differences in female transmission of the extra chromosome are being discussed.     

Pollen storage of Fragaria and Potentilla

Summary Low temperature and humidity were used for the storage of pollen of four species of Fragaria (2n=14, 42 and 56) and two species of Potentilla (2n=14). The stainability of Fragaria pollen was assessed over a number of years by use of aceto-carmine stain and its viability by cross-pollinations; stainability of Potentilla pollen was assessed by acetocarmine. Fragaria pollen so stored remained stainable for seven years and showed the ability to set seed for three years. over the latter period, aceto-carmine staining gave a reasonable prediction of seed set produced by the stored pollen of Fragaria and so is of value in estimating pollen viability in that genus. Potentilla pollen remained stainable for three years.     

Reproductive behaviour of tetraploid alfalfa plants obtained by unilateral and bilateral sexual polyploidization

The objective of the present study was to evaluate the fertility of tetraploid plants obtained from diploid mutants that produced 2n gametes via bilateral (BSP) and unilateral sexual polyploidization (USP) schemes. Controlled matings between selected plants from BSP and USP were carried out according to a complete diallel. The level of male and female fertility of each plant was estimated within full-sib, half-sib and non-inbred crosses. Crosses with unrelated self-fertile and male-sterile testers were also performed. Pollen size and stainability were determined by acetocarmine staining. The number of ovules per ovary was counted and the callose deposition within ovules examined to evaluate embryo sac fecundity. Cross-fertility was generally much higher for USP than BSP plants (on average, 0.3 vs. 0.03 seeds per flower pollinated). Both male and female fertility were inversely related to the inbreeding level of cross combinations. The in vitro pollen germinability was positively correlated to male fertility of BSP plants. The level of in vivo embryo sac sterility was not correlated to female fertility in either BSP or USP plants. Female fertility was restored in both BSP and USP groups when plants were crossed with unrelated tetraploid testers. Male fertility also increased in USP plants but remained rather low in the BSP plants. Scaling up the ploidy level by means of 2n gamete union resulted in tetraploid plants with low fertility. In particular, the BSP process yielded virtually self-sterile and highly cross-sterile plants. The well documented positive effect of sexual tetraploidization on forage yield was accompanied by worsening of fertility traits. This revised version was published online in July 2006 with corrections to the Cover Date.     

Male fertility and occurrence of 2n gametes in East African Highland bananas (Musa spp.)

The quantity and quality of pollen produced by a genotype are important attributes to be considered in the selection of male parents for breeding. The objective of this research was to determine the quantity and quality of pollen in 13 selected East African Highland bananas (EAHB) in relation to six diploids commonly used as male parents. Pollen quantity was scored on a scale of 0–6 while the variation of pollen stainability along the rachis was determined using acetocarmine glycerol jelly. Actual male fertility was determined by using pollen from the EAHB varieties on M. acuminata spp. burmannicoides, ‘Calcutta 4’, as the female. The diameter of 200 viable pollen grains was measured under a microscope with the aid of a graduated eyepiece. Significant differences were obtained for mean pollen stainability and pollen diameter. The pollen stainability for diploids was higher than that for the EAHB. Node numbers contributed significantly to variation of pollen stainability in EAHB (P ≤ 0.01) and ‘Pisang lilin’ (P ≤ 0.001). ‘Pisang lilin’ and the EAHB varieties had about 100 nodes as opposed to about 200 in other diploids. The EAHB varieties produced less pollen than most of the diploids. The actual male fertility of EAHB varieties was low (1 seed/bunch), compared to that of ‘Calcutta 4’ (223.3 seeds/bunch) and ‘Pisang lilin’ (13.7 seeds/bunch). Although the production of 2n pollen in EAHB varieties was low (0–7%), the potential exists for using them in new breeding approaches.     

