Combining ability of quantitative and qualitative traits in rapeseed (Brassica napus L.) varieties at two nitrogen levels

Combining ability of yield associated traits has been studied quite frequently in oilseed rape (Brassica napus L.) but it was hardly ever studied based on nitrogen levels variations. Six parents along with their 15 F2 half diallel crosses were evaluated in two nitrogen (N) levels including N0 and N+. Analysis of variance revealed significant mean squares of general and specific combining abilities (GCA and SCA) for all the traits studied. The high narrow-sense heritability estimates were found for seed yield and harvest index, implying the more importance of additive genetic effects for and consequently high selection efficiency for improving these traits. Due to low narrow-sense heritability estimates for oil and protein contents and therefore more importance of non-additive genetic effects, selection for improving these traits should be done in later segregating generations. The GCA × N level interaction was significant only for oil content which is indicating of more differences of GCA effect of this trait at two nitrogen levels. Significant N × SCA effect mean squares for harvest index and oil content, revealed significant variation of SCA effects of these traits in nitrogen levels application. Most of the crosses with high seed yield at N0 and N+ had at least one parent with positive GCA effect at both N levels. Among the six parents, PF7045/91 appeared to be the best combiner for seed yield at the N0. This variety also showed high GCA at the N+ but its low oil content at the N+ is certainly disadvantageous as the quality of the hybrid is often intermediate between the two parents.

Information on estimates of combining ability of the promising lines of breeding material is important for evolving higher yielding varieties of oilseed rape (Brassica napus L.). An experiment was conducted to quantitatively examine the genetic parameters of phenological traits, plant height, pods on main raceme, pods per plant and seed yield for eight oilseed rape genotypes using a half-diallel crosses. The result of the diallel analysis revealed significant mean squares of general and specific combining abilities (GCA and SCA) for all studied traits, indicating the importance of additive and non-additive genetic effects for these traits. On the other hand estimation of high narrow-sense heritability estimates for days to flowering, duration of flowering and pods on main raceme, indicated the prime importance of additive genetic effects for these traits. L420 and L401 with significant negative GCA effects for days to flowering and days to maturity were suitable for yielding early maturity combinations. L41, Zafar and L22 with significant positive GCA effects for seed yield were superior parents for increasing seed yield. The crosses with significant positive SCA effects for seed yield had at least one parent with significant positive GCA effects for this trait. The crosses including L41×L22, L41×LF2, Zafar×L22 and Zafar×L420 with seed yield of 3421.7, 3400, 3348.1 and 3311.3 kg ha-1 could be promising for determination of superior recombinants for high seed yield coupled with other growth characters in advanced generations of segregation.

To study combining ability effects of developed CMS and restorer lines an experiment was carried out at the experimental farm, Department of Genetics and Plant Breeding, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Salna, Gazipur during Aman 2011 and Boro 2011-12 following RCBD design through line × tester analysis in three replications. Five known CMS lines and sixteen developed Restorer lines were considered for through line × tester analysis. Among sixteen restorer lines, only four showed significant negative GCA effects for all these three traits for earliness. The estimated of gca effects of parents indicated that seven parents and sixteen crosses contributed highly significant negative effects for plant height which were responsible for dwarfing character. Fifteen crosses and eight parents showed significant negative sca estimates for days to first flowering and twenty crosses for maturity. Considering both SCA effects and per se performances for days to 1st flowering and maturity; the crosses of IR 58025A with RG-BU08-005R, RG-BU08-006R, RG-BU08-016R, RG-BU08-018R and RG-BU08-025R were found as the best specific combiner. Among 80 crosses fifty two crosses showed significant positive SCA effects along with above average perse performances for grain yield. Ten crosses of IR 58025A, seven crosses of GAN46A, fourteen crosses of IR 62829A, nine crosses of IR 68888A and ten crosses of BRRI 1A showed significant positive SCA effects along with mean values resulting significant positive SCA effects and above average perse performances with all five CMS lines for grain yield.

