Showing papers on "Diallel cross published in 2003"

Genetic Diversity, Specific Combining Ability, and Heterosis in Tropical Maize under Stress and Nonstress Environments

Abstract: Estimation of genetic diversity and distance among tropical maize (Zea mays L.) lines and the correlation between genetic distance (GD) and hybrid performance would determine breeding strategies, classify inbred lines, define heterotic groups, and predict future hybrid performance. The objectives of this study were to estimate (i) heterosis and specific combining ability (SCA) for grain yield under stress and non-stress environments; (ii) genetic diversity for restriction fragment length polymorphisms (RFLPs) within a set of tropical lines; (iii) GD and classify the lines according to their GD; and (iv) correlation between the GD and hybrid performance, heterosis, and SCA. Seventeen lowland, white tropical inbred lines were represented in a diallel study. Inbred lines and hybrids were evaluated in 12 stress and non-stress environments. The expression of heterosis was greater under drought stress and smaller under low N environments than under nonstress environments. A set of DNA markers identifying 81 loci was used to fingerprint the 17 lines. The level of genetic diversity was high, with 4.65 alleles/locus and polymorphism information content (PIC) values ranging from 0.11 to 0.82. Genomic regions with quantitative trait loci (QTL) for drought tolerance previously identified showed lower genetic diversity. Genetic distance based on RFLP marker data classified the inbred lines in accordance with their pedigree. Positive correlation was found between GD and F 1 performance (F 1 ), SCA, midparent heterosis (MPH) and high-parent heterosis (HPH). Specific combining ability had the strongest correlation with GD. Environment significantly affected the correlations between F 1 , SCA, MPH, and HPH, with lower values of GD revealed in the more stressed conditions.

Genetic distance based on simple sequence Repeats and Heterosis in Tropical Maize Populations

Abstract: Heterotic groups and patterns are of fundamental importance in hybrid breeding of maize (Zea mays L.). The major goal of this study was to investigate the relationship between heterosis and genetic distance determined with simple sequence repeat (SSR) markers. The objectives of our research were to (i) compare the genetic diversity within and between seven tropical maize populations, (ii) test alternative hypotheses on the relationship between panmictic midparent heterosis (PMPH) and genetic distances determined with SSR markers, and (iii) evaluate the use of SSR markers for grouping of germplasm and establishing heterotic patterns in hybrid breeding of tropical maize. Published data of a diallel of seven tropical maize populations evaluated for agronomic traits in seven environments were reanalyzed to calculate PMPH in population hybrids. In addition, 48 individuals from each population were sampled and assayed with 85 SSR markers covering the entire maize genome. A total of 532 alleles in the 7 × 48 genotypes assayed were detected. The analysis of molecular variance (AMOVA) revealed that 89.8% of the variation was found within populations and only 10.2% between populations. The correlation between PMPH and the squared modified Roger's distance (MRD) based on SSR markers was significantly positive (P < 0.05) only for grain yield (r = 0.63). With SSR analyses, it was possible to assign Population 29 (Pop29) to the established Heterotic Group A and propose new heterotic groups (Pop25, Pop43). We conclude that SSR markers provide a powerful tool for grouping of germplasm and are a valuable complementation to field trials for identifying groups with satisfactory heterotic response.

Absence of Epistasis for Grain Yield in Elite Maize Hybrids

Abstract: Certain maize (Zea mays L.) inbred lines are more successful than others in forming elite hybrids. This study was conducted to determine whether epistatic interactions play a significant role in hybrid performance. Statistical epistasis was measured with a modified generation means model using testcrosses. Six progeny generations (P 1 , P 2 , F 1 , F 2 , and a backcross from the F 1 to each parent) were produced for all possible hybrids of a five-parent diallel in both the Iowa Stiff Stalk Synthetic (BSSS) and non-BSSS heterotic groups. Two testers were hybridized to each of the 10 possible hybrid progeny sets in both groups. Each testcross progeny set was evaluated in 10 environments. The nonepistatic model accounted for a large amount of the variation in generation means and fit the data well. Of the 40 maize testcross progeny sets studied, five resulted in a significant epistatic effect for grain yield. Four of the significant epistatic effects showed evidence of linkage, while one was due to unlinked epistatic effects. Our results suggest that parents in a hybrid cross need to be significantly different and testers need to bring out those differences to detect epistasis better by means of testcross generation means.

