General Combiners For Grain Yield Research Articles

Combining Ability Analysis of Maize (Zea mays L.) for Grain Yield and Yield Related Traits Using Line X Tester Method

This study aimed to evaluate the combining ability for yield and yield components in newly developed white maize lines. A total of 22 maize inbred lines, derived from various genetic sources at the Agricultural Research Station during the 2023 growing season, were used to create 40 hybrids. These hybrids, along with two commercial check hybrids (Karimnagar Makka and Kaveri Ekka), were evaluated at Agricultural Research Station. The analysis revealed highly significant differences for all traits studied. Among the inbred lines, KML-122, KML-7, and KML-6 were identified as good general combiners for grain yield and yield-contributing traits, such as days to 50% anthesis, days to 50% silking, days to maturity, and plant height. Based on specific combining ability (SCA) effects, the hybrids KML124×LM13, KML-131×LM-14, and KML-136×LM-13 were identified as specific combiners for yield and yield-attributing traits. The successful identification and utilization of these high-GCA inbred lines can significantly contribute to the development of superior maize hybrids, enhancing overall productivity and sustainability in maize cultivation. Data on twelve morphological traits were recorded, with non-additive effects found to be important for all characters.

Genetic analysis of tolerance to combined drought and heat stress in tropical maize.

Simultaneous occurrences of heat and drought stresses have a detrimental effect on growth, development and yield of maize. Heat and drought is expected to worsen maize yield losses under climate change. Selecting CDHS tolerant maize hybrids creates great opportunity for sustainable maize improvement in the tropics. The objective of current investigation was to dissect the genetic basis of CDHS tolerance in tropical maize and to determine performance of single cross hybrids under CDHS. Ninety six single-cross hybrids resulted from crossing 12 tassel blast tolerant and 12 tassel blast susceptible lines along with two Striga resistant commercial hybrids, a heat tolerant and a heat susceptible check hybrids were evaluated under FIRR, MDRTS and CDHS using 25x4 alpha lattice design with two replications. The results showed significant genetic variation for FIRR, MDRTS and CDHS tolerance among maize hybrids. The majority of single crosses that showed improved grain yield over their respective standard checks under MDRTS also exhibited improved grain yield over the same checks under CHDS, indicating development of CHDS tolerance hybrids. Significant and positive genotypic and phenotypic correlation of grain yield under MDRTS and CDHS implicated common genetic mechanisms controlling yield under MDRTS and CDHS. Stress tolerance indices YI, GMP, MP, HM and STI were identified as best selecting indices under both stresses. GCA variances were larger than SCA variances in each testing environment for most studied traits indicating the impotence of additive gene action than non-additive gene action to control these traits. Majority of stress indices and SCA effects demonstrated that hybrids HB18, HB41, HB91 and HB95 were high yielder under MDRTS and CDHS. Hybrids HB41, HB91 and HB95 and their parents' scored minimum tassel blast. Parents 19 and 7 were well general combiner for grain yield and early maturity under MDRTS and CDHS indicting their valuable source of genes for hybridization. The current findings revealed that CDHS tolerance hybrids can reduce expected yield losses and maintain maize productivity in CDHS prone areas. Promising hybrids should be tested further under various drought and CHDS for commercialization.

Assessment of Inbred Lines of Field Corn for Yield And Yield Attributes Through Line × Tester Method

