Showing papers by "Mark E. Cooper published in 1994"

Relationships among analytical methods used to study genotypic variation and genotype-by-environment interaction in plant breeding multi-environment experiments

Abstract: Following the recognition of the importance of dealing with the effects of genotype-by-environment (G ×E) interaction in multi-environment testing of genotypes in plant breeding programs, there has been substantial development in the area of analytical methodology to quantify and describe these interactions Three major areas where there have been developments are the analysis of variance, indirect selection, and pattern analysis methodologies This has resulted in a wide range of analytical methods each with their own advocates There is little doubt that the development of these methodologies has greatly contributed to an enhanced understanding of the magnitude and form ofG ×E interactions and our ability to quantify their presence in a multi-environment experiment However, our understanding of the environmental and physiological bases of the nature ofG ×E interactions in plant breeding has not improved commensurably with the availability of these methodologies This may in part be due to concentration on the statistical aspects of the analytical methodologies rather than on the complementary resolution of the biological basis of the differences in genotypic adaptation observed in plant breeding experiments There are clear relationships between many of the analytical methodologies used for studying genotypic variation andG ×E interaction in plant breeding experiments However, from the numerous discussions on the relative merits of alternative ways of analysingG ×E interactions which can be found in the literature, these relationships do not appear to be widely appreciated This paper outlines the relevant theoretical relationships between the analysis of variance, indirect selection and pattern analysis methodologies, and their practical implications for the plant breeder interested in assessing the effects ofG ×E interaction on the response to selection The variance components estimated from the combined analysis of variance can be used to judge the relative magnitude of genotypic andG ×E interaction variance Where concern is on the effect of lack of correlation among environments, theG ×E interaction component can be partitioned into a component due to heterogeneity of genotypic variance among environments and another due to the lack of correlation among environments In addition, the pooled genetic correlation among all environments can be estimated as the intraclass correlation from the variance components of the combined analysis of variance WhereG ×E interaction accounts for a large proportion of the variation among genotypes, the individual genetic correlations between environments could be investigated rather than the pooled genetic correlation Indirect selection theory can be applied to the case where the same character is measured on the same genotypes in different environments Where there are no correlations of error effects among environments, the phenotypic correlation between environments may be used to investigate indirect response to selection Pattern analysis (classification and ordination) methods based on standardised data can be used to summarise the relationships among environments in terms of the scope to exploit indirect selection With the availability of this range of analytical methodology, it is now possible to investigate the results of more comprehensive experiments which attempt to understand the nature of differences in genotypic adaptation Hence a greater focus of interest on understanding the causes of the interaction can be achieved

Progressive decline in renal function in diabetic patients with and without albuminuria.

Abstract: This study describes patterns of progression of albuminuria and renal function in a subgroup of 40 patients from a total cohort of 211 diabetic patients (118 type I, 93 type II) followed over a period of 8-14 years. Forty patients (18 with type I diabetes, 22 with type II diabetes) showed progressive increases in albumin excretion rate (AER) and/or decreases in creatinine clearance (CC) during the study period. Of these, AER alone increased in 15 patients, AER increased and CC decreased in 13 patients, and CC alone decreased in 12 patients, with a similar distribution of type I and type II diabetic patients in each group. Of the 28 patients who showed an increase in albuminuria, AER increased at an annual rate of 30-40%, resulting in a 4- to 8-fold increase in AER to > 20 micrograms/min during the study. Of the 25 patients who showed a decrease in renal function, CC decreased at an annual rate of 4-5 ml/min, resulting in an approximate halving of CC to < 90 ml/min during the study. The rate of fall in CC was not related to the presence or absence of concomitant increases in albuminuria. However, a significant preponderance of women in the group showed a decline in CC alone. The decline in CC was associated with an increase in plasma creatinine as well as a progressive decrease in urinary creatinine excretion, but the underlying mechanisms remain unexplained. These data support the concept that a subgroup of diabetic patients may show a decline in renal function in the absence of significant increases in AER.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of endothelium-derived nitric oxide in the pathogenesis of the renal hemodynamic changes of experimental diabetes.