The genetic control of flag leaf length in normal and late sown durum wheat

Abstract: Parental, F1, F2, BC1, BC2, BC11, BC12, BC21, BC22, BC1 self-pollinated and BC2 self-pollinated generations of three crosses involving six cultivars of durum wheat (Triticum turgidum var. durum) were studied for flag leaf length under normal and late sown environments to analyse the nature of gene effects. For most crosses the 10-parameter model was the best descriptor of the data to account for the variability in generation means of this trait but in cross HI 8062×JNK-4W-128 the 6-parameter model was the best (normal sown) while in cross Raj 911×DWL 5002 the 3-parameter model was the best (late sown). Of the epistatic interactions, dominance×dominance (l) and dominance×dominance×dominance (z) played significantly greater roles in controlling the inheritance of this trait. Absolute totals of non-fixable gene effects were much higher than the fixable gene effects in all the crosses in both the environments, indicating the greater roles of non-additive effects in controlling the inheritance of flag leaf length in durum wheat cultivars. Significant partial dominance was observed frequently in most of the crosses. Significant heterosis was attributed to combined effects of dominance×dominance (l), additive×additive×dominance (x) and dominance×dominance×dominance (z) epistatic interactions in the cross Cocorit 71×A-9-30-1 under late sown environment. Biparental mating and/or diallel selective mating, which exploit both fixable and non-fixable components, have been suggested for the improvement of this trait in durum wheat cultivars.

Genetic analysis for developmental behavior of some seed quality traits in Upland cotton (Gossypum hirsutum L.)

Abstract: Analysis of genetic main effects andGE interaction effects for oil index(OID), protein index (PID), and lysineindex (LID) of Upland cotton (Gossypium hirsutum L.) were conducted for2-yr diallel cross data by using a seedgenetic model. Analysis approaches ofunconditional and conditional variances andcorrelations were employed to evaluatedevelopmental behavior of cottonseed. Thephenotypic means were relatively larger forF2 generation than F1 generation,and larger for all generations in 1993 thanin 1994. The results of variance analysisindicated that OID, PID, and LID weresimultaneously controlled by seed nuclear,cytoplasm, and maternal nuclear effects.Genetic effects due to maternal nuclearwere relatively more important at wholedevelopmental period. GE interactioneffects were the main contribution to thetotal variation of OID at first two stages,of PID at the forth stage, and of LIDacross all four stages, respectively. Notonly the phenotypic correlationcoefficients but also the coefficients dueto different genetic effects variedsignificantly between traits themselves atvarious stages. Different genetic effectscaused the variation of the correlationshipbetween traits themselves at various stages.

Effect of Recurrent Selection on Combining Ability in Maize Breeding Populations

Abstract: Recurrent selection (RS) is a population improvement method that increases the frequency of favorable alleles while maintaining genetic variation in breeding populations. Twelve University of Guelph RS maize (Zea mays L.) populations selected via reciprocal recurrent selection (RRS), selfed-progeny recurrent selection (S), or a method combining RRS and S (COM), were assessed for changes in the genetic structure of grain yield, grain moisture, and broken stalks, and two associated selection indices. Partitioning of the entry sums of squares from diallel matings of the original (C 0 ) and advanced (C A ) cycle populations using Gardner and Eberhart's Analysis II and Analysis III indicated genetic improvement occurred for the per se and cross performance of most populations. Accompanying the favorable changes in population performance were less favorable shifts from predominantly additive genetic effects in C 0 to greater nonadditive genetic effects in C A . This shift did not substantially change the general combining ability estimates (g i ) of most populations. However, for grain yield, the underlying components of g; effects were altered in their relative importance. General combining ability (GCA) effects in the C 0 were caused primarily by the population per se effects (v i ), while in C A the GCA effects were caused predominately by parental heterotic effects (h i ).

