Effects of intergenotypic competition on selection within chrysanthemum progenies

Summary Intergenotypic competition affected the growth and onset of flowering of target plants of four chrysanthemum cultivars planted within plots of the same four cultivars at commercial spacing. The relative competitive abilities of two of these cultivars, Pollyanne and Hurricane, strong and weak respectively, were confirmed when they were further grown in balanced, equal-proportion mixtures. Notwithstanding their different competitive abilities, these two cultivars had similar flower yields in pure stands and, for this character at least, would be judged to have equal commercial worth.In a further series of experiments, target plants of the female parent were grown in pre-determined positions within clonally replicated progeny plots and in equivalent positions in pure stands of the female parent. These two types of plot gave similar proportions of total target plant variance due to position, suggesting that individual plants within a segregating progeny are subjected to similar levels of competition. It is inferred that the level of competition approximates to the overall mean competitive ability of the full-sibs comprising the progeny. Selection procedures are discussed in the light of this conclusion.     

Analysis of components controlling early flowering of chrysanthemum at low temperature

Summary Twenty seven clones of chrysanthemum, 19 of which were selected at low temperature, were flowered at 10, 14, 18 and 22°C. The number of days to flower in response to temperature could, for each genotype, be described by a parabola with the parameters: optimum temperature, days to flower at the optimum temperature and curvature which represents the sensitivity to temperature.The low-temperature selections did not have a reduced optimum temperature but reduced sensitivity to temperature accounted for most of the ability to flower at low temperature. The parameters may vary independently. Examples are given to show how these parameters can be combined to construct genotypes with a required temperature response.     

Genetic analysis in Chrysanthemum morifolium. I. Flowering time and flower number at low and optimum temperature

Summary The number of days to flowering and the number of flowers per plant were studied at 12, 13, 15 and 17 C night temperature in 79 F₁ populations from 15 parents. Only a few F₁ plants flowered earlier than their parents; the majority flowered at the same time, later or not at all. The number of flowers of the F₁ plants was higher than that of the parents.Genetic analyses showed a broad sense heritability of 70% for days to flowering and flower number and a highly significant GCA effect for days to flowering.The progenies and parents that flowered early at one temperature were generally early at all temperatures.     

The reaction of Chrysanthemum cultivars to Puccinia horiana and the inheritance of resistance

Summary Four types of reaction of Chrysanthemum morifolium to infection by Puccinia horiana are described. (1) Resistant plants show no macroscopic lesions. Cultivars classified as resistant carry a single dominant gene mostly in a simplex, sometimes in a duplex condition. (2). Incomplete resistance provides good protection but under extreme test conditions some pustules develop slowly. (3) Necrosis inhibits spore formation to a large extent. The progenies of crosses between necrotic and susceptible cultivars are mostly susceptible. (4) Susceptible plants sporulate abundantly.The merits of the three types of resistance are discussed.     

The shriveling of pollinated pistils as an aid to rapid determination of Chrysanthemum pollen viability

Summary Shriveling of pistils observed one day after pollinating the dise florets of Chrysanthemum is normally followed by a good seed set 8 weeks later. When shriveling fails to appear, no seeds will be formed.It is suggested to use the easily visible pistil shriveling as a rapid in vivo test of pollen viability.     

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 flower color in Dendranthema grandiflora Tzvelev. (Chrysanthemum morifolium Ramat.) using cultivars and inbreds. I. Plastid pigmentation

Summary Progeny from controlled crosses of 28 garden chrysanthemum (Dendranthema grandiflora Tzvelev.) inbreds in various combinations as males with 3 heterozygous cultivars and 10 inbreds as females were evaluated for plastid pigmentation in a series of field and glasshouse environments. Disomic inheritance of a dominant gene, which acts to inhibit pigmentation, best explained the data. However, 1 of 8 families involving a glasshouse cultivar with colorless plastids (Puritan) as female and inbreds with yellow plastids as males deviated significantly from the expected 1:1 ratio. This family consistently exhibited an excess of plants with colorless plastids. Although parent clones and cloned progeny from inbred parents were scored the same in field and glasshouse environments, reevaluation in the field of all 8 Puritan families, first evaluated in a glasshouse environment, revealed phenotypic misclassification apparently due to environmental effects. An excess of plants with colorless plastids appeared in the glasshouse but evaluation of the same genotypes in the field resulted in an excess of plants having yellow plastids. Submerging ray florets in a hot-water bath revealed yellow plastids masked by vacuolar pigments, thus reducing chances of misclassification. The data suggest that evaluation of highly variable families in a single environment can lead to misclassification of plastid pigmentation. However, even with evaluation in 2 or more environments, certain families may exhibit an excess of plants with colorless plastids.     

