Tetraploid Parents Research Articles

Evidence for wheat-rye nucleolar competition (amphiplasty) in triticale by silver-staining procedure

Amphiplasty in hexaploid triticale, the artificial amphiploid of tetraploid wheat and diploid rye, is analyzed for the first time using a modified, highly reproducible, silver-staining procedure. A comparative analysis of metaphase somatic cells by phase contrast, C-banding and silver-staining of the hexaploid triticale cv. 'Cachirulo' and its parents, namely, the tetraploid durum wheat cv. 'Enano de Andujar' and the diploid rye cv. 'Petkus' has been made. Two silver-stained nucleolar organizer regions (Ag-NORs) (the chromosome pair 1 R) are observed in all rye plants analyzed, whereas four Ag-NORs (chromosome pairs 1 B and 6 B) are found both in the tetraploid wheat parent and in the triticale. The rye Ag-NORs are absent in the triticale. Since the Agstaining reaction of NORs can be considered as an indication for genetic activity, the silver procedure can be used to visualize gene functionality at the rDNA sites with conventional light microscopy and, consequently, the modified Ag-staining method described can be very useful in analyzing the amphiplasty phenomenon in natural or artificial hybrid combinations and derivatives in the Triticum group and its relatives.

A comparative study of the changes of peroxidase patterns during wheat, rye, and triticale germination

A comparative study on the electrophoretic peroxidase patterns of rye (Secale cereale L.), tetraploid wheat (Triticum turgidum L. durum), hexaploid wheat (Triticum aestivum L.), and hexaploid Triticale during kernel germination has been carried out. Endosperm, embryo, coleoptile, and the first leaf have been analyzed. A drastic change in peroxidase patterns was observed during the first hours of germination in all the materials studied. The triticale peroxidase patterns were similar to tetraploid wheat female parent patterns. The chromosomal locations of two leaf peroxidase isozymes of hexaploid wheat 'Chinese Spring' are also reported. These two isozymes, C9 and C10, are associated with chromosome arms 3DS and 7DS, respectively.

Mono- and Polyembryony among Tetraploid Citrus Hybrids1

Abstract The percents of polyembryonic seeds of 65 tetraploid Citrus hybrids and 33 related, probable tetraploids were scored. These plants arose from crosses of 2 diploid, sexual, monoembryonic cultivars by a total of 6 tetraploid, partly asexual, polyembryonic pollen parents. Plants classed as strictly monoembryonic were recovered in progenies from 3 of the tetraploid parents. Individuals with low percentages of polyembryonic seeds were obtained in all progenies. The likelihood that 1 or 2 genes are responsible for polyembryony is discussed.

THE ROLE OF TRITICUM CARTHLICUM IN THE ORIGIN OF BREAD WHEAT BASED ON GLIADIN ELECTROPHOREGRAMS

Gliadin electrophoregrams (a genotypic characteristic) of five strains of Triticum carthlicum (2n − 28 = AABB) were compared with those of Tetra Canthatch, the AABB component extracted from Canthatch (2n = 42 = AABBDD) common bread wheat and T. durum cv. Stewart to determine if T. carthlicum could have been the donor of the AABB component of hexaploid wheat. Similar comparisons were made among electrophoregrams of synthetic hexaploids (2n = 42 = AABBDD) produced from T. carthlicum and Aegilops squarrosa (2n = 14 = DD) and Tetra Canthatch and the same strains of Ae. Squarrosa. The five strains of T. carthlicum could be classified into two distinct groups on the basis of the electrophoregrams. One was more like that of Tetra Canthatch than the other. Synthetic hexaploids derived from one of three strains of Ae. squarrosa (strangulata varietal group) investigated, produced electrophoregrams similar to those of the natural hexaploid cultivars. The electrophoregrams of six synthetic hexaploids from three strains of Ae. squarrosa and Tetra Canthatch, and three strains of T. carthlicum did not have any bands not present in the diploid and tetraploid parents. On the basis of the gliadin electrophoregrams of three of the T. carthlicum strains examined and the synthetic hexaploids produced from them, T. carthlicum cannot be excluded as a possible progenitor of the AABB component of common hexaploid wheat.

