SCA Effects Research Articles

Combining ability and heterosis in bell pepper grown in the north-western hills of India

In this study, 51 hybrids were developed using Line × Tester mating design, including 17 lines and 3 testers. Analysis of variance for combining ability indicated that differences among parents were significant for all the characters under study except for days to first picking. The σ2 SCA were higher in magnitude than σ2 GCA for almost all the traits except for days to first picking, which indicates the predominant role of non-additive gene action. Lines viz., UHF CAP-23, UHF CAP-1 and UHF CAP-22 and 2 testers viz., Yolo Wonder and California Wonder were the most promising for yield per plant and the majority of yield contributing traits. The SCA effects for fruit yield per plant were significantly desirable in UHF CAP-30 × California Wonder, UHF CAP-2 × Solan Bharpur and UHF CAP-29 × Solan Bharpur. Heterosis over the standard check and other genetic parameters 3 cross combinations viz., UHF CAP-30 × California Wonder, UHF CAP-23 × Yolo Wonder and UHF CAP-22 × California Wonder performed well for a majority of yield and yield contributing traits. These hybrids can be recommended for cultivation after multi-locational testing.

#4465 NO DIFFERENCES IN ALL-CAUSE OR CARDIOVASCULAR MORTALITY BETWEEN DIALYSATE CALCIUM OF 1.25 AND 1.50 MMOL/L: RESULTS FROM A EUROPEAN HEMODIALYSIS COHORT

Abstract Background and Aims The appropriate prescription of dialysate calcium (DCa) concentration for hemodialysis (HD) patients is debated and guidelines are inconsistent. We investigated the association between DCa and all-cause, cardiovascular mortality and sudden cardiac death (SCD). Moreover, we examined the association between serum dialysate calcium gradient (SCa-DCa) and the study outcomes. Method In this historical cohort study, we included adult incident HD patients registered in the clinical database EuCliD® with dialysis initiation between January 1, 2010, and June 30, 2017 (recruitment period) who survived for at least 6 months after starting dialysis (grace period). We observed patients’ outcomes for up to 2 years after the end of the grace period (Figure 1). We categorized patients into 2 groups according to the prescribed DCa in the last 3 months of the grace period (ascertainment period): 1.25 (DCa 1.25) or 1.50 mmol/l (DCa 1.50). We calculated hazard ratio (HR) with 95% confidence intervals (CI) for all study outcomes with Cox Regression. The fully adjusted model included age, sex, ethnicity, diabetes mellitus, cardiovascular disease, liver disease, cancer, vascular access, treatment time, Kt/V, total ultrafiltered volume per session, serum hemoglobin, serum albumin, calcium containing phosphate binders, active vitamin D, Cinacalcet. We added country indicators as random effects. The SCa-DCa (in mEq/l) was calculated as (albumin-correct serum calcium (in mg⁄dl) × 0.5) – (DCa (in mmol/l) × 2) (1). Results We included 12,897 patients with DCa 1.25 and 26,989 patients with DCa 1.50 from 22 countries. The median age was 65 years and the percentage of men was 61% in both groups. In the unadjusted model, patients treated with DCa 1.50 had higher risk of all-cause mortality compared to those treated with DCa 1.25 (HR 1.07 [95% CI 1.01-1.12]. However, this association was not robust when adjusting for potential confounding (HR 1.04 [95% CI 0.97-1.10]). Similarly, we found no evidence of significant adjusted association between DCa and cardiovascular mortality (HR 1.01 [95% CI 0.92-1.11]). We observed a significant adjusted lower association between DCa 1.50 and SCD (HR 0.78 [95% CI 0.65-0.94]). We found significant associations between larger SCa-DCa gradient and all outcomes: all-cause (HR 1.16 per 1 mEq/L increase [95% CI 1.09-1.24]), cardiovascular mortality (HR 1.23 [95% CI 1.12-1.35]) and SCD (HR 1.69 [95% CI 1.41-2.03]). To explore the contribution of gradient components to patients’ risk, we included both DCa and serum calcium level (SCa) in the models. We observed significant associations with all outcomes and SCa, but not with DCa and the interaction between them. In a subgroup analysis of patients with iPTH levels below 130 pg/ml (n = 7,438), we did not find any significant association between DCa and the outcomes. Conclusion In this observational study, no differences in all-cause or cardiovascular mortality were observed with the prescription of DCa 1.50 as compared to 1.25 after adjustment for confounders, whereas the risk of SCD appeared to be lower in the group of DCa 1.50. The association between the SCa-DCa gradient and outcomes appears to be predominantly related to the effect of SCa.

