Recurrent selection in oat for adaptation to diverse environments

In order to test if selection can improve a population's adaptation to diverse environments simultaneously, three cycles of recurrent selection based on grain yield in Iowa, Idaho, and Norway were practiced in an oat (Avena sativaL.) population developed from North American, Scandinavian, and wild species (A. sterilis L.) germplasm sources. Specific objectives were to determine if selection: increased mean yields across environments and within all environments; changed the genetic correlation of yields in different environments; and changed genetic variation for yield within the population. We evaluated 100 to 210 randomly-chosen families from each cycle of selection at three Iowa locations, in Idaho, and in Norway for two years. Grain yield within each location and mean yields across locations increased significantly over cycles of selection. Mean yields across locations expressed as a percent of the original population mean increased at a rate of 2.6% per year. Several families from the third cycle population exhibited both high mean yields across locations and consistently high yields within all locations. Average genetic correlations of yield in different environments were higher in the second cycle than in the original population. A trend of reduced genetic variation and heritability was observed in Iowa only. These results suggest that we successfully improved mean population yield both within and across locations, and yield stability across environments, and in developing families with outstanding adaptation to diverse environments. This revised version was published online in July 2006 with corrections to the Cover Date.     

Correlated responses of fatty acid composition, grain quality, and agronomic traits to nine cycles of recurrent selection for increased oil content in oat

Increases in the groat-oil content of oat (Avena sativa L.) increase the energy value of the grain and improve the feasibility of extracting oat oil for use as a vegetable oil. Nine cycles of recurrent selection for greater groat-oil content conducted in a genetically broad-based oat population resulted in dramatic increases in groat-oil content. Our objectives were todetermine if selection for greater groat-oil content affected fatty acid composition, grain quality traits (test weight and seed weight), or agronomic traits (straw yield, biomass, harvest index, heading date, and height). We evaluated 100 random lines from the base (C0) population and each of the nine selection cycle populations in three environments in order to estimate means, genetic variances, heritabilities, and genotypic and phenotypic correlations of grain quality and agronomic traits. We also evaluated 20 random lines from each population to estimate changes in fatty acid contents. Oleate and stearate contents increased over cycles of selection, as did the ratio of unsaturated to saturated fatty acids. Palmitate, linoleate, and linolenate contents and all grain quality and agronomic traits except harvest index decreased over cycles of selection. There was no evidence for reduced genetic variance or heritability in C9 for any trait, but the genotypic and phenotypic correlations between agronomic traits and oil content fluctuated over cycles. Selection for increased groat-oil content improved oil quality but reduced grain quality and agronomic performance of the population. This revised version was published online in August 2006 with corrections to the Cover Date.     

Responses of different arabica coffee (Coffea arabica L.) clones to varied environmental conditions

Different improved coffee arabica crosseshaving resistance to coffee berry diseaseand leaf rust, plus a standard cultivar,were grown under a range of environmentalconditions in a series of field trials inKenya. The effects of location and year ofproduction and their interactions with theclones were determined for berry yield.These data were used to estimate andcompare methods of analysis of GEI. An AMMImodel, joint regression model and ANOVAwith repeated measurements were used toinvestigate these interactions. The resultsindicated the relative effects of theclones and the environmental conditions,with Meru being the location where therewas greatest discrimination between theclones, probably because it was bettersuited for coffee. Clones,environments and joint regressions combinedaccounted for 31.20% of the interaction,leaving a residual of 68.80%. Significantresidual mean squares showed therelationship between clones andenvironments not to be strictly linear,thus indicating that regression analysisdid not always provide good estimates ofindividual clonal performance acrossenvironments. High correlations wereobtained between mean yield and regressioncoefficients and between ecovalence andmean square deviations as well as thecoefficient of determination. Resultsshowed that the improved clones surpassedthe standard cultivar both in terms ofyield and stability.Different analyses of the various aspectsof genotype response enabled the 21 clonesto be classified into different similaritygroups based on their performance andphenotypic stability as measured by variousstability parameters and the use of biplotsfrom the AMMI analysis.     