Crossability relationships of andean potato varieties of three ploidy levels

The formation of triploids in 4x×2x crosses was studied in primitive potato varieties from the Andes of Peru and Bolivia. Triploid frequencies were as high as 80–100% in some crosses, although the actual number of seeds was low. The ‘triploid block’ varied according to the tetraploid parent, and was never entirely absent. The likelihood of triploid formation was studied in 4x×2x crosses where pollen from both tetraploids and diploids of known genotype was used. Even though the diploids were chosen for their non-production of 2n gametes, as detected in pollen grain size, 66% of the hybrids were tetraploid. The amount and probability of gene-flow between the tetraploid and diploid gene-pools, either directly through 2n gametes or through ‘triploid bridges’ was examined. Most of the 20 cultivars of S. x chaucha produced seed in crosses with tetraploids and diploids, although the fertility of the latter crosses was four times higher. The female fertility of some of the triploids thus allows them to exchange genes with the tetraploids and diploids, although gene-flow occurs more rapidly through direct transfer from diploids to tetraploids via 2n gametes.

Field resistance to late blight and potato root eelworm in group tuberosum dihaploids

An examination of the feasibility of obtaining dihaploids with high levels of field resistance to important potato pathogens, showed that dihaploids may be produced which are more resistant to late blight or to potato root eelworm pathotype E than are their tetraploid parents. The significance of this is discussed in relation to the possible types of gene action involved in conferring field resistance.

Spontaneous and Induced Interspecific Gene Transfer For Crown Rust Resistance in Avena1

Crown rust resistance from Avena tetraploid CI 7232 was transferred to Avena sativa L. utilizing irradiation with thermal neutrons. The relationship between an alien chromosome from CI 7232 and its homologue in hexaploids was also studied.CI 7232, derived from a cross between A. abyssinica Hochst. (2n=28) and A. strigosa Schreb. (2n=14), possesses resistance (Pc‐15) to crown rust (Puccinia coronata Cda. f. sp. avenae Fraser and Led.) from A. strigosa. Earlier, CI 7232 was crossed with the susceptible hexaploid ‘Clarion’, and dark kernel color (D) and resistance (R) from the tetraploid parent were linked in nearly all F8 F10 lines. Only one of 1,355 F7 plants was found to have light kernel color (L) and resistance. We previously reported that all D‐R and L‐R plants were unstable for rust resistance, and that this instability was caused by the failure of a substituted alien chromosome (1′A) to transmitted through the pollen.In this study, seeds from two L‐R plants with 20″ 1′+1′A were irradiated with thermal neutrons (Total dose: Flux ✕ time of 8.8 ✕ 1012 / Nth / cm2). Irradiated seeds were space planted in a field nursery, inoculated with crown rust in early tillering stages, and classified prior to heading. Resistant plants were then crossed as pollen parents to Clarion as a screen for functional male gametes carrying resistance. Two of the resulting I‐Fl's were resistant, and ratios in their respective I‐F2 and I‐F3 populations confirmed monofactorial inheritance. Thus, Pc‐15 had been transferred from the alien chromosome to one in the hexaploid complement which had normal male and female transmission. Metaphase I and tetrad observations in two homozygous and two heterozygous I‐F3 plants revealed completely normal meiosis.In the original, nonirradiated, monosomic alien substitution plants (20″+l′+l′A), L‐R or D‐R alien chromosomes were loosely associated with their hexaploid mate in about 85% of the cells, but recombination between the two marker loci occurred only rarely. The L‐R recombinant chromosomes evidently still carry a large, non. homologous segment of the alien chromosome (including Pc‐15) which completely blocks its pollen transmission.

Effects of ε-amino-n-caproic acid and L-lysine on the development of hybrid embryos of triticale (× Triticosecale)

The injection of either ε-amino-n-caproic acid (EACA) or L-lysine–HCl into the tetraploid wheat parent (Triticum turgidum L. var. durum cv. Jori) as early as 1 day after pollination with rye (Secale sp.) significantly enhanced the development of hybrid embryos in vivo. The success with which the embryos could be artificially cultured was improved accordingly. One millilitre of either compound applied at 1.0 mg/ml concentration resulted in a significant increase in the frequency of normal-appearing embryos. It is concluded that the application of EACA or its analogue L-lysine could be used in a hybridization program involving certain strains of wheat and rye to partially overcome the physiological barrier to hybrid embryo development.

