Genotype-environmental Interactions Research Articles

Performance and Adaptability of Common Bean-Released Cultivars at Three Agro-Ecological Zones in Tanzania

This study focused on examining the genetic performance and stability of common bean genotypes across multiple environments in Tanzania using an alpha-lattice experimental design. The aim was to minimize environmental variability and maximize genetic expression. Three experimental sites were selected to represent the ecologies of the main bean growing areas of Tanzania, which are Tropical Savannah represented by TARI-Seliani, Tropical highlands represented by TARI-Uyole and semi-arid regions represented by Babati region. The sites were planted with are diverse of common bean genotypes, all of which were released for use in Tanzania. Agronomic practices, such as hand-hoe weeding and fertilizer application, were consistently applied. Key data collected included days to 50 percent flowering, growth habit, plant height, pod and seed count, yield per plot, and 100 seed weight. Advanced statistical analyses, including ANOVA, AMMI, and stability tests, were conducted using R software to evaluate yield and yield components. This paper findings discuss about the yield performance, stability, and the discriminating verses representative power across locations. In terms of yield, Babati was the leading site with mean yield of 1413.07 kilogram per hectare (kg/h)with Uyole 96 being the lead genotype (2845.567kg/h). Genotypes that were found to be stable and high-yielding in multiple locations include, Rojo, SUA Kalima, SAKILA, Fibea, and Nyeupe Uyole with the mean yields of 1045.83kg/h, 1023.73kg/h, 1003.33kg/h, 670.4kg/h and 544.77kg/h respectively. In discriminativeness and representativeness, Babati was the most discriminating site among the three locations while Seliani was the most representative among the three. These findings revealed significant variationsand allowed the assessment of genotype performance and environmental interactions.

Regional height growth models for Scots pine in Poland

Site productivity remains a fundamental concern in forestry as a significant driver of resource availability for tree growth. The site index (SI) reflects the overall impact of all environmental factors that determine tree height growth and is the most commonly used indirect proxy for forest site productivity estimated using stand age and height. The SI concept challenges are local variations in climate, soil, and genotype-environmental interactions that lead to variable height growth patterns among ecoregions and cause inappropriate estimation of site productivity. Developing regional models allow us to determine forest growth and SI more appropriately. This study aimed to develop height growth models for the Scots pine in Poland, considering the natural forest region effect. For height growth modelling, we used the growth trajectory data of 855 sample trees, representing the Scots pine entire range of geographic locations and site conditions in Poland. We compared the development of regional height growth models using nonlinear-fixed-effects (NFE) and nonlinear-mixed-effects (NME) modelling approaches. Our results indicate a slightly better fit to the data of the model built using NFE approach. The results showed significant differences between Scots pine growth in natural forest regions I, II, and III located in northern Poland and natural forest regions IV, V, and VI in southern Poland. We compared the development of regional height growth models using NFE and NME modelling approaches. Our results indicate a slightly better fit to the data of the model built using the NFE approach. The developed models show differences in height growth patterns of Scots pines in Poland and revealed that acknowledgement of region as the independent variable could improve the growth prediction and quality of the SI estimation. Differences in climate and soil conditions that distinguish natural forest regions affect Scots pine height growth patterns. Therefore, extending this research to models that directly describe height growth interactions with site variables, such as climate, soil properties, and topography, can provide valuable forest management information.