Abstract: To evaluate the role of nitric oxide (NO) in diabetic hyperfiltration, renal hemodynamic changes and changes in urinary excretion of NO2/NO3 in response to the NO inhibitor nitro-L-arginine methyl ester (L-NAME) and the NO-donating agent glyceryl trinitrate (GTN) were investigated in conscious streptozocin-induced diabetic (D) and age-matched control (C) rats. In all experiments, D rats demonstrated increased glomerular filtration rate (GFR), renal plasma flow (RPF), polyuria, and an increased urinary sodium excretion when compared with C rats. An intravenous bolus of low-dose L-NAME (1 mg/kg body wt) increased modestly systolic blood pressure (sBP) in C rats but had no effect on sBP in D rats. L-NAME induced a marked decrease in GFR and RPF in D rats with no change in filtration fraction (FF). In C rats, no change in GFR was observed, and RPF decreased, resulting in a rise in FF. A supramaximal dose of L-NAME (10 mg/kg body wt) increased sBP in C and D rats to a similar degree. With high-dose L-NAME, GFR decreased in D but not in C rats. There was a greater decrease in RPF in D rats when compared with C animals. An intravenous infusion of GTN induced a modest decrease in sBP in both C and D rats ( P < 0.01). There were no changes in GFR and RPF in D rats, but in the C group, GTN increased RPF ( P < 0.05) with a tendency for a rise in GFR ( P = 0.09). Basal urinary NO2/NO3 excretion was increased in D rats in all experiments. A decrease in urinary NO2/NO3 levels was observed after low-dose L-NAME in D rats, with a similar trend after high-dose L-NAME. NO such changes were observed in C rats. GTN infusion had no effect on urinary NO2/NO3 excretion in D rats but increased urinary NO2/NO3 levels in C rats to levels that were not statistically different from those in D rats. These studies suggest that increased renal production and/or sensitivity to endothelium-derived relaxing factor/NO may play a role in the genesis of diabetic hyperfiltration.

Diabetes-Associated Mesenteric Vascular Hypertrophy Is Attenuated by Angiotensin-Converting Enzyme Inhibition

Abstract: In experimental diabetes, the mesenteric vascular tree undergoes hypertrophy, and this is associated with an increase in mesenteric angiotensin-converting enzyme (ACE) levels. The aim of this study was to determine if inhibition of mesenteric ACE by ACE inhibition would influence diabetes-associated mesenteric vascular hypertrophy. Control or streptozocin-induced diabetic rats were randomized to receive no drug or the ACE inhibitor perindopril. In addition, other diabetic rats were randomized to receive either low-dose insulin that does not alter glycemic control or high-dose insulin, administered as a silastic pellet to achieve euglycemia. After 3 weeks, animals were killed for measurement of mesenteric ACE, vessel weight, and wall:lumen ratio. Diabetes was associated with increased mesenteric ACE levels, increased vessel weight, and an increase in the wall:lumen ratio. ACE inhibition, despite no effect on glycemic control, food intake, urinary urea excretion, or gut weight, prevented the increase in mesenteric ACE levels and attenuated mesenteric vascular hypertrophy as assessed by weight or wall:lumen ratio. The increase in staining by an antibody to the endothelial product, von Willebrand factor, in diabetic rats was totally prevented by perindopril treatment. Euglycemia but not low-dose insulin therapy in the diabetic rats normalized mesenteric vessel ACE, weight, and wall:lumen ratio. In conclusion, ACE inhibition may have a specific role in preventing diabetes-associated vascular hypertrophy, an important process in the genesis of micro- and macrovascular diabetic complications.

Interpretation of randomly amplified polymorphic DNA marker data for fingerprinting sweet potato (Ipomoea batatas L.) genotypes.

Abstract: In this paper we present a method for the generation of randomly amplified polymorphic DNA (RAPD) markers for sweet potato. These were applied to produce genetic fingerprints of six clonal cultivars and to estimate genetic distances between these cultivars. The level of polymorphism within the species was extremely high. From the 36-decamer random primers used, 170 fragments were amplified, of which 132 (77.6%) were polymorphic. Ten primers resulted in no detected amplification. Of the remaining 26 primers for which amplification was achieved, only one did not reveal polymorphism. Six primers used alone enabled the discrimination of all six genotypes. Pattern analysis, which employed both a classification and ordination method, enabled the grouping of cultivars and the identification of primers which gave greatest discrimination among the cultivars.

Microalbuminuria: prognostic and therapeutic implications in diabetes mellitus.