A line × tester analysis comprising forty eight test-crosses generated by crossing 24 S3 inbred lines derived from commercial maize hybrid 981 with two testers. Heterosis study of these crosses against two standard checks was evaluated at Bangladesh Agricultural Research Institute, Gazipur during rabi 2015-16. The objectives of the study were to estimate general and specific combining ability effects of the inbred lines and to assess the test cross performance and estimate the amount of standard-heterosis of the hybrids for grain yield and yield related characters. Highly significant genotypic differences were observed indicated wide range of variability present among them. Five lines viz. Line 11, Line 14, Line 17, Line 24 and Line 30 were good general combiner for grain yield and possessed high means. Nine crosses showed (Line 18 × BIL22, Line 23 × BIL22, Line 27 × BIL22, Line 7 × BIL28, Line11 × BIL28, Line14 × BIL28, Line 24 × BIL28, Line 25 × BIL28 and Line 30 × BIL28) significant and positive specific combining ability effect for grain yield. The information on the nature of gene action with respective variety and characters might be used depending on the breeding objectives. These crosses, Line 24× BIL28 (11.40 t/ha), Line 18 × BIL22 (11.30 t/ha) and Line 25 × BIL28 (11.20 t/ha) showed higher yield, could be utilized in maize breeding activities. Estimation of heterosis was carried out using two commercial hybrids BARI Hybrid Maize-9 (BHM-9) and NK-40. The percent heterosis for grain yield varied from -23.39 to 4.6% against BHM-9. Among the 48 crosses, 13 crosses exhibited significant positive heterosis for grain yield.
 Bangladesh J. Agril. Res. 46(4): 469-489, December 2021

Heterosis and Combining Ability Studies in A 5x5 Diallel Crosses of Maize Inbred Lines

The present study was conducted to evaluate the genetic architecture of five diverse maize genotypes using combining ability analyses. General combining ability (GCA) mean squares were non-significant for grain yield and its related components. Specific combining ability (SCA) mean squares were highly significant for grain yield, the number of grains per row and cob girth while non-significant for days to tasseling, days to silking, plant height, cob height and cob length. These studies suggested the preponderance of non-additive type of gene action for grain yield, cob girth and number of grains per row and additive gene action for days to tasseling, days to silking, plant height, cob height and cob length. The genotypes MIL2020-51 and MIL2020-52 were good general combiners for grain yield, grains per row, cob height and plant height. These lines were the poorest general combiner for days to 50% tasseling and days to 50% silking which suggested that these genotypes had sufficient genes for inducing earliness. The crosses MIL2020-51 x MIL2020-54, MIL2020-52 x MIL2020-53, MIL2020-51 x MIL2020-55, MIL2020-53 x MIL2020-55and MIL2020-52 x MIL2020-55 were the best performing combinations for grain yield. These crosses involved good x good and good x poor general combiners. The reciprocal cross combinations MIL2020-55 x MIL2020-53, MIL2020-52 x MIL20220-51, MIL2020-54I x MIL2020-52, MIL2020-55 x MIL2020-51, MIL2020-54 x MIL2020-51and MIL2020-55 x MIL2020-54 showed large positive estimates for grain yield suggesting that cytoplasmic inheritance also had a role in the expression of grain yield. SCA variances were higher than GCA variances for grain yield, plant height, cob height, number of grains per row, cob girth and cob length which highlighted major role of non-additive genes in the inheritance of these traits. Additive gene action was found more important for number of days to 50% tasseling and number of days to 50% silking

Estimates of Combining Ability and Association among Morpho-Agronomic Traits of Single Cross Maize (Zea mays L.) Hybrids

Screening genotypes have a crucial role to increase the efficiency of selections in plant breeding program. Therefore, this study was emphasized to determine combining ability and the association between traits among themselves and yield. The experiment was conducted at Haramaya University Research Station (Raare) for two years (2018 and 2019) using 4x7 alpha-lattice design with three replications. Pooled analysis of variance revealed highly significant (p≤0.01) variations among crosses for grain yield and related traits. According to the result of combining ability analysis, parental line L3 was identified as a good general combiner for grain yield, ear diameter, 1000-kernel weight, and days to maturity. Similarly; L1, L2, and L8 proved as the best general combiner for number of kernels per row. Crosses L1×L6, L3×L5, L4×L6, L4×L8, and L5×L7 were found good specific combiners for 1000-kernel weight. Furthermore, the cross L5×L6 was the best specific combiner for ear diameter, whereas L4×L7 for both number of kernels per row and 1000-kernel weight. Likewise, the crosses L1×L5, L3×L8, L6×L7, and L7×L8 were identified as the best specific combiner towards earliness. Moreover, thousand kernel weight showed significant positive correlation with grain yield, conversely, days to anthesis, days to silking, ear aspect, and Puccinia sorghi exhibited significant negative correlation with grain yield at genotypic and phenotypic levels. Ear length, 1000-kernel weight, number of kernel rows per ear, and Turcicum leaf blight had positive direct effect on grain yield at genotypic and phenotypic level. In general, the result presented in the study might be useful for further breeding process to improve the productivity of maize.

