Polygenic Inheritance of Bracts Number in Sunflower

The inheritance of the studied traits in cotton breeding studies directs the selection method, and it is crucial to identify suitable parents and promising hybrids to be transferred to the next generations. Ten F2 hybrid populations generated by line × tester mating design were compared with their parents and F1 hybrids for seed cotton yield per plant, ginning out-turn, fiber length, fiber fineness, and fiber strength. The general/specific combining ability variance ratio in F1 and results of a minimum norm quadratic unbiased estimation indicated that the dominant gene effect for seed cotton yield, additive gene effect for ginning out-turn and fiber fineness, both dominant and additive gene effects for fiber length and fiber strength were greater. Significant correlation coefficients between F1 and F2 hybrid performance and general combining ability effects for ginning our-turn and fiber length confirmed additive gene effects in the control of these traits. Although F2 populations were higher than their parents and lower than F1 populations regarding seed cotton yield and fiber strength, F2 populations had the finest fibers. As a result of the combined evaluation of average performance, general combining ability effects, and predicted additive effects for parents, Fiona and Gloria for ginning out-turn, İpek-607 for fiber length, Özbek-100 for fiber fineness, and Flash for fiber strength were the best combiners. Claudia × Özbek-100 was determined as the most promising F1 hybrid combination for both hybrid variety breeding and transfer to the next generations in terms of all traits. Gloria × Flash, Claudia × Özbek-100, and Gloria × Özbek-100 hybrid combinations within the F2 populations should be transferred to the next generations by applying the bulk method.

New Technologies, Tools and Approaches for Improving Crop Breeding

Most of the current QTL mapping methods are developed for the backcross and F2 populations. The inter-crossed F3 population is also popular and has been well devised in genetic study. As the F3 population can provide more recombinants than the backcross and F2 populations, it can facilitate the detection of closely linked QTL. In this paper, we propose a statistical model to estimate the effects and positions of QTL for the F3 population by considering the differences in the genome structure between the F3 and F2 populations. As the genotypes of QTL are usually unknown, the statistical model is a finite mixture model. By treating the mixture model as an incomplete data problem, the EM algorithm is implemented to obtain the maximum likelihood estimates of the parameters. Simulations were used to illustrate the performance of the proposed method and evaluate the relative efficiency in the F3 population (as comparing to that of the F2 population) in QTL mapping under several factors, such as sample size, genetic distance between QTL (and markers), the proportion of trait variance contributed by QTL (i.e. heritability). It is found that the QTL mapping by using the F3 population is more powerful and precise in separating closely linked QTL and in estimating the parameters as compare to the use of the F2 population, especially for small sample size, close genetic distance and low heritability. The paper can help outline a strategy of detecting tightly linked QTL for the advanced intercross populations to improve the resolution of genetic architecture of quantitative traits.

The cost of F1 hybrid soft red winter wheat (Triticum aestivum L.) seed developed with chemical hybridizing agents is from two to three times that of conventionally bred cultivars. Unlike pureline cultivars, it is not possible to save seed from a hybrid wheat crop to produce an identical crop the next year. Costly F1 hybrid seed has led to speculation about using F2 seed for subsequent crop production. The objective of this research was to evaluate this production alternative by comparing F1 hybrids with their respective F2 populations and parents for a number of agronomic traits. Three families (each consisting of an F1, a derived F2, and the original parents) were grown in four environments in Maryland during 1986 and 1987. Treatments were planted in a randomized complete block design in a split‐plot arrangement of treatments with families as whole plots and generations as split plots. A significant 8.3% yield decline was found for the F2 populations compared with the F1 hybrids averaged over the environments and families. However, seven of the 12 family‐environment combinations had no significant differences for yield between the F1 and F2 populations. High parent heterosis of 4.5% for yield was observed for the hybrids averaged over all families and environments. Only four of 12 family‐environment combinations were found to have significant high‐parent heterosis. Although significant differences among family members existed for other agronomic traits studied (i.e., spike emergence date, tiller length and variability, test weight, harvest moisture content, and milling and baking quality), none of these differences was judged undesirable for the production of an F2 population. It is concluded that an F2 population, derived from an F1 hybrid wheat, could be successfully used by a farmer for crop production given current hybrid seed costs and market prices. Success is dependent upon the hybrid from which the F2 population is derived and the environment in which it is grown. Furthermore, the low levels of high‐parent heterosis suggested that pureline cultivars probably would provide the most economical results for a farmer at the present time.