Abstract: Thirty years following the development of the first radioimmunoassay for albumin, microalbuminuria is widely acknowledged as an important predictor of overt nephropathy in patients with Type 1 diabetes and of cardiovascular mortality in Type 2 diabetes. In addition, there is accumulating evidence to suggest that diabetic patients with microalbuminuria may have more advanced retinopathy, higher blood pressure, and worse dyslipidaemia than patients with normal albumin excretion rates. Recent studies have focused on the role of intervention, principally with antihypertensive therapy and intensive glycaemic control, in reducing microalbuminuria. While successful in reducing urinary albumin excretion it remains to be established whether such therapies will be translated into a reduction in renal failure and decreased cardiovascular morbidity and mortality.

Vasopressin V1 and V2 receptors in diabetes mellitus

Abstract: Diabetes mellitus causes hypertonicity, increased plasma arginine vasopressin (AVP), polydipsia, and polyuria. Downregulation of AVP V2 receptors may contribute to the polyuria through diminished V2 receptor-mediated free water retention. After 2 wk of streptozotocin-induced diabetes mellitus, the diabetic rats had raised plasma glucose, AVP, and osmolality levels (P < 0.001) compared with nondiabetic controls (Sham). Insulin treatment (4 U long-acting insulin sc, daily) partially lowered these values (P < 0.01). There was a reduction in the number of renal and hepatic V1 receptors in the diabetic and diabetic+insulin animals compared with the sham animals (P < 0.05). The receptor affinity remained unchanged. In parallel, there was a reduction in maximum AVP-activated total inositol phosphate production in the liver and kidney of the diabetic and diabetic+insulin animals compared with the sham animals (P < 0.05). The density and affinity of renal V2 receptors and AVP-stimulated adenosine 3',5'-cyclic monophosphate production in the diabetic and diabetic+insulin animals were unchanged compared with the sham. These results demonstrate differential regulation of AVP receptors and suggest that downregulation of renal V2 receptors does not contribute to the polyuria of diabetes. In contrast, downregulation of V1 receptors might contribute to diminished V1 receptor-mediated biological responses to AVP seen in diabetes mellitus.

Complementary effects of pravastatin and nicotinic acid in the treatment of combined hyperlipidaemia in diabetic and non-diabetic patients

Abstract: Background: Given that treatment with a single drug is frequently unsuccessful in patients with combined hyperlipidaemia, there is a rationale for the study of regimens using drugs that have complementary therapeutic profiles. We therefore set out to compare the efficacy of a combined pravastatin and nicotinic acid regimen with higher dose monotherapy using either drug in patients with non-insulin-dependent diabetes and in non-diabetic patients with combined hyperlipidaemia.Methods: Forty-four patients with total-cholesterol levels of 6.5 mmol/l or higher and triglyceride levels of 2.5 mmol/l or above were randomly assigned to receive either pravastatin alone (40 mg/day) or nicotinic acid alone (1500 mg/day) for 12 weeks. At the end of this period, the participants received a combination of pravastatin (20 mg/day) and nicotinic acid (1000 mg/day) for a further 12 weeks. The lipid parameters measured included levels of total cholesterol, triglycerides, low-density-lipoprotein (LDL) cholesterol and high-den...

Retrospective analysis of the relationships among the test environments of the Southern Queensland sugarcane breeding programme

Abstract: Repeatability of aspects of genotype by environment (GxE) interactions is an important factor to be assessed in designing more efficient selection programmes Sugar yield data from multi environment trials (METs) which were part of the sugarcane breeding programme in southern Queensland were analysed Data were obtained from 71 environments consisting of trials planted from 1986 to 1989 Retrospective analysis on these data was conducted to assess the repeatability of the clone by environment (CxE) interactions over locations and years This analysis focussed on identifying similarities among test environments in the way they discriminated among clones for sugar yield Analyses of variance and pattern analyses on environments over years based on standardised data were conducted The pattern analyses were done sequentially according to the accumulated data sets over years Squared Euclidean distances among environments were averaged over data sets and years before pattern analyses across the data sets were conducted A graphical methodology was developed to present the results of the cumulative historical analysis CxE interactions of a magnitude which affected selection decisions were present in each data set studied Pattern analyses on cumulative data sets identified environmental groupings that were based on geographical positions Each location generated a different pattern of discrimination among the clones These results emphasised the importance of clone by location (CxL) interactions in southern Queensland and the need to concentrate more on testing across locations than on ratooning ability within a location The classifications identified similarities among ratoon crops within a location, differences among locations and differences between ratoon crops and their plant crop (PC) This suggested that some aspects of CxL and clone by crop-year (CxY) interactions were repeatable across years The potential applications of these results to increase efficiency of the sugarcane breeding programme, such as the possibility of applying indirect selection among environments generating similar discrimination among clones, are discussed