English

Twenty-one crosses developed from the frame of line × tester analysis along with ten parents were grown in two replicates experiment. Data on days to flowering, days to maturity, plant height, number of pods/plant, number of primary branches, number of secondary branches, number of tertiary branches, number of seeds per pod and seed yield per plant (g), revealed high significant differences exist among lines, testers and crosses for all traits studied. The ratio value of general combining ability variance to specific combining ability variance suggests the preponderance of non-additive type as well as additive gene action for some traits. Genotype Pusa-362 was the best general combiner for days to flowering. Genotype ICCL-87322 was identified as the best general combiner for the number of seeds per plant. Genotype BG329 was identified as the best general combiner for seed yield per plant (g) followed by KPG-59. Genotype PG-92-4 recorded desirable and significant GCA across five traits consistently. Cross PG-92-4 X Pant-186 recorded five significant SCA in the positive direction for secondary branches, number of tertiary branches, number of pods per plant, seed yield per plant and hundred seed weight. This cross is considered the most important compared to other materials under study. The proportional contribution of line × tester interaction was evident for most of the traits followed by the contribution of maternal lines. Days to flowering, days to maturity, primary branches, secondary branches, tertiary branches, pod per plant, seed per pod and seed yield per plant (g) recorded higher SCA variance suggesting non-additive gene action exit in expressing of these traits. The presence of a high SCA effect suggests that heterosis breeding can be exploited. Selection for those characters should be undertaken in later generations when these traits are fixed in homozygous lines. Key words: Chickpea, Cicer reticulatum, combining ability, gene action, heritability.

Combining Ability Analysis for Seed Yield and Attributing Traits in Linseed (Linum usitatissimum L.)

A complete set of 79 entries comprising of twelve parents, their 66 F1s and one check RLC-92 were evaluated during rabi 2020-21 at two locations i.e., ARS, Dahod, and BTRS, Anand, under two dates of sowing i.e., 2nd fortnight of October and 1st fortnight of November. The present study aimed to investigate the combining ability analysis over environments for seed yield and attributing traits in linseed (Linum usitatissimum L.). Among the all four environments, E1 had higher mean value for seed yield per plant and all other important yield contributing traits by sowing in second fortnight at Dahod conditions best for linseed cultivation. Combining ability analysis revealed importance of both additive and non-additive variances with prime role of non-additive genetic variance for seed yield per plant and its related traits in all environments as well as pooled over environments suggesting heterosis breeding would be more useful for development of superior hybrids if sterility system available. Among the parents; Shekhar, GS 384, KB 9610 and K 29 were good general combiners for seed yield per plant and test weight and capsules per plant. The parent viz., IPI 10, H 45, GS 384 and RLC 133 were good general combiners for earliness. The cross Indira × ILS 264, Gaurav × H 45 and RLC 133 × Shekhar showed higher sca effects for seed yield and test weight. Most of the crosses with high per se performance involved at least one good general combining parent such as Shekhar, GS 384, KB 9610 and K 29 through out for all studied characters.

Combining ability analysis for grain yield and quality characters in pearl millet [Cenchrus americanus (L.) Morrone

The objective of the present study is to estimate the combining ability effects among parents and their crosses in pearl millet, to identify promising cross combinations for grain yield and its component traits. In combining ability analysis, the extent of sca variance was higher than gca variance for all of the characters demonstrating the predominance of non-additive gene action except for panicle length and 1000-grain weight. The estimates of general combining ability suggested that parents, RIB 17 S/109, RIB 16300, RIB 37-40 S/17, RIB 13-16 S/17, ICMA 96666 and ICMA 94111 were good general combiners for yield and its contributing characters. The best hybrid, ICMA 94111 x RIB 16296 involved low x low performing parents which exhibited high positive and significant SCA effect for grain yield and most of the yield contributing and quality traits like protein, iron and zinc. These good combiner lines may be exploited to develop iron and zinc rich hybrids along with grain yield to alleviate malnutrition in people of the country. Keywords: Pearl millet, combining ability, gene action, male sterile line, tester.

