Genetic variation,heritability and correlations of agro-morphological traits in tall fescue (<Emphasis Type="Italic">Festuca arundinacea</Emphasis> Schreb.)

To study the genetic variation, heritability and genetic correlations of some agro-morphological traits in tall fescue, 25 parents from a genetically broad-base germplasm were polycrossed and their respective half-sib families were generated. Clonally propagated parents and their half-sib families were grown as spaced single plants using a randomized complete-block design with three replications, and observed for seven traits in 2006 and 2007. The estimates of broad-sense heritability were moderate to high for the traits studied. Narrow-sense heritability estimates from analyses of progenies and from regression of half-sib (HS) progenies on parents suggested that genetic variation for these traits was largely controlled by additive gene action. Association of dry matter yield (DMY) with plant height, number of fertile shoot, curbs width and spring growth was positive and significant. With the exception of number of days to pollination, correlation coefficients of the traits between the parents and offspring were not significant. Based on parent-offspring regression, genetic gain from selection for DMY was high, demonstrating genetic potential for improving this trait. Overall, there was high genetic variation and moderate heritability for most traits in the tall fescue populations evaluated. In conclusion, to improve herbage yield, selection would be more effective based on forage yield components.     

Genetic characterization of an Italian Giant Reed (Arundo donax L.) clones collection: exploiting clonal selection

This study is the first report of combining ability and heterosis for important vitamins and antioxidant plant pigments in cauliflower. Five CMS lines were crossed with 8 male fertile lines in line × tester design to develop 40 hybrids. These hybrids along with parental lines were evaluated for different vitamins and anti-oxidant pigments to reveal extent of heterosis and genetic combining ability. The CMS line Ogu12A was good general combiner (gca effect) and Ogu16A was poor general combiner for most of the important traits under study. Most of the heterotic hybrid combinations were associated high specific combing ability (sca effect). However, gca effect was also important in developing quality heterotic hybrids. The proportions of $\sigma_{\text{gca}}^{ 2} /\sigma_{\text{sca}}^{2}$ were less than unity in all the cases indicating the role of non-additive gene action for most of the traits. Highest number of heterotic hybrids in positive direction was recorded for ascorbic acid content followed by anthocyanin content. The accumulated average heterosis of the 40 hybrids was in positive direction for ascorbic acid, anthocyanin and lycopene concentration whereas it was in negative direction for carotenoids and chlorophyll pigments. Very high heterosis for ascorbic acid, anthocyanin and carotenoids in cauliflower indicated the scope for development of F₁ hybrids with higher concentration of these vitamins and anti-oxidant pigments. It is possible to develop heterotic hybrids for different vitamins and anti-oxidant plant pigments through selection of parental lines based on desirable genetic combing ability.     

Genetic and phenotypic parameters in common bean segregant populations from intra and inter-gene pool crosses of elite lines

This study aimed compare segregating populations of common bean (Phaseolus vulgaris L.) derived from intra and inter-gene pool crosses of elite lines by estimates of some genetic and phenotypic parameters. Four elite lines highly adapted to Brazilian conditions were used (ESAL 686 and BRS Radiante: Andean gene pool; BRSMG Majestoso and BRS Valente: Mesoamerican gene pool). Two intra-gene pool (“A”: ESAL 686 × BRS Radiante; “B”: BRS Valente × BRSMG Majestoso) and two inter-gene pool segregant populations (“C”: BRS Radiante × BRSMG Majestoso and “D”: ESAL 686 × BRS Valente) were obtained. The parental lines, the cultivar Pérola and fifty-five F_2:3 progenies of each population were evaluated in the rainy season 2010/2011, and afterwards (F_2:4) in dry season of 2011. Estimates of genetic variance ( $\hat{\sigma }_{G}^{2}$ ), heritability on a progeny mean basis ( $\hat{h}_{p}^{2}$ ), heritability realized ( $\hat{h}_{R}^{2}$ ) and gain expected from selection (GS) were obtained at joint analysis, in each population, for the traits number of days to flowering (DTF), 100 seed weight (100SW) and seed yield (SYD). It was observed that for all traits, inter-gene pool crosses (“C” and “D”) showed higher estimates of $\hat{\sigma }_{G}^{2}$ , $\hat{h}_{p}^{2}$ , $\hat{h}_{R}^{2}$ and GS than intra-gene pool crosses (“A” and “B”), which indicates more genetic variability. However, for SYD, the higher variability was associated to lower average of seed yield, showing that even utilizing adapted parents the inter-gene pool crosses are inferior to crosses between lines of the same gene pool.     