Combining ability of inbred lines of maize and stability of their respective single-crosses

Abstract: The utilization of diallel crosses for identification of superior combinations is a common practice in maize (Zea mays L.) breeding programs. This methodology allows the estimation of the combining ability of genotypes being evaluated. In this work, five inbred lines were evaluated as to their general (GCA) and specific (SCA) combining abilities, by using a complete diallel scheme. The single-crosses produced between these inbred lines were evaluated in seven environments, along with two checks, by using a randomized complete block design. Traits analized were: grain yield, plant height, ear height, ear placement, and prolificacy. A diallel analysis was carried out, following an adaptation of Griffing's method IV, in addition to hybrid stability and adaptability analyses. Significant differences were detected for entries and environments for all traits. The interaction genotype vs. environment was significant for all traits. GCA's were significant for all traits, while SCA's were non-significant only for ear placement. For grain yield, both additive (GCA) and non-additive (SCA) effects were important, while for the remaining traits additive effects were more important. The high yielding single-cross was obtained from the cross of lines L-08-05F and L-38-05D. Those inbred lines showed higher GCA's and their cross also had high SCA; also, it is responsive to environment improvements and reasonably stable. The second in rank high yielding single-cross, L-46-10D x L-08-05F, showed wide adaptability and stability.

Handbook of formulas and software for plant geneticists and breeders

Abstract: This multiauthor volume presents program codes of specialized statistical and genetics related software programs, demonstrating their use through practical examples. It also includes an extensive listing of programs available on the internet for linkage and mapping software. Information on programs related to the following are included: genotype environment interaction and stability analysis, genetic diversity estimation, best linear unbiased predictors (BLUPs), principal component, and additive main effects and multiplicative interation (AMMI) analyses, quantitative trait loci by environment (QTL × E) analysis, GGE biplot analysis, diallel analysis, path analysis, trend analysis, and field plot analysis

Genetics of spike length in durum wheat

Abstract: Gene effects were analyzed using mean spike length of 12 populations, viz., both parents, F1, F2, first back cross generation, BC1 and BC2, second backcross generations, BC11,BC12, BC21 and BC22 along with BC1 self and BC2 self derived by selfing BC1 and BC2populations of three crosses involving six diverse cultivars of Triticum durumto determine the nature of gene actions governing spike length through generation mean analysis under normal and late sown environments. The six-parameter model was adequate in most of the cases to explain genetic variation among the generation means under both the sowing environments. Additive (d) gene effect was significant in all the cases, whereas dominance (h) gene effect was not so frequently observed significant. Epistatic effects, particularly digenic types were predominant over additive and dominance effects in most of the cases under both normal and late sown environments except in the cross Cocorit 71 × A-9-30-1 (normal sown).Additive × dominance × dominance (y), trigenic interaction played significant role in controlling the inheritance of this trait in the cross HI 8062 × JNK-4W-128under late sown condition. Duplicate epistasis was observed in the cross HI 8062× JNK-4W-128 (normal sown). Non-fixable gene effects were of higher magnitude than fixable gene effects in almost all cases, confirmed the major role of non-additive gene effects to control the inheritance of spike length in durum wheat. Significant heterosis over better parent was not observed. Similarly, inbreeding depression was not commonly observed. Favourable and suitable environment must be considered before finalizing breeding programme for its simple inheritance to get desirable improvement for high grain yield. Hybridization systems, such as biparental mating and / or diallel selective mating, which exploit both additive and non-additive gene effects, simultaneously, could be useful in the improvement of spike length in durum wheat.

Genetic distance and its association with heterosis in cacao

Abstract: The efficiency of cacao breeding program can be increased by choosing superior crosses to be made between divergent clones. We assessed the genetic distance among five clones with RAPD data (genetic distance - GD) and with yield component data (Mahalanobis distance - MD). The clones were evaluated in a diallel, during five years, for five yield components. A total of 130 RAPD bands were scored. GD and MD were used to determine the correlation between genetic distances among clones and the performance of their hybrids. The correlation between GD and MD was 0.67 (P=0.03). Both distances were related to heterotic performance of hybrids for wet seed weight/plant and wet seed weight/fruit. The average hybrid performance for the same two yield components was correlated with only MD. Hence, genetic distances measured by RAPD and yield components can be used as a guide to the choice of the superior crosses.

Analysis of general and specific combining abilities of popcorn populations, including selfed parents

Abstract: Estimation of general and specific combining ability effects in a diallel analysis of cross-pollinating populations, including the selfed parents, is presented in this work. The restrictions considered satisfy the parametric values of the GCA and SCA effects. The method is extended to self-pollinating populations (suitable for other species, without the selfed parents). The analysis of changes in population means due to inbreeding (sensitivity to inbreeding) also permits to assess the predominant direction of dominance deviations and the relative genetic variability in each parent population. The methodology was used to select popcorn populations for intra- and inter-population breeding programs and for hybrid production, developed at the Federal University of Vicosa, MG, Brazil. Two yellow pearl grain popcorn populations were selected.