Genotypic variation for stolon and other morphological attributes of white clover (Trifolium repens L.). Populations and their influence on herbage yield in the summer rainfall region of New South Wales

Abstract: A random sample of 60 germplasm accessions from the Australian white clover germplasm collection was characterized in the field at Glen Innes, N.S.W. Genotypic variation for stolon and other morphological attributes was measured in one season. Herbage yield was evaluated over seven seasons to quantify the magnitude of accession-by-season interaction. There were significant (P < 0.01) differences among accessions, seasons, and accession-by-season interactions for herbage yield. Classification was used to group the accessions on their seasonal herbage yield. A summer active group, a winter active group and a group showing autumn activity for herbage yield were identified. There was significant (P < 0.01) variation among accessions for all plant attributes measured and their accession mean repeatability was moderate to high. There were strong genotypic correlations among the morphological attributes. Five of the morphological attributes (stolon density, stolon branching, plant spread, plant height, stolon thickness and leaf length) expressed a strong genotypic correlation with average herbage yield over seven seasons. The genotypic variation estimated for herbage production and plant attributes signifies the potential of the collection to be used as a source of variation for the genetic improvement of productivity and perenniality of white clover for Australian environments.

Microalbuminuria in diabetes.

Abstract: This statement summarises current understanding of the role of microalbuminuria in diabetic nephropathy and describes its natural history and clinical relevance. It outlines core facts and makes recommendations for the management of patients with persistent microalbuminuria.

An investigation of the grain yield adaptation of advanced CIMMYT wheat lines to water stress environments in Queensland. I. Crop physiological analysis

Abstract: Wheat improvement in Australia has made extensive use of germplasm developed by the International Maize and Wheat Improvement Center (CIMMYT). The opportunity for further yield improvement in Queensland was investigated by comparing CIMMYT lines and Queensland cultivars in irrigated and dryland environments at three locations. CIMMYT lines were identified, with greater than 20% yield advantage in individual environments and between 15 and 20% yield advantage over the six environments. The line mean repeatability for yield was moderate (0.492), with the variance component for line by environment (L × E) interaction 4.2 times that for lines. Therefore, while the CIMMYT lines expressed considerable L × E interaction, there was scope for further yield improvement. The water stress differential between the irrigated and dryland environments at the three locations strongly influenced L × E interaction for grain yield. Pre-anthesis water stress generated more L × E interaction for grain yield than post-anthesis stress. At the two locations where pre-anthesis water stress was severe in the dryland environment, there was no association (P > 0.05) between yield under irrigated and dryland conditions. However, at the location where there was little pre-anthesis stress and a degree of post-anthesis stress there was a strong association (P < 0.01) between yield under irrigated and dryland conditions. Grain yield was positively associated with the yield component grain number per unit area in all environments. Grain weight showed little L × E interaction across environments and the majority of L × E interaction for grain yield resulted from L × E interaction associated with grain number per unit area. Grain number per unit area was positively associated with the component grains per fertile tiller but not tiller number per unit area. Grains per fertile tiller was in turn positively associated with total dry matter at anthesis; however, there was no direct association between total dry matter at anthesis and grain number per unit area. There was a weak association between days to anthesis and grain yield in four of the six environments.

An investigation of the grain yield adaptation of advanced CIMMYT wheat lines to water stress environments in Queensland. II. Classification analysis

Abstract: The objective of this study was to use classification methodology to characterize the genotypic variation and line by environment (L × E) interaction for grain yield of a sample of advanced CIMMYT wheat lines and three local check cultivars tested over six Queensland environments. The environments were managed to differ in the magnitude of water stress they imposed on the lines at the critical developmental stage of anthesis. The grouping of lines was based on grain yield. The yield differences among the groups were investigated in terms of yield components and dry matter production and partitioning attributes. Groups of CIMMYT lines which outyielded the two groups which contained the three Queensland cultivars were identified. The yield advantage of the groups of CIMMYT lines decreased with increasing severity of water stress at anthesis and in the environment where the most severe stress was characterized there were no yield differences among the groups of lines. The yield advantage of the groups of CIMMYT lines was generally associated with a higher number of grains per unit area and in some cases a higher grain size. While phenology variation could account for some of the yield differences among the line groups there was considerable yield variation among line groups with similar phenology patterns across the environments. Additional measurements taken on the lines to characterize differences in dry matter production and the partitioning of the dry matter to yield components were not effective in explaining the yield variation among the groups of lines after the effects of phenology were taken into account. While the incidence of the large L × (water-stress) interactions encountered in this study would complicate selection for yield, the identification of groups of advanced CIMMYT lines which outyielded the Queensland cultivars in five of the six environments suggests that the L × (water stress) interactions do not preclude scope for further improvement of grain yield of wheat in Queensland.