Induced changes in growth and flowering of chrysanthemum after irradiation and in vitro culture of pedicels and petal epidermis

Summary To increase the genetic variation for yield in Chrysanthemum morifolium cv. White Spider, pedicel segments and petal epidermis were induced in vitro to regenerate adventitious buds either directly from the original tissue or indirectly via callus. Besides, pedicels were irradiated before in vitro culture with an X-ray dose of 8 Gy. All treatments yielded variation in flower morphology. Changes in flower colour were largely restricted to treatments involving irradiation.Treatments yielding many morphological variants also yielded most production variants. Plants regenerated from petals differed from those originating from pedicels. Clones were found that had retained the morphology of White Spider, but outperformed the controls in flowering time and flower number.     

Life history studies of the leafminer Liriomyza trifolii on susceptible and resistant cultivars of Dendranthema grandiflora

Summary The feeding, fecundity, mortality and rate of development of Liriomyza trifolii (Burgess) on 12 cultivars of Dendranthema grandiflora (Tzvel.) (Syn. Chrysanthemum morifolium (Ramat.)) were determined in no choice experiments. Number of feeding punctures, number of eggs laid and total number of larvae varied between cultivars but these characters were not strongly associated with leafminer population increase. Good indicators of host plant resistance were larval mortality, number of pupae and duration of the larval period. Of these three, larval mortality which could be as high as 98% was most suitable.Based on life history data it was predicted that Liriomyza trifolii cannot survive on the resistant cultivar Penny Lane. This prediction was verified experimentally.     

Differential responses of bread wheat characters to high temperature

Summary Agronomic and yield data were collected from two trials each containing 16 bread wheat genotypes, planted two years under late sowing conditions of high temperature (above 30° C) and one year under a normal sowing time environment. The aim was to study the character response and yield correlations with yield components and other characters under high temperature conditions with full irrigation. The results show that yield, seeds per spike, biomass, and plant height are more thermo-sensitive than spike number per square meter, 1000 kernel weight, and test weight. The grain-filling rate was more temperature-sensitive than days to anthesis and duration of grain-filling. Simple phenotypic correlation analysis indicated that yield was highly and positively correlated with seeds per spike, biomass, and harvest index (HI), independent of seasons and genotypes under high temperatures. The seeds per spike accounted for variation of yield ranging from 35.2 to 78.1%. Effect of earliness on the yield under high temperature was highly dependent on the temperature regime during the heading stage. Grains per spike, biomass, HI, and test weight could be considered potential selection criteria for yield under high temperature. Analysis of yields under normal and late sowing conditions failed to reveal any association between the yield potential in normal sowing date and the performance of varieties under high temperature.     

Effect of environment and genotype on bread-making quality of spring-sown spring wheat cultivars in China