Genetic studies were conducted to examine the heritage of resistant to cotton leaf curl virus. Genetic components of variance revealed higher σ2GCA and Additive (σ2A) than σ2SCA and Dominance (σ2D), which indicated additive genes were more reliable for inheritance of resistance to CLCV. The ratio of variances σ2gca/σ2sca was higher than unity (one) and further proved from degree of dominance [σ2A/σ2D]0.5 which was greater than one and confirmed supremacy of additive genes at both locations and generations. The heritability narrow sense (h2) and broad sense (H2) was found higher which suggested role of additive genes, which are fixable. Therefore selection would be effective in early segregating generation according to the symptoms of cotton leaf curl virus. The GCA effects for CLCV showed that among the parents, Mac-7 found as good general combiner with highest significant negative GCA effects at both locations in F1 and F2 which considered as CLCV resistant parent. The SCA effects exhibited that hybrid, Mac-7 x USD16-3058, CIM-602 x Mac-7 and NIA-Noori x Mac-7 showed significant negative SCA effect in both generations and locations. It was noted that cross combinations involved good x poor and poor x good general combiner with significant SCA effect was due to complementary gene action which produce desirable transgressive segregants, these can be further studies through bi-parental mating of diallel selective mating or any other form of recurrent selection in early generation with single plant selection to exploited both additive an non-additive gene action.

Although an average plant height is more preferable in most of agronomic crops, less reduction of this trait in stress condition makes yield components and seed yield sustainable in rapeseed varieties. Combining ability, heterosis and heritability of plant height at application and non-application of nitrogen environments (Hp and Hs, respectively) and its related stress tolerance indices were detected in half F2 diallel crosses of six spring rapeseed varieties. Significant mean squares of general and specific combining abilities (GCA and SCA) were detected for Hp, Hs, mean productivity (MP), geometric mean productivity (GMP) and stress tolerance index (STI), indicating the importance of additive and non-additive genetic effects for them. A high narrow-sense heritability estimate was exhibited for STI, emphasizing the prime importance of additive genetic effects for this stress tolerance index. A significant correlation among Hp, Hs, MP, GMP and STI showed the efficiency of these stress indices for improving plant height in plant breeding programme. In comparison to SCA effects, most of the crosses had significant high parent heterosis for Hp, Hs and all the stress indices. RGS003 with a significant positive GCA effect of Hs was considered as a suitable parent for improving this trait and most of the combinations of this genotype had significant negative SCA effects.

The combining ability analysis of 225 F3s in greengram developed from half diallel crosses among six parents revealed importance of both additive and non-additive gene actions in the inheritance of pods per plant, seeds per pod, 100-seed weight and yield per plant. There were significant differences in gca and sca effects for the characters studied. OGG-12 was the best general combiner for pods/ plant and grain yield per plant where as OGG-57 was for seeds/ pod, OGG-12 and LGG-460 for 100-seed weight. Among the 15 crosses, six crosses showed significant positive and seven crosses had significant negative SCA effects for seed yield/plant. Significant positive SCA effects were observed in two crosses for pods/plant, four crosses for seeds/ pod and three crosses for 100-seed weight. Although some crosses were showing positive SCA effect for yield and its components, the frequency of unfavorable cases were more. Only TARM-1 × OGG-12 exhibited favorable SCA effect for all characters. Considering all the characters simultaneously, OGG-12 was the best combiner followed by TARM-1 and LGG-460

Combining ability was studied for grain yield and its component using the F1, F and F, of a 6 x 6 diallel set in barley. Both GCA and SCA variances were significant for all the traits in each generation. The GCA effects were associated with per se performance of parents for almost all the traits, ayoti, DL 70 and PL 102 were found to be good general combiners for most of the characters and thus, could be used effectively in a barley breeding programine. Significant and desirable SCA effects for grain yield revealed that seven, six and five crosses in F, F, and F, respectively. involved high x high and high low general combiness Jyoti x DL 70, PL 102 x DL 70 and Jyoti x PL 102 in each gene- ration involved parents of high x high general combiners. These hybrids showed high mean coupled with significant SCA effects in F, and F, which reflected the presence of additive X additive interaction effects. Therefore, it is expected that better strains may be obtained in advanced generations through standard selection procedures. Some of the crosses invol ved high x low general combiners Such crosses may throw out desirable transgressive segregates.

To estimate the general and specific combining ability (GCA and SCA) effects of plant height, yield components, seed yield and oil content, three testers and six lines of spring type of rapeseed varieties were crossed using line ? tester fashion. Significant mean squares of parents and crosses for all the traits indicated significant genetic variation among the parents and their F1 crosses. Significant mean squares of parents vs crosses revealed significant average heterosis for all the traits except seeds per pod, 1000-seed weight and oil content. High narrow-sense heritability estimates for all the traits except seeds per pod, indicating the importance of additive genetic effects for these traits. Due to more importance of additive genetic effects for most of the traits, only a few of the crosses exhibited significant SCA effects. A significant positive correlation between seed yield and some of yield components including pods on main axis, pods per plant and 1000-seed weight indicates that these traits can be used as suitable selection criteria for improving of seed yield. The crosses including Opt ? R01, RG06 ? R01, RG06 ? R08 and RGS3 ? R08 with 3241.91, 3213.68, 3334.28 and 3237.45 kg ha-1 of seed yield detected as prior combinations for improving of this trait and all of these combinations had also positive SCA effect for this trait.