Genetic Components of Yield Stability in Maize Breeding Populations

Abstract: Phenotypic stability has long been recognized as an important target in plant breeding. Stability is influenced in part by the genetic structure, i.e., level of heterogeneity and heterozygosity, of the cultivar. Yet, very little is known about the genetic components underlying stability, and how population improvement strategies influence stability. We examined 12 maize (Zea mays L.) breeding populations selected via reciprocal recurrent selection (RRS), selfed progeny recurrent selection (S), or a method combining RRS and S (COM), to examine changes in the genetic structure of the phenotypic stability of three traits (grain yield, grain moisture, and broken stalks), and two associated selection indices. Partitioning of the genotype × environment sums of squares from diallel matings of the original (C 0 ) and advanced (C A ) cycle populations into linear trends indicated that only grain yield and the unadjusted performance index (UPI) followed a predictable linear response. Grain yield and UPI linear trends were further partitioned by Gardner and Eberhart Analysis III to examine the genetic components of stability. We found that recurrent selection (RS) improved grain yield stability, and that this trait is heritable, predictable, and mostly controlled through additive gene action. Improvement in grain yield stability was observed both in cross and per se performance and was accompanied by significant improvement in the mean performance of the populations. However, the improvement in grain yield stability did not result in substantial changes in the general combining ability (g i ) estimates of most populations. Our results indicate that grain yield stability can be improved through RS by selecting solely for mean performance across multiple environments.

Analysis of reproductive traits in crosses among maternal lines of rabbits

Abstract: A crossbreeding experiment, between three maternal lines of rabbits, was carried out to estimate the effects of the crosses on reproductive traits. The experiment was designed as a complete diallel cross involving the lines, A, V and H, selected for litter size. A total of 1190 does, distributed between the nine types originating from the diallel cross, and born, reared and bred on the same com- mercial farm, were controlled. The recorded traits were the total number of young born, the number of born alive and the number of stillborn per litter (3759 records), and the interval between kindlings (2505 records). A repeatability animal model was used first to obtain the REML estimates of the com- ponents of variance. This was followed by a generalised least squares analysis and the estimates of the type of doe effects were obtained. Finally the differences among the lines within direct and maternal effects, and the corresponding values of the individual heterosis were estimated. Important differ- ences in the direct effects were found between lines V and A. All the maternal effects were not signifi- cant. Favourable heterosis (4-10%) was found for prolificacy traits in the crosses of line A with lines V and H, being the heterosis, very dependent on the performance and history of the lines involved. reproduction / crosses / maternal / lines / rabbits

Análise dialélica em clones de cana-de-açúcar

Abstract: Aiming at the evaluation of the gene action predominant in sugarcane characters of economic importance and the identification of crossing with favorable genetic potential to the development of new cultivars, eight genotypes were evaluated according to the unbalanced diallel cross scheme. Progenies obtained from 44 crosses were evaluated on a 7 x 7 lattice experimental design with three replications at the Centro de Pesquisa e Melhoramento da Cana-de-acucar (CECA) of the Universidade Federal de Vicosa. The following characters were studied: juice Brix %, stalk number, average stalk weight, tons of stalks per hectare, tons of Brix per hectare and flowering percent. The results emphasized the importance of either the additive and the non-additive genetic effects in the expression of those characteristics. The genotypes SP82-6108 and IAC86-2210 showed potential for increasing the sugarcane productivity, that is also valid for the following crossing combinations: SP82-6108 x SP88-754, SP82-6108 x SP87-365, SP81-1763 x SP82-6108, IAC86-2210 x SP88-754, IAC86-2210 x SP86-96, IAC86-2210 x SP81-1763, SP88-819 x SP87-365, SP84-2029 x SP87-365 and SP88-754 x SP87-365.