Genetic studies on yield and yield attributing traits in sesame (Sesamum indicum L.)

Six diverse parents were crossed in a half diallel fashion to study the heterosis and combining ability in sesame. Parents, 15 F1s with one check was planted in RBD design at College Farm, NAU, Campus Bharuch during kharif-2021. The mean sum of squares due to genotypes and hybrids were significant for all the traits while, due to parents were significant for most of the traits. The mean sum of squares due to parents vs. hybrids were found to be significant for some traits. The gca and sca ratio was less than unity indicated that non-additive components play a greater role in the inheritance of most of the traits. Parents, Ingorala 5 and DC 4 had high per se and also good general combiner for seed yield and its traits, while hybrids AT 476 x Ingorala 5 and AT 332 x Ingorala 5 had the highest standard heterosis and sca effects for seed yield and some of its traits. Keywords: Sesame, Heterosis, Combining ability, Gene action

Heterotic Classification of Inbred Lines of Maize Based on Combining Ability for Kernel Yield

Grouping of maize inbred lines into heterotic groups is an initial step in exploitation of heterosis. Hence a field study was conducted to classify 27 inbred lines into two heterotic groups by evaluating the performance of 54 crosses along with lines and testers in a simple lattice design. The 27 inbred lines were crossed to two broad based heterotic testers. Highly significant differences were noticed for kernel yield per plant, days to anthesis, days to silking and plant height among all the genotypes. One cross PI 330 × LM 13 was found to be promising among the crosses. Highly significant GCA and SCA effects for kernel yield per plant was recorded. Five inbred lines were identified as good general combiners for kernel yield per plant while nine test crosses were found to be good specific combiners. Out of 27 inbred lines, the testers could classify 15 inbred lines into heterotic groups based on GCA and SCA effects and mean kernel yield per plant. The study demonstrated the applicability of combining ability effects in classifying the inbred lines.

Estimating the combining ability and genetic parameters for growth habit, yield, and fiber quality traits in some Egyptian cotton crosses

It is crucial to understand how targeted traits in a hybrid breeding program are influenced by gene activity and combining ability. During the three growing seasons of 2015, 2016, and 2017, a field study was conducted with twelve cotton genotypes, comprised of four testers and eight lines. Thirty-two F1 crosses were produced in the 2015 breeding season using the line x tester mating design. The twelve genotypes and their thirty-two F1 crosses were then evaluated in 2016 and 2017. The results demonstrated highly significant differences among cotton genotypes for all the studied traits, showing a wide range of genetic diversity in the parent genotypes. Additionally, the line-x-tester interaction was highly significant for all traits, suggesting the impact of both additive and non-additive variations in gene expression. Furthermore, the thirty-two cotton crosses showed high seed cotton output, lint cotton yield, and fiber quality, such as fiber length values exceeding 31 mm and a fiber strength above 10 g/tex. Accordingly, selecting lines and testers with high GCA effects and crosses with high SCA effects would be an effective approach to improve the desired traits in cotton and develop new varieties with excellent yield and fiber quality.

Exploitation of combining ability and heterosis potential for improvement in okra (Abelmoschus esculentus) genotypes

The present investigation was undertaken with the objective to carry out combining ability and heterosis for 13fruit yield and its attributing traits in 14 parents and their 24 crosses in okra (Abelmoschus esculentus (L.) Moench)at vegetable research farm, CCS Haryana Agricultural University, Hisar, Haryana during spring-summer season2019–20 and rainy (kharif) season 2020–21. Four crosses, viz. HB-20-3-4 × Hisar Naveen (HN), Hisar Mutant (HM)-1× Hisar Unnat (HU), HBMS-1 × Hisar Unnat (HU) and HB-76-2-4 × Hisar Naveen (HN) showed highly significantpositive economic heterosis for yield and its contributing traits.Parents HB-20-3-4 and HM-1 were found to be thebest general combiner for most of the economic traits. While, cross HB-60-1 × HN followed by HBMS-1 × HU, HB-20-3-4 × HN, HM-1 × HU and HB-96-2 × HU demonstrated strong SCA effects for yield and its attributes. The ratio of general combining ability (σ2GCA) and specific combining ability variances (σ2SCA) was less than one for all the quantitative traits indicating the non-additive gene effects predominated in determining the expression of allthese characters and demonstrates variability in genotypes, which provide ample scope for improvement of yield and its contributing traits in okra. Line HB-60-1 when crossed with Hisar Naveen, and HBMS-1 with Hisar Unnat gavesuperior hybrids as compared to other crosses. Hence, these parents can be exploited for further genetic improvement programmes and isolation of desirable segregants in okra.