Studying the effect of environmental variables on the genotype × environment interaction of tomato

Genotype × environment interaction (GEI) affects marketable fruit yield and average fruit weight of both hybrid and open-pollinated (OP) tomato genotypes. Cultivars vary significantly for marketable fruit yield, with hybrid cultivars having, on average, higher yield than OP cultivars. However, information is scanty on environmental factors affecting the differential response of tomato genotypes across environments. Hence, the aim of this research was to use factorial regression (FR) and partial least squares (PLS) regression, which incorporate external environmental and genotypic covariables directly into the model for interpreting GEI. In this research, data from an FAO multi-environment trial comprising 15 tomato genotypes (7 hybrid and 8 OP) evaluated in 18 locations of Latin America and the Caribbean were analyzed using FR and PLS. Environmental factors such as days to harvest, soil pH, mean temperature (MET), potassium available in the soil, and phosphorus fertilizer accounted for a sizeable portion of GEI for marketable fruit yield, whereas trimming, irrigation, soil organic matter, and nitrogen and phosphorus fertilizers were important environmental covariables for explaining GEI of average fruit weight. Locations with relatively high minimum and mean temperatures favored the marketable fruit yield of OP heat-tolerant lines CL 5915-223 and CL 5915-93. An OP cultivar (Catalina) and a hybrid (Apla) showed average marketable fruit yield across environments, while two hybrids (Sunny and Luxor) exhibited outstanding marketable fruit yield in high yielding locations (due to lower temperatures and higher pH) but a sharp yield loss in poor environments. Two stable hybrid genotypes in high yielding environments, Narita and BHN-39, also showed high and stable yield in average and low yielding environments.     

Response to conventional and organic environment of thirty-six lentil (<Emphasis Type="Italic">Lens culinaris</Emphasis> 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.     

Selection for brown stripe downy mildew resistance in maize

Summary The maize (Zea mays L.) cultivar Makki Safed 1 (MS1) with susceptibility to brown stripe downy mildew (BSDM) caused by Sclerophthora rayssiae var. zeae Payak & Renfro, was subjected to two cycles of mass selection and one cycle of full-sib family selection. Selection was carried out primarily for BSDM resistance.The mass selection was practised under artificial epiphytotic conditions in a disease nursery. Full-sib progenies and performance trials on MS1 and its improved versions were grown in diseased and disease free environments.Mass selection resulted in a significant improvement for resistance to BSDM. A cycle of full-sib selection resulted in an additional improvement for resistance to the disease. The disease rating of the improved version was 1.5 against 4.5 for the original population (scale: 1, highly resistant to 5, highly susceptible). The yield of the improved populations of MS1 was significantly greater than that of MS1 in the disease nursery. In disease free experiments, the improved populations showed almost no yield advantage over MS1. There were also no significant differences between the original population and the improved population after three selection cycles for ear length, ear girth, number of kernel rows per ear, number of kernels per row, 1000-kernel weight, plant height, ear height and days to silk.     