Univariate and multivariate analyses were used to identify associations between eight enzyme marker loci and 11 quantitative traits of maize (Zea mays L.). The material analyzed included inbred lines Wf9 and Pa405, single-cross hybrid Wf9 X Pa405, and the F2 generation of the selfed single-cross hybrid. Each enzyme locus assayed was associated with at least one quantitative trait, and all quantitative traits were associated with genotypes at particular enzyme loci. Significant associations also were found between the level of heterozygosity per individual and nine of 11 quantitative traits. The total contribution to heterosis, for seed yield per plant, of genes linked with the eight enzyme loci, was 27% of the F2 mean and 18% of the difference in mean between the F1 hybrid and the inbred parents. Genes linked with Glu1 accounted for nearly one third of the total dominance effect detected by the eight enzyme loci. The chromosome segments marked by loci with significant effects on seed yield were markedly overdominant. The large heterotic effects of chromosome segments marked by particular loci suggest that enzyme loci could be used to help transfer genes responsible for heterosis to inbred lines. We conclude that analyses of additional inbred lines, F1 hybrids, and F2 populations in more environments will halp identify specific associations between enzyme loci, or chromosome segments which they mark, and important agronomic traits.

A study was undertaken to evaluate the genetic variability among gamma-irradiation-induced sunflower mutants for partial resistance to phoma black stem, caused by Phoma macdonaldii, and to identify putative molecular markers associated with partial resistance. A population of 60 mutant lines and the original line AS613 were evaluated with an aggressive French isolate of P. macdonaldii (MP6) under controlled conditions. Mutants with partial resistance to phoma black stem were identified. Variance in partial resistance and molecular markers, generated with 17 amplified fragment length polymorphism (AFLP) primer combinations, were estimated. Genetic analysis revealed that partial resistance in the mutant line M6-54-1 was controlled by recessive gene(s). The F1 hybrid (developed by crossing M6-54-1 with a susceptible inbred ENSAT-B4) was, however, significantly less susceptible than the susceptible parent, indicating that the difference between the F1 hybrid and its parents in reaction to phoma black stem cannot be fully explained by the recessive gene model. Dominance between alleles (epistasis) caused reduced susceptibility in the F1 progeny, which were also clearly reflected in distributions of phenotypic reactions of F2 and backcross seedlings. Generation mean analysis confirmed that epistatic effects contributed significantly to genetic variation in phoma black stem resistance in M6-54-1. Using multiple regression analysis, eight AFLP markers associated with partial resistance to phoma black stem were identified. Predicted reactions of all mutants to the disease based on their marker profiles were not significantly different from the observed values. The same AFLP primer combinations were used to map quantitative trait loci in the F2 population and F3 families, and one AFLP marker (E33M61-11) was found to be tightly linked to phoma black stem susceptibility.

Despite being one of the important characteristics in determining pasta quality in durum wheat (Triticum turgidum ssp. durum), there is no direct report on inheritance of β-carotene concentration. The objectives of this study were to determine the inheritance of β-carotene concentration and the number of genes involved in six crosses of durum. For the cross PDW-233 (P1) × Bhalegaon-4 (P2), F1, F2, BCP1 and BCP2 populations were developed. For all other crosses, only the F1 and F2 populations were developed. β-carotene concentration was determined for all populations and parents of each cross grown at Hol, Maharastra, India. The cross PDW-233 × Bhalegaon-4 was also evaluated at Dharwad, Karnataka, India. Low β-carotene concentration was partially dominant in most of the crosses. Broad sense heritability was 67 and 91% at Dharwad and Hol, respectively, for the cross PDW-233 × Bhalegaon-4 and varied from 74 to 93% for the other five crosses indicating the presence of additive gene effects. The frequency distributions of the trait in the F2 populations were not normal and were skewed towards the lower parent. Segregation of β-carotene concentration in the six F2 populations indicated that at least two major genes and two or three minor genes with modifying effects govern the trait. Analysis of variance indicated that environment had comparatively little influence on the trait and this should allow for easy selection. The joint scaling test revealed additive × additive, additive × dominance and dominance × dominance epistatic interactions in the cross PDW-233 × Bhalegaon-4.