Genetic analysis of yield and its attributes in bread wheat (Triticum aestivum L. em. Thell) under irrigated and rainfed conditions

Experiments were conducted to study genetics and combining ability for yield and its attributes under Irrigated (E1) and Rainfed (E2) conditions using F1 hybrids derived from Line X Tester mating design by crossing eleven lines with three testers. Significant differences were observed among all the genotypes for all the traits in both E1 and E2 environments. The σ2gca/σ2sca ratio indicated the predominance of non-additive gene action for all the characters in both environments. Therefore, this component of the variance can be utilized in the breeding program through the exploitation of heterosis and the selection process for identification of superior plant types should be postponed to further generations like F4 or F5. Based on combining ability effect and per se performance in rainfed conditions, parents UP2572 and VL3001 were identified as good general combiners for grain yield per plant. In cross combinations, cross PRL/2*PASTOR//PBW343*2/KUKUNA/3/ROLF07/4/BERKUT//… × WH1142 and UP2572 × WH1142 were identified as the best specific combiners for grain yield per plant under irrigated and rainfed conditions, respectively. So, these identified parents and cross combinations can be exploited for developing water stress tolerant cultivars by identifying transgressive segregants in further breeding cycles.

Combining Ability and Heterosis of QPM Hybrids for Yield, Qualitative and Quantitative Traits under Heat stress in Different Environments

With increasing climate change relates to rise in mercury causing heat stress in maize. Heat stress tolerance has appeared to be one of the foremost trait to overcome this situation. Relative magnitude of variances depicted additive and non-additive gene action for the expression of these characters were more extrusive for all the traits studied. GCA and SCA both showed huge collaboration with climate for all the characteristics. Parents NBPGR-36548 (P4), VL-153237 (P5) and BHU QPM-2 (P2) were found to be good general combiners for grain yield per plant, chlorophyll content, oil content and starch content. Indicating that they could be good parental lines in hybridization programs. The scope of heterosis communicated by various crosses was from 0.71 % (P2 X P6) to 45.11% (P5 X P6) in E1, from 0.42% (P1 X P7) to 5.69% (P1 X P8) in E2 and 18.92% (P4 X P8) in E3. The better performing five crosses P5 X P7, P5 X P6, P4 X P8, P5 X P9 and P4 X P5. Crosses between good x average, average x average and good x good shows greater economic heterosis and exhibited high SCA effects for yield under HS. These best Hybrids showed no side effects of leaf firing, tassel blast, root lodging and no severe loss of yield in the present investigation. These crosses additionally should be assessed further multi location in enormous scope.

Assessing Combining Ability of Doubled Haploid Maize (Zea mays L.) Breeding Lines for Grain Yield and Yield Components under Heat Stress Condition