Breeding of high yielding and dwarf oil palm planting materials using Deli <Emphasis Type="Italic">dura</Emphasis> × Nigerian <Emphasis Type="Italic">pisifera</Emphasis> population

In practice, progeny and individual palm selection are believed to be the most suitable breeding approach for improvement of quantitative traits in oil palm because their phenotypic expressions are strongly influenced by abiotic factors. Therefore progeny selection approach was applied in this study for the selection of high fresh fruit bunch (FFB) and dwarf oil palm planting materials. Cross between Deli dura and Nigerian pisifera resulted into 34 D × P full sib progenies with 1036 seedlings. For six consecutive years, data were collected on yield and yield component traits, while vegetative traits were recorded once. Bi-parental analysis was carried out using analysis of variance, followed by progenies mean comparison, variance components, heritabilities and cluster analysis. Highly significant (P ≤ 0.01) progeny effect was recorded in this study and this had a pronounced effect on the expression of all the quantitative traits. Progenies performance of FFB varied significantly and it ranged from 166.49 to 220.06 kg/palm/year (kg/p/yr) with trial mean of 192.93 kg/p/yr. Palm height after 8 years of field planting ranged from 1.67 to 2.78 m (control cross) with trial mean of 2.12 m. Broad sense heritability (\({\text{h}}_{\text{B}}^{2}\)) was found to be very low (<17.60%) for all the yield traits, however this parameter was high for vegetative traits with palm height having \({\text{h}}_{\text{B}}^{2}\) of 90%. Cluster analysis based on all the quantitative traits grouped all the 34 DP progenies into nine distinct clusters. From this study, five progenies (DP3, DP4, DP5, DP8 and DP24) were identified to be high yielding and dwarf palms compare to trial mean. At density of 140 palm/ha, they will produce FFB of 28.63–30.81 t/ha and average of 29.69 t/ha which is about 27.15% higher in FFB when compared to the current planting material with FFB of 23.35 t/ha. In addition, the selected progenies possessed average annual palm increment of 29.82 cm/yr with range of 26 and 32.5 cm/yr which was 57.33% shorter than the current planting material with palm height increment of 45–75 cm/yr.     

Analysis of quantitative variability for seed yield and related characters in Lotus corniculatus L. cv. Leo

Summary Quantitative variability for seed yield and six other characters was analysed in Lotus corniculatus L. cv. Leo. The material consisted of 144 polycross progenies and 100 parents.Wide variability existed for all characters. The characters with the greatest variability were seed yield, forage grading and plant height. The polycross progeny test was employed to study the general combining ability of the parents. Highly significant differences existed for all seven characters under study.Parent-offspring genotypic and phenotypic correlations were high and significant for all characters except genotypic correlations for seed yield and seeds per pod. High h² values (broad sense) were obtained for seed size and days to flowering. Traits with moderate to high h² were seed yield (71% in parents, 64% in progenies), plant height, forage grading, and seeds per pod. The character pods per inflorescence had the lowest h².Positive estimates of % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabiGaaiaacaqabeaadaqaaqaaaOqaaiqabo8agaqcaK% aaavaabeqaceaaaeaacaqGYaaabaGaaeiraaaaaaa!3A89!\[{\text{\hat \sigma }}\begin{array}{*{20}c} {\text{2}} \\ {\text{D}} \\ \end{array} \] were obtained only for seed size. The ratio of dominance variance to additive variance indicated partial dominance for this character. Except for seed yield, in all other cases these estimates had very high sampling errors. In all cases except pods per inflorescence and seeds per pod high positive estimates of % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabiGaaiaacaqabeaadaqaaqaaaOqaaiqbeo8aZzaaja% qbaeqabiqaaaqcaauaaiaaikdaaKaaGeaacaqGbbaaaaaa!3B30!\[\hat \sigma \begin{array}{*{20}c} 2 \\ {\text{A}} \\ \end{array} \] were obtained.The data indicated that it may be possible to simultaneously improve seed yield and maintain forage yield. Seed yield had positive and significant associations with seed size, seeds per pod and pods per inflorescence. The associations of days to flowering with forage grading (negative) and with pods per inflorescence (positive) were also significant.     