1. Se realizó un estudio en el algodón "Upland" con el propositó de investigar el grado de dominancia, el número de genes envueltos, la contribución estimada por cada par de genes, la naturaleza de la acción génica y la heritabilidad del largo de fibra. Fueron también objeto de estudio las relaciones entre el largo de fibra y varios caracteres de la fibra, especialmente perímetro, espesor de la pared y fineza, todos los cuales son de importancia comercial. 2. Para este estudio se seleccionaron las variedades Florida 1377 y D.P.L. 45-867, las cuales representan los extremos en la variación del largo de fibra en el algodón "Upland". Estas variedades difieren ampliamente la una de la otra con respecto al perímetro y al espesor de la pared de la fibra. Después de efectuados los cruces entre estas variedades, las generaciones F1 y F2 fueron sembradas simultáneamente con las generaciones progenitoras. 3. Se midió a mano el largo de fibra del algodón de cada una de las 1388 plantas de la F2, de las 24 plantas de la F1, de las 26 plantas de la variedad Florida 1377 y de las 41 plantas de la variedad D.P.L. 45-867 4. El largo de fibra medio en la Florida 1377 fué de 0.61 pulgada y el de la D.P.L. 45-867 fué de 1.37 pulgadas. La diferencia media fué, por tanto, de 0.76 pulgadas. El largo de fibra medio en las generaciones F1 y F2 fué de 1.06 pulgadas. La segregación en la F2 fué típica de un carácter cuantitativo. La distribución de frecuencia comprendió un gran número de clases (19), señal de que había un gran número de genes segregando para esta característica. Se encontró una diferencia significativa entre el promedio de los progenitores y los de las generaciones F1 y F2, lo cual indica dominancia parcial de fibra larga sobre corta. Esta misma indicación se obtiene al examinar la distribución de la F2. Esta condición puede entorpecer la selección para fibra larga en la F2. El número mínimo de genes envueltos, estimado por la fórmula de Castle- Right, fué 9.38. A base de este estimado, se calculó que la contribución promedio por cada par de genes en la determinación del largo de fibra fué de 0.08 pulgadas. Los datos obtenidos no permitieron determinar si la acción génica envuelta era aritmética o geométrica. El largo de fibra tuvo un alto grado de heritabilidad, que alcanzó 85 por ciento en la F2. 5. Se estudiaron las relaciones que hay entre el largo de fibra y el perímetro, espesor de la pared y la fineza. Entre el largo y el perímetro de la fibra se obtuvo una correlación de —0.319, la cual resultó ser significativa. Aparentemente, el combinar fibra larga y perímetro grande en una misma variedad resultará algo difícil.

Late flowering sometimes occurs in F1 hybrids between rice varieties (Oryza sativa L.), although the parental varieties show similar days-to-flowering (DTF). The genetic architecture prompting the occurrence of such late flowering is poorly understood. To clarify the genetic architecture of late flowering in F1 hybrids from a cross between rice varieties, 'Koshihikari' and 'IR64', we performed quantitative trait locus (QTL) analysis using an F2 population (selfed progeny of an F1 plant), in which heterozygous genotypes should segregate in a certain proportion in a Mendelian manner. The QTL analysis detected three significant QTLs. At one QTL (putatively Heading date 1), the 'Koshihikari' allele increased DTF, and at the other two QTLs (putatively Heading date 6 and Oryza sativa Pseudo-Response Regulator 37/Heading date 2), the 'IR64' alleles increased DTF. All alleles at these three QTLs showed partial dominance. The combination of the QTLs explained 82.2% of the total phenotypic variance of DTF in the F2 population, with contribution from epistasis between QTLs. There was no difference between DTFs of F1 hybrids and heterozygous genotypes for the three QTLs. Our results demonstrated that the complementary effects accompanied by epistasis of at least three QTLs were responsible for late flowering in F1 hybrids.

