Effect of Zinnia angustifolia HBK genotype on morphology and flowering of Z. angustifolia × Z. elegans Jacq. hybrids

Summary Interspecific hybrids were generated from crosses between 4 Zinnia angustifolia clones (maternal parents) and an inbred line of Z. elegans Orange King (paternal parent) to investigate the influence of Z. angustifolia genotype on morphology and flowering of hybrids. Leaf length, leaf width, flower diameter, number of ray petals, and days to flowering of interspecific hybrids were significantly influenced by Z. angustifolia clonal genotype. Genetic analysis of hybrid morphology and development was performed using 2 parental Z. angustifolia clones and 18 F₁ (9 seedlings from each of 2 populations generated from reciprocal crosses between parental clones) as maternal parents in crosses with Z. elegans Orange King. Genotype of Z. angustifolia significantly affected plant height, fresh weight, number of nodes, and days to flowering of interspecific hybrids. Control of these traits was through the Z. angustifolia nuclear genome. Improvement in interspecific hybrid morphology or development, i.e., shorter stature, earlier flowering, or larger flowers, may be possible by selection of superior-performing Z. angustifolia clones as parents.     

Morphology,cytology and forage potential of Pennisetum americanum (L.) K. Schum. x P. Purpureum Schum. amphidiploids

Summary F₁ hybrids between short-day photoperiod- sensitive maiwa bulrush millet, Pennisetum americanum (2n=14), and elephant grass, P. purpureum (2n=28), are triploid (2n=21), sterile, and can only be propagated vegetatively. Fertile amphidiploids, (2n=42, with 21 bivalents) were produced by colchicine treatment. Good seed set was obtained upon selfing the amphidiploids and the progeny exhibited variable pollen fertility and bivalent univalent and multivalent formation.Reciprocal crosses between elephant grass and the colchicine-induced amphidiploid failed to produce seeds. The maiwa millet x amphidiploid cross resulted in poor seed set and the reciprocal failed. Maiwa x amphidiploid hybrids were pollen sterile with 2n=21, rather than the expected 2n=28, indicating chromosome elimination.Morphologically, the amphidiploids and maiwa x amphidiploid hybrids closely resembled elephant grass and the F₁ hybrid. The amphidiploids showed no superiority over the F₁ hybrid and elephant grass in either forage yield or quality but one maiwa x amphidiploid genotype surpassed a promising local elephant grass selection in forage dry matter yield and flowered for a relatively short period.     

Development of a triticale resistant to the greenbug: An historical perspective

Summary A greenbug [Schizaphis graminum (Rondani)] resistant strain of rye (Secale cereale L.) Insave F.A. from Argentina was crossed with Chinese Spring wheat (Triticum aestivum L.) and also with Elbon and Balbo cultivars of common rye. Juvenile plants of the primary wheat X rye hybrid were treated with colchicine. Partially fertile amphidiploids were obtained that are resistant to greenbug Biotypes B and C. F₁ and F₂ populations of seedling plants derived from crosses of Insave F.A. with Elbon and Balbo rye were tested for reaction to the greenbug to determine the genetic basis of inheritance. The results confirmed previous reports that resistance in Insave F.A. is conditioned by a single dominant gene.Deceased     

The influence of genotype and environment on seed and embryo development in barley (Hordeum vulgare L.) after crossing with Hordeum bulbosum L.

Summary Seed and embryo development was studied in crosses between H. bulbosum and the barley genotypes VK 16032, Vada and Vogelsanger Gold and subsequently the F₁ and F₂ progenies from VK 16032 x Vada and VK 16032 x Vogelsanger Gold. Both seed and embryo development are strongly influenced by the barley genotype. Favourable environmental conditions can promote seed and embryo development in genotypes with existing good characters. Dominant inheritance for good seed development and incomplete dominance for large embryos is evident. Linkage between small embryo size and winter habit exists in Vogelsanger Gold.     

Heterotic patterns in hybrids involving cultivar-groups of summer squash, Cucurbita pepo L.