Genetic potential to improve seed and forage yield simultaneously in smooth bromegrass under water deficit conditions

This study was conducted to assess genetic potential of smooth bromegrass for water stress and to identify the association among different seed and forage production related traits. Thirty-six genotypes were clonally propagated and evaluated in the field under two moisture environments (normal irrigation and water stress) during 2013–2015. High variation was observed among genotypes for all of the measured traits. Water stress had negative effects on seed yield and its components and reduced genotypic variation of measured traits. On average, water stress reduced seed and forage yield by 38 and 14%, respectively. Genetic coefficient of variation for seed yield and its components was higher under stress, providing opportunities for a greater selection differential. The estimates of heritability were higher in normal condition than water stress condition for all of the evaluated traits, which is advantageous for successful selection. Moreover, the majority of seed yield components had higher heritability estimates than seed yield. The higher heritability estimates of some seed yield components, compared to SYP, suggests a potential for indirect selection. The results showed that selection for both forage and seed yield is possible simultaneously in normal irrigation as well as in water stress environment. Genotypes 7, 8, 26 and 27 had high forage yield, while genotypes 23 and 27 had high seed yield under both normal irrigation and water stress condition. Three genotypes ranked among the top three for both seed and forage yield and under both normal irrigation and water stress condition. They are promising parents for further use in developing improved cultivars by cross-breeding.     

Productivity,persistence and traits related to drought tolerance in smooth bromegrass

This study was conducted to evaluate drought tolerance and persistence in a germplasm of smooth bromegrass and association of forage productivity with different traits. Thirty‐six genotypes of smooth bromegrass were clonally propagated and evaluated under two soil moisture environments for three years (2013–2015). High genotypic variation was observed among genotypes for all the measured traits. Drought stress decreased mean values for traits related to productivity. Also, the long‐term stress for three years reduced the persistence of plants. Results indicated that indirect selection based on components of forage yield, which had high heritability and high correlation with yield, would be more effective to improve drought tolerance in this germplasm. The results of principal component analysis showed that there was a negative relationship between phenological traits with the persistence‐related traits and yield production. This suggests that selection for earliness may indirectly promote persistent genotypes. The results showed that some Hungarian genotypes are valuable gene sources for persistence. The most persistent genotypes from both groups (Iranian and foreign) were identified using the biplot method. These genotypes may be useful for the development of populations for future studies.     

Correlations between the stability and adaptability statistics of popcorn cultivars