Maize (Zea mays L.), a leading cereal worldwide and staple food of many countries, is a multipurpose crop used for human food, animal feed and industry purposes. Maize has wider genetic adaptability to grow under different agro-ecological environments. 29 and 48 DH lines derived from MPS 1 and MPS 2, respectively, were crossed with more than one testers belonging to opposite heterotic in L x T fashion. The resultant double haploid testcrosses, and their parents were evaluated along with checks during kharif (in South Asia: the autumn crop sown at the beginning of the summer rains) 2019 at three locations. Among female lines of MPS1, DH line ZL19337 was identified as good general combiner and registered significant negative GCA effect for days to 50 per cent anthesis and days to 50 per cent silking. While, DH lines ZL19641 and ZL19357 recorded significantly positive GCA for plant height and grain yield, respectively. Among female lines of MPS 2, DH line ZL19492 was identified as good general combiner and recorded significant negative GCA effects for days to 50 per cent anthesis, and days to 50 per cent silking. Similarly, DH lines, ZL19534 and ZL19572 were identified as good general combiners for grain yield and ear position, respectively. Among testers of MPS1, ZL1840 was identified as the good general combiner for days to 50 per cent anthesis, days to 50 per cent silking and plant height and CAL14113 for ear height and grain yield. Similarly, VL1010996 was identified as the good general combiner for days to 50 per cent anthesis, days to 50 per cent silking, plant height, ear height, ear position and grain yield in MPS 2. Hybrid ZH2063 exhibited desired SCA effects for days to 50 per cent anthesis and days to 50 silking and ZH2010 was identified as a good specific combiner for days to 50 per cent anthesis and grain yield in MPS 1. Hybrid ZH20158 recorded desirable SCA effects for the trait days to 50 silking, While, ZH20251 and ZH20183 were identified as good specific combiners for plant height and grain yield in MPS 2.

The Combining Ability for Grain Yield and Some Related Characteristics in Rice (Oryza sativa L.) Under Normal and Water Stress Conditions.

Drought is considered a major threat to rice production. This study aimed to determine the effects of drought stress on the estimates of heterosis and the combining ability of rice genotypes for the number of days to 50% heading, plant height, number of panicles per plant, panicle length, number of filled grains per panicle, and grain yield per plant. Field experiments were conducted at the Rice Research and Training Center, Kafr El Sheikh, Egypt, during the rice-growing season in 2018 and 2019. Eight rice genotypes (Giza178, Giza179, Sakha106, Sakha107, Sakha108, WAB1573, NERICA4, and IET1444) were crossed in a half-diallel cross in the rice-growing season in 2018, which yielded a wide range of variability in numerous agronomic traits and drought tolerance measurements. In 2019, these parents and their 28 F1 crosses were produced by employing a three-replication randomized complete block design under normal and water stress conditions. The results showed remarkable differences across the studied genotypes under normal and water stress conditions. Under both conditions, Sakha107 was the best general combiner for earliness and short stature. Giza179 and Sakha108 were the best general combiners for grain yield per plant and one or more of its characteristics. Furthermore, in both normal and water stress conditions, Giza179 exhibited the highest general combining ability effects for all attributes that were evaluated. Under normal and water stress conditions, the Giza179 × Sakha107 cross demonstrated substantial and desirable specific combining ability effects on all the examined traits, which suggested that it could be considered for use in rice hybrid breeding programs. Therefore, we recommend that these vital indirect selection criteria to be considered for improving rice grain yield under drought conditions.

Selection of Suitable Pearl Millet Hybrids for Arid and Semi-Arid Conditions through Combining Ability Analysis

Present investigation was carried out to study combining ability effects for grain yield and its component traits in 77 hybrids of pearl millet. From the results of GCA effects, it was revealed that a number of parents namely, ICMA 98222, ICMA 93333, ICMA 30199, ICMA 30201 (female parents), and BIB 481-500, BIB 561-570 and BIB 571-581 (male parents) were found to be good general combiner for grain yield and most of its component characters. On the basis of GCA effects, lines ICMA 98222, ICMA 88004, ICMA 93333, ICMA 30199, ICMA 30201 and testes BIB 571-580, BIB 561- 570, BIB 511- 520, BIB 481- 500, BIB 531- 540 were good general combiner for more than nine yield contributing characters. The SCA effects of the crosses namely, ICMA 97111 x BIB 561- 570, ICMA 98222 x BIB 481- 500, ICMA 88004 x BIB 501- 510 and ICMA 93333 x BIB 551-560 were significant and were identified as superior for seed yield and related traits over the environments. Therefore, these parents and hybrids were recommended for utilization in development of promising populations as well as hybrid development.