Quantitative analysis of the effect of selection history on sugar yield adaptation of sugarcane clones.

Abstract: An objective of the CSR sugarcane breeding programme in Australia was to assess the scope for broadening the genetic base of the commercial sugarcane germ plasm through interspecific hybridization with Saccharum spontaneum clones. The contribution of both selection history and S. spontaneum to sugar yield and its components was investigated in the germ plasm pool assembled. The analysis was conducted on a data-set of 256 clones, consisting of parents and full-sib families generated from 32 biparental crosses, tested in six environments. The minimum number of generations back to S. spontaneum ancestor in the clone's pedigree was used as a germ plasm score. The geographical origin and selection history of each parent and their use in the biparental crosses were used to develop a selection history score for parents and offspring. The variation for seven attributes, cane yield, commercial cane sugar %, sugar yield, stalk number per stool, stalk weight, fibre % and ash % juice was partitioned according to the germ plasm and selection history scores. Significant (P<0.05) clone variation and clone x environment interaction for all attributes was present. The germ plasm scores accounted for a significant (P<0.05) component of the clone variation for all of the attributes except cane yield. There was an increase in sugar yield with an increase in the minimum number of generations back to a S. spontaneum clone. The selection history groups accounted for a high proportion of the variation among parental clones for all of the attributes except cane yield. This suggested that parents were the outcome of strong selection pressure for the commercial cane attributes. However, the selection history groups for the offspring produced by random mating of parents did not account for a high proportion of the variation for the attributes. Using the mixture method of classification we partitioned the 256 clones into five groups for patterns of performance for the seven attributes across the six environments. The five groups emphasized major differences in the patterns of performance for the seven attributes across environments. The distribution of germ plasm and selection history scores in each of the five groups indicated that their patterns of performance were associated with selection history and minimum generations to S. spontaneum. Therefore, both the analysis on selection history and germ plasm scores (extrinsic classification) and the analysis on the mixture method of classification (intrinsic classification) emphasized the influence of selection history on the sugar yield of sugarcane.

Disparate effects of castration on renal structure and function in the streptozotocin diabetic rat.

Abstract: Diabetic children are protected from the complications of diabetes until puberty, suggesting the involvement of a hormonal mechanism. In order to investigate the contribution of sex steroids to the development of diabetic nephropathy, castrated Wistar-Kyoto rats were made diabetic with streptozotocin and compared with intact diabetic rats. In intact rats, 32 weeks of diabetes resulted in hyperfiltration (p = 0.0001) and a marked increase in albuminuria (control, 1.3 x/divided by 1.3 vs diabetes intact, 11.8 x/divided by 1.3 mg/day, p < 0.001). Concomitant structural changes included glomerular basement membrane thickening (diabetes, 199.2 +/- 7.9 vs control, 175.9 +/- 3.9 nm, p = 0.02) and increased mesangial volume (diabetes, 194 +/- 14 vs control, 129 +/- 20 microns 3, p = 0.02). Although castration resulted in blood pressure lowering of 12 mmHg (p = 0.0003), albuminuria increased to the same extent in intact and castrated diabetic rats (castrated diabetic 10.5 x/divided by 1.3 mg/day). Glomerular filtration rate was lower in castrated rats than in intact rats prior to induction of diabetes, but increased similarly with induction of diabetes. Castrated diabetic rats had increased mesangial volume (castrated diabetic, 213 +/- 20 microns 3), but glomerular basement membrane thickness was lower than in intact diabetic rats (castrated diabetic, 179.5 +/- 4.5 nm). Thus, there is a dissociation between basement membrane thickening and albuminuria in this model of diabetic kidney disease. The mechanism of action of castration on glomerular function and structure remains to be elucidated but may relate to indirect effects such as reduction of blood pressure or renal polyol accumulation or a direct effect of sex steroids.