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Notizen: Summary Adaptation reactions of 33 genotypes of safflower Carthamus tinctorius L. were studied under 7 different climatic conditions. The genotpyes were divided into two sets. Set I consisted of 15 genotpyes selected from the local populations. Set II had 15 introduced and local varieties. Three control genotpyes, Ute, Ferio, and Local Arak, were common to both sets. Genotpye-environment interaction was not significant for Set I but it was highly significant for Set II. Three environmental indices were obtained and used in the adaptation analyses of the genotpyes in Set II. One of the environmental indices, designated EI, was dependent on the genotypes of Set II. The other two indices, designated EI-1 and EI-2, were independent of the genotpyes of Set II. The methods of Eberhart and Russell (1966) were used in analyses of adaptation by Index EI and the methods of Freeman and Perkins (1971) for Indices EI-1 and EI-2. The mean square associated with genotype-environment interaction was partitioned into two components, heterogeneity of regression and its residual, under EI-1 and EI-2. Both components were highly significant for both cases. However, the mean square of heterogeneity of regression was equal to its residual under EI-1 and even smaller than its residual under EI-2. These observations indicate that a major part of genotpye-environment interaction can not be accounted for by differences in the regressions of the individual genotypes. As well as this overall test, individual regression analyses for single genotypes were also considered. None of the genotypes had significant regression mean square under EI-1. Only two introduced genotypes had significant regression mean squares when EI-2 was used. The overall test of equality of the slopes of the regression for the genotypes of Set II was rejected at the 1% level under EI. This test indicated that genotypes of Set II were significantly different in their association with the EI. The significant differences among the genotypes of Set II were also shown by an F test of the pooled deviation mean square divided by the pooled error mean square. Individual regression analyses for single genotpyes of Set II were considered under EI. Mixed adaptation reactions were observed for different genotypes. Among 18 genotypes of Set II, regression mean squares were significant for only 10 genotpyes. Therefore, it appeared that the dependent environmental indices are more useful than the independent environmental indices when statistical theory of regression is used in the analysis of adaptation. Observations in the present study were not in agreement with the hypothesis that the relation between the performance of different genotypes in the various environments and some measure of these environments is linear or nearly so. Among the 12 introduced genotypes, only one, Ute, was identified as stable and high-yielding. Among the 15 selected from the locally adapted populations, eleven did not differ significantly from Ute in mean yield but four exceeded Ute significantly in mean productivity. The present study thus indicates that the Iranian safflower breeding project has been successful in identifying genotpyes which give high and stable yields under diverse environmental conditions. It does not indicate that introduced and exotic germplasms are unimportant in the breeding projects; it is quite possible that still more desirable genotypes can be developed by incorporating introduced genetic variability into the local germplasm.

Notizen: Abstract Carbon isotope discrimination (Δ) has been suggested as a selection criterion to improve transpiration efficiency (W) in bread wheat (Triticum aestivum L.). Cultivars ‘Chinese Spring’ with low A (high W) and ‘Yecora Rojo’ with high Δ (low W) were crossed to develop F1, F2, BC1, and BC2 populations for genetic analysis of Δ and other agronomic characters under well-watered (wet) and water-stressed (dry) field conditions. Significant variation was observed among the generations for Δ only under the wet environment. Generation x irrigation interactions were not significant for Δ. Generation means analysis indicated that additive gene action is of primary importance in the expression of Δ under nonstress conditions. Dominance gene action was also detected for Δ, and the direction of dominance was toward higher values of Δ. The broad-sense and the narrow-sense heritabilities for Δ were 61 % and 57% under the wet conditions, but were 48% and 12% under the draughted conditions, respectively. The narrow-sense heritabilities for grain yield, above-ground dry matter, and harvest index were 36%, 39%, and 60% under the wet conditions and 21%, 44%, and 20% under dry conditions, respectively. The significant additive genetic variation and moderate estimate of the narrow-sense heritability observed for Δ indicated that selection under wet environments should be effective in changing Δ in spring bread wheat.