Clarification and Reevaluation of Population-Based Diallel Analyses

Abstract: Plant breeders and geneticists often use diallel mating designs to obtain genetic information about a trait of interest from a fixed or randomly chosen set of parental lines. Diallel analyses of broad-based populations have frequently been conducted by means of three analyses presented by Gardner and Eberhart in 1966. The original paper of Gardner and Eberhart used sequential model fitting to obtain estimates of effects and corresponding sums of squares. This approach, although having a long history, suffers from shortcomings which have led to confusion about what hypotheses the analyses actually test. The objectives of this paper were to delineate clearly all models implicitly required to perform Gardner and Eberhart Analyses II and III, and to present explicit formulas for effects in terms of the population means which are fundamental and unambiguous. While developing formulas of effects, we discovered a typographic error associated with variety effects in the original example of Analysis II. Our results also indicate that Analyses II and III effect formulas are rather nonintuitive both biologically and genetically, and incorporate multipliers that are functions of the number of parents. Another specific result shows that the varietal effects obtained in Gardner and Eberhart's Analysis III are unconstrained estimates, while those from the Analysis II are estimates constrained by the assumption of no heterosis. These results have implications for the use and interpretation of such effects. A SAS computer program for analyzing diallels among broad-based populations according to Gardner and Eberhart's Analyses II and III is also reported.

Heterosis and Combining Ability for Yield Components and Fiber Quality Parameters in a Half Diallel Cotton (G. hirsutum L.) Population1

Abstract: Combining ability and heterosis were determined in a population obtained from the half diallel crossing of 6 different cotton genotypes for yield components and fiber quality parameters. For breeding purposes, to improve the investigated characters some suitable parents were selected for different characters: DPL 5690 for number of bolls per plant, Acala SJ-5 for boll weight and fiber length; Nazilli-84 and Carmen for seed cotton yield and lint percentage; Tamcot CAMD-E for earliness and fiber fineness; and PD 6168 for fiber strength. When the crosses were evaluated for the investigated characters Tamcot CAMD-E x Carmen, Nazilli-84 x PD 6168, DPL 5690 x Tamcot CAMD-E and Tamcot CAMD-E x PD 6168 are considered promising combinations for further research. It was concluded that applying 3-way crosses, or modified backcross or recurrent selection to genotypes having good combining ability would improve yield and fiber quality.

Diallel analysis of fusarium head blight resistance in soft red winter wheat

Abstract: Fusarium graminearum Schwabe, the causative agent of Fusarium head blight (FHB), is an economically important pathogen of wheat (Triticum aestivum L.). Breeding FHB resistant wheat requires knowledge of the underlying genetic control of FHB resistance. While soft red winter (SRW) wheat breeders have begun to characterize germplasm for resistance, little information is available on the value of cultivars as parents in breeding for FHB resistance. Two diallel series of crosses, each involving nine SRW parents, were evaluated in both the greenhouse and field near Lexington, KY. The progeny and parents from the diallels were point inoculated with F. graminearum in both environments. FHB severity, deoxynivalenol (DON) level, and kernel damage were recorded. FHB severity ranged from 4.9 to 84.3% in the greenhouse and from 16.4 to 86.7% in the field. Significant general and specific combining ability effects were observed in both diallels in both environments. The nature of the resistance varied with diallel and with screening environment. On the basis of ratios of variance components, resistance in diallel 1 depended primarily on additive genetic effects, while in diallel 2 in the field dominance effects prevailed. Correlations between the greenhouse and field screening environments were low (0.36 in diallel 1 and 0.14 in diallel 2). Genotype × environment interactions were highly significant and due almost exclusively to rank change interactions. These results do not support indirect selection in a greenhouse environment for resistance expressed in the field.

Genetic Analysis of Adult-Plant Resistance to Leaf Rust in Five Spring Wheat Genotypes

Abstract: Inheritance of adult-plant resistance to leaf rust, caused by Puccinia triticina, was studied in the progeny of a one-way diallel cross involving five CIMMYT-derived adult-plant resistant wheat (Triticum aestivum) genotypes and a susceptible wheat ‘Avocet-YrA’. F1 progenies, F2 populations, F2-derived F3, and F4-derived F5 lines were field evaluated under artificial epidemics with leaf rust race MCJ/SP. Adult-plant resistance to leaf rust was incompletely dominant in crosses with the susceptible parent and was found to be controlled by additive interactions of Lr34 with at least two to three additional genes. Transgressive segregation giving rise to plants or lines with higher and lower levels of resistance than the parents was observed in all F2 and F5 derivatives of the resistant-parent intercrosses and suggested that, apart from Lr34, some of the other additive genes were nonallelic. Although specific combining ability was significant in some generations, general combining ability was found to...