To determine the levels of heterosis in F1 hybrids, four current pea (Pisum sativum L.) cultivars from southern Australia were used as female parents and crossed with 18 introduced genotypes. The 22 parents, 72 F1 hybrids and, depending on the environment, either 54 or all 72 F2 families were grown in replicated plots in four environments. Grain yield, total dry matter, harvest index, branches per plant, pods per plant, seeds per pod, hundred seed weight, plant height, onset of flowering and flowering periods were evaluated. For both the F1 and F2 generation, heterosis was determined as the superiority over the mid-parent and also over the better parent. In addition, the superiority over the best commercial cultivar was calculated. Most hybrids were higher yielding than their mid-parent but were less stable in yield across environments. Four F1 hybrids were significantly higher yielding than the best parent, by up to 26%. There were significant correlations between F1 hybrid and mid-parent value for plant height, pods per plant and hundred seed weight but not for yield. Overall, grain yield heterosis was mainly due to more pods per plant in the hybrids. The level of heterosis for yield in a poor yielding environment was higher than that in a high yielding one. Both additive and non-additive gene effects were important in the expression of all studied traits. The average level of heterosis for grain yield and total dry matter in the F2 population was half of that in F1 hybrids. The low level of inbreeding depression from the F1 to the F2 generation suggested that epistatic gene action also contributed to the expression of grain yield. Some F2 populations maintained the high yield levels of the corresponding F1 hybrids.

  The inheritance of resistance to head bug (Eurystylus oldi) was studied in ten populations of sorghum derived from crossing three susceptible sorghum elite varieties (ICSV 111, ICSV 112 and ICSV 400), and two resistant sorghum varieties (Malisor 84-7 and KSV 4). Parental lines, F1 and F2 populations were sown on a Randomized Complete Block Design in two replications. Artificial infestation of head bugs on sorghum was employed in carrying out the experiment. Samples of 5 panicles each from every artificially infested plot were observed. Resistance to head bug in sorghum seems to be controlled by a single pair of recessive genes in Malisor 84-7 x ICSV 400 and Malisor 84-7 x ICSV 111. The cross, KSV 4 x ICSV 112 appeared to be controlled by double recessive pair of genes. Head bug population affects quality of grains rather than the yield produced. There is a negative correlation (-0.095) between head bug population and the germination percentage of the grain. Positive relationship exists between glume size and head bug population, which suggests that longer glumes harbour more head bug.   Key words: Head bug (Eurystylus oldi), Infestation, Anthesis, Resistance, Susceptible, Inheritance. &nbsp

Alleles of the inducible nitric oxide synthase locus (Nos2) cosegregated highly significantly (P < 0.0001) with blood pressure in an F2 population [F2(S x MNS), n = 171] derived from a cross of inbred Dahl salt-sensitive (S) rats with Milan normotensive rats (MNS). In contrast, alleles at the constitutive brain nitric oxide synthase locus (Nos1) did not cosegregate with blood pressure in several F2 populations. Nos2 was mapped on rat chromosome 10. Nine genetic markers, including the angiotensin-converting enzyme (Ace) and Nos2 loci spanning roughly 46 cM on rat chromosome 10, all cosegregated strongly with blood pressure in the F2(S x MNS) population. Nos2 showed the highest LOD score of 6.3. Ace and Nos2 are 30 cM apart. In an F2 population [F2(S x WKY), n = 159] derived from a cross of S rats with Wistar-Kyoto (WKY) rats, Nos2 alleles did (P = 0.0070), but Ace alleles did not (P = 0.91), cosegregate with blood pressure. We conclude that the Nos2 locus rather than the Nos1 locus is a candidate for influencing blood pressure in the S rat. There are probably two separate but linked quantitative trait loci (QTL) for blood pressure on rat chromosome 10, one marked by Ace and the other marked by Nos2. In F2(S x MNS) functionally variant alleles at both QTL influence blood pressure, but in F2(S x WKY) only the QTL marked by Nos2 is segregating alleles influencing blood pressure.