In plant breeding, correlations between the statistics of stability and adaptability of popcorn cultivars are not yet well understood. Therefore, the objectives of the present experiment was to investigate the correlations between s_di² \sigma_{\rm di}^{2} and b_i \beta_{\rm i} from Eberhart and Russell, ω_i from Wricke, \textS_\texti⁽¹⁾ {\text{S}}_{\text{i}}^{(1)} , \textS_\texti⁽²⁾ {\text{S}}_{\text{i}}^{(2)} and \textS_\texti⁽³⁾ {\text{S}}_{\text{i}}^{(3)} from Huehn, P_i from Lin and Binns and the rank-sum from Kang, and indicate the most reliable method for selecting popcorn cultivars. These statistics were estimated by data of crop yield from 19 Brazilian genotypes under 21 environments and popping expansion under 16 environments. The ω_i, \textS_\texti⁽¹⁾ {\text{S}}_{\text{i}}^{(1)} , \textS_\texti⁽²⁾ {\text{S}}_{\text{i}}^{(2)} , \textS_\texti⁽³⁾ {\text{S}}_{\text{i}}^{(3)} and s_di² \sigma_{\rm di}^{2} were positively and significantly correlated indicating that just one in these five statistics is sufficient for selecting stable genotypes although they were not correlated with the means of crop yield and popping expansion. The b_i \beta_{\rm i} was negatively and significantly correlated with P_i for crop yield indicating that the most adaptable genotypes tend to have the lowest estimates of P_i. Although P_i was not correlated with ω_i, \textS_\texti⁽¹⁾ {\text{S}}_{\text{i}}^{(1)} , \textS_\texti⁽²⁾ {\text{S}}_{\text{i}}^{(2)} , \textS_\texti⁽³⁾ {\text{S}}_{\text{i}}^{(3)} , or s_di² \sigma_{\rm di}^{2} statistics, it displayed positive correlation with the Index 1 (crop yield and popping expansion +  \textS_\texti⁽¹⁾ {\text{S}}_{\text{i}}^{(1)} rank) and Index 2 (crop yield and popping expansion + W_i) indicating that superior popcorn genotypes are also stable. Finally, both P_i and the rank-sum are useful statistics in breeding programmes where crop yield, popping expansion and stability are essential traits for selecting genotypes.     

Genetic parameters for growth traits and stem-straightness in <Emphasis Type="Italic">Eucalyptus urophylla</Emphasis> × <Emphasis Type="Italic">E. camaldulensis</Emphasis> hybrids from a reciprocal mating design

An inter-specific hybrid breeding program involving Eucalyptus urophylla (U) and Eucalyptus camaldulensis (C) was implemented in order to provide genotypes better adapted to southern China with improved growth rate, stem-straightness and wind-resistance. A trial involving 36 reciprocal crosses from six parents each of C and U that had been preselected for superior growth and stem-straightness was established at a site in Luokeng in Guangdong province. Ten, pure-species families using the hybrid parents as open-pollinated female parents were included as controls. Survival and growth traits at ages 2 and 8.3 years and stem-straightness at age 2 years were assessed. Inter-specific hybrids generally performed better than the pure species in terms of survival, growth traits and stem-straightness. Female U by male C crosses generally outperformed those involving male U and female C. Further indication of the significant reciprocal effect was supported by negative and low correlations between paired groups of full-sibs that differed only in the direction of the cross. Components of female additive genetic variance and narrow-sense heritability calculated from this estimate (\(\sigma_{\rm Af}^{2}\) and \(h_{\rm f}^{2}\)), respectively) were generally higher than those of the male \(\left( {\sigma_{\rm Am,}^{2} h_{\rm m}^{2} } \right)\), providing evidence for maternal effects. The narrow-sense heritability (h²) estimates based on general hybridizing ability for growth traits and stem-straightness were generally low at both ages, and of low precision at 8.3 years. The ratio of hybrid additive-to-dominance variance \(\left( {{{\sigma_{\rm A}^{2} } \mathord{\left/ {\vphantom {{\sigma_{\rm A}^{2} } {\sigma_{\rm D}^{2} }}} \right. \kern-0pt} {\sigma_{\rm D}^{2} }}} \right)\) was of little practical consequence at age 2 years and had further decreased by age 8.3 years. Trait-trait genetic correlations amongst hybrids were generally positive and moderate to high. Hybrid vigour, gauged by comparison with the performance of the pure species progeny was significant, though correlations between pure species and hybrid progeny-based estimates of parental performance were weak, indicating that making parental selections in pure species trials may not be a successful strategy.     

Genome-wide association study of yield components and fibre quality traits in a cotton germplasm diversity panel

