Quantitative-genetic analysis of reciprocal crosses between a winter and a spring cultivar of common wheat (Triticum aestivum L.)

The winter wheat cultivar Sakhalin (parent A) and the spring wheat cultivar Khush-hal (parent B), assumed to be both nuclear-genetically and plasmotypically different, were reciprocally crossed and the F₁ generation of the reciprocals backcrossed to either parent. The populations (AxB)F₁, (AxB)F₂, [(AxB)F₁xA]F₁ and [(AxB)F₁xB]F₁, and their reciprocals (BxA)F₁, (BxA)F₂, [(BxA)F₁xA]F₁ and [(BxA)F₁xB]F₁, assumed to have the plasmotypes of the parents A and B respectively, were spring sown in the same field from unvernalized (experiment #1) and vernalized (experiment #2) seeds. The results of the analyses of variance of the data recorded in the two experiments are fairly similar. In both the experiments the plasmotypically A populations have produced more heads and higher grain yields per plant than their plasmotypically B reciprocals. The components of the family means and of half the differences between the reciprocals within the families show that vernalization has not affected the efficiency of the nuclear genes of parent A but has reduced the efficiency of the nuclear genes of parent B in both the homozygous and the heterozygous states. This in turn has affected the components of family mean squares and those of the family x reciprocals interaction mean squares in the analysis of variance tables.     

Log-Linear Model Analysis of the Disease-Genotype Association Problem: Two-Loci Case

The log-linear model is modified in order to adapt it to the disease-genotype association problem, where two loci are involved. By so doing, the structure of associations among the genetic variables can be determined, and sources of distortion can be identified in certain test statistics and coefficients of association.     

Combining genotype, environment and attribute variables in regression models for predicting the cell-means of multi-environment cultivar trials

 The main objectives of this study were: (1) to develop models which combine variables of genotype, environment and attribute in regression models (GEAR) for increasing the accuracy of predicted cell-means of the genotype×environment two-way table, and (2) to compare GEAR models with the additive main effects and multiplicative interaction (AMMI) model. GEAR models were developed by regressing the observed values on principal components of genotypes (PCG) and environments (PCE). Genetic and environmental attributes were also added to the GEAR models. GEAR and AMMI models were applied to multi-environment trials of triticale (trial 1), maize (trial 2) and broad beans (trial 3). The random data-splitting and cross-validation procedure was used and the root mean square-predicted difference (RMSPD) was computed to validate each model. GEAR models increased the accuracy of predicted cell-means. Attribute variables, such as soil pH, rainfall, altitude and class of genotype, did not improve the best GEAR model of trial 1, but they increased the predictive value of other models. Two iterations of the computer program further refined the best GEAR model. Based on the RMSPD criterion, GEAR models were as good as, or better than, some AMMI truncated models for predicting cell-means. The approximate accuracy gain factors (GF) of the best GEAR model over the raw data were 2.08, 3.02 and 2.22, for trials 1, 2 and 3, respectively. The GF of the best AMMI model were 1.74, 2.28 and 2.32 for trials 1, 2 and 3, respectively. The analysis of variance of the predicted cell means showed that the genotype×environment interaction (GEI) variance was reduced by about 20% in trial 1 and 81% in trial 2. A bias associated with the predicted cell reduced the GEI variability. Advantages of using GEAR models in muti-environment cultivar trials are that they: (1) increase the precision of cell-mean estimates and (2) reduce the GEI variance and increase trait heritability. Received: 15 August 1997 / Accepted: 28 October 1997     

Environmental and genotype-by-environment influences on chick size in the Yellow-browed leaf warbler Phylloscopus inornatus

Summary I investigated genetic and environmental factors affecting fledgling chick size in the Yellow browed leaf warbler Phylloscopus inornatus. The proportion of variation among broods is >45% for both tarsus length and body weight; this can be attributed at least in part to effects of the shared nest environment. A high off-spring-parent regression for weight also appears to be partly due to an environmentally induced correlation and the regression is reduced when effects of laying date are controlled for. A cross-fostering experiment demonstrated a significant nest of origin x nest of rearing interaction. The presence of genotype-environment interaction affecting chick size may be quite general in birds. It is shown how this can account for observed patterns of the dependence of the magnitude of offspringparent regression on prevailing conditions, as has been found in other studies. In P. inornatus the failure to detect significant genetic variance in chick body weight and tarsus length may be due to high standard errors on the estimates, but it may also reflect true low levels of genetic variance in chick size if the genotype-interaction effect described occurs regularly in this species.     