Notizen: Summary Computer simulation was used to compare Hallauer's cyclic single cross selection (CSCS) with reciprocal recurrent selection (RRS). Three epistatic and three non-epistatic models with 60 loci determining a single character provided the genetic base. The rate of advance over seven cycles was always greater for CSCS than for RRS on either a cycle or generation basis. No genetic conditions were found where CSCS failed to respond. The advantages of CSCS increases as the proportion of non-additive genetic variance increases. Genetic advance of the hybrid population was shown to result from the joint effects of an average change in gene frequency and complementary effects (nicking) of selection. Nicking effects accounted for most of the advance for some starting conditions. RRS generally had higher selection limits with no epistasis or low gene frequency of the dominant allele. CSCS generally had higher limits with epistasis or high frequency of the dominant allele. We suggested that CSCS begin with divergent genetic populations and strong selection intensity for three cycles. Final selection of superior single crosses was indicated when the lines were completely inbred.

Notizen: Abstract There is renewed interest in wheat landraces as important sources of genetic variation for agronomic characters. Fifty-three pure lines of bread wheat (Triticum aestivum L.) derived from seven landraces collected from southeastern Iran were used to estimate genetic variation and heritability for 13 developmental and quantitative characters. Path-analysis was used to partition the genetic correlations between grain yield and six grain yield-related traits. Mean values of landraces were also compared with three improved cultivars from California and Iran. Genotypic differences among the landraces and among the pure lines collected from the landraces were highly significant for all characters considered. Compared with the modern cultivars, the landrace genotypes were, on average, later in days to heading and taller than the cultivars but had lower values for number of grains per spike, 1000-grain weight, grain yield and harvest index. Some landrace genotypes were similar to the modern cultivars for grain yield. Moderate to high genetic variation was displayed by number of grains per spike, number of spikes per plant, 1000-grain weight, and harvest index. The heritability estimates ranged from 59% for grain yield to 99% for days to anthesis. Expected genetic advance (as % of the mean) was ≈34% for number of spikes per plant, number of grains per spike, and 1000-grain weight. Days to heading and to anthesis correlated positively with number of spikes per plant, shoot biomass, and straw biomass but negatively with number of grains per spike and harvest index. The strong direct effect of number of spikes per plant on grain yield was completely counterbalanced by its indirect negative effects via number of grains per spike and 1000-grain weight. Number of grains per spike and 1000-grain weight were positively correlated with grain yield, and they had large direct effects. These two characters, however, were negatively correlated and exhibited a substantial counterbalance effect via one another and via number of spikes per plant. The landraces could be improved by intercrossing the promising genotypes identified in this study, with simultaneous selection for earliness, fewer number of spikes per plant, greater number of grains per spike and heavier grains. For further improvement, crossing programs between the landraces and introduced germplasm may be necessary.

Notizen: Abstract Little is known of genes that influence root development and drought resistance in bread wheat. The evapotranspiration efficiency (ETE = ratio of vegetative dry weight to total water used) of spring bread wheat tall landrace ‘Chinese Spring’ is relatively high. We used 42 ditelosomic and dimonotelosomic lines of Chinese Spring to identify chromosome arms that influence plant characters and ETE. Multiple regression analyses indicated that 96% of the variation observed in ETE was explained by variation in vegetative dry weight and total water used. Variation in plant height, number of spikes (tillers), root dry weight and shoot dry weight (excluding grains) together explained 88% of the variation observed in plant vegetative dry weight. Chromosome arms involved in expression of days to heading and maturity, plant height, number of spikes, root dry weight, shoot dry weight, number of grains, grain weight, and carbon isotope discrimination (Δ) were identified. Specifically, both arms of chromosome 2A, the long arm of chromosome 2B, and the short arm of chromosome 2D might carry genes with positive effects on number of spikes, root dry weight, and shoot dry weight. None of the aneuploids produced grain yield greater than Chinese Spring. The short arms of chromosomes 6A and 4D might carry genes that suppress Δ. Chromosome 1D might carry genes that increase relative water loss. The chromosome arms belonging to homoeologous group 2 might carry genes with positive effects on ETE. The genetic basis of ETE in modern wheats could be broadened by substituting specific chromosome arms of landrace wheats carrying desired characters into their genomes.