Natural outcrossing in common buckwheat

Common buckwheat is an obligate cross pollinating crop because of its sporophytic self-incompatibility system. Therefore a study to assess the extent of natural outcrossing was undertaken for two years at Morden and Portage la Prairie, Manitoba using the semi-dwarf character, which is due to a homozygous genotype with regard to a single recessive gene, as a marker. The semi-dwarf genotype was grown in 100 m rows running in four directions at 90 ° from a central 36 m² plot of a normal, tall variety. At maturity, seed samples were taken from the semi-dwarf population at designated intervals. At least 200 F₁ seeds from each sample were grown in the greenhouse to the 3-4 leaf stage and the proportion of tall plants was used to determine the percentage of outcrossing. Approximately 50% outcrossing occurred where the semi-dwarf plants were immediately next to the normal plants and then the proportion decreased with increasing distance. Although outcrossing occurred throughout the distance tested, there were no significant differences from 12 m onward from the pollen source. Lack of directional influence in outcrossing and a sharp reduction in the proportion of tall plants within a 3 m distance from the pollen source suggested that wind was not a major factor in dispersing the buckwheat pollen over long distances. Although a substantial cross pollination was limited to a few metres from the pollen source, nearly 1% outcrossing occurred even at 100 m. Since the distance in this experiment was limited to 100 m from the pollen source, the present results do not allow us to recommend the minimum isolation distance required to meet certain standards for buckwheat seed production. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cytogenetic and morphological characteristics of new types of diploids (2n=22, 24, 40) derived from consecutive selfing of aneuploids in brassica crops

Summary New types of diploids in Brassica crops were synthesized after three consecutive selfing of aneuploids derived from backcrossing of sesquidiploids (2n=29, AAC) with B. campestris (2n=20, AA). The cytogenetic and morphological characteristics of plants with 2n=22, 24 and 40 in the S₃ generation were analyzed in order to establish the extent in which these addition and polyploid lines were stabilized. A high frequency of 11_II (79.7%), 12_II (84.6%) and 20_II (100%), were observed at metaphase _I of pollen mother cells in 2n=22, 24 and 40 plants, respectively. The chromosome configuration at methaphase _II also indicates that a certain level of stability has been attained cytogenetically. Although pollen stainability was relatively high, the seed set percentage was still low. Variation in morphological characteristics indicate the incorporation of one or more chromosome pairs from the C genome of B. oleracea. Other diagnostic characters such as the formation of determinate inflorescence, branching from the base of the stem, and the shift from self-incompatibility to self-compatibility must have resulted from the interaction between A and C genomes. Thus plants with 2n=22, 24 and 40 have been stabilized to some extent and can be developed into new breeding lines of Brassica. It is suggested that limited pollination could be effective in increasing the seed fertility of these plants.     

Effect of Boron on Seed Yield in Lucerne (Medicago sativa L.)

The present study aimed at studying the effect of boron on pollen characteristics, translocation of water soluble sugars and its importance as a specific nutrient for seed production in lucerne. Aquous solutions of borax (0, 2500, 5000, 7500, 10 000 and 20 000 ppm) were sprayed at flowering stage. After 20 days, the fresh flowers were collected from the plants of all the treatments separately. The pollen was dusted on glass slides containing Muntzing's mixture for staining. After 6 hours, the data on pollen size, stainability and germination were recorded in 10 randomly selected microscopic fields. The estimation of water soluble sugars and boron content in flowers was done by standard methods. Data on grains per pod, grains per inflorescence and 1000 seed weight were recorded at seed maturity. With increasing rates of applied B, pollen germination, water soluble sugars, boron content and number of seeds per pod and per inflorescence increased but pollen fertility decreased. The pollen size and 1000 seed weight was not affected by boron concentrations. The results indicate that boron plays a definite role in increasing the seed yields through stimulating the physiological processes during reproductive phase.     

Meiotic restitution mechanisms and 2n pollen formation in a Solanum tuberosum dihaploid and in dihaploid × wild species hybrids*

A Solatium tuberosum dihaploid that proved to be a 2n pollen producer, exhibited two types of meiotic abnormality involved in 2n pollen formation: premature cytokinesis at prophase II and parallel/tripolar spindles in meiosis II. For this reason such a dihaploid was preferentially used as a seed parent in crosses with the diploid species S. tarijense, S. sanctae-rosae, and S. phureja. Diploid interspecific hybrids were evaluated for male fertility, for 2n pollen production and stability over three years and for meiotic nuclear restitution mechanisms. Pollen stainability ranged from 6 to 85% and 2n pollen from 5 to 35% among hybrids. The meiotic mechanism generating 2n pollen was that of spindle abnormality in meiosis II and consequent dyad/triad formation. High correlation was found between fused/parallel spindles and dyads.     