Improvement of end-use quality in bread wheat depends on a thorough understanding of current wheat quality and the influences of genotype (G), environment (E), and genotype by environment interaction (G × E) on quality traits. Thirty-nine spring-sown spring wheat (SSSW) cultivars and advanced lines from China were grown in four agro-ecological zones comprising seven locations during the 1998 and 1999 cropping seasons. Data on 12 major bread-making quality traits were used to investigate the effect of G, E, and G × E on these traits. Wide range variability for protein quantity and quality, starch quality parameters and milling quality in Chinese SSSW was observed. Genotype and environment were found to significantly influence all quality parameters as major effects. Kernel hardness, flour yield, Zeleny sedimentation value and mixograph properties were mainly influenced by the genetic variance components, while thousand kernel weight, test weight, and falling number were mostly influenced by the environmental variance components. Genotype, environment, and their interaction had important effects on test weight, mixing development time and RVA parameters. Cultivars originating from Zone VI (northeast) generally expressed high kernel hardness, good starch quality, but poor milling and medium to weak mixograph performance; those from Zone VII (north) medium to good gluten and starch quality, but low milling quality; those from Zone VIII (central northwest) medium milling and starch quality, and medium to strong mixograph performance; those from Zone IX (western/southwestern Qinghai-Tibetan Plateau) medium milling quality, but poor gluten strength and starch parameters; and those from Zone X (northwest) high milling quality, strong mixograph properties, but low protein content. Samples from Harbin are characterized by good gluten and starch quality, but medium to poor milling quality; those from Hongxinglong by strong mixograph properties, medium to high milling quality, but medium to poor starch quality and medium to low protein content; those from Hohhot by good gluten but poor milling quality; those from Linhe by weak gluten quality, medium to poor milling quality; those from Lanzhou by poor bread-making and starch quality; those from Yongning by acceptable bread-making and starch quality and good milling quality; and those from Urumqi by good milling quality, medium gluten quality and good starch pasting parameters. Our findings suggest that Chinese SSSW quality could be greatly enhanced through genetic improvement for targeted well-characterized production environments.     

Effects of irradiance and juvenility on the selection of chrysanthemums

Summary Chrysanthemum morifolium seedlings and cuttings from those seedlings were grown to flowering at 17°C, short days (8 h) and two levels of irradiance (10 and 30 W m^–2). The cuttings flowered more readily than the seedlings at both irradiances, Especially at 10 W m^-2 many seedlings remained vegetative. The delay in flowering of the seedlings was accompanied by a higher number of leaves produced before flowering.The number of leaves produced by the seedling in excess of the number of leaves produced by the cutting from that seedling varied considerably between genotypes. The correlations between seedlings and the corresponding cuttings for days to flowering and number of leaves were low but generally significant.It is concluded that cuttings are preferred over seedlings in breeding programmes that aim at developing chrysanthemums for low light winter production.     

Adaptation to low/high input cultivation

Summary Many aeas of world, particular those where agriculture is largely practiced by resource-poor farmers with little or no use of external inputs, have not benefitted from the spectacular yield increases achieved by the combination of modern breeding technologies and use of inputs. The paper argues that because breeding is mostly conducted in presence of high inputs, it has systematically missed the opportunity to exploit genetic differences at low levels of inputs. Many studies show that these differences do exist, particularly in the case of fertilizers, and that these differences can only be identified is selection is conducted under the target level of inputs. Although this was predicted by theory more than 40 years ago, and has been supported by a large body of experimental data, very few breeders select in sub-optimal or stress conditions. The most common justification is the high environmental variation, and hence the lower heritability expected in low input conditions. While this is not supported by experimental evidence, the paper shows that in the case of a typical crop grown in low-input and climatically marginal conditions such as barley, genetic gains are possible by using locally adapted germplasm and by selecting in the target environment. Similar conclusions, in relation to the use of a low-input selection environment, have been reached recently in maize. It is concluded that the best avenue to a sustainable increase of agricultural production in low-input agricultural systems is through locally based breeding programs.     

Interaction among sporophytic S loci in self-incompatible garden chrysanthemums

Summary Certain parent-progeny crosses were studied to determine whether several S loci acted independently or epistatically to produce incompatibility in garden chrysanthemums, Chrysanthemum morifolium Ramat. The ratios of compatible: incompatible crosses with the original parent, as the pollen parent, were nearly 1:3, 1:1, and 1:1 for the I₁, backcross (BC), and BCF₂ generations, respectively. In particular, crosses between each progeny and the original parent showed that the number of compatible crosses was much higher than expected if each S locus acted independently. Therefore, interaction must have existed among pollen S alleles from different S loci. This information was used to demonstrate a method by which garden chrysanthemums could be inbred by sib mating in successive generations.Scientific Journal Series Paper Number 13,001 of the Minnesota Agricultural Experiment Station.     