Heterotic response for total yield among five cultivar-groups of summer squash, Cocozelle, Vegetable Marrow, Zucchini, Crookneck and Straightneck, was studied in two sets of diallel crosses evaluated in two harvest seasons. Each diallel cross included two representatives of each the five cultivar-groups. Griffing and diallel GGE biplot (genotype main effect and interaction) analyses were carried out. The relative importance of the specific combining ability variance on total variance was greater than that reported earlier for intragroup crosses. Highly significant heterosis was manifested only in combinations of Crooknecks or Straightnecks crossed to Cocozelles, Vegetable Marrows or Zucchinis. GGE biplots showed a consistent arrangement where testers of ssp. texana interacted with cultivars of ssp. pepo and vice versa. We propose that the heterotic pattern of texana-pepo crosses could be potentially used to achieve increased yields in hybrids by introgressing one group into another in a manner that would maintain fruit attributes of the cultivar-group. This revised version was published online in July 2006 with corrections to the Cover Date.     

Inheritance of flower color in Dendranthema grandiflora Tzvelev. (Chrysanthemum morifolium Ramat.) using cultivars and inbreds. II. Vacuole pigmentation

Summary Dendranthema grandiflora Tzvelev (Chrysanthemum morifolium Ramat.) garden cultivars Vulcan, with deep red ray florest, and Superior, with orange ray petals, were crossed as female with 16 inbred clones and the progeny assessed visually for flower color in 3 environments. Intensity of vacuole pigmentation in ray florets appeared to vary continuously. Evaluation was facilitated by placing plants in 7 color classes ranging from red, the most intense, through orange, an intermediate intensity, to yellow, the apparent lack of vacuole pigmentation. A simple hexaploid model with additive gene action, suggested by the 7 color classes, was inappropriate, as more than 50% of the plants in Vulcan families were red and more than 60% of the plants in Superior families were orange. Comparing evaluations of parental clones in 2 glasshouse and 2 field environments and considering data from an experiment, in which progeny first classified in the glasshouse were reevaluated in the field, revealed substantial shifts in classification. In the glasshouse, more individuals appeared in the red and orange classes, while field evaluation placed more individuals in classes adjacent to red and orange. However, the predominance of progeny in the color class of the common parent, that is, red for the Vulcan and orange for the Superior families, occurred in both glasshouse and field. Plants scored as other than red appeared in crosses between Vulcan and 3 red inbreds, suggesting that red ray petals are not conditioned by a homozygous genotype. The orange of Superior and orange progeny may be due to a single dominant gene causing mosaic-like distribution of red vacuole pigmentation over yellow plastid pigmentation. Because cloned genotypes were classified differently in diverse environments, critical genetic analysis of vacuole pigmentation will require cloned progeny and multiple-environment evaluation.     

Inheritance of resistance to Russian wheat aphid in barley

Summary The inheritance of resistance to Russian wheat aphid Diuraphis noxia (Mordvilko), in two resistant barleys, Hordeum vulgare L., ASE/2CM//B76BB and Gloria/Come, was studied in the field and in the greenhouse. The resistant genotypes were crossed with susceptible genotypes Esperanza and Shyri. Resistance reactions of F1, BC1, and F2 plants, and individual F2 plant derived F3 families indicated that resistance in each genotype was controlled by the same single dominant gene.     

Multiple allelism at a major locus affecting fruit coloration in Cucurbita pepo

The l-2 (light coloration-2) locus in Cucurbita pepo (pumpkin, squash, gourd) has a major effect on fruit color intensity through its complementary interactions with at least three other loci. From a sixth-generation backcross progeny of which a wild gourd having striped fruits was the donor parent and a cultigen having ‘plain light’-colored fruits(genotype l-2/l-2) was the recurrent parent, a true-breeding line was isolated that had a fruit color phenotype that differed from both parents. The fruits of this line were not striped and had a color pattern resembling‘light type 2’ (genotype L-2/–-), but of weaker expression. This newly established line was then crossed with near-isogenic lines of genotypes l-2/l-2 and L-2/L-2 and the resulting filial and backcross progenies were observed under field conditions. The results indicated that the new phenotype is recessive to ‘light type 2’ but dominant to ‘plain light’ and that it is conferred by a single gene. The results of a testcross for allelism indicated that this gene is an allele at the l-2 locus and it is herein designated L-2 ^w. Dominance relationships at the l-2 locus are L-2 > L-2 ^w >l-2. This revised version was published online in July 2006 with corrections to the Cover Date.     