A genome-wide association study (GWAS) was conducted on a diversity panel of 103 cotton accessions over three seasons to determine genetic contributions to a range of cotton yield components including fibre quality, plant architecture and stomatal conductance traits. The accessions covered breeding lines, released cultivars and some obsolete cultivars that contributed significantly to modern breeding pools. They were genotyped with Illumina’s CottonSNP63 K single nucleotide polymorphism (SNP) assay. Broad-sense heritability was low for yield component traits (\(h_{B}^{2}\) = 0.14–0.43), except for gin turnout and boll weight (\(h_{B}^{2}\)) = 0.74 and 0.59, respectively), and low to high for fibre quality traits (\(h_{B}^{2}\) = 0.26–0.89). Population structure analysis revealed extensive admixture and cryptic relatedness amongst the accessions. Genome-wide linkage disequilibrium (LD) analyses showed LD decayed, on average, within a physical distance of 5 Mbp and reduced to 2 Mbp at r ² ≥ 0.2, suggesting that few markers are necessary for association mapping in cotton. A mixed linear model accounting for population structure and cryptic relatedness identified 17 and 50 significant SNP associations for fibre length and micronaire, respectively. GWAS failed to detect significant associations in other traits, with the contribution of any single SNP to the phenotypic falling below 5%. This may be due to the low level of DNA polymorphism in cotton and/or insufficient resolution provided by the cotton SNP chip. Whole genome sequencing combined with whole genomic selection approaches that do not require prior knowledge about the effect or function of individual SNPs may be better suited than GWAS for trait dissection and prediction in cotton breeding.     

Cytoplasmic male sterile and doubled haploid lines with desirable combining ability enhances the concentration of important antioxidant attributes in <Emphasis Type="Italic">Brassica oleracea</Emphasis>

The Brassica vegetable crops are rich source of important antioxidant compounds having anticancer and health promoting properties. Development of F₁ hybrids with better nutritional traits is one of the main breeding objectives in different vegetable crops. Our study is the first report of determining heterotic combinations utilizing cytoplasmic male sterile (CMS) and doubled haploid (DH) inbred lines for antioxidant compounds in snowball cauliflower. Twenty genetically diverse Ogura CMS lines of cauliflower and six DH male fertile inbred lines were crossed to develop 120 F₁ hybrids in line?×?tester mating design. The resulting 120 test cross progenies along with 26 parents and 4 standard checks were evaluated in 10?×?15 alpha lattice design with three replications during next cropping season. The CMS lines Ogu33-1A, Ogu122-5A and Ogu119-1A were good general combiner and CMS line Ogu118-6A was poor general combiner for majority of traits. Most of the heterotic hybrids were associated with high positive SCA effects. The proportions of σ²A/D and \(\upsigma^{2}_{\text{gca}} /\upsigma^{2}_{\text{sca}}\) ratios were less than unity in all the cases indicating preponderance of non-additive gene action in the genetic control of all the traits. Highest number of heterotic hybrids with SCA effects in desired positive direction was recorded for ascorbic acid content and phenolic content followed by total carotenoid content. The F₁ hybrids with better combining ability and better per se performance could be useful in accumulation of favourable allele for higher concentration of important anti-oxidant compounds.     

Genetic variation within eight populations of perennial forage grasses

Information on both mean performance and genetic variation is important in determining the value of germplasm for breeding via recurrent selection. The objectives of this experiment were to evaluate different methods of controlling spatial variation for forage yield, and to estimate genetic variances and heritability in eight perennial forage grass populations. Polycross families of two populations of smooth bromegrass (Bromus inermis Leyss.), two populations of hybrid wheatgrass (Elytrigia×muctonata (Opiz ex. Bercht.) Prokud.), and four populations of orchardgrass (Dactylis glomerata L.) were field tested for 2 years. Spatial variation was present in all three progeny tests, but was well accounted for by either the incomplete block design or a nearest neighbour analysis (NNA) of yield potentials. Low rank correlations between adjusted family means for the incomplete block design vs. the NNA created the unanswered question of which would provide a more appropriate estimate of family mean performance. Genetic variation was detected in six out of eight populations for forage yield, four out of six populations for ground cover, all four orchardgrass populations for maturity and one of four orchardgrass populations for leafspot reaction (caused by Drechslera spp.). Excessive year-family interactions prevented detection of genetic variation for leafspot reaction in the other populations. Heritability estimates ranged from 0.30 to 0.42 for forage yield. In all three species, there was a trend toward a negative relationship between population mean and genetic variance, suggesting that less elite populations may need to contribute other traits to be useful in the short term.     