Assessment of grain quality traits in rice under normal and water deficit condition

Heterosis and combining ability was studied in F1 hybrids of maize with respect to grain yield and yield attributing traits using twenty-two hybrids which were developed through Line × Tester mating design. The parents and their hybrids were subjected to assess the combining ability and nature of gene action governing the quantitative traits. The results inferred that the predominance of non-additive gene action was observed for all the traits. Among the parents, the overall study of gca effects suggested that parent UMI 1200-7-26-1-6-1, N 14, N 107 and N 285 were significant general combiner for yield, these can be used to improve hybrids with desirable traits in future. Significant positive SCA effects were found for all the studied traits. Among the hybrids, N 14 × UMI 1200-7-26-1-6-1 showed desirable standard heterosis percentage over the checks CO 6 and NK 6240 along with good sca effects and per se performance for grain yield and other important yield contributing traits over different locations thus it can be used for commercial seed production programme.

In rabi season 2012, six diversed maize inbred lines were crossed in all possible combinations without reciprocals by using a half diallel mating design to obtain 15 single cross. Inbred parents and their F1 single crosses with a check were evaluated in rabi season 2013 to evaluate the role of general and specific combining ability and heterosis for some quantitative traits. Significant general combining ability variances was observed only for cob height and specific combining ability variances were observed for plant height, cob height, cob length, cob girth, number of kernels per cob, cob weight and hundred grain weight. The GCA/SCA ratio was less than unity for all studied traits except shelling percentage; this means that these traits are pre-dominantly controlled by non-additive gene action. Based on GCA estimates, it could be concluded that the best combiners were ML01, ML05 and ML29 inbred lines for most of the studied traits. This result indicated that these inbred lines could be considered as good combiners for improving these traits. Significant positive SCA effects were found for all studied traits except number of kernels per row and shelling percentage. Based on SCA effects, it could be concluded that the crosses ML01×ML02, ML02×ML05, ML02×ML29 and ML05×ML15 could be exploited by the maize breeders to increase maize yield. Three F1 hybrids such as ML02×ML15, ML02×ML29 and ML05×ML15 proved to be the outstanding hybrids to immediate further steps for commercial cultivation. In a conclusive decision the F1 hybrid, ML02×ML29 was the best combination as evaluated through combining ability and standard heterosis.

Twenty short-statured maize inbred lines were collected from CIMMYT India and Mexico through the Plant Breeding Division, Bangladesh Agricultural Research Institute (BARI), Gazipur. The experiment was conducted from November 2020 to April 2021 in three different agroecological regions such as BARI, Gazipur, RARS Barisal and RARS Rangpur. Seven inbred lines were selected on the basis of genetic diversity and per se performance and they were crossed separately in a 7 × 7 half diallel fashion, producing 21F1 hybrids in 2019 which were evaluated at three locations. However, variances due to GCA were much higher in magnitude than SCA for all the characters indicating preponderance of additive gene effects on the inheritance of these characters. Two parents viz., P3 (CML33) and P4 (CML41) were good general combiners and two crosses viz., P4 × P5 (CML41 × CML31) and P5 × P7 (CML31 × CML124) expressed significant positive SCA effects coupled with significant positive heterosis for grain yield and for most of the yield contributing characters over the two commercial check varieties BHM 9 and NK40. Four crosses: P1 × P5 (CML116 × CML31), P1 × P6 (CML116 × CML32), P2 × P6 (CML72 × CML32) and P3 × P4 (CML33 × CML41), exhibited significant and negative SCA effects for both plant and ear height which were desirable for short stature. Genotypes x location interaction was also significant for maximum characters, suggesting that genotypes interacted significantly in different environments.