Inheritance of white flower colour and congested growth habit in certain Buddleia progenies

Summary Buddleia fallowiana var. alba (FA) was crossed with B. davidii Nanhoensis Alba (NA) and both were crossed with the B. davidii cultivars Pink Delight (PD) and Royal Red; seedlings from the FA x NA progeny were backcrossed to the two parents. The pattern of inheritance of white or coloured flowers indicates two loci controlling white flower colour. FA is homozygous for a recessive gene, labelled alb-1, and NA is heterozygous for a dominant gene, Alb-2.In most segregating progenies some of the white flowered seedlings had a congested habit of growth and this is tentatively ascribed to two dominant complementary genes. NA is heterozygous for Con-1, which is tightly linked with Alb-2. FA and PD are heterozygous for Con-2.     

Effect of maternal genotype on development ofPhaseolus vulgaris L. ×P. lunatus L. interspecific hybrid embryos

Summary CertainPhaseolus vulgaris L. ×P. lunatus L. crosses were performed to study the effect of maternal heterozygosity on development and growth of the interspecific hybrid embryos. Interspecific embryos had a much slower growth rate in vitro compared with embryos derived from self-pollination ofP. vulgaris parents. Thus, interspecific embryos could be identified by growth rate in vitro. TheP. vulgaris maternal genotype affected both the number and size of 15-day-old interspecific embryos. Specifically, 76 Spartan Arrow produced significantly more interspecific embryos than did Great Northern as the seed parent, while maternal intraspecific hybrids produced smaller embryos than did maternal pure lines. There were no reciprocal differences between hybrid maternal parents for embryo number or size. Embryo size at excision and final size after culturing were closely correlated (r²=+0.93). The crossP. vulgaris 76 Spartan Arrow ×P. lunatus P.I. 214170 produced both the largest mean size at excision and the fastest growth in culture, indicating that specific combining ability affected both characteristics.Journal Paper No. J-12208 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 2495     

Inheritance of N2 fixation efficiency in cowpea

Summary Host plant genetics of N₂ fixation in the cowpea (Vigna unguiculata (L.) Walp.) — Rhizobium symbiosis was investigated in the field with a mixed strain inoculum and in the greenhouse with a single strain inoculum. Five cowpea genotypes, including H-Brown Crowder and L-Bush Purple Hull, were used to generate populations for genetic studies. Diallel analysis for general combining ability (GCA), specific combining ability (SCA) and reciprocal effects was carried out for the N₂ fixation variables nitrogenase activity, nodule number, nodule weight, and top dry weight, in the field study. Generation mean analysis and heritability estimates were performed on the greenhouse population which included P₁ (H-Brown Crowder), P₂ (L-Bush Purple Hull), F₁, F₁. F₂, BC₁, and BC₂. Positive and significant correlations were observed between nitrogenase activity and both nodule weight and nodule number. Correlation coefficients between top dry weight and the other 3 variables were not significant. Estimates of SCA were highly significant for all variables except top dry weight, while those of GCA were significant only for nodule weight. Generation mean analysis revealed that additive gene action was more prominent than dominance and interallelic gene action for nodule number and nitrogenase activity, while the opposite was true for nodule weight and top dry weight. Narrow sense heritability estimates were moderately high for nodule number (0.55) and nitrogenase activity (0.62), and low for nodule weight (0.39) and top dry weight (0.17).Texas Agricultural Experiment Station Technical Article 20385. Research supported in part by a grant under USAID PASA AG/TAB 610-9-76 (USDA-CSRS-701-15-59).     