Heterosis and combining ability for floral and yield characters in rice using cytoplasmic male sterility system

Developing high-yielding rice genotypes is decisive to ensure global food security with current population growth and the threat of environmental pressures. Cytoplasmic male sterility (CMS) system provides a valuable approach for commercial exploitation of heterosis and producing high-yielding and quality hybrid rice. Three CMS lines and ten diverse restorers were crossed using line × tester mating design. The obtained thirty F1 hybrids and their thirteen parents were evaluated. Yield traits as well as certain floral traits characters that influence the efficiency of crossing and hybrid seed production as the duration of floret opening (min), stigma exsertion (mm), stigma length (mm), opening floret angle, and anther length (mm) were assessed. Highly significant variations were detected among parents, crosses, and parents vs. crosses for all the studied traits. The CMS line L2 and the restorer T5 were determined as good combiners for stigma exsertion, stigma length, opining floret angle, and duration of floret opening. Besides, the hybrids L1 × T1, L1 × T3, L2 × T2, L2 × T5, L3 × T4, L3 × T5, and L3 × T9 exhibited positive SCA effects for most floral traits. Moreover, the CMS lines L1 and L3 as well as the restorers T1, T2, T3, T6, and T9 were identified as good general combiners for grain yield and certain related traits. The hybrids L1 × T1, L1 × T5, L1 × T7, L2 × T3, L2 × T4, L2 × T5, L2 × T10, L3 × T1, L3 × T2, and L3 × T6 displayed positive SCA effects for grain yield and one or more of its attributes. Both additive and non-additive gene effects were involved in the governing inheritance of all evaluated traits. The biochemical variations among the certain evaluated genotypes were further studied. The esterase and peroxidase isozymes were applied for verifying the genetic diversity at the protein level among the used CMS lines, restorers, and their crosses. All the applied isozymes displayed polymorphism for the parents and their crosses. The banding pattern and intensity differences provided accurate results on the reliable variability among the tested genotypes.

Elucidation of gene action and combining ability for grain and forage yield and contributing traits in sorghum [Sorghum bicolor (L.) Moench

The present investigation was undertaken to achieve information on gene action and combining ability in sorghum [Sorghum bicolor (L.) Moench]. The experimental material consisted of eleven parents and their 28 Line × Tester crosses. The evaluation was carried out during Kharif, 2020 at Sorghum Research Station, S. D. Agricultural University, Deesa. The ratio of σ2D/σ2H being more than unity was found for days to flowering, which suggested a more significant role of additive genetic variance in the inheritance of this trait. In contrast, the rest of the yield and its component traits showed non-additive genetic variance. The gca effects indicated that parents, SR 3019, CSV 31 and GJ 43 were found as good general combiners for grain yield per plant. While, parents DS 156, CSV 31 and SPV 2682 were good general combiners for dry fodder yield per plant and its contributing traits. Based on estimates of sca effects, the most promising hybrids for grain yield per plant were viz., SR 2980 × CSV 31, SR 3019 × SPV 2573 and DSF 117 × SPV 2682, whereas for dry fodder yield per plant were viz.,SR 3048 × CSV 31, GJ 43 × SPV 2573 and DSF 168 × SPV 2573. The good general combiners for yield and contributing traits can be utilized in intensive crossing programme and select transgressive segregants for desired characters in segregating generations to develop superior lines. Keywords: L × T analysis, Gene action, combining ability, Grain yield, Dry fodder yield

Combining ability and heterosis studies in different crop sites for yield and yield contributing traits in sorghum (Sorghum bicolor (L.) Moench)