The nature and extent of heterosis, combining ability under the influence of character associations, and path analysis in Basil (Ocimum basilicum L.)

The genus Ocimum contains 35 aromatic species of annual, perennial, and shrub. Basil essential oil has a pleasant scent that both energizes and purifies the environment. It is consumed worldwide because of its anti-oxidant and anti-aging properties. The study aimed to find superior hybrids of the basil that produced high amounts of essential oil of better quality. It estimated heterosis while also combining ability, path, and other genetic parameters. We examined basil's general and special combining abilities and other genetic variables that determine yield, chemical makeup, and economic traits. The mean squares for variances in general and specific combining abilities (GCA and SCA) were significant for all thirteen traits, demonstrating that additive and non-additive genes influence these attributes. The hybrid L1 × T3 produced the highest essential oil (6.39 ml/plant), followed by L2 × T1 and L3 × T1 (5.13 ml/plant). The hybrid L1 × T2 and L5 × T1, with the most considerable SCA effect, produced better performances for the (-) linalool content (71.61% and 61.67%). The narrow-sense heritability for the eight characteristics under investigation ranged from 0.0038% to 62.95%. Narrow-sense heritability was moderate in terms of plant height and herb yields. It was high for branches/plant, essential oil yield, and camphor content (%). The genetic advance was also high in most characters, except for three traits: medium inflorescence length, and Chavibetol concentration. We investigated correlations between traits and contributions of the characters toward essential oil yield, as well as differential heterosis in hybrids for the stated variables, to gain a clear picture of the genetic advancement of the basil crop. With the exception of two traits—days to flowering and essential oil—the amplitude of SCA was greater than GCA variance, demonstrating the preponderance of non-additive gene action in the basil. The hybrids L1 × T1 followed by L1 × T3 and L2 × T1 were best for the essential oil yield of better quality. The L × T design is utilized for the first time and described in the Ocimum. These improved hybrids could be beneficial to large-scale farming.

Assessment of combinational ability of inbred lines of winter rye by the topcross method

Dentification perspective on combinational ability of the inbred lines of winter rye is an important stage in hybrid breeding. The purpose of researches - to estimate the general and specific combinational ability of the inbred lines of winter rye by a method of full top crossings. As a maternal form 30 homozygous lines of rye bearing sterile cytoplasm Pampas type served. As testers 4 male fertile homozygous lines used : mfН-1432, mfН-1423, mfН-1147 and mfН-1842. Test crossings carried out in 2019 on spatially the isolated plots. In total 120 simple interlinear hybrids of F1 were received. Their test carried out in 2020 on plots 8,0 m2 in 2 repetitions at norm of seeding of 500 grains on 1 m2. As the standard used population variety Valdai. Productivity of hybrids F1 varied from 5,08 to 7,55 t/hectare at average productivity in experience 6,27t/hectare. Hybrids with participation of the line msH-1185-1 were the most yielding. Their productivity varied from 6,92 to 7,48 t/hectare depending on a tester. Frequency of hybrids of F1 with authentically high competitive heterosis made 20 of 120 or 16,7 %. In dispersion of a sign of productivity the essential contribution was made both the general (GCA), and specific (SCA) combinational ability. However fell to the share of effects GCA 91,2 % of all dispersion of productivity, and to SCA share - 6,9 %. The high relation variances by GCA/SCA is pointed to rather high genetic divergence by the inbred lines taken for crossing. Authentically high GCA showed 7 sterile lines: ms H-1185-1, msH-1185-2, msН-1179, msН-1238, msН-700, msН-48, msН-1247. Among lines testers of the best on GCA there was mfН-1147. High effects of SCA showed the msН-451, msН-577, msН-842, msH-1185-2 and msН-1190 lines, and also testers of mfН-1432 and mfН-1423. It is characteristic that average productivity of hybrids with participation of lines with high GCA was authentically above, than average productivity of hybrids with participation of lines from high SCA (6,76 t/hectare against 6,24 t/hectare, tfact=3,38> t05=2,22). Significantly low GCA possessed 9 sterile lines. Positive correlation between effects of GCA lines and level of their own productivity is revealed (r=0,59, t fact =2,30> t 05=2,22)