Heterosis expression in crosses between maize populations: ear yield

Abstract: The phenomenon of heterosis has been exploited extensively in maize (Zea mays L.) breeding. The objective of this study was to evaluate the genetic potential of ten maize populations for ear yield following the diallel mating scheme. Six parental populations were obtained through phenotypic selection of open-pollinated ears in Rio Verde, GO, Brazil, (GO populations) and four parental populations were synthesized in Piracicaba, SP, Brazil (GN populations): GO-D (DENTADO), GO- F (FLINT), GO-A (AMARELO), GO-B (BRANCO), GO-L (LONGO), GO-G (GROSSO), GN-01, GN-02, GN-03 and GN-04. Experiments were carried out in three environments: Anhembi (SP) and Rio Verde (GO) in 1998/99 (normal season crop) and Piracicaba (SP) in 1999 (off-season crop). All experiments were in completely randomized blocks with six replications. Analysis of variance grouped over environments showed high significance for heterosis and its components, although mid-parent heterosis and average heterosis were of low expression. The interaction treatments x environments was not significant. Total mid-parent heterosis effects ranged from de -4.3% to 17.3% with an average heterosis of 3.37%. Population with the highest yield (7.4 t ha-1) and with the highest effect of population (vi = 0.746) was GN-03, while the highest yielding cross was GO-B x GN-03 with 7,567 t ha-1. The highest specific heterosis effect (sii' = 0.547) was observed in the cross GO-B x GN-03.

Comparison between molecular markers and diallel crosses in the assignment of maize lines to heterotic groups

Abstract: Maize (Zea mays L.) inbred lines usually are assigned to heterotic groups, based either on pedigree or on the estimates of the specific combining ability (SCA). SCA estimates, however, require the production and evaluation of crosses in field trials, which makes the process lengthy and costly. Inbred lines can be assigned to heterotic groups based on the genetic divergence among lines, based on the data obtained by molecular markers. The advantage of using molecular markers is the possibility of evaluating only the more promising crosses between the most divergent lines. The use of molecular markers for this purpose has proven itself to lie efficient for temperate maize populations, where the genealogies of the inbred lines are well established within a narrow genetic basis. Limited study has been conducted on the genetic diversity within tropical maize. Objectives of our study are: to assign 18 s 3 maize lines to heterotic groups based on genetic divergence obtained from RFLP markers; to compare the results based on RFLP marker data with those based on estimates of SCAs among these 18 lines evaluated in diallel crosses; to discuss the usefulness of RFLP markers in the establishment of correct heterotic group. The 18 s 3 lines originated from BR-105 and BR-106 tropical maize populations. Intra- and interpopulation single crosses were evaluated for grain yield in two and six environments, respectively, using a lattice design and having commercial hybrids as checks. It was observed that the assignment of the 18 s 3 lines to heterotic groups on the basis of RFLP markers was very similar to those obtained based on estimates of SCAs. It was also verified that intrapopulation analyses were not necessary because they were similar to the interpopulation analyses.

Diallel analysis of production traits among domestic, exotic and mutant germplasms of Lycopersicon.

Abstract: The effects of wild germplasm on tomato fruit shelf life have not yet been completely evaluated. Three different genotypes of Lycopersicon esculentum (a cultivated variety, a homozygote for nor and a homozygote for rin), LA1385 of L. esculentum var. cerasiforme, LA722 of L. pimpinellifolium, and 10 diallel hybrids were assayed. Mean values of fruit shelf life, weight, shape, and mean number of flowers per cluster were analyzed after Griffing (1956, Aust. J. Biology 9: 463-493), method 2, model 1. Both general and specific combining abilities (GCA and SCA) were significant for the four traits. Negative unidirectional dominance was detected for fruit weight and shelf life, while bidirectional dominance was detected for fruit shape and mean number of flowers per cluster. SCA was greater than GCA for shelf life, so nonadditive effects predominantly accounted for this trait. In the heterozygous state, rin had smaller mean effects than nor. Wild accessions were able to prolong shelf life per se, and in crosses to the cultivated variety. The cross between the homozygote for nor and LA722 yielded the longest shelf life among hybrids.

