Evaluation of Early Generation Testing in Chickpea1)

Inter-generation correlations between F₂-F₃, F₂-F₄ and F₃-F₄ in six crosses of chickpea were calculated by using individual plant/progeny means. In general, correlation values in case of plant height, seeds per pod and 100-seed weight were higher between F₃ and F₄ than those between F₂ and F₃ and F₂ and F₄. However, inter-generation correlations were mostly non-significant in case of pods per plant and grain yield. These results clearly show that selection in F₃ can be fruitful for seeds per pod and 100-seed weight. However, selection for pods per plant and grain yield in early generations may not show any relationship with later generation performance for these traits.     

Divergent Selection for Heading Date in Barley

Divergent selection for heading time was performed in two F₂ barley population. Five populations were obtained for each cross: F₅ SSD (unselected control), 3E and 3L (from three cycles of selection for earliness or lateness), 2E1L and ZL1E (from two cycles of direct and one of reverse selection). These populations, together with corresponding parents and F₂ generations, were evaluated over two years. The response to selection was 5.6 and 6.5 days inane direction (earlier heading) and 7.7 and 6.7 clays in the other direction (later heading) in the two crosses, respectively. 3E and 3L populations were highly transgressive as compared to their parents. A sizeable amount of genetic variability was still present after two cycles of selection. Heading was probably controlled by a polygenic system with prevailing additive effects and alleles for earliness and earliness somewhat equally distributed in the parents. Selection fur heading time led to significant changes in plant height, yield and kernel weight. Early progenies were higher yielding than lace ones.     

Genetic studies for seed size and grain yield traits in kabuli chickpea

Seed size, determined by 100-seed weight, is an important yield component and trade value trait in kabuli chickpea. In the present investigation, the small seeded kabuli genotype ICC 16644 was crossed with four genotypes (JGK 2, KAK 2, KRIPA and ICC 17109) and F₁, F₂ and F₃ populations were developed to study the gene action involved in seed size and other yield attributing traits. Scaling test and joint scaling test revealed the presence of epistasis for days to first flower, days to maturity, plant height, number of pods per plant, number of seeds per plant, number of seeds per pod, biological yield per plant, grain yield per plant and 100-seed weight. Additive, additive?×?additive and dominance?×?dominance effects were found to govern days to first flower. Days to maturity and plant height were under the control of both the main as well as interaction effects. Number of seeds per pod was predominantly under the control of additive and additive?×?additive effects. For grain yield per plant, additive and dominance?×?dominance effects were significant in the cross ICC 16644?×?KAK 2, whereas, additive?×?additive effects were important in the cross ICC 16644?×?JGK 2. Additive, dominance and epistatic effects influenced seed size. The study emphasized the existence of duplicate epistasis for most of the traits. To explore both additive and non-additive gene actions for phenological traits and yield traits, selection in later generations would be more effective.     

Combining ability of soybean (Glycine max) for low phosphorus tolerance on acidic soils of Western Ethiopia

Determining the gene actions governing the inheritance of traits of interest has paramount importance in designing a breeding approach to improve the progeny populations. This study was undertaken to determine the combining ability of nine selected parental lines in the F₂/F₃ segregating populations for low P tolerance. The experiment was laid out in an alpha lattice design in two locations, that is Mettu and Assossa of Western Ethiopia that are characterized by soils with low P and pH. General combining ability (GCA) effects were highly significant for grain yield, pod length, days to maturity and plant height, while specific combining ability (SCA) effects were highly significant for grain yield, 100-seed weight, pod length and plant height. The parent Hardee-1 was identified as the best general combiner for yield, number of seeds per pod, pod length, plant height and pod number. The results suggest that additive gene action was important for several of the studied traits, implied by significant GCA effect, which might indicate selection for these traits could be effective in later segregating generations.     