Selection for increased forage yield in alfalfa at different NaCl levels

Summary Alfalfa (Medicago sativa L.) forage yield may be reduced by moderate levels of salinity. Increasing forage yield in saline environments through plant breeding could partially ameliorate this problem. However, prior indirect selection either in cell culture, at germination, or during seedling growth has not resulted in agronomically relevant levels of salt tolerance. This study was conducted to determine whether mean forage yield of alfalfa grown in saline environments could be increased. To reduce the number of possible selection schemes, forage yield data for five harvests from Sonora and its parental cultivar African grown in a greenhouse and irrigated with 0, 30, 60, or 80 mM NaCl were used to simulate one cycle of selection at each NaCl environment. Greatest gains in forage yield were expected under non-saline conditions with decreased gains under saline conditions. Selection based on yield in regrowth harvests was also predicted to be more efficient than that based on seedling harvest. Experimental populations were developed from Sonora and African at each NaCl level using phenotypic selection for increased mean forage yield for harvests 3 to 5. After each of two cycles of selection, forage yield from selected, control (plants selected randomly under non-saline conditions), and parental populations was evaluated at 0, 30, 60, and 80 mM NaCl. Gains in forage yield were observed in African when the selection and evaluation environments were the same, but in Sonora this was observed only at 0 NaCl. Selection at 0 NaCl did not increase forage yield at 60 or 80 mM NaCl in either germplasm source. This suggests that selection for increased forage yield may be successful at low to moderate NaCl levels in germplasm with ample variation for yield when grown in saline environments, while selection for increased forage yield in non-saline conditions may be ineffective.     

Genotype by environment effects and selection for drought tolerance in tropical maize. I. Two mode pattern analysis of yield

Ten trials evaluated the performance of several late tropical maize populations (La Posta Sequía, Pool 26 Sequía and Tuxpeño Sequía) selected for tolerance to drought during flowering and grain filling and also for yield potential. Families (S₁ or full-sib) had been selected recurrently for six to eight years on an index of traits. Pattern (clustering and ordination) analysis was used to analyse the relative performance of entries that included cycles of selection for drought tolerance in the populations and non-drought tolerant checks. Mean environment (E) yields ranged from 1.0 to 10.4 t ha^-1. Analysis of variance showed that 97.9% of the total sums of squares was accounted for by E, and that, of the remaining sums of squares the G × E (genotype by environment interaction) was almost 3 times that of the contribution of G alone. Cluster analysis separated the checks, the earlier maturing drought tolerant entries and the later maturing drought tolerant entries. This was verified by principal component (PC) analysis of the G × E matrix. Grouping of the environments (i.e. based on entry performance), resulted in the separation of different types of droughts, and of medium and high yielding well-watered environments. The patterns of discrimination observed indicated that the yield gains under drought would have been unlikely to occur if selection had been done only in well-watered environments. Within each population, selection improved broad adaptation (higher mean yield) to both drought and well-watered environments and cycles of selection ‘jumped’ from non-drought-tolerant to drought-tolerant groups as their specific adaptation to drought environments increased.     

Mixed models including environmental covariables for studying QTL by environment interaction

The study of the phenotypic responses of a set of genotypes in their dependence on the environment has always been an important area of research in plant breeding. Non-parallelism of those responses is called genotype by environment interaction (GEI). GEI especially affects plant breeding strategies, when the phenotypic superiority of genotypes changes in relation to the environment. The study of the genetic basis of GEI involves the modelling of quantitative trait locus (QTL) expression in its dependence on environmental factors. We present a modelling framework for studying the interaction between QTL and environment, using regression models in a mixed model context. We integrate regression models for QTL main effect expression with factorial regression models for genotype by environment interaction, and, in addition, take care to model adequately the residual genetic variation. Factorial regression models describe GEI as differential genotypic sensitivity to one or more environmental covariables. We show how factorial regression models can be generalized to make also QTL expression dependent on environmental covariables. As an illustrative example, we reanalyzed yield data from the North American Barley Genome Project. QTL by environment interaction for yield, as identified at the 2H chromosome could be described as QTL expression in relation to the magnitude of the temperature range during heading. This revised version was published online in July 2006 with corrections to the Cover Date.     