К качеству зерна озимой пшеницы

The quality of grain means a set of technologico-biochemical, baking and food properties determining the economic value of a grain variety. When choosing source material for selection, the degree of grain preservation in adverse environmental conditions is taken into account as well as the genotypic potential of grain yield and quality. It is believed that in the arid conditions of the Volga region, the main limiting factor in the formation of high-quality grain is the amount of precipitation during the growing season of wheat and the uniformity of its distribution, so more than 25 indices of the winter wheat quality are evaluated annually, including the quantitative expression of indices of the rheological properties of dough. Experimental data indicate that such indices as water absorption capacity (WAC, %); energy absorbed by dough during mixing (W·h/kg); dough stability, (min); dough dilution (C2, N·m); and starch retrogradation index (C5, N·m) provide sufficient information for selection. The dough formation time seems the least promising indicator: genotype-environmental interactions on this index were manifested in 100% of cases. In the process of studying the ball-shaped forms of winter soft wheat it has been revealed that they have a high crop yield and excellent grain quality, namely the dough stability, which is 10.3, 9.9, 9.7, and 8.4 min in the studied samples Nos. 209–212, respectively. They also exceed the Saratov 90 variety by C2 , which characterizes dough dilution, having values of 0.57, 0.52, and 0.47 N·m, while having excellent baking qualities. The variation limits of the index of flour whiteness were 60.5–71.9 in the red-grain group of winter wheat and 57.5–69.6 in the white-grain one. The average value of this index is 66.3 and 57.5, respectively. Extra-quality flour can be obtained from the Smuglianka variety and lines with breeding numbers 17-17, 34-17, 1081-17, 1096-17, and 1093-17. Of all the others, we can get highest-grade flour without exception. The correlation between the indicators of meal whiteness and flour whiteness in the red-grain and white-grain forms of winter wheat is 0.7660 at the 1% significance level and 0.9311, respectively. This means that it is possible to assess the whiteness of flour from the color of whole-milled grain with a high probability.

Genotype-Environment Interaction Analysis of NQO1, CYP2E1, and NAT2 Polymorphisms and the Risk of Childhood Acute Lymphoblastic Leukemia: A Report From the Mexican Interinstitutional Group for the Identification of the Causes of Childhood Leukemia.

Background: Acute lymphoblastic leukemia (ALL) is the main type of cancer in children. In Mexico and other Hispanic populations, the incidence of this neoplasm is one of the highest reported worldwide. Functional polymorphisms of various enzymes involved in the metabolism of xenobiotics have been associated with an increased risk of developing ALL, and the risk is different by ethnicity. The aims of the present study were to identify whether NQO1, CYP2E1, and NAT2 polymorphisms or some genotype-environmental interactions were associated with ALL risk in Mexican children.Methods: We conducted a case-control study including 478 pediatric patients diagnosed with ALL and 284 controls (children without leukemia). Ancestry composition of a subset of cases and controls was assessed using 32 ancestry informative markers. Genetic-environmental interactions for the exposure to hydrocarbons were assessed by logistic regression analysis.Results: The polymorphisms rs1801280 (OR 1.54, 95% CI 1.21–1.93), rs1799929 (OR 1.96, 95% CI 1.55–2.49), and rs1208 (OR 1.44, 95% CI 1.14–1.81) were found to increase the risk of ALL; being the risks higher under a recessive model (OR 2.20, 95% CI 1.30–1.71, OR 3.87, 95% CI 2.20–6.80, and OR 2.26, 95% CI 1.32–3.87, respectively). Gene-environment interaction analysis showed that NAT2 rs1799929 TT genotype confers high risk to ALL under exposure to fertilizers, insecticides, hydrocarbon derivatives, and parental tobacco smoking. No associations among NQO1, CYP2E1, and ALL were observed.Conclusion: Our study provides evidence for the association between NAT2 polymorphisms/gene-environment interactions, and the risk of childhood ALL in Mexican children.

Mapping colitis susceptibility in mouse models: distal chromosome 3 contains major loci related to Cdcs1

Inflammatory bowel disease (IBD) summarizes a group of chronic intestinal disorders with Crohn's disease and ulcerative colitis being most prominent. Though much effort is put into identification of causative factors, its etiology is still not understood. Risk factors for disease development include genetic predisposition and environmental triggers. Crucial for identification and analysis of relevant factors are mouse models. Experimental IBD in mice occurs spontaneously or is induced by chemicals, cell transfer, pathogens, or genetic mutation. These models were utilized for analyzing genetic contribution to disease and genotype-environmental interactions. In these studies, a variety of modifier loci were identified, thereby demonstrating the complexity of disease. A major contribution of distal chromosome 3 was independently replicated in several studies. The first colitogenic QTL in this region was detected using the IL-10-deficient mouse model and called cytokine deficiency-induced colitis susceptibility (Cdcs)1. This quantitative trait locus contains at least three subintervals with independent genetic factors. This locus or defined subintervals were replicated in at least seven studies, using models based on dysregulation of innate or adaptive immunity or pathogen control. In this review we illustrate the various models used for genetic mapping of susceptibility to experimental IBD and display Cdcs1-related loci as well as the mechanism of their contribution identified so far.