Forty eight hybrids, utilizing six male sterile lines and eight restorers of Sorghum (Sorghum bicolor (L.) Moench) were evaluated for general and specific combining ability, variance components and standard heterosis. Among the lines ICSA 427 and ICSA 433 and testers ICSR 13009 and ICSR 13031 were found to be good general combiners for grain yield per plot and other yield contributing traits. The estimates of σ2gca and σ2sca suggested a non-additive genetic variance for all the traits studied. Most of the cross combinations showed higher magnitude of specific combining ability effects volving high × high (H × H) and high × low (H × L) combining ability effects of lines and testers for grain yield per plot and other yield contributing traits. The estimates of standard heterosis for grain yield per plot ranged from -49.53 and -50.46 (ICSA 435 × ICSR 13004) to 41.96 and 39.35 (ICSA 433 × ICSR 13043) over CSV-41 and CSH-16, respectively. Out of 48 cross combinations, six registered highly significant positive heterosis (over CSV-41 and CSH-16) for grain yield per plot. Key words: Sorghum, male sterility, heterosis, combining ability.

Combining Ability Study for Grain Yield and Agronomic Traits of Quality Protein Maize (Zea mays L.) Inbred Lines Adapted to Mid-Altitude Agroecology of Ethiopia

In spite of the importance of quality protein maize to alleviate protein deficiency, almost all maize varieties cultivated in Ethiopia are normal maize varieties, which are devoid of lysine and tryptophan. Perusing the combining ability of QPM inbred for grain yield and its components is vital to design appropriate breeding strategies for the development of nutritionally enhanced maize cultivars. A line x tester analysis involving 36 crosses generated by crossing 9 elite maize inbred lines with 4 testers were evaluated for different desirable agronomic traits during the 2019 main season at BNMRC and JARC. The experiment was conducted using alpha lattice design with 3 replications. The objectives were to determine the combining ability of quality protein maize inbred lines, adapted to mid altitude agroecology of Ethiopia for agronomic traits. The crosses were evaluated in alpha lattice design replicated 3 times. Analyses of variances showed significant mean squares due to crosses for almost all the traits studied. GCA mean squares due to lines and testers were significant (P<0.05 or P<0.01) for most studied traits. SCA mean squares were also significant for most attributes across locations. The comparative importance of GCA and SCA variances observed in the current study for most studied traits indicated the preponderance of additive genetic variance in governing these attributes. Only L3 was the best general combiner for grain yield. Inbred line L3, for days to anthesis and L5 for days to silking had negative and significant GCA effects. L5 and L6 displayed negative and significant GCA effects for plant and ear height. Crosses, L2xT4, L3xT4, L4xT4, L5xT2, L6xT3, L7xT2, L9xT1 and L9xT4 were good specific combiners for grain yield. In general, these genotypes help as a source of promising alleles that could be used for forthcoming breeding work in the development of quality protein maize cultivars with desirable traits.

Genetic Analysis of Yield Attributes in Rice for Water Deficit Under Egyptian Conditions التحليل الوراثى لصفات المحصول فى الارز للاجهاد المائى تحت الظروف المصرية

Rice parental genotypes with good combining abilities provide an efficient tool to enhance rice yield under water deficit conditions. Using 15 F1 hybrids derived from a half diallel mating involving six parental genotypes, two experiments were carried out during 2019 and 2020 growing seasons to investigate the genetic analysis and combining ability for yield and its components under irrigated (E I) and water stress (E II) environments. Eight agronomic traits were studied over a period of two seasons, and cluster analysis based on 16 SSR primers found that the genotypes under study differed greatly in terms of variation. Overall, all yield attributes have been significantly affected by water deficit and was governed by both additive and non-additive gene actions. Based on the mean values and GCA effects, Gaori and IET1444 are suitable for incorporation of earliness and drought tolerance traits. Obviously that Gaori, IET1444, IRAT 170 and WAB 450 would serve as good general combiners for grain yield attributes under (E II) conditions. Due importance should be given for six combinations viz, Giza 177 x IRAT 170, Giza 177x Gaori, Sakha 101x IRAT 170, Sakha 101x IET 1444, Gaori x WAB 450 and IET 1444x WAB 450 to identify as new genotypes with high grain yield under water deficit condition. There might be a great possibility to get the best new combinations through crossing genotypes with highest genetic distance. Therefore, these findings should be considered when selecting elite genotypes for developing superior new rice crosses under water-stress conditions.