Conditions under which selection for mean productivity, tolerance to environmental stress, or stability should be used to improve yield across a range of contrasting environments

Computer simulations were conducted to determine whether conclusions obtained for the special case of a single stress and a single non-stress environment apply to the more general situation where a population of testing environments includes a range of stress and non-stress environments. Mean productivity, tolerance to environmental stress, and a regression coefficient stability parameter of genotypes across environments were compared to determine conditions under which these selection criteria should be used to improve yield across a range of contrasting environments. The results obtained from a worked example based on the single crosses from a 7 × 7 diallel cross in maize and the simulation experiment showed that the conclusions of Rosielle & Hamblin (1981) cannot be directly applied to a population of stress and non-stress environments. Selection for mean productivity should increase yield in both stress and non-stress environments unless the genetic variance in stress environments is more than double that in non-stress environments, and the genetic correlation between yields in contrasting environments is highly negative. Mean productivity and tolerance were shown to be positively correlated even if the genetic variance in stress environments is half that in non-stress environments. Genotypes with a high tolerance to stress were found to have low regression coefficient stability parameters, even when a range of stress and non-stress environments was used. This revised version was published online in July 2006 with corrections to the Cover Date.     

Specific and General Adaptation and Yield Stability of Wheat (Triticum aestivum L.) Genotypes

Mean grain yield performance of 12 wheat and one triticale genotypes were measured at four locations over four consecutive years, using a randomized complete block design with four replications. The genotypes used were commercial cultivars and advanced lines from different wheat breeding projects located in different areas in Iran. Two locations were in semiarid regions and the other two locations in the temperate zones. The combined analysis of variance indicated highly significant genotype-environment (GE) interactions. From combinations of locations and years three sets of environments were generated. Set I and set II, each, consisted of eight environments (two locations and four years) representing semiarid and temperature environments, respectively. Set III consisted of 16 environments including both semiarid and temperate conditions. Set I and set II were used to measure specific adaptation of the genotypes while set III was employed for measuring general adaptation. The methods of Eberhart and Russell (1966) were used for partitioning GE interactions. The mean square associated with the heterogeneity of regression was highly significant under all sets of environments. These observations indicated that a major part of GE interaction could be accounted for by differences in the regression of the individual genotypes. All the genotypes had significant regression mean square under set I, set II, and set III environments, with the exception of two genotypes under set II. However, mean yields, regression coefficients, and the mean squares associated with deviation from regression greatly varied over the sets of environments. Only three genotypes, a commercial cultivar and two new advanced line, were identified as having specific adaptation and yield stability to semiarid environments. Among all the genotypes, only a commercial cultivar was identified as adapted and stable to temperate conditions. Two of the three genotypes which were adapted to semiarid environments also showed general adaptation to set III environments. However, the mean yield of these two genotypes under semiarid conditions (set I) were significantly greater than their respective mean yields under set III environments. Thus, wider adaptability was compensated by lower mean yield. The present study indicates that, while a wide range of environments is necessary and recommended for measuring general adaptation reactions and yield stability of various genotypes, one should not ignore the possibility of finding some genotypes with specific adaptation to specific environments and thus maximizing yield production. Stable genotypes with general of specific adaptation should be utilized in breeding projects in order to develop even more desirable lines.     

Correlated response to recurrent selection for groat-oil content in oats

Summary One hundred random oat (Avena sativa L.) lines from a base (C₀) and each of three populations (C₁, C₂, and C₃) improved for groat (caryopsis) oil content by phenotypic recurrent selection were evaluated for correlated changes in several unselected agronomic traits. In addition, the parents of the base population and four check varieties were evaluated for the same traits. Phenotypic recurrent selection for high groat-oil content resulted in no significant correlated response in mean expression of any trait. Mean grain yield, biomass, groat yield, and harvest index of the improved populations were equal or superior to the mean of the parents and, with the exception of harvest index, equivalent to the mean of the check varieties. Mean test weight and seed weight of all populations were lower than for parents or check varieties. Selection for high groat-oil content caused a decline in genotypic variance for test weight and groat fraction, but reductions in genotypic variance for heading date and plant height may have resulted from culling for good agronomic type. Broad-sense heritability remained moderate to high for all traits except groat fraction. Phenotypic and genotypic correlation coefficients revealed negative, though mostly nonsignificant, relationships between groat-oil content and several traits, which may reflect a purported bioenergetic limitation to increasing groat-oil content in oats. Oil yield, however, was positively correlated with grain and groat yield, groat fraction, biomass, and harvest index. Results suggest that development of high-oil oat cultivars with current levels of production traits via phenotypic recurrent selection is possible.Journal Paper no. J-13038 of the Iowa Agric. and Home Econ. Exp. Stn., Ames, IA 50011. Project 2447.     