Rubber tree early selection for yield stability in time and among locations

Rubber production in the rubber tree [Hevea brasiliensis (Willd. ex Adr. de Juss.) Muell. Arg.] can be expressed differently in different environments. Thus the objective of the present study was to select productive progenies, stable and responsive in time and among locations. Thirty progenies were assessed by early yield tests at three ages and in three locations. A randomized block design was used with three replications and ten plants per plot, in 3 × 3 m spacing. The procedure of the mixed linear Reml/Blup model—restricted maximum likelihood/best non-biased linear prediction was used in the genetic statistical analyses. In all the individual analyses, the values observed for the progeny average heritability ( $ \hat{h}_{pa}^{2} $ ) were greater than those of the additive effect based on single individuals ( $ \hat{h}_{a}^{2} $ ) and within plot additive ( $ \hat{h}_{ad}^{2} $ ). In the joint analyses in time, there was genotype × test interaction in the three locations. When 20 % of the best progenies were selected the predicted genetic gains were: Colina G_G = 24.63 %, Selvíria G_G = 13.63 %, and Votuporanga G_G = 25.39 %. Two progenies were among the best in the analyses in the time and between locations. In the joint analysis among locations there was only genotype × location interaction in the first early test. In this test, selecting 20 %, the general predicted genetic gain was G_G = 25.10 %. Identifying progenies with high and stable yield over time and among locations contributes to the efficiency of the genetic breeding program. The relative performance of the progenies varies depending of the age of early selection test.     

Yield stability and adaptation of Nordic barleys

Summary Grain yield was studied in a collection of 220 Nordic barley lines at diverse locations in the Nordic countries. Two-row (2r) and six-row (6r) lines differed very significantly in reaction to the growing conditions within and between the two locations, Svalöv (in southern Sweden) and Højbakkegård (in Denmark). This difference was also highly significant at Viikki (in Finland), but not at As (in Norway) or between Viikki and As. Genotype × location (GL) and genotype × year (GY) variance components were used to estimate phenotypic yield stability by Shukla's stability variance (% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaaiaacaqabeaadaqaaqaaaOqaaiaabo8adaahaa% WcbeqaaiaabkdaaaGcdaWgaaqcbaCaaiaabMgaaSqabaaaaa!3B73!\[{\text{\sigma }}^{\text{2}} _{\text{i}} \]). Only 7 lines did not contribute significantly to GL- and GY-interactions, and their yield levels were 7–27% lower than that of the highest yielding line (5057 kg/ha). Estimates of GL- and GY-stability parameters were not significantly correlated. Neither responsiveness, measured by the regression coefficient (b _i ), nor phenotypic yield stability, measured by the deviations from regression (Tai's _i ) were correlated with yield. Pedigree studies showed that both b _i and % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaaiaacaqabeaadaqaaqaaaOqaaiaabo8adaahaa% WcbeqaaiaabkdaaaGcdaWgaaqcbaCaaiaabMgaaSqabaaaaa!3B73!\[{\text{\sigma }}^{\text{2}} _{\text{i}} \] can be changed by recombination and/or induced mutations. Mixing of near isogenic lines with different resistance genes, and selection within a landrace, also resulted in changes in responsiveness. Recently released 2r-cultivars were more unstable than older 2r-cultivars revealed by positive correlation between the year of release and _i . Cultivars originating from southern Scandinavia were higher yielding than cultivars originating from the central or the northern regions of Scandinavia.     