Genotype × environmental interactions for analyzing adaptability and stability in different clones of Dalbergia sissoo Roxb

In total 36 superior clones of Dalbergia sissoo Roxb., screened from 300 selections conducted in natural and growing range of India and Nepal, were multiplied using single nodal cuttings and established to evaluate genotypeenvironmental interactions for adaptability and stability at the age of 30 months in three geographical locations in the state of Punjab, India. Clone 124 had maximum adaptability and stability (bi = 1.04) to perform exceedingly well over the locations. Clones 36 and 1 were stable with mean regression coefficient of 0.84 and 1.22, respectively. Nonetheless, clone 41 performed exceedingly well for all the characters to attain maximum population mean, and the performance varied substantially across the locations. Therefore, clone 41 was considered as productive but non-adaptive clone. Though some of the clones were sensitive to sites, 14 clones for height, 16 for collar diameter, 12 for DBH and 7 for volume were relatively un-sensitive with higher regression coefficient. Nonetheless, clone 124 was the most stable with average bi value of 1.04 and productive, which could play an important role in future breeding and commercial deployment of stable and productive planting stock of Dalbergia sissoo.

The SCARB1 rs5888 SNP and Serum Lipid Levels in the Guangxi Mulao and Han Populations

Backgroud: The associations of scavenger receptor class B type 1 (SCARB1) rs5888 single nucleotide polymorphism (SNP) and serum lipid levels are inconsistant among diverse ethnic populations. The present study was undertaken to detect the association of rs5888 SNP and serum lipid levels in the Guangxi Mulao and Han populations.Methods: Genotypes of the SCARB1 rs5888 SNP in 801 subjects of Mulao and 807 subjects of Han Chinese were determined by polymerase chain reaction and restriction fragment length polymorphism combined with gel electrophoresis, and then confirmed by direct sequencing.Results: Serum apolipoprotein (Apo) B levels and the T allelic frequency were higher in Mulao than in Han. Serum high-density lipoprotein cholesterol (HDL-C) levels in Mulao were different among the genotypes, the subjects with TT genotype had lower HDL-C levels than the subjects with CC or CT genotype in female (P < 0.05). For the Han population, serum triglyceride (TG), HDL-C, ApoAI, ApoB levels and the ratio of ApoAI to ApoB in males were different among the genotypes, the T allele carriers had lower serum HDL-C, ApoAI levels and ApoAI/ApoB ratio and higher serum ApoB levels than the T allele noncarriers (P < 0.05 for all), the subjects with TT genotype had higher serum TG levels than the subjects with CC or CT genotype. Serum HDL-C levels in Mulao females and serum HDL-C, ApoAI, ApoB levels and the ApoAI/ApoB ratio in Han males were correlated with genotypes by the multiple linear regression analysis. Serum lipid parameters were also influenced by genotype-environmental interactions in Han but not in Mulao populations.Conclusions: These results suggest that the rs5888 SNP is associated with serum HDL-C levels in Mulao females, and TG, HDL-C, ApoAI, ApoB levels and the ApoAI/ApoB ratio in Han males. The differences in serum ApoB levels between the two ethnic groups might partially attribute to different SCARB1 genotype-environmental interactions.

Chlorophyll Fluorescence-Based Studies of Frost Damage and the Tolerance for Cold-Induced Photoinhibition in Freezing Tolerance Analysis of Triticale (×Triticosecale Wittmack)

Freezing tolerance of 60 breeding lines of winter hexaploid triticale (×Triticosecale Wittmack) was studied in the field-laboratory experiment. The experiment was repeated over three winters. The survey was also carried out in plants grown and cold-acclimated in the laboratory. In both the experiments, plant survival analysis and chlorophyll fluorescence-based studies on energy flows in photosystem II (PSII) (JIP-test) after freezing of detached leaves were performed. In the laboratory experiment, the temperature of 50 % electrolyte leakage from leaves and the resistance against cold-induced photoinhibition were additionally investigated. In the case of plants’ cold-acclimated in the field, determination of the freezing tolerance of PSII gave similar results as the determination of freezing tolerance of whole plants. Both traits were strongly affected by genotype–environmental interactions, but these effects were less visible for PSII characteristics. In the laboratory experiments, a strong correlation between freezing tolerance and the tolerance for cold-induced photoinhibition of photosynthesis was observed. The possibility of the use of chlorophyll fluorescence-based techniques for the determination of freezing tolerance in triticale is discussed.