Specific adaptation of barley varieties in different locations in Ethiopia

Barley is one of the most important cereal crops grown for the livelihoods of the poor farmers of Tigray region in northern Ethiopia. As many low input and marginal environments it has benefited less from the yield increases achieved by modern breeding. This has been largely attributed due to genotype × environment intraction (GEI). To investigate the causes of GEI, ten barley varieties including local checks (two farmers developed varieties, four modern varieties and three rare local varieties) were tested over 21 environments. Participatory methods were applied to sample an adequate number of environments spanning the regional diversity. The yielding ability and stability of the varieties was graphically depicted by GGE and PLSR biplot. There were two major groups of environments, the central and northern highlands, the latter with less rainfall and poorer soils. Rainfall per month and total nitrogen level were the environmental variables that differentiated these two groups. In Tigray, rainfall in June and July were negatively correlated with yield, reflecting waterlogging problems. The different varieties were either specifically or widely adapted across the two environments. The variety ‘Himblil’, originating in Tigray, was the highest yielding and also most stable in the region of origin. However, it was inferior to improved varieties (Shege and Dimtu) at high yield levels. The association of earliness with grain yield indicates that the trait can be effectively manipulated within the existing materials. We recommend breeding for drought/water logging resistance based on selection in the target environment as the best strategy to provide stable and high yielding varieties for Tigray.     

Genotype by environment interactions in barley (<Emphasis Type="Italic">Hordeum</Emphasis><Emphasis Type="Italic"> vulgare</Emphasis> L.): different responses of landraces,recombinant inbred lines and varieties to Mediterranean environment

Genotype-by-environment interactions (GEIs) can affect breeding progress because they often complicate the evaluation and selection of superior genotypes. This drawback can be reduced by gaining insights into GEI processes and genotype adaptation. Here, we have studied the GEIs over a set of 24 barley genotypes that were grown across six environments (location-by-year combinations) in Sardinia, Italy. Three groups of genotypes were analysed: barley landraces (LANs), recombinant inbred lines (RILs), and commercial varieties (VARs). The additive main effects and multiplicative interaction (AMMI) model was used for data analysis, and results evidenced no significant differences in grain yield averages for the 24 genotypes. However, there was a relevant GEI for yield mainly between two of the six environments (one characterised by warm pre-anthesis period and high spring rainfalls, and the other characterised by opposite features) and two groups of genotypes (VAR and LAN). Moreover, a negative trade-off between yield levels of genotypes was seen when the barley genotypes were grown in the contrasting environments. Overall, intermediate GEI levels were seen for RILs in comparison to LANs and VARs, and some of the RILs provided valuable yield levels (e.g. RILs 23 and 52). The results thus show the potential usefulness of LANs as a genetic resource for breeding, e.g. to obtain genotypes adapted to Mediterranean environments, such as the RILs analysed in this study. Most of the actual work was carried out when the first author was a PhD student in ‘Agro-meteorology and ecophysiology of agricultural and forest systems’ and she was affiliated to Dipartimento di Scienze Agronomiche e Genetica Vegetale Agraria, Università degli Studi di Sassari, Via E. de Nicola, Sassari 07100, Italy.     