A comparison of traditional and haploid-derived breeding populations of oilseed rape (Brassica napus L.) for fatty acid composition of the seed oil

Summary Microspore embryogenesis technology allows plant breeders to efficiently generate homozygous micros-pore-derived breeding populations of oilseed rape (Brassica napus L.) without traditional generations of inbreeding. This study was conducted to compare the frequency distribution of microspore-derived population and single seed descent populations with respect to fatty acids of seed oil. Both microspore-derived populations and single seed descent populations were produced from each of three crosses made between selected parents containing contrasting amount of erucic, oleic, linoleic and linolenic acids. The fatty acid content of F₃ plants derived lines (F₅ seed) developed by single seed descent was compared to that of microspore-derived populations. The means, ranges and distribution pattern of seed fatty acid contents were similar in both populations for each fatty acid studied, although a few heterozygous lines were observed in the single seed descent populations. The results indicated that microspore-derived population form random, homozygous F₁ plant derived gametic arrays for all fatty acids evaluated. Selection for altered fatty acid composition in microspore-derived and single seed descent homozygous populations should be equally efficient, in the absence of linkage of traits investigated.     

Estimation of genetic components of variation for salt tolerance in chickpea using the generation mean analysis

Chickpea (Cicer arietinum L.) is known to be salt-sensitive and in many regions of the world its yields are restricted by salinity. Recent identification of large variation in chickpea yield under salinity, if genetically controlled, offers an opportunity to develop cultivars with improved salt tolerance. Two chickpea land races, ICC 6263 (salt sensitive) and ICC 1431 (salt tolerant), were inter-crossed to study gene action involved in different agronomic traits under saline and control conditions. The generation mean analysis in six populations, viz. P₁, P₂, F₁, F₂, BC₁P₁ and BC₁P₂, revealed significant gene interactions for days to flowering, days to maturity, and stem Na and K concentrations in control and saline treatments, as well as for 100-seed weight under salinity. Seed yield, pods per plant, seeds per plant, and stem Cl concentration were controlled by additive effects under saline conditions. Broad-sense heritability values (>0.5) for most traits were generally higher in saline than in control conditions, whereas the narrow-sense heritability values for yield traits, and stem Na and K concentrations, were lower in saline than control conditions. The influence of the sensitive parent was higher on the expression of different traits; the additive and dominant genes acted in opposite directions which led to lower heritability estimates in early generations. These results indicate that selection for yield under salinity would be more effective in later filial generations after gene fixation.     

Genetic and environmental variation in protein content of rice (Oryza sativa L.)

Summary The inheritance of protein content in rice was studied in the six possible hybrid populations among four varieties: Calrose from the USA, Ku Jung Do from Korea, and Kitaminori and Isao Mochi from Japan. Each population consisted of 100 random lines.Standard unit heritabilities for the correlation of F₂ panicle values with F₃ hill-plot protein values were not significantly different from zero, and variance component heritabilities for F₃ hill-plots were low. Among the F₃ populations significant genetic variation for protein content was observed in the crosses of Ku Jung Do × Calrose, and Kitaminori × Calrose. Genotypic, phenotypic, and environmental estimates of correlations among protein content, kernel weight, heading date, and plant height were examined. High protein content was significantly correlated with light kernels, early heading, and short stature.Low protein heritabilities were tentatively attributed to genotype × year interaction, to an environmental gradient affecting protein content in the field, and to within-line segregation for the early generations tested. It was suggested that selection for protein content be deferred until later generations. However, selection for high protein content may in some cases be incompatible with selection objectives for other traits.     

Repeatability of regression stability indexes for grain yield of oats (Avena sativa L.)