Heterosis and Estimation of General and Specific Combining Ability as Base for Selected Superior Recombination of the Some Crossed Cotton Genotypes

The objective of this study was to determine the general and specific combining abilities and heterosis of some cotton genotypes for yield, its components and fiber traits using line x tester mating design. Nine parents (six line and three testers) were crossed in a line x tester mating design in 2020 season. Nine parents along with their eighteen F1 crosses were studied in a randomized complete block design (RCBD) with three replications during 2021 at Sakha. Agricultural. Research. Station. Kafr El-Sheikh, Governorate, Egypt. Based on line x tester analysis, the variance due to genotypes, parents, crosses and parent vs. cross exhibited significant differences (P. 0.01) for most yield, yield components and fiber traits. The variance due to GCA of lines x testers and SCA of line x tester interactions were highly significant for most studied traits, indicating the importance of both additive and non-additive gene actions in controlling these traits. The estimates of GCA and SCA effects revealed that the parent and some crosses were having desirable and significantly GCA and SCA effects, respectively. High mean performances and significantly GCA effects values were observed of line Giza 92, Giza 75 and tester Giza 97 for most studied traits, hence, these parents can be used as for generation superior cotton hybrids. The best values of mean performances, SCA effects and heterosis were found in the combinations Giza 94 x Giza 92, Giza 97 x Suvin for most yield and yield components and the cross Giza 97 x (Giza 75 x Sea) for yield and fiber traits. These crosses are considered as the promising crosses to be used in breeding programs for produce hybrid cotton and improvement for these traits in Egypt.

Combining Ability of Cowpea (Vigna unguiculata (L) Walp) Genotypes for Resistance to Cowpea Bacterial Blight in Uganda

The low productivity of cowpea is partly attributed to a number of constraints including diseases such as cowpea bacterial blight (CoBB). Cowpea bacterial blight has the capacity to cause up to 92% yield loss under severe infections. The objective of this study was to determine the combining ability for resistance to CoBB among cowpea genotypes in Uganda. Nine selected parents were crossed to produce 63 progenies. F1 progenies were evaluated and data gathered included days to 50% flowering, CoBB disease scores and grain yield. The mean squares for rAUDPC due to GCA and SCA effects were significant (P≤0.001) and non-significant respectively. The broad sense coefficient of genetic determination (BCGD) and narrow sense coefficient of genetic determination (NCGD) were 44.3% and 29.1% respectively for rAUDPC. Parents WC 26 (-0.023) and NE 31 (-0.035) had highly significant negative GCA effects for rAUDPC and were therefore good general combiners for this trait. Crosses SECOW 3B x ACC 26 X SECOW 1T and WC 26 x NE 32 had negative significant SCA effect for rAUDPC with a values of -0.073 and -0.06, respectively while Crosses ACC 26 x SECOW 1T x NE 40 (-0.07) and NE 40 x WC 26 (-0.06) had significant negative reciprocal effects for rAUDPC. This study revealed that genetic inheritance for cowpea bacterial blight was controlled predominantly by additive gene effects. Parents WC 26 and NE 31 identified as good general combiners for resistance to CoBB could be utilized as sources of resistance while Crosses SECOW 3B x ACC 26 X SECOW 1T, WC 26 x NE 32, ACC 26 X SECOW 1T x NE 40 and NE 40 x WC 26 that were the best specific combiners for resistance to CoBB could be put under further evaluation as potential varieties.