Genotype-by-environment effects on the performance of recombinant inbred lines of Virginia-type peanut

Peanut (Arachis hypogaea L.) is known to be sensitive to genotype-by-environment interaction (GEI) effects. While previous studies have reported strong GEI effects on peanut yield, most of those studies involved a relatively small number of unrelated genotypes. We examined the extent of GEI effects in elite Virginia-type peanut using a large population of recombinant inbreed lines (RILs). Two-hundred-sixty-six F₇ RILs derived from different cultivars were grown in three environments. Net pod yield (NPY) was evaluated along with 11 other traits. ANOVA revealed that genotype and environment affected all of the examined traits, except for the triplet trait. The substantial influence of the environment was also demonstrated in a genetic-parameter analysis, in which the phenotypic variation coefficients were almost double those for genotypic variation. Still, relatively high heritability and genetic gain values were found for pod weight and NPY. Since NPY is the main target for selection, it was analyzed further. Path analysis showed that NPY is most directly influenced by pod weight and the shelling ratio. A significant GEI effect on NPY was identified using an AMMI model that described 42.7% of the total variation. This GEI component was subjected to a principal components analysis, which confirmed that the variability due to the different environments was greater than the variability that could be attributed to the different genotypes. Yet, several lines had stable yields across environments. These results demonstrate the importance of multi-location phenotyping for QTL analyses and crop improvement in peanut.     

Phenotypic,genotypic and environmental correlation in tomato (Lycopersicon esculentum)

Summary Twelve inbred lines of tomato and their 132 hybrids (reciprocals were considered separately) were studied in four environments: glasshouse and open air, with and without plastic cover. Nine characters were recorded and the phenotypic and environmental correlations between them were obtained within environments and for the complete set of data. Characters showing the highest phenotypic correlation with yield were fruits per cluster and earliness in harvesting, but neither of them is useful for indirect selection for yield. To the contrary, leaves between racemes can be used when selecting for fruits per cluster. Environmental correlations were generally low, excepting total yield in fruits per cluster.Broad sense heritabilities were obtained, which were rather high for fruit weight, locules per fruit, fruits per cluster and leaves between clusters. Some cases in which phenotypic correlations were rather constant for the different environments in spite of the great differences recorded for the genotypic correlation coefficients, are explained because of the great weight (i.e., considering heritabilities) of environmental correlations on phenotypic correlations.     

Grain-yield characteristics of oat lines surviving uniform and shuttle selection strategies

Summary Four selection strategies were used on four sets of oat lines to select for grain yield. Two of these used uniform environments whereby sequential selection of the high-yielding lines occurred in continuous high- or continuous low-productivity environments. These are referred to as high and low uniform selection strategies, respectively. The other two selection strategies were conducted by sequential selection of the high-yielding lines in alternating high- and low-productivity environments. They are referred to as high and low shuttle selection strategies, respectively, with high and low designating the productivity of the first environment in the sequence. After three or four cycles of selection, the surviving lines and a random sample from each set were evaluated for mean grain yield, grain yield response to improving environments, and stability of grain yield, in a range of environments typical of oat production on Iowa farms.Grain yield and regression response for all selection strategies, when calculated across all sets of lines, were significantly greater than corresponding values for random samples. Stability was unchanged. The uniform-high and uniform-low strategies gave the greatest and the smallest gains in mean grain yield, respectively, with the shuttle strategies giving intermediate gains. Shuttle selection in predominantly high-productivity environments increased grain yield more than shuttle selection in predominantly low-productivity environments. The uniform-strategy followed by the shuttle-high strategy identified entries with superior performance in high productivity environments. Increased gain in mean grain yield across all environments was associated with increased number of selection cycles conducted in high-productivity environments.Journal Paper No. J-15252 of the Iowa Agric. and Home Econ. Exp. Stn., Ames, Iowa 50011, USA. Project No. 2447.     