Evidence for possible selective survival and function of gametes on progeny characteristics of Bromus inermis Leyss

Summary Approximately 85% of the S₁, S₂ and S₃ plants in 142 smooth bromegrass progenies were morphologically similar within lines. Progenies developed from diallel crosses possessed greater uniformity than was expected from hybridization of S₁ octaploid smooth bromegrass. Behaviors observed are interpreted on the basis of selective survival and functioning of gametes and can be explained by the fusion of like gametes.Results of cooperation between the Crops Research Division, Agricultural Research Service, US Department of Agriculture, and the Research Division, College of Agricultural and Life Sciences, University of Wisconsin, Madison, Wisconsin 53706.Geneticist (deceased).     

Cytology of tetraploid x hexaploid timothy (Phleum pratense L.)

Ten pentaploids were isolated from seedling populations developed from seed of tetraploid plants grown in association with hexaploid timothy. About 80% of the prophase sporocytes exhibited severe or moderate pycnosis. These pycnotic accumulations appear to arrest the meiotic processes and apparently result in sporocyte lethality. Surviving sporocytes at diakinesis possessed nuclei with configurations that varied from 1 VI+14 II+1 I to 9 II+17 I. It is suggested that the conventional sorts of irregularities (univalents, inversions and translocations) cannot account for the low percentages of stainable pollen. Pairing relations indicated that considerable duplication and/or autosyndesis occurred in the genomes combined, and suggest that even though the tetraploid (2n=28) and hexaploid (2n=42) forms of Phleum pratense are closely related they are not identical. A portion of the sterility observed may be due to nuclear-cytoplasmic interaction.Results of co-operative work of the Crops Research Division, A.R.S., U.S. Department of Agriculture, and the Wisconsin Agricultural Experiment Station, Madison, Wis.Geneticist, Crops Research Division, A.R.S., U.S. Department of Agriculture, and Graduate Assistant, Department of Agronomy, Wisconsin Agricultural Experiment Station.     

部分高粱转换系与不同高粱细胞质的育性反应

利用部分高粱转换系与具相同核背景不同细胞质的高粱不育系杂交,调查F_1代植株花粉育性和主要农艺性状,结果表明4种细胞质之间育性反应存在着明显的差异,A_1与A_2型细胞质之间差异较小;A_1、A_2与A_3、A_4型之间差异较大。A_1和A_2型细胞质与部分高粱转换系杂交F_1代的自交结实率之间的相关达极显著水准。A_2、A_3型细胞质对F_1代主要农艺性状的影响与A_1型对这些性状的影响无显著差异。A_2型细胞质可以在高粱杂交种生产中加以利用。A_3型细胞质与前两种细胞质的育性反应截然不同。找到了A_3型细胞质的恢复源和能同时恢复A_1、A_2、A_3型细胞质的材料。初步确定了能够鉴定高粱4种不同细胞质的鉴定系。通过对同核异质,异核同质育性反应的研究,表明4种细胞质完全不同,细胞质对育性反应起着决定性的作用,育性反应不因核背景的改变而发生显著变化,不同细胞质育性恢复机制不同。     

A unique introgression from Moricandia arvensis confers male fertility upon two different cytoplasmic male-sterile lines of Brassica juncea

A Brassica juncea line carrying an introgression from Moricandia arvensis restored male fertility to two cytoplasmic male‐sterile (CMS) B. juncea lines carrying either M. arvensis or Diplotaxis catholica cytoplasm. Genetics of fertility restoration was studied in the F₁, F₂, F₃ and backcross generations of the cross between CMS and fertility‐restorer lines. No male‐sterile plants were found in F1‐F₃ generations of the cross between CMS [M. arvensis] B. juncea and the restorer. However, a 1: 1 segregation for male sterility and fertility was observed when the F1 was pollinated with non‐restorer pollen from a euplasmic line. These results clearly show that restoration is mono‐genic and gametophytic. In CMS lines carrying D. catholica cytoplasm, the restorer conferred male fertility to the F1 and showed 3: 1 and 1: 1 segregations for male fertility and sterility in F₂ and BC1 generations, respectively, indicating a monogenic, sporophytic mode of fertility restoration. The results were also supported by pollen stainability in the F1 which was about 65% in M. arvensis‐based CMS and >90% in D. catholica‐based CMS. The above results are discussed in the light of previous molecular studies which showed association between CMS and atpA in both systems.     