Pollen selection in breeding tomato (lycopersicon esculentum Mill.) for adaptation to low temperature

Summary F₂ and BC₁ progenies from crosses between tomato (Lycopersicon esculentum) varieties differing for growth capacity at low temperature were produced under controlled conditions by hand pollination under two temperature regimes (22°C D/15°C N, normal temperature (N), and 15°C D/8°C N, low temperature (L)) with pollen formed under both regimes, resulting in four pollination treatments: NN, NL, LN and LL. Vegetative growth of the offspring was compared under a rather low temperature regime (19°C D/10°C N). Populations from different treatments within the progeny of a particular F₁ often differed significantly for average dry weight of 7 weeks old plants, the average of the NN population always being higher. Variances for dry weight were sometimes larger for LN populations, but this never resulted from a larger number of vigorous plants. Differences between populations within each progeny seemed to result in part from differences in the conditions for embryo development. Pollen selection at low temperature did not appear to be efficient for sporophyte breeding in this experiment.     

Application of RAPD markers in the characterisation of Chrysanthemum varieties and the assessment of somaclonal variation

Characterisation of fifteen commercial varieties of Chrysanthemum was carried out through RAPD analysis. Varieties could be distinguished from each other and the level of similarity between varieties seemed to be not very high. In vitro cultures were establish from four varieties and were subjected to different proliferation conditions. Five individuals from each variety and treatment were analysed using RAPD at the beginning of the treatment and after a month of culture. Variation was detected at both stages of the culture period. The rate of variation found showed differences between varieties, but no significant difference was found between culture conditions. This revised version was published online in August 2006 with corrections to the Cover Date.     

Small differential interactions for partial resistance in rice cultivars to virulent isolates of the blast pathogen

Summary Six rice genotypes, differing in partial resistance, were exposed to three isolates of the blast pathogen. Of the variance due to host and pathogen genotypes, 39% was due to host genotype effects, 60% was due to isolate effects, and only 1% was due to host genotype × isolate interactions. Although small, this interaction variance was highly significant and mainly due to the IR50 × W6-1 and IR37704 × JMB8401-1 combinations. Although behaving largely as race-non-specific (large main effects only), the partial resistance cannot be classified as race-non-specific. The results suggest that minor genes for partial resistance operate in a gene for gene relationship with minor genes in the pathogen.     

A mutant of a mutant of a mutant of a...: Irradiation of progressive radiation-induced mutants in a mutation-breeding programme with Chrysanthemum morifolium Ram.

Summary Radiation-induced sports in Chrysanthemum morifolium Ram. have been reported for several years. It has become an everyday practice to produce flower-colour mutants from outstanding cross-breeding products, even before they are distributed for the commercial production of cut flowers.One of the most successful and recent examples is that of cv. Horim, of which hundreds of mutants were produced by successive use of radiation-induced mutants in the mutation-breeding programme. Over about 4 years a variety of flower-colour mutants was obtained, not only largely including the outstanding characteristics of the original cultivar but sometimes even with an appreciable improvement in quality and yield. It is expected that the latter types, the Miros group, will soon completely supersede the spontaneous or radiation-induced Horim sports and mutants and take over the leading position of the Horim group in the production of all-year-round (AYR) cut flowers.     

Genetic analysis in Chrysanthemum morifolium. II. Flower doubleness and ray floret corolla splitting

Summary The inheritance of flower doubleness and floret corolla shape was studied in 70 F₁ populations from 16 parents. Singleness is partially dominant over doubleness. The overall segregation for doubleness in crosses of the type double × single was 29% single, 58% semi double and 12% double. The percentages varied with the parents.The anemone flower type is inherited as if it were a single. Crosses between plants with ligulate (split lengthwise) and tubular corollas produced ligulate, tubular and intermediate types in various ratios depending on the parents used. Flower doubleness and corolla shape are not linked.     

The response to temperature of leaf area in tomato genotypes. II. The rate of leaf production

Summary Genotypic variation in the response to temperature of the rate of leaf production is reported. Leaf production was measured as the rate of successive leaves passing a specific length and by dissecting plants to obtain the rate of leaf initiation. These results together with the results of leaf size from the previous paper. are compared to the effect of temperature on the total leaf area. The use of information from these experiments in selecting for increased leaf area at low temperature is discussed.Guestworker Project Group Tomato Physiology.