Combining Ability for Quantitative Traits Under Normal And Heat Stress Conditions in Maize (Zea Mays L.)

Investigation was carried out to ascertain the genetic architecture for heat tolerance and yield components from diallel crosses in maize (Zea mays L.). The combining ability in both the normal and heat stress conditions revealed highly significant mean squares due to general combining ability (GCA) and specific combining ability (SCA) in both the direct and reciprocal crosses for all the characters except for anthesis-silking interval in normal condition of the reciprocal crosses. Estimate of components of variance for 13 characters revealed higher SCA variance than that of GCA and reciprocal crosses for all the characters. CML 411 was good general combiner for grain yield in both the conditions, whereas, CML 306 and CML 307 were good general combiners in heat stress condition, and CML 164, CML 304 and CML 305 were average general combiners in normal condition. On the basis of high yield, high SCA and at least high GCA of seed parent, the CML 411*CML 305 and CML 411*CML 307 were identified as promising hybrids for normal and heat stress conditions, respectively. Bangladesh J. Bot. 50(3): 659-669, 2021 (September)

Combining ability analyses of grain yield and kernel micronutrient content in maize (Zea mays)

The present study was aimed to assess the general combining ability of parents and specific combining ability of their crosses for yield and yield related traits. Nine inbred lines were crossed with two testers using line × tester mating design. Nine lines, two testers and 18 experimental hybrids were evaluated along with two checks in this study for grain yield and protein content, besides kernel micronutrients (phosphorous, caicium and iron) during kharif 2019 in a randomized block design at experimental farm of BAC, Sabour. The line CLQRCY44 and HKI1532 were found as good general combiner for grain yield and quality traits followed by DHOLI inbred 55 and CLO2450. Lines DHOLI inbred 55 and CML451 were found as good general combiner for earliness, lines CLQRCY44, CLO2450 and DHOLI 55 for quality traits like protein content, calcium content, phosphorous and iron content. Among the crosses, HKI1532 × 95IOWA (67.43 q/ha), LM13 × SUWAN (65.87 q/ha) and CML425 × SUWAN (63.30 q/ha) were the promising crosses for grain yield. CLO2450 × SUWAN and LM13 × SUWAN exhibited highly significant and desirable SCA effects for grain yield. CLO2450 × 95IOWA exhibited highly significant and desirable SCA effects for protein content. HKI1532 × 95IOWA (67.43 q/ha) was the promising hybrid for grain yield and micronutrient content. Therefore, these crosses can be utilized for developing high yielding micronutrient enriched hybrid varieties in maize (Zea mays L).

English

Maize (Zea mays L.) is the most important cereal crop on which many smallholder farmers in sub-Sahara Africa (SSA) depend on as a sole source of calories, proteins, and vitamins. However, conventional maize is deficient in two essential amino acids, lysine, and tryptophan. Thereafter, Quality Protein Maize (QPM) developed to combat protein malnutrition. In SSA low soil nitrogen is also the most limiting factor in maize production and productivity. To determine the combining ability of QPM inbred lines for grain yield and other agronomic traits under low and optimum N environments, 121 genotypes generated using 11 QPM inbred lines in a complete diallel mating design with 5 checks were evaluated under both low and optimum N environments at 3 locations in the 2018 cropping season. Significant differences were observed among the genotypes for major characters under both low and optimum N environments. Under low and optimum N environments, non-additive gene actions were more important than additive gene action for grain yield, number of ears per plant, plant and ear height, ear length and diameter. Under low N environments, more contributions of reciprocal effects than GCA effects were observed for number of ears per plant, plant aspect, ear diameter. Parental lines TL156579, TL156583, and TL148288 were considered as a good general combiner for grain yield under low N environments. Parental line TL156612 showed higher positive GCA effects when used as female while parental line TL156612 showed higher negative GCA effects when used as a male parent for grain yield under low N environments.   Key words: Complete diallel, general combining ability, low soil nitrogen, lysine, optimum soil nitrogen, quality Protein maize, reciprocal effect, tryptophan.