Gluten index compared with SDS-sedimentation volume for early generation selection for gluten strength in durum wheat

Gluten strength is an important end-use quality factor in durum wheat [Triticum turgidum L. ssp. durum (Desf.) Husn.], affecting pasta manufacture and cooking quality. The objective of this research was to determine the inheritance and heritability of gluten index in comparison with the widely used SDS-sedimentation (sodium dodecyl sulphate) technique for selection for gluten strength. Seven durum populations were grown in replicated, multi-location, multi-year field trials in Saskatchewan, Canada, during the period 1995 to 2002. Gluten index and SDS-sedimentation volume were determined on all plots after harvest. Both traits were affected by genotype, and to a lesser extent by year or location. Genotype environmental interactions were generally minor. The majority of genotypes in each population had similar relative ranking for gluten index and SDS-sedimentation volume in each environment. Both traits were highly heritable, ranging from 0.80 to 0.97, and both were complexly inherited with estimates of effective factors ranging from 3 to 21. Gluten index and SDS-sedimentation volume were highly correlated, indicating that they are measuring similar aspects of gluten strength. SDS-sedimentation volume was positively associated with protein concentration (r2 = 0.52), but gluten index was not. Therefore, gluten index would be more desirable than SDS-sedimentation volume for use in selection where there are within-trial protein concentration trends.Key words: Gluten strength, SDS-sedimentation, gluten index, heritability, inheritance

Inheritance of test weight and kernel weight in eight durum wheat crosses

High test weight and uniform kernel size are important grading factors for durum wheat [Triticum turgidum L. ssp. durum (Desf.) Husn.] because both are associated with semolina yield. The objective of this research was to determine the inheritance and heritability of test and kernel weights to facilitate development of selection strategies. Eight durum populations were grown in replicated, multi-location, multi-year field trials. Test weight and kernel weights were determined on all plots after harvest. Both traits were affected by genotype and to a lesser extent by year or location. Genotype environmental interactions were generally minor. Trial means for test weight ranged from 72.7 to 81.0 kg hL-1 and from 31.5 to 50.9 mg for kernel weight. All populations showed bi-directional transgressive segregation for both traits, and the estimated number of effective factors controlling them ranged from 4 to 23, indicating quantitative inheritance. With the exception of one population, heritability of test weight ranged from 0.80 to 0.92 and of kernel weight from 0.83 to 0.93. Both traits generally showed positive phenotypic and genotypic correlations with plant height. Also, mean test weight and kernel weight were higher for the gibberellic acid-sensitive (tall) than for the insensitive (semidwarf) group within populations segregating for gibberellic acid response.Key words: Test weight, kernel weight, inheritance, heritability

Characterization of inbred strains and substrains of mice by determinations of C-type viral protein p30 expression in various organs

The radioimmunoassay method for detection of the major core C-type viral protein p30 is a tool for the characterization and control in inbred strains of mice. 27 mouse strains could be separated into eight groups based on examination of six organs. It is also possible to separate substrains if they are genetically different. Several genes play a role in the expression of p30, but also genotype-environmental interactions seem to affect the p30 expression.