Yield stability in Coffea canephora from diallel mating designs monitored for 14 years

Abstract: The genetic parameters of several agronomic traits were estimated in Coffea canephora in a triangular diallel with six parents and in a partial diallel with 18 parents. The yield data came from harvests obtained over 14 years divided into an initial 6-year cycle, a second cycle of 5 years after cutting back and a third cycle of 3 years after topping. Risk incidence was also observed over several years. The general combining abilities (GCA) were the principal sources of variation for the various traits considered. Parents derived from the Yangambi selections (Democratic Republic of Congo) proved to be best for yields in the three cropping cycles. The rank correlations between the GCA of the various traits indicated that first-cycle production was still not enough to predict the GCA for yield over 14 years. Susceptibility to leaf anthracnose and to drought could lead to modifications in successive classifications, with a more significant impact on production during the first cycle. The differences in susceptibility to Coffee Berry Borers had an impact on yield, which increased in line with coffee tree age. There was a rather good relation between inherent values and values in parent combinations and it was thus possible to choose parents on their own performance.

Heterosis in relation to combining ability in brinjal (Solanum melongena L.)

Abstract: Combining ability analysis was carried out through diallel method using eight parent with eight characters. The analysis revealed that none of the parents were found good combiner for all character. However, parents DBR-8, Pant Rituraj, BB2, KS-331 and CHBR-1 were good general combiner as many as four to five character the ratio of gca/sca observed less than unity for all the character, revealed predominance of non-additive variance. The maximum heterosis for yield was exhibited by cross H-8 x CHBR-1. There was high heterosis response in most of the hybrids which support the role of non-additive gene effects. Selection should be practiced for improvement of traits like days to first flowering and plant height while yield related traits such fruits per plant, fruit length, fruit diameter and branches per plant may be exploited through heterosis breeding.

Genetic variability, heritability and genetic advance in pea (Pisum sativum L.)

Abstract: Genetic variability, heritability and genetic advance analysis was done using 45 F1 hybrids, 45 F2 generations and his parents obtained from a (10 x 10) diallel mating design for eight traits viz.; length of the pod (cm), no. of pods/plant no. of seeds/pod, no. of branches/plant, 100-grain weight (g), grain yield/plant (g), harvest index (%) and protein content (%). The magnitude of variability was higher for length of the pod and no. of pods/plant in F1 population. The mean performance and range of variability of crosses for eight characters showed significant differences in both the generations for all the traits under study. High heritability coupled with low genetic advance for harvest index, length of the pod, no. of seeds/pod, protein content and 100grain weight were observed in both the generations. These traits were moderately influence by non-additive gene action. Therefore, selection of these traits may be more effective for breeding point of view.

Diallel Analysis for Combining Ability in Ridge Gourd

Abstract: Forty-five hybrids developed by using ten parents in half diallel for combining ability in ridge gourd. The GCA and SCA for yield and yield components were significant indicating presence of variability in combining ability of the parents. The parents Col, Panvel and Inamppangari were the best general combiners for yield and yield components. The parents with high per se performance also exhibited high GCA effects. The combination Atigre x Pusa Nasdhar and Atigre x Tendoli appeared to be best as they produced significantly high SCA effects for weight and number of fruits vine -1 , days to first harvest, average fruit weight, vine length, position of first female flower, number of female flower vine -1 can exploited directly for yield heterosis. The other crosses Kawalapur x RG - 108. Tendoli x Punjab Sadabahar, Jaipur x Col and Inampangari x RG 108 indicated significant SCA effects for earliness.

Genetic Variability and Correlation Studies of Yield and its Attributing Characters in Maize ( Zea mays L.)

Abstract: Genetic variability and correlations were studied in seven inbred lines of maize and their 21 direct cross combinations obtained from a diallel cross. Based on the data recorded on eight yield related traits, the values of genotypic correlation were slightly higher than the corresponding phenotypic values. Phenotypic and genotypic correlations between grain yield on one hand and plant height, ear height and ear length on the other were positive and significant. Genotypic and phenotypic coefficients of variation were high for grain yield, ear height, 100-kernel weight, ear length and number of kernel rows/ear. Genotypic variation was found to be good indication of phenotypic variability. Heritability estimates and genetic advance were high for grain yield, ear height, plant height and ear length.