The heritability values of sugar contents in strawberry fruit were estimated from the parent-offspring regression of seven F1 populations, obtained from a common pollen parent 'Toyonoka'. The estimated heritability values for total sugar, hexose (fructose plus glucose) and sucrose contents were 0.568, 1.153 and 0.004, respectively; high additive genetic effects were found in total sugar and hexose contents. Therefore, an optimum method for breeding strawberry cultivars that contain large amounts of sugar and hexose may be to use parental lines with high total sugar and hexose contents, and to select F1 individuals with high sugar contents. The low heritability of sucrose content in this experiment may be attributable to the cultural practices and environmental factors because harvesting strawberry fruits took a long time.

ObjectiveCombining ability analysis forms the basis for selecting suitable parents and hybrid combinations. The performance of combining ability is influenced significantly by environmental conditions. Therefore, it is essential to comprehensively evaluate advantageous parents and hybrid combinations through multi-year experiments.MethodsIn this study, seven parental lines were crossed using a complete diallel design [p(p−1)/2], producing 21 combinations. Yield-related traits, including boll number per plant, seed cotton per plant, lint cotton per plant, boll weight, lint percentage, and seed index, were measured in the parental lines and their hybrid F1 generations over two consecutive years. Combining ability and interannual stability were subsequently analysed.ResultsCotton yield traits were significantly influenced by environmental factors such as weather, temperature, and soil conditions. Interannual variation and genotype-year interactions contributed substantially to variation in yield traits. The interactions between year and both general combining ability (GCA) and specific combining ability (SCA) were significant or highly significant, with GCA stability being relatively low. Yield traits were governed by both additive and dominance genetic effects, with additive effects being predominant. The comparison coefficients for stability of GCA for lint cotton per plant and seed cotton per plant across years were relatively high (51.372% and 55.187%, respectively), whereas SCA stability coefficients for lint percentage and boll weight were comparatively lower (44.986% and 48.645%, respectively). Parent Xinluzao62 (Parent 7) exhibited both high and stable GCA and can therefore be recommended as a backbone parent for yield improvement. Additionally, eight hybrid F1 combinations showing excellent and stable SCA were identified, suitable for use as dominant combinations.ConclusionThe GCA and SCA for yield traits in upland cotton are notably influenced by environmental factors such as climate and soil. Yield performance varies considerably across different years and locations. Therefore, selections based on multi-year and multi-location trials provide more reliable results, offering a solid theoretical basis for developing high-yield cotton varieties.

The aim of the work was to study the patterns of inheritance of the trait of high oleic content in the F2 and generation BC1 of winter rapeseed in order to obtain new knowledge about the genetic mechanisms of the high oleic acid contents in seed oil and scientifically based approaches to the development of the breeding germplasm with a high content of oleic acid. The studies were carried out in 2021– 2022 in the field. The material was reciprocal F1 hybrids from crossings of the high-oleic line VN-1848 (79.3%) and two lines from the cultivars Sarmat and Selegor of VNIIMK breeding with the traditional content of oleic acid in seed oil – 62.1 and 60.5%, respectively. Hybrids F1 were used to produce BC1 seeds. F2 and BC1 generations were obtained in 2022. In F2 hybrids, splitting into two phenotypic classes was observed in a ratio of 15 : 1. The first one included lines with oleic acid content in seed oil less than 79%, the second one – lines with high rates of this trait at the level or higher than the parental high-oleic component (18 : 1 &gt; 79%). This proposes the control of a trait by two pairs of non-allelic genes with an additive effect. As a result of backcrosses using the high-oleic lines VN-1848 as the maternal component, 55 genotypes with a low content of oleic acid (18 : 1 &lt; 79%) and 11 genotypes with high levels of this trait (18 : 1 &gt; 79%) were obtained. This corresponded to a splitting ratio of 3 : 1. All χ2 values turned out to be less than 3.8, p &gt; 0.05.The results of the studies confirm our assumption that the oleic acid content in seed oil is controlled by two pairs of non-allelic genes; the manifestation of this trait in plants is observed only when all alleles are in a homozygous recessive state.