Response to conventional and organic environment of thirty-six lentil (Lens culinaris Medik.) varieties

Thirty-six lentil varieties were evaluated under organic and conventional environment for three consecutive years in order to see whether the promising genetic material for an organic plant breeding program are different from those of a conventional system. The genetic material studied originated from various countries. In the conventional trial plots standard cultural practices (P mineral fertilization & pest control) were applied throughout the growing season, while in the organic ones no fertilizers or pest agrochemicals were applied. Significant regression, but of low value, between grain yield ranking and earliness or harvest index ranking was detected. Combined ANOVA indicated significant differences between genotypes, years, environments and genotype × environmental interactions (GEI). It was observed that under conventional management most of the genotypes had a higher yield compared to the organic one. The mean grain yield ranking of the genotypes in each of the environments revealed that some of the genotypes occupied the same ranking position at both the organic and the conventional environment (non-crossover GEI), while others exhibited a significant alteration in their ranking (crossover GEI) under the two environments. Crossover GEI and non-cross over GEI revealed two types of lentil varieties. Varieties with specific adaptation and varieties with broad adaptation. It was concluded that grain yield was in general higher when lentil varieties were grown under a conventional environment compared to the grain yield produced under an organic environment. Yet, there are lentil genotypes with a higher yielding ability under the organic management and therefore should be targeted by the breeder.

Gene system governing stomatal number and specific leaf weight in bread wheat ( Triticum aestivum L.)

Gene effects were analysed using mean stomatal number and specific leaf weight of 12 populations, consisting of both parents (P 1 and P 2 ), F 1 , F 2 , first backcross generations (BC 1 and BC 2 ), second backcross generations (B 11 , B 12 , B 21 , B 22 ) and backcross selfed generations (B 1 s and B 2 s) of four crosses involving three drought-tolerant and three drought-susceptible cultivars of Triticum aestivum L. to determine the nature of gene action governing stomatal number (SN) and specific leaf weight (SLW) through generation mean analysis in moisture stress (E 1 ) and moisture non-stress (E 2 ) environments. The digenic epistatic model was found to be inadequate for stomatal number and the additive-dominance model was found to be adequate for specific leaf weight in most of the crosses. Additive gene effects were predominant for SLW, while for SN both additive and dominance components of variance were important. Epistatic effects, particularly the additive × dominance (j) type of interaction, were present for both the characters. The duplicate type of epistasis was observed for stomatal number in the cross VL421/HS240 in the moisture stress environment. Significant heterosis was observed for the crosses Hindi 62/HS240 and VL421/HS240 over the standard check (SC) in the moisture stress environment (E 1 ) for both the characters. Genotype-environmental interactions and/or differential gene expression appeared to account for the different results found between environments. Hybridization systems, such as biparental mating and/or diallel selective mating, could be useful for the improvement of these traits, which would help in identifying drought-tolerant progenies.

The Potential for the Transcriptome to Serve as a Clinical Biomarker for Cardiovascular Diseases

See related article, pages e74–e83 The ability to measure the level of expression of tens of thousands of genes simultaneously with a variety of technologies has introduced the concept of deriving molecular signatures based on specific patterns of gene expression. This notion is conceptually resonant with regard to oncogenesis, and coupled with the ready availability of tumor tissue, has led to the introduction of molecular signature–based biomarkers for several solid and hematologic tumors.1,2 Recently, molecular signature analysis (MSA), prospectively validated in large patient cohorts, has become available to physicians managing patients with breast cancer,3 and ongoing clinical trials suggest that MSA could be a valuable tool to predict diagnosis, prognosis, and individual responses to therapies. The promising results of microarray technology in oncology raise the issue of whether and how this tool could be used in other areas. In the cardiovascular field, there is a need for improved tools to detect inflammatory diseases of the myocardium and to guide immunosuppressive treatment in cardiac allograft recipients. The current gold standard for detecting myocarditis or monitoring cardiac allograft rejection—histopathological examination of endomyocardial biopsy specimens—is limited by imperfect sensitivity4 and requires, in the case of transplant recipients, repeated invasive procedures. The availability of high-throughput genomic technology could contribute substantially to the management of inflammatory diseases of the myocardium. From a conceptual basis, genetic susceptibility does play in role in these disorders. For example, various single nucleotide polymorphisms correlate with cardiac transplant outcomes.5,6 Therefore, the advent of high-throughput genotyping holds great promise to assess one patient’s individual risk for developing rejection episodes, and testing of pharmacogenomic markers could help to guide the complex immunosuppressive regimens. Moreover, gene expression profiles may aid in the diagnosis and management of cardiac allograft rejection and myocarditis by reflecting complex genotype–environmental interactions. …