Genetic variation, heritability and progeny testing in meadow bromegrass

Meadow bromegrass is a recently introduced pasture grass in western Canada. Its leafy production and rapid regrowth have made it a major grass species for pasturing beef animals in this region. Because relatively little breeding work has been done on this species, there is little information on its breeding behaviour. The main objective of this study was to estimate genetic parameters and assess breeding methodologies for meadow bromegrass. Forty half‐sib (polycross and open‐pollinated) and full‐sib (selfed) progenies were evaluated for dry matter and seed yield, fertility index, harvest index, plant height, plant spread, crude protein, neutral detergent fibre and acid detergent fibre. Genetic variation for seed yield, harvest index, and plant height was significant in the open‐pollinated and selfed tests. Genetic variation estimates for dry matter yield were negative (polycross), not significant (open‐pollinated), or significant (selfed). Estimates of genetic variation for quality traits were not significant, except for acid detergent fibre (selfed). Correlations among characters indicated that it is possible to simultaneously improve seed and forage yield. Rankings of progenies by the half‐sib tests for forage and seed yield were not altered by the use of the synthetic parental value (SV_i), which includes information from selfed progeny. The polycross progeny test did not discriminate parents as well as the open‐pollinated and selfed tests; this may have been a result of non‐random pollination in the polycross. Correlation among the progeny tests, showed that open‐pollinated and selfed progeny tests agreed for all characters, except for harvest index, while correlation between polycross and selfed tests were significant for six characters but not dry matter yield, and acid and neutral detergent fibres. The most dissimilar tests were polycross and open‐pollinated, with significant correlations found only for fertility index, height, spread and neutral detergent fibre. It was concluded that there was significant variation and moderate heritability for most traits in the meadow bromegrass populations evaluated, and that the open‐pollinated progeny test is the method of choice for selecting parents for synthetics of this species.     

Estimating gene action,combining ability and heterosis for grain yield and agronomic traits in extra-early maturing yellow maize single-crosses under three agro-ecologies of Ghana

Maize (Zea mays L.) is the most important cereal crop produced in Ghana. However, yield of the crop is generally low, producing just about 1.7 t/ha. The low yield is attributed to continuous use of local/unimproved varieties. Generally, hybrid varieties have proven to out-yield the local/unimproved varieties due to improved vigour. Development of hybrid varieties depend on good understanding of combining ability and inheritance of important quantitative traits such as grain yield (GY). 45 half-diallel crosses generated from 10 extra-early maturing yellow inbred lines were evaluated in 2015 under rain-fed conditions. The objectives were to determine the genetic control, breeding value and estimate heritability for GY and agronomic traits of the inbred lines under contrasting growing environments in Ghana. General combining ability (GCA) and specific combining ability (SCA) were important in the inheritance of GY and agronomic traits of the inbred lines. However, GCA was more important than SCA across environments to suggest that additive gene action was more important than non-additive gene action in the inheritance of GY and agronomic traits in the inbred lines. High broad-sense heritability, for GY and other agronomic traits indicated preponderance of additive gene action in trait expression, thus, selection based on phenotypic expression could be feasible. Inbred lines P1, P4 and P8 were good combiners for high GY. The genotype, P4 × P8, was identified as the ideal and most yielding single-cross hybrid across research environments and should be further tested on-farm before commercialization.     

Genetic parameters and selection gains in early clonal evaluation trials: implications for cassava breeding

The objective of this study was to estimate and compare genetic parameters in early cassava breeding phases (clonal evaluation trials—CET and preliminary yield trials—PYT) in full-sib (F₁) and self-pollinated (S₁) families, besides estimating the genetic gains. Twenty-three F₁ and six S₁ families were evaluated using the augmented block design in CET and the randomized complete block design in PYT for fresh root yield (FRY), root dry matter content (DMC) and starch yield (STY). In CET, most of the variance was due to environmental (\(\sigma_{e}^{2}\)) followed by variance within F₁ and S₁ (\(\sigma_{Clone/Fam}^{2}\)) families, with the exception of DMC in S₁ families. PYT presented the opposite behavior. In contrast, specifically for S₁ families, the variance between families (\(\sigma_{ Fam}^{2}\)) was more important than \(\sigma_{e}^{2}\) and \(\sigma_{Clone/Fam}^{2}\) in PYT. The heritability of families (\(h_{Fam}^{2}\)) was lower than individual broad-sense heritability (\(h_{g}^{2}\)) in all trials and families. Regardless of the family type and trial, family accuracy (\(r_{ggFam}\)) was lower than the clone accuracies (\(r_{ggCl}\)). Predicted gains using the selection index (SI) applied to best linear unbiased prediction (BLUP) were higher in PYT compared with CET and higher in F₁ families in comparison with S₁. There was also low coincidence in clone selection in both trials (30 and 45% for F₁ and S₁ families, respectively). For cassava breeding, it is recommended to obtain a higher number of clones per family and to use the SI with moderate intensity, particularly in CET.     