Heterosis and Combining Ability Analysis in Maize Using Line X Tester Model

Twenty-two lines were crossed with 2 testers in a Line × Tester mating design in 2017-18 and the resulting 44 crosses along with the lines, testers and three checks i.e., BARI Hybrid Maize 9 (BHM 9), 981 and Elite were evaluated in a alpha lattice design with two replications, during rabi, 2018-19. Highly significant differences were found among the genotypes for all the characters studied. Parent and parents vs crosses were significant for all the characters except ASI indicating greater diversity in the parental lines of the traits. Three lines (viz., BMZ 55, BMZ 53, BMZ 4) showed significant negative GCA effect for both days to 50% tasseling and silking, indicating good general combiners for earliness. BMZ 15, BMZ 55, BMZ 53 and BMZ 68 showed significant negative GCA effects for both plant and ear height. BIL 79, Pinacle 17 and BIL 182 exhibited desirable significant positive GCA for grain yield. Considering desirable GCA effects those parents could be used extensively in hybrid breeding program to accumulate those favorable genes. However, two cross combinations BIL 182 x CML 429 and BIL 79 x CML 429 were found promising considering SCA effect, mean performance and could be utilized for enhancing hybrid production. Considering BHM 9 as check, the percent standard heterosis for grain yield varied from -52.6 to 0.6%. None of the crosses showed significant positive heterosis for grain yield except BIL 79 × CML 429.
 Bangladesh J. Agril. Res. 46(3): 261-274, September 2021

Genetic assessments, dominance estimates of economic traits of gynoecious cucumber (Cucumis sativus) under Himalayas

In India generally monoecious and cross-pollinated cucumber (Cucumis sativus L.) hybrids/varieties are grown. The use of stable gynoecious cucumber varieties/hybrids would increase the productivity of cucumber in India. In the past, despite improvement in monoecious cucumber varieties/hybrids, little effort has been done into the development of stable gynoecious hybrids. To address this issue 3 genetically diverse gynoecious lines and improvement, and 6 testers were crossed in line × tester fashion to develop 18 crosses during 2017. These 18 crosses along with 9 parents evaluated at the Krishi Vigyan Kendra, Kandaghat, Himachal Pradesh and Dr. YSPUHF, Solan, Himachal Pradesh during pre-kharif season 2018–19 to determine the mode of gene action, combining ability, extent heterosis and potence ratio for 12 quantitative traits. Experimental results depicted that the dominant component of variance (σ2S) was found higher than the additive component of variance (σ2S) for all the traits indicating a predominant role of non-additive gene action governing yield and its contributing traits during both the years. Gynoecious inbred lines KTG-40, 2870G and testers K-90, UHF-16 were found most promising general combiners for fruit yield. The cross combination KTG-40 × K-90 and 2870G × K-90 isolated based on heterosis manifested and SCA effects. Further, the performance of top 7 heterotic crosses illustrate the presence of overdominance in most of the crosses for traits under study, suggesting the importance of heterosis breeding for the development of early, high-yielding, disease tolerance stable gynoecious hybrids in cucumber.

Diallel Analysis for Quantitative Traits in Rice Germplasm (Oryza sativa L.) Across Locations

A diallel cross from seven parents and their F1 hybrids were evaluated across three locations using a Randomized complete block design with three replications for their quantitative traits performance. Parameters assessed include plant heights, days to 50% headings, panicle lengths, panicle weights, number of seeds per panicle, number of productive tillers, number of panicle branches, yield per plots which were extrapolated to yield in tonnes per hectare and 100 grain weights. Results obtained showed a significant difference among parents and F1 hybrids performance across different locations evaluated. GCA and SCA effects were computed, variance components that is additive, dominance, heritability in both narrow sense and broad sense were also computed.

Estimating gene action and combining ability for yield and fiber quality in cotton (Gossypium hirsutum L.)