Peroxisome proliferator-activated receptor-gamma2-Pro12Ala and endothelial nitric oxide synthase-4a/b gene polymorphisms are associated with essential hypertension

Objective Peroxisome proliferator-activated receptor-gamma2 (PPARγ2) belongs to the family of the nuclear hormone receptors and has been recently implicated in vascular biology. PPARγ2(Pro12Ala) gene polymorphism is associated with obesity, body mass index and diabetes mellitus. The endothelial nitric oxide synthase (eNOS) (4a/b) gene polymorphism contributes to coronary heart disease and hypertension risk. We tested whether both polymorphic variants were associated with hypertension risk, and their inter-relationship with plasma homocysteine. Design A case–control study was conducted selecting 235 subjects with arterial hypertension and 223 normotensive matched controls. Methods Genotyping for the PPARγ2(Pro12Ala) and the eNOS(4a/b) were performed by mutagenically separated polymerase chain reaction and by polymerase chain reaction. Glucose, lipid profile, plasma creatinine, homocysteine and microalbuminuria were measured. Results We found a significant contribution of the PPARγ2(Pro12Ala) and eNOS(4a/b) gene polymorphisms to hypertensive risk in our population (odds ratio, 1.9 and 1.6, respectively), confirmed by multiple logistic regression analysis. Those subjects with normal plasma homocysteine values had an increased hypertensive risk with an odds ratio of 2.6 for the PP genotype of the PPARγ2 gene and an odds ratio of 1.8 for the a allele of the eNOS gene. Conclusions Both analyzed polymorphisms were associated in a synergistic manner with hypertension. This effect manifested only in those subjects with normal homocysteine plasma values. Our findings suggest complex genotype–environmental interactions on hypertensive risk.

Peroxisome proliferator-activated receptor-gamma2-Pro12Ala and endothelial nitric oxide synthase-4a/bgene polymorphisms are associated with essential hypertension.

Peroxisome proliferator-activated receptor-gamma2 (PPARgamma2) belongs to the family of the nuclear hormone receptors and has been recently implicated in vascular biology. PPARgamma2(Pro12Ala) gene polymorphism is associated with obesity, body mass index and diabetes mellitus. The endothelial nitric oxide synthase (eNOS) (4a/b) gene polymorphism contributes to coronary heart disease and hypertension risk. We tested whether both polymorphic variants were associated with hypertension risk, and their inter-relationship with plasma homocysteine. A case-control study was conducted selecting 235 subjects with arterial hypertension and 223 normotensive matched controls. Genotyping for the PPARgamma2(Pro12Ala) and the eNOS(4a/b) were performed by mutagenically separated polymerase chain reaction and by polymerase chain reaction. Glucose, lipid profile, plasma creatinine, homocysteine and microalbuminuria were measured. RESULTS We found a significant contribution of the PPARgamma2(Pro12Ala) and eNOS(4a/b) gene polymorphisms to hypertensive risk in our population (odds ratio, 1.9 and 1.6, respectively), confirmed by multiple logistic regression analysis. Those subjects with normal plasma homocysteine values had an increased hypertensive risk with an odds ratio of 2.6 for the PP genotype of the PPARgamma2 gene and an odds ratio of 1.8 for the a allele of the eNOS gene. Both analyzed polymorphisms were associated in a synergistic manner with hypertension. This effect manifested only in those subjects with normal homocysteine plasma values. Our findings suggest complex genotype-environmental interactions on hypertensive risk.

Evaluation of malting barley quality using exploratory data analysis. I. Extraction of information from micro-malting data of spring and winter barley