Inheritance of resistance to powdery mildew (Erysiphe graminis f. sp. hordei) in eleven primitive barley varieties

The inheritance of the powdery mildew resistance of eleven primitive barley varieties was investigated. crosses with varieties with identified resistance genes revealed that at least three different genes are present in a group of six genotypes from Greece (Hor736, Hor847, Hor878, Hor1159, Hor1379 and Hor1873) and one from Turkey (Hor1188). One dominant gene is common to these seve genotypes and in the Greek accessions a second gene is present. The expression of this second gene was respectively dominant in the crosses with Hor736 and Hor1159, recessive in the crosses with Hor878 and Hor1873, and depended on the employed powdery mildew isolate in the crosses with Hor847 and Hor1379. The detected genes differ from the resistance genes of the crossing partners, viz. Ml-al2, Ml-(Ab), Ml-(CP) and Ml-(1402). The accessions from China (Hor824 and Hor4021) each possess two resistance genes which differ from Ml-a12, Ml-(La) and Ml-(CP). The major gene is common to both accessions and is either identical, allelic or closely linked to a gene in the variety Nigrate. The Columbian accession Hor1894 possesses one resistance gene linked to a resistance gene in Nigrate but this gene differs from the Ml-a locus. The variety Palestine (Hor3997) possesses two resistance genes of which one is allelic or closely linked to Ml-(at).     

Gene for broad, contiguous dark stripes in cocozelle squash (Cucurbita pepo)

Alternating intense (dark) and light stripes on the fruits are a fairly common feature of Cucurbita pepo, a highly variable species encompassing various kinds of pumpkins, squash, and gourds. The intense stripes can be narrow and broken or broad and contiguous. Narrow, broken intense striping is conferred by allele l-1 ^St, which is dominant to allele l-1 for non-striped, lightly colored fruits and recessive to allele L-1 for non-striped, intensely colored fruits. Cocozelle-type squash often exhibit broad, contiguous intense stripes. The inheritance of this characteristic was studied by transferring it from cocozelle squash and preparing nearly isogenic lines having broad-striped, narrow-striped, and non-striped light-colored fruits. In the broad-striped near-isogenic line, the intense stripes averaged 37% wider than in its narrow-striped counterpart. The broad-striped line was crossed with the narrow-striped line, the non-striped light-colored line, and the non-striped intense-colored `Fordhook Zucchini'. Broad striping was dominant to narrow striping and to non-striped light and conferred by a single gene; it was recessive to non-striped intense. The gene for broad striping was found to be allelic to that for narrow striping and to that for non-stripe dintense and is herein assigned the symbol l-1 ^BSt. Dominance relationships at the l-1 locus were observed to be L-1>l-1 ^BSt >l-1 ^St >l-1. This revised version was published online in July 2006 with corrections to the Cover Date.     

In vivo embryoids from anthers of Narcissus biflorus Curt

Summary Mature anthers of some plants of Narcissus biflorus Curi., cultivated under subtropical conditions at Jammu, were found to contain monads, microspore mother cell embryo sacs, and multinucleate embryoids. In addition, multicellular embryoids resembling those obtained in vitro through anther culture were also observed. All these structures arise from the microspore mother cells which do not follow regular course of microsporogenesis.     

Inheritance of a resistance specific to tomato spotted wilt tospovirus in Capsicum chinense ‘PI 159236’

Summary Inheritance studies were conducted to determine the genetic basis of resistance in pepper against one Tospovirus isolate classified as tomato spotted wilt virus (TSWV). F₁, backcrosses and F₂ populations were developed using the resistant parent Capsicum chinense PI 159236 (CNPH 679) and the susceptible parent C. annuum Magda (CNPH 192). Segregation ratios strongly indicated that the resistant response (a localization, hypersensitive-like reaction) to TSWV fits a single-dominant gene model. Under our experimental conditions, the penetrance of this gene was very high. This gene (tentatively named Tsw) is highly effective only against TSWV isolates. The resistance governed by the Tsw gene was not effective against isolates belonging to tomato chlorotic spot virus (TCSV) and groundnut ring spot virus (GRSV), two other previously described Tospovirus species.     

A comparative study on anther development in male-fertile and male-sterile plants of Pelargonium crispumL'Her. ex Ait.

Summary Anther development of male-fertile and male-sterile plants in Pelargonium crispum was anatomically examined. Three cultivars, i.e., Lemon crispum, Crispum minor and Prince Rupert, were used. Lemon crispum and Crispum minor are male-fertile, whereas Prince Rupert is male-sterile. The tapetum in every cultivar examined behaved like an amoeba. The tapetal cells of the anther form plasmodial masses. Then, the plasmodial masses fuse producing a periplasmodium. The periplasmodium degenerates and finally disappears. There are no differences in tapetal behaviour between fertile and sterile anthers. In the sterile anthers the endothecium and lip cells do not develop sufficiently. Young microspores show normal growth at early stages. After the completion of their cell wall formation, however, the microspores in the sterile anthers lose their cytoplasm and become empty. On the other hand, the microspores in the fertile anthers increase the volume of their cytoplasm and become fertile pollen grains.     