Summary Two lines of descent were established from an F₃ bulk lot of oats (Avena sativa L.) initiated by mixing seeds from approximately 250 crosses. For one line of descent, seeds were radiated with thermal neutrons or X-rays from F₃ through F₆, followed by five generations of bulk propagation. The second was propagated for 10 generations. No artificial selection was practiced in either line of descent. Grain yield data from 20 random strains from each of four generations from the radiated (F₇, F₈, F₉, and F₁₁) and five from the nonradiated (F₃, F₆, F₇, F₈, and F₁₂) line of descent and 20 check cultivars tested in 14 environments were used for estimating regression stability indexes of oat strains.The 14 environments were assigned randomly to two sets of seven, and regression stability indexes were computed for the 180 experimental oat strains for both sets. Intrageneration correlations between regression stability indexes from the two sets of environments ranged from –0.35 to 0.64 (18 d.f.), and only one of nine was significant, indicating poor repeatability for estimates of this statistic computed from different sets of environments.Correlations between regression stability indexes from two sets of environments, one in which the environments varied by soil nitrogen levels and a second in which they varied by soil phosphorus levels, ranged from –0.01 to 0.28, none of which was significant.The relative magnitudes and ranking of the regression stability index values for the oat genotypes were nearly identical when environmental productivity indexes were assessed with any number of check cultivars from 2 to 20.Journal paper No. J-8080 of the Iowa Agriculture and Home Economics Experiment Station. Ames. Iowa. USA 50010. Project 1752.     

Selection for protein content in soybean from single F<Subscript>2</Subscript> seed by near infrared reflectance spectroscopy

Soybean seed averages about 40% protein and is a dominant source of protein in animals and human foods. Increasing protein in soybeans is a goal in soybean breeding programs. Initial selection for protein among progeny from breeding populations is often based on non-destructive Near Infrared Reflectance (NIR) spectroscopy analysis of a 5 g or more seed sample in the F₃ or later generations. NIR spectroscopy analysis for protein on single F₂ seed would allow selection at the earliest possible time and improve selection efficiency for protein content; however this practice has not been evaluated. The objective of this study was to test effectiveness of NIR spectroscopy analysis of single F₂ seeds to select for increased protein content from two populations developed from high and average protein content parents. F₂ seeds from a single F₁ plant of each population showed a normal distribution with transgressive segregation for protein concentration. In both populations, F₃ seeds produced from plants from single F₂ seeds with either low or high protein content were analyzed for protein by NIR spectroscopy. Protein means and ranges of F₃ seed selected from high protein F₂ seeds were higher in protein than F₃ seed from low protein F₂ seeds which produced low means and ranges in protein content. This shows that analysis of single F₂ seed for protein content using NIR spectroscopy was effective in selecting for increased protein in the F₃ generation. Analysis of single F₂ seeds from breeding populations will improve breeding efficiency for protein in soybean breeding programs.     

Inheritance of groat protein percentage in Avena sativa L. × A. Fatua L. Crosses

Summary Gene action and heritability of groat protein percentage were determined in F₁, F₂, and F₃ generations of nine crosses between three Avena sativa L. cultivars and three A. fatua L. selections. Relationships among groat protein percentage, grain yield, and 100-seed weight also were evaluated. The three A. sativa parents were Dal (high grain yield and intermediate groat protein percentage), Goodland (low grain yield and high groat protein percentage), and Stout (high grain yield and low groat protein percentage). The three A. fatua parents were chosen for the study on the basis of vigorous plant growth and high groat protein percentage. The study was conducted at Madison, Wisconsin in 1979 and 1980.There was partial dominance towards low groat protein percentage. Narrow sense heritability estimates for groat protein percentage were low in Dal and Goodland crosses and intermediate in Stout crosses. In the F₂ generation, groat protein percentage was significantly higher in shattering than in nonshattering plants in 1979, but not in 1980. There were significant, positive correlations between groat protein percentage, 100-seed weight, and grain yield in F₁ and F₂ generations, but they were not large numerically. Relationships among these traits were either negative or nonsignificant in the F₃ generation. Although our results indicated that selection for higher groat protein percentage is possible when a low protein A. sativa cultivar is used, most of our simple cross progenies from A. sativa x A. fatua crosses had weak straw and were susceptible to crown rust (Puccinia coronata Cda. var. avenae Fraser and Led.).     