Effect of Cultivar, Polyploidy and “Reciprocal” Hybridization on Characters Important in Breeding Triploid Seedless Watermelon Hybrids1

Abstract C5 (sister line of ‘Sweet Princess’), ‘Sugar Baby’ and ‘Florida Giant’ cultivars of watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai], and their hybrids were compared at the diploid (2x), triploid (3x) and tetraploid (4x) chromosome levels. Ovary, fruit and seed shape was significantly rounder in the polyploids than in the diploids. There was no change in fruit shape in the already round cultivar, ‘Sugar Baby’. Fruit weight and ploidy level were inversely related. Hollow heart was more severe in the polyploids. The polyploids had a significantly thicker rind, contained larger seed, and were more field resistant to anthracnose than were the diploids. “Reciprocal” triploid hybrids [C5 (4x) x ‘Sugar Baby’ (2x) compared to ‘Sugar Baby’ (4x) x C5 (2x)] had significantly different means for ovary shape, fruit shape and anthracnose resistance. The “reciprocal” triploid hybrids differed significantly in 1 of 2 seasons for the traits fruit weight, hollow heart incidence, rind thickness, and seed shape. In breeding seedless watermelon hybrids it is important to consider the parent cultivar used as the seed (tetraploid) parent.

The significance of 2N gametes in potato breeding

Phureja-haploid Tuberosum hybrids, which produce 2n gametes in addition to n gametes, were used to obtain diploid progenies in 2x - 2x matings, and tetraploid progeny in 4x - 2x matings. Seven of these diploid clones were intermated in a modified diallel design, and also crossed to seven cultivars, to obtain 21, 16-clone diploid; and 49 (35, 2x X 4x and 14, 4x X 2x) 24-clone tetraploid families, respectively. These progenies were included together with the 14 parental clones, in a tuber yield trial conducted in two locations in Wisconsin. Heterotic responses were striking in 4x X 2x progenies. Three of these entries had mean yields of 5.0, 5.0 and 5.2 lbs/hill, for 24 unselected clones, thus outyielding not only the mid-parent but also the best tetraploid cultivars in the experiment, which are highly selected; Wis 643 (4.8 lbs/hill), and Kennebec (4.8 lbs/hill). As a group, the 14, 4x X 2x families averaged 4.4 lbs/hill, while the mean of all seven cultivars was 4.0 lbs/hill, and the mid-parent was at 3.4 lbs/hill. This unusually high mean performance of 336 unselected clones represented in the 14, 4x X 2x progenies, is interpreted as a manifestation of the capacity of 2n pollen, formed by first meiotic division restitution (FDR), to pass onto the progeny the already heterotic diploid genotype in a largely intact array. Beneficial intra and inter-locus interactions are presumably compounded upon syngamy with an unrelated n egg from the tetraploid parent. -The performance of 2x X 4x progenies was at or below that of the midparent. The failure of these families to perform as well as 4x X 2x families may be a reflection of the incapacity of 2n megasporogenesis to avoid meiotic reassortment as efficiently as FDR does, which would result in inbred 2n gametes. However, the method of 2n megasporogenesis is not known.Hereditary variances were large, both within and among families, and indicated considerable nonadditivity in the action of genes affecting tuber yield at both levels of ploidy. Inbreeding was strongly depressing at both ploidy levels.

Flowering behaviour and seed fertility in dihaploidSolanum tuberosum

Aspects of female fertility were studied in clones from the Pentlandfield dihapoid collection which has been derived predominantly from British tetraploid potatoes. Dihaploids from different tetraploid parents differed significantly in such features as flower initiation and bud abscission. Compared with tetraploids, a higher proportion of dihaploid clones reached anthesis but otherwise their flowering behaviour was similar. They produced fewer ovules per ovary and set less seed which was of lower viability. Taken together the results indicated a considerable reduction in female fertility in the first dihaploid generation.