Using of GGE biplot in determination of genetic structure and heterotic groups in wheat (Triticum aestivum L.)

The present study was undertaken to analyze diallel data using GGE biplot model to gather information about genetic interrelationships among parents and identification of heterotic combinations for yield and yield components in bread wheat varieties. For this purpose, 8 bread wheat genotypes tested across in half-diallel crosses design, GGE biplot technique was used. Parents included the genotypes of Kouhdasht, Karim, Ehsan, Mehregan, N-92-9, Line 17, N80-19 and Atrak. The hybrids obtained from the one-way cross (28 hybrids) in agricultural years of 2016-17 were evaluated as randomized complete block design in two replications on the research farm of Gonbad Kavous University. The evaluated traits included the grain yield, weight of spike grains, number of grains in spike and number of spikes. Additive main effects and genotype × environment interaction (GGE) were employed in the evaluation of genotypes; analyses showed significant (P< 0.01) G × E, (genotype × environment interaction) with respect to plant seed yield. GGE biplot analysis showed that Karim was as the best general combiners for grain yield, number grain per spike and grain weight per spike, whereas Ehsan had the highest GCA effects for number of spikes. Ehsan and Karim had higher specific combining ability than other genotypes. The studied genotypes for this trait were divided into two heterotic groups where the first group included the genotypes of Kouhdasht, N-92-9, N80-19 and Atrak and the second group contained the genotypes of Line 17, Mehregan and Karim. Mehregan line had a weak combining ability with all testers and N-92-9 had also more power than others. Based on the biplot, the Karim genotype with high general adaptation was introduced as the ideal genotype in terms of grain yield, spike number, grain number per spike and grain weight, so the Karim genotype can be adapted to obtain high yield hybrids.

Evaluation and Classification of Yellow Maize Inbred Lines Using Line X Tester Analysis Across Two Locations

Ten yellow maize inbred lines and three testers were top crossed in line × tester scheme in 2019 season. The resulted 30 top crosses with two check hybrids were evaluated at two locations in 2020 growing season to assess mean performance, general and specific combining ability and their interaction with locations as well as elucidate type of gene action. The recorded data were days to 50% silking, plant height, ear height, ear length, ear diameter, No. of rows/ear, No. of kernels/row and grain yield (ardab/fed). The results showed that, the mean squares due to locations (Loc), genotypes (G), crosses (Cr.), G × Loc and Cr. × Loc interactions were significant for all the studied traits. Highly significant differences were observed among the evaluated lines (L), testers (T) and its corresponding hybrids for all traits. non-additive gene action gave an important role in the inheritance of all the studied traits. The inbred lines L2, L4 and L6 showed the best desirable GCA effects for earliness, L6, L7 and L10 for shortness and L4, L5, L6, L7 and L9 for lower ear placement. Whereas the inbreeds L3, L6 and L7 were the best general combiners for grain yield. The crosses L2×T1, L8×T1, L1×T2, L7×T2, L3×T3, L6×T3 and L10×T3 had the best SCA effects for grain yield. The ten inbred lines were classified into three different heterotic groups using HSGCA method. These groups could be used for selecting the best parents for making crosses in maize breeding programs.