Genetic variation in nutrient response functions

Summary Genetic differences in the non-linear growth response function of Pinus sylvestris seedlings to five nutrient levels are analyzed to estimate the causes of variation. Analyses of genotypic differences as quadratic response functions, as stability coefficients, and as separable functions indicate that the estimation of genetic effects can vary widely depending on the analytical model assumed. The existence of different reaction norms is demonstrated.     

Differential effects of low concentrations of aluminium on the growth of four genotypes of white clover

Summary The effects of aluminium (Al³⁺) on the growth of four cultivars of white clover dependent upon NO₃ ⁻−N were examined. Plants were grown in flowing solution culture with carefully maintained low concentrations (0, 12.5, 25 and 50 mmolm⁻³) of Al, and with P and pH (4.5) also held constant and appropriately low. A three-week treatment period resulted in major effects on the growth and elemental composition of shoots and roots at all concentrations of added Al. There were inherent differences between the cultivars in growth but the relative effects of Al were similar in each case. Examination by S.E.M. and x-ray microanalysis of one cultivar grown at 50 mmolm⁻³ Al, indicated that Al in the roots was associated with P, especially in old, outer epidermal cells. Aluminium reduced NO₃ ⁻ uptake and there were significant effects of Al on nitrate reductase activity (NRA). In contrast to the other characteristics, there were differential effects between the cultivars in NRA, both in the presence and absence of Al.     

Direct Haplotype‐Specific DNA Sequencing

Abstract

Determining haplotype‐specific DNA sequence information is very important in a wide range of research fields. However, no simple and robust approaches are currently available for determining haplotype‐specific sequence information. We have addressed this problem by developing a very simple and robust haplotype‐specific sequencing approach. We utilise the fact that DNA sequencing polymerases are sensitive to 3′end mismatches in the sequencing primer. By using two sequencing primers with 3′end corresponding to the two alleles in a given SNP locus, we are able to obtain allele‐specific DNA sequences from both alleles.

We evaluated this direct haplotype‐specific approach by determining haplotypes within the intron 2 sequence of the fructan‐6‐fructosyltransferase (6‐ft) gene in Lolium perenne L. We obtained reliable haplotype‐specific sequences for all primers and genotypes evaluated. We conclude that the haplotype‐specific sequencing is robust, and that the approach has a potentially very wide application range for any diploid organism.     

Influence of growth regulators on direct embryo formation from leaf explants of Phalaenopsis orchids

Leaf explants of two Phalaenopsis, P. amabilis and P. Nebula, were used to test the effects of auxins (2,4-D, IAA, IBA, NAA), cytokinins (2iP, BA, kinetin, TDZ, zeatin), GA₃, ancymidol, polyamines (putrescine, spermine, spermidine), ACC, AgNO₃ and CoCl₂ on the amount of direct embryo formation on different leaf locations (the cut end, the adaxial side, the abaxial side and the leaf tip). The results showed that there was a genotypic effect on direct embryo formation induced by cytokinins that 13.32 μM BA and 4.92 μM 2iP was the most effective in P. amabilis and P. Nebula, respectively. Besides, explant position highly affected embryogenic competence of leaf cells in both species that the cut end showed highest embryogenic response, the adaxial side was the second, and then the abaxial side and the leaf tip. Altogether, cytokinins tested were all effective in both species, and ACC at 20 μM had 35% of embryogenic response in P. amabilis. However, auxins, GA₃, ancymidol and polyamines were inhibitory in both species.