Abstract This paper presents an exploratory multivariate approach for analysis of malting barley quality data. By using principal component analysis (PCA) and partial least squares regression (PLSR) complex malting quality data are combined into functional factors which are used for malting barley quality characterisation. Fifty barley samples were used in this investigation, representing 15 spring barley and 10 winter barley varieties grown at two locations in Denmark. The samples were micro-malted and mashed and analysed for 13 quality parameters according to official methods of the European Brewery Convention. These data were combined and reduced into a few latent (functional) factors using PCA by which it is demonstrated that the modification of β-glucan plays a major role in both spring and winter barleys. Additionally, the spring barley and winter barley samples display different covariate latent structures, mainly in the nitrogen and diastatic power patterns. It is furthermore shown that graphic display as facilitated by exploratory data analysis, can be utilized in order to evaluate genotype-environmental interactions by considering the position and movements of the individual objects (genotypes in this instance) in the score plots. Thus, in contrast to the classical analysis of variance, the samples can be individually evaluated and the corresponding loadings can be used to validate the genetic and environmental effect of a given sample in a quality perspective. Several of the investigated malting quality parameters are highly intercorrelated. This fact is utilized by applying PLSR to barley and malt data for the prediction of wort quality in order to exclude the mashing step. This approach was successful for the modification-dependent wort parameters, extract, wort β-glucan and viscosity.

Inheritance of excised-leaf water loss and relative water content in bread wheat (Triticum aestivum)

Little information is available on the genetics of excised leaf water loss and relative water content in wheat. An experiment conducted on the F1 generation from a half-diallel set of crosses involving two drought tolerant, two moderately tolerant and two sensitive varieties was initiated to investigate the inheritance of excised-leaf water loss and relative water content. This experiment was conducted under glass-house and field conditions at tillering and anthesis stages of plant development. Additive gene action, in general, played a major role in determining the inheritance of these traits. General combining ability (GCA) was the main source of genetic variation among crosses, while specific combining ability (SCA) was negligible. Strong phenotypic correlations existed between per se performance and GCA effects in the majority of cases. Heterosis was unimportant. Genotype-environmental interactions and/or differential gene expression appeared to account for different results found between environments and growth stages, respectively. Selection for relative water content appeared to be more effective at anthesis, while for excised-leaf water loss at both stages of plant growth. In addition to drought resistance, wide differences for morphological characters and relative positions of parental arrays revealed the possibility of obtaining desirable segregants for drought stress conditions from the cross Kharchia 65 × WH 147.

Environmental Influences on Epilepsy Gene Mapping in El Mice

The epileptic EL mouse has been studied extensively as a genetic model for idiopathic complex partial seizures in humans. The seizures in EL mice occur during routine handling at approximately 90 days of age, but can be induced at younger ages (50 days) by repeated rhythmic vestibular stimulation, e.g., tossing. Six seizure frequency quantitative trait loci (QTLs), EU-E16, were previously mapped in crosses between EL and non-epileptic strains using mechanical tossing procedures beginning at 30 days of age. The presence of these seizure frequency QTLs depended upon genetic background and the type of cross. Here we confirm Chromosome 2 and 9 QTLs in a backcross to the seizure-resistant ABP/LeJ strain with mice tested beginning at 200 days of age. However, the mapping of epilepsy genes was influenced by the seizure testing procedure, i.e., repeated tossing. The maximum Z-score for Ell (Chromosome 9) was 3.7 after 6 tests, but decreased to 2.4 after 15 tests. In contrast, the maximum Z-score for Ell (Chromosome 2) was 2.0 after 6 tests, but increased to 3.9 after 15 tests. In addition to nonallelic interactions (epistasis), our findings indicate that the genetic complexity of tossing-induced seizure susceptibility in EL mice also arises from genotype-environmental interactions involving the seizure test, seizure history, and age.

TESTS FOR CROSSOVER GENOTYPE-ENVIRONMENTAL INTERACTIONS

Two statistical tests for crossover genotype-environmental interactions are illustrated. One test, suitable for investigating two-factor interactions in factorial experiments, was used to show that interactions between wheat cultivars and temperatures for median germination time did not involve significant changes in rank order. A second test was used to compare yields of three cultivars of spring wheat evaluated in nine environments and to demonstrate that the differences between HY320 and Fielder involved significant crossover interactions, whereas the differences between HY320 and Neepawa, and between Fielder and Neepawa, did not involve crossover interactions. Calculations required for the two tests are shown. The importance of the tests for investigating genotype-environmental interactions and related topics is discussed.Key words: Genotype-environmental interactions, qualitative interaction, statistical tests, Triticum aestivum L., wheat (spring)