Breeding value of 2n pollen (diplandroids) in tetraploid x diploid crosses in potatoes

The relative breeding value of first division restitution (FDR) and second division restitution (SDR) 2n male gametes from diploids, and n (2x) gametes from tetraploids were compared. This was done by measuring tuber yield of 105 4x families obtained from 4x x 2x (FDR), 4x x 2x (SDR), and 4x x 4x crosses at two locations. All tetraploid families obtained from 4x x 2x (FDR) matings exhibitedheterosis (the mean of the F1 exceeded that of the higher yielding parent), and outyielded other tetraploid families and 4x cultivars at both locations. The tuber yield of 4x x 2x (SDR; families was higher than that of the families derived from 4x x 4x matings, although the 2x parents had significantly lower yield than tetraploid parents. Specific combining ability (S.C.A.) was found to be significant when families obtained from each category (4x x FDR, 4x x SDR and 4x x 4x) were analyzed individually. Both general combining ability (G.C.A.) (2x) and S.C.A. were significant when families obtained from: 1) 4x x FDR plus 4x x SDR; 2) 4x x FDR plus 4x x 4x; and 3) all categories, were analyzed. Only S.C.A. was found to be significant when 4x x SDR and 4x x 4x families were analyzed together. Consistent results were obtained at each of, and over, the two locations. These results strongly demonstrated that FDR gametes were superior in breeding value to either SDR or n (2x) gametes, and were more homogeneous, Gametes formed by SDR might be superior to n (2x) gametes although they were as heterogeneous. Distinct yield differences between 4x x FDR and 4x x SDR families plus the significant G.C.A. (2x) detected when these two categories were compared, substantiated the cytological interpretation of genetically distinct modes of diplandroid formation.

Stabilised breakage of a duplicated chromosome segment in Aloe

In one individual of the triploid hybrid Aloe “Sherman Hoyt” (2n=21) a large supernumerary segment on the end of the long arm of an L2 chromosome was shown to be a reversed duplication formed by the distal breakage of a U-type chromatid bridge at anaphase I in the tetraploid parent. The segment misdivides and is partially or wholly lost during mitotic anaphase at a constant rate. Sectors of tissue lacking the segment do not become established, indicating that its loss is lethal to the daughter cell line after a few mitotic divisions. This constant rate of breakage combined with the elimination of deficient cell lines results in a system which is stable overall.

Male parthenogenesis in tetraploid job's tears

Male parthenogenesis was discovered in induced autotetraploid Job's tears, utilising a genetic marker for leaf hairiness, in natural crosses between recessive tetraploids and dominant diploids. In a progeny raised from seeds harvested from the diploid dominant parent one plant showed the recessive character of the tetraploid parent but diploid chromosome number indicating that this was derived through androgenesis in the tetraploid.

Origin of Unreduced Embryo Sacs in Diploid Potatoes

THERE are clear advantages in carrying out potato breeding at the diploid level, but it is likely that the expression of maximum productivity occurs at the tetraploid level1. One way in which diploids can be brought to the tetraploid level is by 2x–4x or 4x–2x crosses. It has long been known that a large proportion of the progeny of such crosses is tetraploid2,3, and it is generally recognised that unreduced gametes with the somatic chromosome number (2n) are produced by the diploid parent and these, with normal gametes (n) of the tetraploid parent, give tetraploid offspring.

SEED PROTEIN HOMOLOGIES AND THE EVOLUTION OF POLYPLOIDY IN AVENA

Crude seed protein of the nine oat species was fractionated by disc electrophoresis on polyacrylamide gel. Correlation coefficients calculated from optical density curves obtained from the stained gels showed that individual species possessed characteristic, albeit variable, profiles. Pattern variability among and within species was greater in the case of the diploids than in the case of the polyploids. The very few profile types in A. strigosa 4x and in the hexaploid A. sativa suggested that the variation in these polyploids is due more to independent origin of the types than to differentiation following polyploidization. Virtual identity between individual A. strigosa 2x and 4x profiles suggested a strict autopolyploid origin for some 4x types while complementing pairs of A. strigosa 2x profiles indicated an intervarietal origin for other A. strigosa 4x types. A diagnostic band at 11.0 cm in the profiles of A. magna and A. murphyi suggested that these species rather than A. strigosa 4x had functioned as the tetraploid parent of the hexaploid A. sativa. The profile of A. murphyi complemented by a specific A. strigosa 2x profile simulated a specific A. sativa type. The adaptive success of the genus is assessed in the light of variation and homologies in the seed protein patterns of the various species.