Genetic evaluation of segregating populations is one of the primary activities of cotton breeders. Seven cotton genotypes were crossed in a line ? tester mating design. The population of 12 F1, 12 F2 and their parents were tested in Randomized Complete Block Design with three replications at the Nazilli Cotton Research Institute of T?rkiye during the 2014/2015 cotton-growing season. The genetic variability was significant for all characters studied. ?2GCA/?2SCA indicated non-additive gene action in controlling seed cotton yield (F2), ginning out-turn (F1) and fiber quality traits for both generations. The highly favourable GCA effects for seed cotton yield and fiber strength were recorded in the Carmen cultivar. Carmen ? Carisma hybrid exhibited high mean performance and SCA effects for seed cotton yield and fiber strength, while the performance of Gloria ? ST-468 was superior in terms of ginning out-turn. We concluded that individual plants with desired traits should be selected in later generations due to the preponderance of non-additive gene actions.

Early generation combining ability of maldandi restorers in rabi sorghum [Sorghum bicolor (L.) Moench

In this study, a reported restorer on maldandi cytoplasm DSMR 8 was used to identify combining ability in early segregating generation. A large F2 population of the cross M31-2A × DSMR 8 was raised. Among them, fifteen superior restoring plants were selected and forwarded to the F3 generation. These fifteen F3 plants were crossed to three male sterile lines having both milo and maldandi cytoplasmic sources (M31-2A, 401A, and 104A) in L × T design. Among lines, MR 4 showed significant positive gca effects for six traits. Among 45 crosses 18 recorded high sca and the remaining 27 crosses showed low sca. The crosses M 31-2A × MR 12 and M 31-2A × MR 14 showed maximum overall sca status as they were having significant positive sca effects. Out of 15 lines, only five lines viz., MR 4, MR 12, MR 1, MR 13, and MR 2 could be forwarded to the next generation as these lines were transgressive seggregants for combining ability because of good gca and better per se performance when crossed to maldandi cytoplasm.

Studies on gene action and combining ability in rice (Oryza sativa. L) hybrids

The study was carried out to learn about the nature of gene action and combining ability in rice hybrids for grain yield and its component traits. For this, eight lines were crossed with four testers in an L x T mating design. The analysis of variance revealed significant variance for all the characters studied among the parents and hybrids. GCA variances were higher than SCA variances for most of the characters, indicating the predominance of additive gene action, while SCA variances were higher than GCA variances for number of productive tillers per plant, pollen fertility, hulling, milling, head rice recovery and grain yield per plant, indicating the predominance of non-additive gene action. The testers JMS 13A (3.91) and CMS 59A (2.46), as well as the lines MTU 1153 (9.52), RNR 28355 (3.26) and RNR 26085 (3.09), were the best combiners for grain yield and important yield components due to positive GCA effects. Based on SCA effects and corresponding mean performance for grain yield and its component traits, the hybrids CMS 59Ax RNR 26015, CMS 23A x JGL 25960, CMS 64Ax RNR 26015 and JMS 13Ax MTU 1153 were identified as the best specific combiners. These hybrids could be tested in multi-environment trials for commercial use. Keywords:  CMS lines, Gene action, Combining ability, GCA, SCA, Line x Tester &nbsp

HETEROSIS AND COMBINING ABILITY STUDIES IN PEARL MILLET

The present research was carried out to assess combining ability and heterosis through a complete 5x5 diallel experiment for grain yield and related parameters in Pearl millet (Pennisetum glaucum L.). GCA effects were highly significant for days to 50% flowering, panicle length and plant height while non- significant for grain yield per plant, no. of productive tillers and panicle girth. SCA effects were highly significant for grain yield and non- significant for rest of the characters. These studies suggested that non- additive gene action was more important regarding the inheritance of grain yield while additive gene action had major role in the inheritance of days to 50% flowering, no. of productive tillers, panicle girth, panicle length and plant height. The parent MGP-84 was good general combiner for the parameters studied. 15RBS-01 was good general combiner for all the characters except days to flowering. The crosses, MGP-84 x 13RBS-09, MGP-304 x 15RBS-01, MGP-84 x 13RBS-10, 13RBS-10 x 15RBS-01, 13RBS-09 x 15RBS-01, MGP-84 x 15RBS-01 and MGP-84 x MGP-304 were the best combinations for grain yield which involved good x good and good x poor general combiners. SCA variance for grain yield was higher than GCA variance indicating that non-additive gene action had major role in its inheritance. GCA variances for days to flowering, productive tillers, panicle girth, panicle length and plant height were higher than SCA variances which suggested that additive gene action had played key role in the inheritance of these traits