A half diallyl cross among eight new yellow maize inbred lines, i.e. Gm. 142, Gm. 224, Gm. 233, Gm. 152, Gm. 297, Gm. 330, Gm. 201, and Gm. 303, was made in 2015 summer season. Twenty eight F1 crosses along with two yellow commercial check hybrids, SC162 and SC168 were evaluated in randomized complete block design with four replications at two locations (Gemmeiza, Gharbia and Sids, Bani Sweif, Egypt) in 2016 summer season to study the combining ability to identify the most superior parental inbred lines that produce superior hybrids and develop high yielding new yellow single crosses. Results indicated that mean squares of crosses exhibited significant or highly significant for all studied traits. Mean squares due to GCA and SCA were significant or highly significant for all studied traits at combined over the two locations, except GCA for ear diameter trait and SCA for ear length trait, which were non-significant. The ratio of GCA/SCA was more than unity for all studied traits at combined over the two locations, except days to 50% silking and ear diameter traits, indicating that additive gene was more important than non-additive gene action. The interaction between GCA and SCA and locations were highly significant for all studied traits, except GCA x Loc. for ear diameter trait and SCA x Loc. for ear length trait. The magnitude of the interaction was highest for GCA × locations than the SCA × locations for plant height, ear height, ear length and grain yield, indicates that additive genetic variance was influenced by environment and the additive component interacted more with the environment than the non-additive and vice versa for days to 50% silking and ear diameter. According to analysis of GCA effects, the best general combiners were P3 (Gm.233) for earliness; P4 (Gm.152), P5 (Gm.297), P6 (Gm.330) and P7 (Gm.201) for plant height (shortness); P5 (Gm.297), P6 (Gm.330) and P7 (Gm.201) towards lower ear position; P4 (Gm.152) and P6 (Gm.330) for ear length; P1 (Gm.142) for ear diameter; and P1 (Gm.142), P5 (Gm.297) and P8 (Gm.303) for grain yield. Based on mean performance and SCA effects analysis, there were seven crosses No. 1, 2, 5, 7, 9, 25 and 26 (P1 x P2, P1 x P3, P1 x P6, P1 x P8, P2 x P4, P5 x P8 and P6 x P7) were the best combinations where they recorded significant or highly significant positive SCA effects for grain yield.

Two field experiments were carried out during the 2014 and 2015 seasons to evaluate certain genotypes of Egyptian cotton under well irrigated and water stress conditions. The cross combination Giza 69 x Australy recorded the best values for better parent heterosis for all physiological measurements and earliness index under well irrigated and deficit conditions. Of the female parents, Giza 86 was found to be a good general combiner for most yield characters under both normal and stress conditions, followed by Giza 94. Data illustrated that Giza 45 was the best general combiner for most fiber quality traits under both conditions. The cross combinations Giza 86 x Dandra and Giza 69 x Pima S6 showed significant positive SCA values for seed cotton and lint yield/plant under well irrigated and water deficit conditions. However, the combinations Giza 77 x PimaS6 and Giza 94 x 10229 recorded significant positive SCA effects for seed cotton yield/plant under stress. Whilst, the cross Giza 68 x 10229 recorded significant desirable SCA effects for most fiber quality properties. In this context, the estimates significant positive general and specific combining ability effects indicated that the epistasis and/or dominance effects for F1 hybrid in cotton could be important to a certain extent.

Combining ability of maize germaplasm is of great value to maize breeders. Thus, combining ability for grain yield and agronomic traits was studied in a line x tester crossing program. Thirty six testcrosses produced by crossing (18 inbred lines x 2 testers) along with two commercial check hybrids i.e. SC 10 and SC 128 were grown in replicated yield trail using randomized complete block design with 4 replications in 2011 at two locations, i.e. Sakha and Sids Research Stations. Data were recorded for days to 50% silking, plant and ear heights, number of ears per plant and grain yield (ard./fed.). Mean squares of entries and entries x locations exhibited highly significant to indicate that the two locations differed between them as soon as mean squares due to lines and testers were highly significant for all studied traits, indicating the presence of wide diversity among inbred lines and among testers for these traits. The best performance and desirable GCA effects were recorded for L4 for grain yield and silking date , L14 and L18 for plant and ear heights and L3, L4 and L5 for number of ears / plant. Based on mean performance of F1 crosses per se, cross L4 x T2 significantly out yielded the check hybrids SC 10 and SC 128. Significant positive SCA effects were found for the same single cross. The additive type of gene action played an important role in the inheritance of all studied traits except for grain yield and number of ears/plant, where non-additive gene effects played an important role in the inheritance of these traits. Moreover, the magnitude of σ2GCAxLoc interaction was higher than σ2SCA x E interaction for all studied traits, indicating that the additive type of gene action was affected more by environment than non-additive one.