Selection potential for tuber total nitrogen and total solids content in a tetraploid breeding population

A 2-year study of 10 crosses involving 20 different tetraploid parents from the USDA potato breeding program showed significant differences in tuber content of total nitrogen (TN, crude protein) and total solids among offspring means and among parents. Offspring TN ranged from 0.20–0.50% in 1968 and from 0.20–040% in 1969 (fresh-weight basis). Heritabilities in the narrow sense ranged from 24–34% (1 and 5 replicates, respectively) for TN and from 24–38% for solids. TN selection was indicated to be potentially as effective as solids selection. The expected gain from selecting 10 of 100 clones in a 5-replicate, 1-year test was calculated as 6.4% of the parental mean for TN and 3.4% for solids.

Transfer of stem rust seedling resistance from wild diploid einkorn to tetraploid durum wheat by means of a triploid hybrid bridge

Transfer of stem rust resistance from diploid wild einkorn, Triticum boeoticum, to susceptible Mindum and Spelmar, varieties of cultivated T. durum, was achieved by means of a triploid hybrid bridge and subsequent backcrossing to the tetraploid parent. Seedlings of the second hybrid generation segregated for resistance to race 14 of Puccinia graminis f.sp. tritici which was used as test race in this investigation. The F3 and F4 progenies included segregants which displayed seedling resistance also to races 17, 19, 21, 40, 53, 194, 222, 315 and 322. Since these were the same races which proved avirulent to the T. boeoticum donor but virulent to the T. durum recipients, it was concluded that the full pattern of resistance determined in the wild diploid parent of this cross was transferred to the tetraploid durum-like hybrid derivatives.

Karyomorphological Studies in <i>Pennisetum</i>

A comparative study on karyology of Pennisetum typhoides and P. purpureum and their hybrid and amphiploid revealed considerable differences in the size, shape and position of centromere of the chromosomes of the constituent genomes. The diploid and tetraploid parents exhibited quantitative differences in size in respect of chromosomes of the homologous genomes A and A' and this was evident in the F1 hybrid. The cultivated species P. typhoides possessed more of asymmetry in karyotype than the wild species. The chromosomes of ‘B’ genome of P. purpureum also exhibited asymmetry but less than the ‘A’ genome.The concommittant morphological specialisation and the asymmetry of karyotype in P. typhoides (AA') also point out that dominant features of P. purpureum resident in ‘B’ genome and less specialisation appear to be associated with symmetry of B' genome. The changes in the karyological features in the F1 and its amphiploid were not as expected to the value of parents. It is concluded that the alteration of the karyotype might be due to hybridity and would suggest alteration of the genetic control in expression of somatic complement.

RIND AND LEAF OILS OF TRIPLOID INTERSPECIFIC CITRUS HYBRIDS AND THEIR DIPLOID AND TETRAPLOID PARENTS

SummaryRind and leaf oils of triploid Citrus hybrids from 5 crosses, and their diploid and tetraploid parents, were analysed by gas chromatography. Two‐thirds of the chromosome complement of each hybrid was evidently contributed by the 4n parent. Overall, a wide range of percentages of the oil components occurred among hybrids and parents. There were differences significant at 1% in 80 of 90 parent‐hybrid group comparisons. There was no regular, dominating effect of the 4n parents, and in many cases the influence of 4n and 2n parents seemed about equal. However, among hybrids involving 4n lemon there was often a tendency for leaf oil levels to follow those of that 4n parent. The general absence of such an effect in the rind oils, and in the leaf oils of the other crosses, parallels the implication of an earlier study in which autotetraploids of several Citrus species were usually similar to their parental diploids, in their percentages of rind oil components.Where 2 or 3 sets of hybrids had a common parent, either 2n or 4n, there was also no constant effect of that parent, from set to set, as compared to other parents involved. Variation in the percentages of any specific oil component was great among the 6 sister triploids in many crosses. Individuals sometimes approached the level of one parent, and sometimes that of the other. Transgression of one or more hybrids beyond either parent frequently occurred, and was particularly prominent with decanal, linalool, and linalyl acetate. Percentages of components in the leaf were often different from those in the rind.It is clear that these polyploid hybrids of rather closely related species show many inherited differences in oil components. These differences are principally quantitative and probably reflect genetic recombinations which have altered intermediate biochemical pathways.