Single and Multiple Traits Selection in a Segregating Population of Wheat, Triticum aestivum L.

The breeding materials used in this study were the F₃, F₄ and F₅-generations of the cross between Giza 158 × Sonora 64 (Triticum aestivum L.). The objective of this study was to compare the relative merits of Smith-Hazel, desired gain selection indices, independent culling levels and single trait selection in improving grain yield, heading date and several agronomic traits. Highly significant differences among F₃ families and a satisfactory genotypic coefficient of variability were obtained for all the traits studied. The genotypic correlations were high between yield and each of spike weight, kernels/spike and spikes; plant, intermediate with 1000 kernel weight and very low with heading date, plant height and spike1 length-After two cycles of selection, the results of the gains realized indicated that the most effective method for improving yield was the Smith-Hazel index (SH₇) of seven traits followed by the desired gain index of seven traits (DG₇), SH₅, independent culling levels, DG₅ and direct selection (or grain yield/plant. Direct selection for heading date, plant height and spike length was the best method for improving these traits, but undesirable correlated responses in the other traits were obtained.     

Evolutionary changes of weed competitive traits in winter wheat composite cross populations in organic and conventional farming systems

Seedling root and shoot growth in hydroponics and allelopathic activity using a bioassay have been studied in very diverse populations of winter wheat grown under either organic or conventional conditions for a number of generations and subjected only to natural selection. The study was conducted on seeds from generation 6 (F₆) and 11 (F₁₁) from three composite cross populations (CCPs) produced by the Organic Research Centre in the UK. Since the F₅ the populations were maintained under organic and conventional conditions in Germany. Two parallel populations were created from each CC, resulting in a total of six organic and six conventional CCPs. The sets of parallel populations showed similar evolutionary trends indicating that the observed changes are related to differences in management rather than chance. Seedling root length and seedling root and shoot weight in the F₁₁ of the organically-managed CCPs were significantly greater than in the organic F₆ CCPs. In the conventionally-managed CCPs no such differences were observed. Both organic and conventional CCPs produced for quality showed higher early root and shoot growth than those produced for yield pointing to genetic differences among population types and highlighting the importance of early vigour for NUE. There were no significant differences in the allelopathic activity of the populations and between generations. The Shannon-Weaver diversity indices were similar for the studied traits in organic and conventional CCPs and hence no major changes in diversity had occurred between F₆ to F₁₁. As changes in plant height were small and weed pressure in the fields low it is concluded that the observed differences are more related to NUE, rather than intra-specific competition for light or the direct effect of increased weed pressure in the organic system.     

Direct and indirect selection for yield in chickpea

Summary The efficiency of indirect selection for seed yield was compared with direct selection for yield per se in chickpea. A total of 2500 single F₂ plants, derived from 50 crosses with 50 plants from each cross, were divided into five sub-populations (SP1 to SP5) of 500 plants each by including 10 plants from each of the 50 crosses. The five sub-populations were advanced upto F₆ by exercising 10% selection intensity for four successive generations for number of pods per plant in SP1, number of seeds per pod in SP2, seed weight in SP3, seed yield in SP4 and random selection in SP5. The efficiency of direct and indirect selection for yield was evaluated by comparing groups of 50 F₆ lines from each sub-population. SP1 and SP3 F₆ lines showed higher mean grain yield than the other three methods. SP1 and SP3 were found to be almost equally efficient in developing F₆ lines which were significantly superior to the check. This suggests that indirect selection for yield via pod number and seed weight is more efficient than direct selection for yield.     