Genotype × environment interactions and simultaneous selection for high oil yield and stability in rainfed warm areas rapeseed (<Emphasis Type="Italic">Brassica napus</Emphasis> L.) from Iran

Partitioning of the genotypes by environment interaction (GEI) is important in order to determine the nature of the GEI. The objectives of this study were to assess the presence and nature of GEI for nine agronomic traits of rapeseed cultivars, and to identify cultivars with favorable levels of stable oil production. Nine rapeseed cultivars, including seven open pollinated and two hybrids, Hyola308 and Hyola401, were grown in ten environments under rain-fed warm areas of Iran. The GEI was significant for all traits and was partitioned into components representing heterogeneity due to environmental index and the remainder of the GEI. Among the all traits with a highly significant heterogeneity, the largest amount of heterogeneity removed from the GEI was for seeds per pod and seed weight. We found GEIs for both oil content and seed yield were largely influenced by differences in correlations among pairs of cultivars (86.8 and 71.4% of the GEI sum of squares, respectively), suggesting that crossover GEIs (i.e., change in genotype rankings among environments) are present. The mean correlation of each cultivar with all other cultivars ([`(r)]<sub>ii<sup>￠</sup></sub> \bar{r}_{{ii^{\prime}}} ) ranged from 0.53 to 0.83 for oil content and 0.86 to 0.96 for seed yield. A comparison was done of the significance of Sh-σ<sub>i</sub><sup>2</sup> (stability variance derived from total GEI) and Sh-S<sub>i</sub><sup>2</sup> (adjusted stability variance derived from residual GEI) assignable to each genotype for oil content and seed and oil yield. Based on Sh-σ<sub>i</sub><sup>2</sup>, three cultivars were unstable for oil content, whereas six cultivars were unstable for seed and oil yield. The removal of heterogeneity revealed that one unstable cultivar for oil content and three unstable cultivars for oil yield were judged to be stable. All cultivars with [`(r)]_ii^￠ \bar{r}_{{ii^{\prime } }}  ≤ 0.63 were labeled unstable for oil content, whereas all with [`(r)]<sub>ii<sup>￠</sup></sub> \bar{r}_{{ii^{\prime } }}  ≤ 0.94 were considered unstable for seed yield. The relationships between [`(r)]_ii^￠ \bar{r}_{{ii^{\prime } }} and Sh-σ_i² were significant (P < 0.01) for oil content and seed yield. The results of rank correlation coefficients showed significant positive correlations of Yield-Stability statistic (YS_i) with oil content and oil yield. Cultivars such as Option500 and Hyola401 were identified as having stable, high levels to seed yield and oil content.     

Relationships among economic characters in lentil

Summary There are several reports of the association among lentil characters based on a few, relatively similar lines grown in single environments. Their results have often been inconsistent because of inadequate sampling of genotypes and environments. This study examined associations between economic characters in lentil over a wide range of genetic material and environments in West Asia. The first part of the study concerned correlations within large samples from the world lentil collection grown in two seasons, and the second part covered a smaller sample of genetic material from the collection sown over a wider range of conditions.The results showed similar phenotypic correlations over two seasons, contrasting in rainfall, in the world lentil collection. Similar genetic and phenotypic correlations were also shown by the smaller sample of germplasm over 10 environments. These results indicated low importance of covariance due to environmental and genotype-environment interaction effects. Seed yield was positively correlated with straw yield, indicating selection for either character will increase the other trait. The correlation between seed protein content and seed yield was small and negative, while the correlation of protein with straw yield was positive in sign. This suggests that the current ICARDA goals of selection for high seed and straw yield will not have a major correlated effect on seed protein content. There was a strong positive correlation between seed size and cooking time (r=0.96), therefore seed size can be used to predict cooking time.     

Selection indices for sugarcane improvement at three stages of selection

Summary Selection indices at different stages of selection were estimated for a biparental mating population of sugarcane (Saccharum officinarum L.). At the seedling stage indices constructed from primary characters are better than selection for yield alone. At the clonal stage the superiority of index selection over direct selection was marginal. In the seedling stage, selection based on index can lead to better selection efficiency in succeeding clonal stages. This was confirmed by a sample study.