Magnitude of inbreeding depression and genetic variation analysis of agro‐morphological traits in orchardgrass

Inbreeding depression is the reduction in the fitness of inbred offspring relative to progeny from unrelated parents. In orchardgrass (Dactylis glomerata L.), limited efforts have been made to evaluate the effects of deliberate selfing on agro‐morphological traits and to estimate the genetic variation of traits. Twenty‐five genotypes of orchardgrass, along with 25 S₁ (full‐sibs) and 25 families of half‐sibs, were created in 2012 and used to assess the consequences of the first generation of inbreeding and outcrossing for offspring fitness and to estimate heritabilities, genetic parameters and correlations of agro‐morphological traits during the period of 2013–2014 in the field. Different levels of inbreeding depression were observed for the traits, with higher values for plant height, days to inflorescence emergence and dry matter yield. The degree of inbreeding or outbreeding effects varied among the studied genotypes. This facilitates the development of inbred lines for further studies. The results showed that some of the studied genotypes were self‐fertile, thereby indicating the possibility of developing inbred lines from these genotypes. Heritabilities ranged from 0.10 for the number of stems per plant to 0.64 for spread among the studied populations. Spread had high heritability as well as high correlation with forage yield, thereby indicating that this trait could be used to improve forage yield indirectly.     

Reed Canarygrass Forage Yield and Nutrient Uptake on a Year-round Wastewater Application Site

Reed canarygrass (Phalaris arundinacea L.) is often planted at wastewater treatment sites to provide ground cover and remove nutrients. Our overall objective was to determine the forage yield and nutrient uptake under year-round potato wastewater application in northern latitudes. Specifically, we determined the effect of N fertilization rate on forage dry matter yield and N and P uptake by reed canarygrass, and compared the forage yield, persistence and nutrient uptake of reed canarygrass relative to those of orchardgrass (Dactylis glomerata L.), smooth bromegrass (Bromis inermis Leyss), timothy (Phleum pratense L.) and quackgrass [Elytrigia repens (L.) Nevski]. With only wastewater application, reed canarygrass had a forage yield of 5.8 Mg ha⁻¹, with N and P uptake of 113 and 30 kg ha⁻¹, respectively. Forage dry matter yield, N uptake and P uptake increased to 14.5 Mg ha⁻¹, 383 kg ha⁻¹ and 64 kg ha⁻¹, respectively, with an N fertilization rate of 224 kg ha⁻¹. Forage yield and N uptake of reed canarygrass, orchardgrass, timothy and smooth bromegrass were similar and exceeded those of quackgrass. Reed canarygrass P uptake exceeded that of the other grasses. Reed canarygrass was less persistent than quackgrass or smooth bromegrass.     

Genetic analysis of quantitative traits across environments in linseed (Linum usitatissimum L.)

Summary Fourteen lines of linseed (Linum usitatissimum L.) were evaluated for general and specific combining ability through line × tester cross analysis using five diverse testers in two different environments. Seventy F₁'s and nineteen parental genotypes were raised in completely randomized block design with two replications with respect to yield and yield related traits. Considerable genetic variation was observed for all the traits studied. The additive as well as non-additive gene effects played significant role in the inheritance of yield and related traits with preponderance of non-additive gene effects for all the traits studied. Higher proportion of general combining ability × environment interaction variance as compared to specific combining ability × environment estimates was recorded. Additive genetic variances were more sensitive than non-additive genetic variances to the changing environment. Low estimates of heritability (narrow sense) for primary branches per plant, capsules per plant, seeds per capsule, seed yield per plant, harvest index and oil content and medium heritability for days to 50% flowering, days to maturity, plant height and 1000-seed weight was observed. Among the female parents LCK-9816, Parvati, Himalini, KL-168 were good general combiners for yield and related traits along with oil content, whereas among male parents, Surbhi and KL-224 were good general combiners for yield related traits and oil content but KL-221 was good general combiner for seed yield and related traits.