Genetics of Seed Yield and its Components in Common Bean (Phaseolus vulgaris L.) of Middle-American Origin

Genetic variance, heritability, and expected response from selection arc useful in devising alternative methods and criteria of: selection. The objectives of this study were to estimate these for seed yield and its components from 200 F₂: populations involving 80 cultivars and lines of mostly small-seeded dry bush bean (Phaseolus vulgaris L.) of habits growth I, II, and III of Middle-American origin. All cultivars and lines were crossed in eight sets of ten parents each in a Design II mating system. The F₂ populations, without parents, were evaluated in the field in a replicates-in-sets design at two locations in Colombia in 1983. Estimates of additive genetic variance were significant for yield, pods/m², seeds/pod, and seed weight. Interaction with environments was also significant. Values for nonadditive genetic variance were not significant for either yield or yield components. The estimates of narrow sense heritability, based on the F₂ population mean and unbiased by genotype x environment interaction, were 0.21 ± 0.13 for yield. 20 ± 0.13 for pods/m², 0.57 ± 0.13 for seeds/pod, and 0.74 ± 0.15 for seed weight. The expected direct response from selection of the top 20 % of F₂ populations for yield per se would result in a 4.30 % increase in yield with a correlated response of 0.21 % in seed weight. In contrast, the expected gain from direct selection for seed weight would result in a 11.76 % increase in seed weight with a, correlated gain of 0.28 % for yield. Direct selection for pods/m² would decrease yield, seeds/pod and seed weight, while direct selection for seeds/pod would reduce pods/m² and seed weight but increase seed yield by 0.37 %. Data on yield from replicated trials in the early segregating generations could be utilized for identification and selection of promising crosses and families or lines with crosses for dry bean yield improvement.     

Direct and Correlated Responses to Four Cycles of Divergent Selection for Heading Date in Barley*

In order to investigate the direct and correlated responses to selection for heading date in barley, two F₂ populations were subjected to four cycles of divergent selection. For each cross, eight populations selected for earliness (from 1E to 4E) and for lateness, (from 1L to 4L) and four unselected populations (1, 2, 3 and 4 SSD) were obtained and than compared together with parental lines. Selection caused a change greater than one day/cycle in Doth directions, and the cumulative responses were -5.4 and -5,9 days in the direction of earliness, 7.7 and 7,1 days in the opposite direction. Such results suggest that in the two base populations the heading, date is under the control of a polygenic system with prevailing additive effects and a slight directional dominance toward earliness. Early populations showed a reduction of ear moisture and an increase of plant height, ear extrusion, kernel weight and harvest index, whereas late populations showed the opposite changes. Grain yield was linearly reduced by selection for lateness, whereas no substantial change was evidenced in the opposite direction, so that 4E significantly out-yielded 4L in both crosses.     

Inheritance pattern of mungbean yellow mosaic disease resistance and gene action for different traits in mungbean (Vigna radiata (L.) Wilczek) under protected and unprotected field conditions

Understanding of mungbean yellow mosaic disease resistance is crucial to develop resistant varieties to combat worldwide threat of the disease epidemics. This study was aimed to determine nature of disease resistance in terms of number of genes governing it and genetics of related traits. Experimental site was located on 31.43°N and 73.06°E with an elevation of 186 m, and evaluation trials were conducted during spring season due to high disease epidemics in this season. Two contrasting genotypes, that is, NM 6‐68‐2 (resistant) and NM 1‐32‐1 (highly susceptible), were crossed to raise six populations, that is, P₁, P₂, F₁, F₂, BC₁ and BC₂ for evaluation under protected and unprotected field conditions using chi‐square test and generation mean and variance analysis. It was discovered that disease resistance was governed by two major genes with additive effects. Disease resistance can easily be incorporated through backcrossing and direct selection following hybridization. Direct selection should be practised at earlier generation for plant height, chlorophyll contents and number of seeds per pod due to preponderance of additive effects whereas at later generations for seed yield per plant, 100 seed weight, harvest index, number of pods per plant and pod length due to involvement of duplicate epistasis.     

The inheritance of nitrate content in lettuce (Lactuca sativa L.)