Genetic studies on the interspecific cytoplasm substitution lines of japonica varieties of Oryza sativa L. and O. glaberrima Steud.

Summary Interspecific cytoplasm substitution lines of Oryza sativa and O. glaberrima, i.e. (sativa)-glaberrima and (glaberrima)-sativa, have been bred by means of successive backcrosses, using three japonica varieties of sativa and two glaberrima strains.In all the six substitution lines with the cytoplasm of the glaberrima strains, the fertility increased with succeeding backcrosses, and eventually completely fertile plants whith the characteristics of the parental japonica variety appeared. This indicates that the glaberrima cytoplasm exerted no effect on the genome manifestation of these japonica varieties. Of the five substitution lines with the cytoplasm of each of the japonica varieties, four lines produced male sterile (M.S.) plants only in the backcross generations. In the remaining substitution line with the cytoplasm of the japonica variety Akebono, there was simultaneous segregation for male sterile (M.S.) and pollen fertile plants bearing indehiscent anthers (ID.M.F.) in the backcross generations. In the compulsively selfed progeny of ID.M.F. plants, pollen fertile plants with dehiscent anthers (D.M.F.) occurred with M.S- and ID.M.F. plants. Morphologically, these three types were supposed to have the same genetic background as the glaberrima parent. It was established that D.M.F.-and ID.M.F. plants were homozygous and heterozygous for a dominant nuclear gene restoring pollen fertility, respectively, and the M.S. plants and the two glaberrima strains used in this study carried a recessive gene for pollen sterility in homozygous condition. The restorer gene was assumed to derive from the japonica variety Akebono. The expression of the restorer gene was of the sporophytic type. The pollen sterility of the substitution lines that possessed the cytoplasm of the japonica varieties was of cytoplasmon-genic nature.     

Sc2053诱导小麦雄性不育形态学和细胞学观察

应用化学杂交剂Ｓｃ２０５３诱导小麦雄性不育的形态学和细胞学特征观察结果显示，经处理的小麦植株变矮，植株及麦穗呈现浅绿色，穗子呈爆裂状，花药不开裂，呈现雄性不育株的形态特征，这些特征可做为估算小麦群体化学杀雄效果即绝对不育率的依据。经Ｓｃ２０５３处理的小麦雄性不育有无花粉和花粉败育两种类型。无花粉型是在小孢子刚形成时发生败育，从而是产生无花粉的空壳型花药。花粉败育型是小孢子只发育到单核花粉，二胞花粉     

Development of a cytoplasmic-nuclear male-sterile line of soybean

The F₁ of N8855 x N2899, a cross between two cultivars of G. max (L.) Merr., was found to be male-sterile. After it was back-crossed with the recurrent parent N2899 for four successive generations, a cytoplasmic-nuclear male-sterile line and its maintainer line, designated as NJCMS1A and NJCMS1B, respectively, were obtained. NJCMS1A was stable in male sterility with 98.29% plants being male-sterile at 0% pollen germination, while its female fertility was normal. The pollen abortion of NJCMS1A occurred at the binucleate stage. Then the vacuolation and disintegration of cytoplasm became further pronounced in NJCMS1A pollen. In addition, the abnormal phenomenon of 2 ∼ 3 styles surrounded by 20 ∼ 30 stamens was found in a few flowers of some male-sterile plants at BC₁F₁ and BC₂F₁. This revised version was published online in August 2006 with corrections to the Cover Date.     

棉花温敏雄性不育系特棉S-1的形态学和细胞学特征研究

 以温敏雄性不育系特棉S-1及其正常可育品种D7为实验材料,对其形态学、细胞学特征进行了深入、系统的研究。结果表明：形态学研究发现,温敏雄性不育系特棉S-1的花器官明显较对照小,但是其它形态学特征差异很少;细胞学研究发现,特棉S-1败育主要发生在四分体形成期,花粉母细胞退化、花粉母细胞无荚膜、四分体质核分裂不同步、多分孢子、花粉粒畸形、花粉粒粘连、绒毡层提前解体及药隔组织薄壁细胞的退化等为棉花温敏雄性不育系特棉S-1的细胞学败育特征。