Notizen: Summary Nine pure lines of bread wheat collected from landraces of southwestern Iran and one local Iranian cultivar from the same area were used to estimate genetic variation and heritability for 12 developmental and yield component characters. Path-analysis was used to partition the genetic correlations between some of the characters into direct and indirect effects. Mean values for these lines were also compared with those of five improved cultivars from Iran and California. The goal of the experiment is to breed improved landraces and/or modern cultivars for areas of low input agriculture in southern California, southwestern Iran, and regions with similar environmental and agronomic conditions. Moderate genetic variation was displayed by the number of effective heads per plant, number of grains per head, and grain weight in the landrace genotypes. The heritability estimates ranged from 43 to 97%. Expected genetic advance with selection of the highest 5%, expressed as percent of the mean, was around 20% for number of heads per plant, number of grains per head, and 1000-grain weight. Days to booting, to heading, and to anthesis were positively correlated but none of them were significantly associated with days to maturity. Plant height had a negative genetic correlation with number of grains per head, 1000-grain weight, grain yield, and harvest index. The genetic correlation between number of heads per plant and number of grains per head, 1000-grain weight, and harvest index was also significantly negative. Harvest index had a negative genetic correlation with days to booting, to maturity, plant height, number of heads per plant, and straw yield and a positive correlation with number of grains per head, 1000-grain weight, and grain yield. Days to maturity, plant height, number of heads per plant, number of grains per head, 1000-grain weight, and harvest index each had a positive direct effect on grain yield. The first two characters exhibited the highest and lowest direct effects, respectively. The positive direct effects of days to maturity, plant height, and number of heads per plant, however, were partially or completely counter-balanced by their strong negative indirect effects through number of grains per head, 1000-grain weight, and harvest index. Pathanalysis indicated that late and tall landrace genotypes tend to produce more heads per plant, but with fewer number of grains per head, smaller grains, and lower harvest index. Comparisons between the local lines and the improved cultivars revealed that, in general, the former were much taller and produced a larger number of non-effective tillers. Mean number of grains per head, grain weight, harvest index, and grain yield of local lines were smaller than those of improved cultivars. Our observations indicate that the landraces could be improved by selecting for shorter genotypes with smaller numbers of tillers per plant, but with larger numbers of grains per head and heavier grains.

Notizen: Abstract Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), is an important pest of wheat (Triticum aestivum L.) in the United States of America. Developing adapted wheat cultivars with genetic resistance to RWA is an effective control strategy. Genetic studies were conducted to determine the mode of inheritance of gene(s) conferring resistance to RWA in an Iranian landrace wheat line, G 5864. For the inheritance study, G 5864 was crossed with the susceptible wheats ‘Yecora Rojo’ and ND 2375. Seedlings of F1, reciprocal F1, F2, BC1 to the susceptible parent (BCS), and BC1 to the resistant parent (BCR) were screened for RWA reaction. Several phenotypic segregation ratios were tested in the F2 populations for goodness of fit; the 9:3:3:1 ratio (resistant: rolled leaves: stunted plants: susceptible) was an acceptable fit in all cases. Thus, resistance in G 5864 seemed to be controlled by two independent dominant genes with additive gene effects. The allelic relationships of gene(s) in this line with genes in other resistant lines, PI 137739 (Dn1), PI 262660 (Dn2), PI 372129 (Dn4), PI 294994 (Dn5), and PI 243781 (Dn6), were also studied. Segregation patterns observed in G 5864 × resistant (R × R) F2 populations were inconclusive. However, no susceptible plants were observed in these F2 populations. If previous reports concerning the number of resistance genes present in the other resistant lines are correct, then given the high manifestation of resistance observed in G 5864, and given the absence of susceptible plants in the R × R F2 populations, it is indicated that RWA resistance in G 5864 is either controlled by different alleles at the same loci as the other resistance genes, or that G 5864 shares a resistance gene with each of the other resistant lines.