The introgression of S alleles into forage rape,Brassica napus L. from turnip. Brassica campestris L. ssp. Rapifera

Summary Forage rape. B. napus, is self-compatible, the work described illustrates the introgression of functional incompatibility alleles into B. napus from turnips, B. campestris, in two generations. By grading seed, produced by backcrossing turnip/rape hybrids to rape, the frequency of 2n=38 semi articial B. napus recovered, amply justifies the cytological screening involved in such breeding programmes.     

Genetics of resistance in the wheat cultivar chhoti lerma against stem rust race 122

Summary Genetics of rust resistance against stem rust race 122 in Chhoti Lerma was studied both by conventional and aneuploid analysis. Observations on F₁, F₂ and F₂ backcross progenies revealed the operation of two recessive genes, controlling resistance in Chhoti Lerma. Monosomic analysis confirmed the operation of two recessive genes conferring resistance to race 122 located on chromosomes 1D and 7D. A minor gene or modifier was also located on chromosome 1B. This was concluded from the fact that F₂ of mono's x Chhoti Lerma exhibited skewness in favour of resistant plants.     

Partial self-compatibility in ‘Tombul’ and ‘Montebello’ hazelnuts

Summary Self-pollination of hazelnut (Corylus avellana L.) cultivars in 1988 and 1990 revealed the existence of partial self-compatibility in Tombul and Montebello. Percent cluster set in these cultivars averaged 44 and 20%, respectively, but was less than 10% in 8 other cultivars investigated. Percent cluster set from pollination with Segorbe averaged 62 and 41% in 1988 and 1990, respectively. Self-pollination produced 40% fewer nuts per cluster and twice as many blanks as cross-pollination. All cultivars and selections have an active sporophytic incompatibility system.Evaluation of self-compatibility in seedlings from the cross Montebello × Compton revealed that the partial self-compatibility of the maternal parent was transmitted to some of the progeny. Self-pollination resulted in greater than 10% cluster set in two selections, OSU 41.134 and OSU 43.025, in both years, but only in 1988 in OSU 42.089 and Willamette. Three other selections had very low set in both years. Results of incompatible crosses with standard testers were generally in agreement with those of self-pollination, except that the S₂ tester induced greater set on 3 genotypes in 1988 and the S1 tester on 2 genotypes in 1990 than self-pollination. The partial self-compatibility of Montebello, OSU 41.134, and OSU 43.025 appears to be due to a failure of their stigmas to prohibit pollen tube growth in incompatible crosses. There is no evidence of a pollen-part mutation in Montebello, nor is there evidence that partial self-compatibility is due to the interaction of S-alleles, as Barcelona, which has the same alleles as these three genotypes, failed to set nuts in all incompatible crosses.     

Study of the parentage of grape cultivars by genetic interpretation of GPI-2 and PGM-2 isozymes

Summary Two highly variable enzyme systems of glucosephosphate isomerase (GPI) and phosphoglucomutase (PGM) were used to investigate the parentages of grape cultivars. Of 35 parent/offspring combinations that we investigated, 30 combinations gave alleles in the offspring which were presented in the reported parents, whereas 5 combinations gave alleles in the offspring which were not extractable from the reported parents. The Gpi-2 genotype of Hiro Hamburg and the Pgm-2 genotype of Pione indicated that Koshu Sanjaku and Cannon Hall Muscat may not have been the paternal parent respectively. The Gpi-2 genotype of New Niagara and the Gpi-2 and Pgm-2 genotypes of Beniyamabiko indicated that Niagara and a hybrid from DxK151 x Delaware may not have been the maternal parent respectively. The Gpi-2 genotype of Cannon Hall Muscat grown in Japan indicated that this cultivar may not have originated as a tetraploid sport of Muscat of Alexandria.