Summary The inheritance of nitrate content in lettuce was analysed using 16 F₂ populations and three F₃ populations. Frequency distributions of nitrate content in F₂ and F₃ populations were unimodal and symmetrical, indicating a quantitative inheritance. Both significant positive and negative deviations of the F₂ mean from the mid-parent value were found, indicating dominance or epistasis. Deviations towards low nitrate content were more frequent than deviations in the other direction. Estimates of heritabilities for nitrate content in the F₂ populations ranged from 18% to 69% and were in most cases above 50%. Crosses between low nitrate cultivars did not have lower estimates of heritability in the F₂ than crosses between cultivars with larger differences in nitrate content. In one case a genotype x experiment interaction for nitrate content of parental cultivars was found.Three F₃ populations of crosses between cultivars with low nitrate content were analysed. Estimates of heritabilities for F₃ line means ranged from 78% to 91% and estimates of the genetic standard deviation of nitrate content in unselected advanced generations ranged from 0.24–0.33 g kg^–1. The estimates of heritabilities and of genetic variation in advanced generations offer good prospects of selection of low nitrate genotypes in lettuce. A comparison of efficiency of selection in the F₂ generation and F₃ line selection is made.     

Single plant selection for yield in lentil

Summary Individual plant selection for yield in lentil is problematic at a commercial crop density primarily because of inter-plant entanglement by tendrils. Visual plant selection for yield was compared with random selection in the F₅ at three plant densities (66, 133 and 200 seeds/m²) by an evaluation of F₇ progeny yields over two seasons in two populations of lentil. Random plant sampling was as effective as visual plant selection in isolating high-yielding F₇ lines. The plant density of the selection environment did not affect the response to selection. The correlations between the seed number of selected F₅ plants and the mean yield of their F₇ progenies were r=+–0.26 and –0.06 in two populations, indicating the lack of positive response to plant selection for seed number. The results show that 1) random sampling is the most economic of the methods tested of plant selection for yield and 2) the plant density of the environment for plant selection can be low enough to avoid inter-plant entanglement by tendrils, allowing a focus in plant selection on characters, other than yield, of importance to the breeding program and with a higher heritability than yield.     

Genetic analysis of the high oleic acid content in cultivated sunflower (Helianthus annuus L.)

Summary Sunflower lines breeding true for very high oleic acid content in their oil (average levels higher than 85%) were crossed with standard sunflower lines with mean oleic acid levels of 30%. Analysis of the oil of F₁ seeds indicated dominance for high oleic levels and control of the genotype of the embryo. Segregating generations were obtained selfing heterozygous high oleic BC_nF₁ plants from several generations of a backcrossing program to incorporate the high oleic character to standard inbred lines and testcrossing these plants to low oleic material. Analysis of F₂ and testcrossed seeds showed three kind of segregations, in both F₂ and testcrossed populations, with different proportions of low, intermediate and high oleic types. Genetic analysis of these data supported the hypothesis, that the high oleic character is controlled by three dominant complementary genes OL₁, OL₂ and OL₃. Additional data showing F₁ seeds with intermediate oleic content and segregations for high oleic in progenies of intermediate types, suggest the presence of major factors modifying high oleic acid content.     

亚麻温敏雄性不育系F1、F2的优势分析

通过对以温敏亚麻雄性不育系1S为母本配制的6个杂交组合F1、F2代主要农艺性状和产量性状杂种优势的测定和分析,结果表明：不同杂交组合F1、F2代在株高和工艺长度上的平均优势均表现为负向超父本优势,而各产量性状上的平均优势均表现出很强的正向超父本优势;但与F1代相比,F2代平均优势明显下降。产量性状构成因素平均优势大小顺序为：单株产量＞单株果数＞千粒重＞每果粒数。不同组合间F1、F2代杂种优势表现差异较大,其中1S×黑亚15号组合产量性状的超父本优势最强,F1、F2代均表现出很强的杂种优势。