General Combining Ability Effects Research Articles

A Comprehensive study of wheat genotypes for combining ability and heritability in drought tolerance

A major challenge in wheat cultivation is the negative impact of water scarcity on growth and yield. Therefore, it is crucial to develop wheat varieties with both high productivity and resilience to drought stress to support food production and improve global food security. The study aims to identify general and specific combining abilities and to understand the genetic mechanisms responsible for key traits by employing half-diallel analysis. In the current study, a half-diallel set comprising 10 x 10 wheat genotypes was subjected to crosses in all feasible combinations, excluding reciprocals, under drought stress conditions. Significant mean squares were observed for both General Combining Ability (GCA) and Specific Combining Ability (SCA) components among the 10 parents and 45 F1 progenies across eleven traits. Assessment of variance components (s2g and s2s), narrow-sense heritability (Hn), broad-sense heritability (Hb) and the GCA/SCA ratio allowed for the determination of the relative contributions of additive and non-additive genetic components. High narrow-sense heritability was noted for traits such as days to 75 % flowering, spike length and biological yield, indicating their predominantly additive genetic control. Conversely, the remaining eight traits exhibited low narrow-sense heritability, suggesting their inheritance is primarily governed by non-additive genetic factors, thus indicating the potential benefits of heterosis breeding. Based on GCA effects, P5 demonstrated superior general combining ability across traits, except for biological yield. P1, P3, P8 and P9 exhibited better combining ability for grain yield per plant. Specific cross combinations including P7×P10, P3×P4 and P5×P6 displayed notable specific combining ability and could be leveraged to develop superior pure lines in subsequent breeding endeavors.

Estimation of standard heterosis and heterotic grouping of elite sorghum [Sorghum bicolor (L) Moench] inbred lines under moisture stress conditions

The development and selection of appropriate parents are prerequisites for sorghum hybrid variety development. The lack of a broad genetic base is the most significant constraint to sorghum crop improvement. The assignment of sorghum germplasm lines to appropriate heterotic groups is critical for increasing sorghum productivity. The experiment was conducted to determine the amount of standard heterosis and to categorize sorghum inbred lines into distinct heterotic groups. In the 2019 main cropping season, 42 sorghum genotypes were tested using an alpha-lattice design with two replications. Combined analysis of variance showed that there was a highly significant difference (p < 0.01) among the genotypes for all studied traits. The maximum grain yield was obtained from the hybrids 4x14 (6.32 tha-1), followed by the hybrids 8x15 (5.92 tha-1), 1x15 (5.88 tha-1), 13x14 (5.78 tha-1) and 6x15 (5.57 tha-1), with an average value of 5.0 tha-1. Similarly, the 4x14 hybrid exhibited a maximum grain yield with 30.71 % heterosis, which was greater than the standard check (ESH-4) for grain yield. The two heterotic (A and B) groups were identified based on their specific combining ability effects, whereas three heterotic groups were identified based on their general combining ability effects to develop superior hybrids from broad base and suitable parents. Finally, based on yield performance, heterotic response and combining ability estimates for grain yield and its components, the hybrid crosses 4x14, 8x15, 1x15, 11x14, 11x15, 13x14, and 6x15 were found to be the most promising and potential hybrids that could be exploited commercially after critical evaluation for their superiority and yield stability across locations over the years.

Diallel Analysis of Wheat Resistance to Fusarium Head Blight and Mycotoxin Accumulation under Conditions of Artificial Inoculation and Natural Infection.

Breeding resistant wheat cultivars to Fusarium head blight (FHB), caused by Fusarium spp., is the best method for controlling the disease. The aim of this study was to estimate general combining ability (GCA) and specific combining ability (SCA) for FHB resistance in a set of eight genetically diverse winter wheat cultivars to identify potential donors of FHB resistance for crossing. FHB resistance of parents and F1 crosses produced by the half diallel scheme was evaluated under the conditions of artificial inoculation with F. graminearum and natural infection. Four FHB related traits were assessed: visual rating index (VRI), Fusarium damaged kernels (FDK), and deoxynivalenol and zearalenone content in the harvested grain samples. Significant GCA effects for FHB resistance were observed for the parental cultivars with high FHB resistance for all studied FHB resistance related traits. The significant SCA and mid-parent heterosis effects for FHB resistance were rare under both artificial inoculation and natural infection conditions and involved crosses between parents with low FHB resistance. A significant negative correlation between grain yield under natural conditions and VRI (r = -0.43) and FDK (r = -0.47) under conditions of artificial inoculation was observed in the set of the studied F1 crosses. Some crosses showed high yield and high FHB resistance, indicating that breeding of FHB resistant genotypes could be performed without yield penalty. These crosses involved resistant cultivars with significant GCA effects for FHB resistance indicating that that they could be used as good donors of FHB resistance.

Genetic Potential of Newly Developed Maize Hybrids under Different Water-Availability Conditions in an Arid Environment.

Drought is a crucial environmental stress that tremendously impacts maize production, particularly under abrupt climate changes. Consequently, breeding drought-tolerant and high-yielding maize hybrids has become decisive in sustaining its production and ensuring global food security under the global fast-growing population. The present study aimed to explore drought tolerance and agronomic performance of newly developed maize inbred lines and their hybrids. Ten newly developed maize inbred lines were crossed with two high-yielding testers using a line × tester mating design. The developed twenty hybrids alongside two high-yielding commercial hybrids were evaluated under water-deficit (5411 m3/ha) and well-watered (7990 m3/ha) conditions in dry summer climate conditions. Highly significant variations were detected among the evaluated hybrids for all studied agronomic traits under well-watered and water-deficit conditions. The inbred lines L10 and L6 were particularly notable, demonstrating the most significant negative general combining ability (GCA) effects for earliness, which is crucial for stress avoidance in both environmental settings. Inbred lines L11, L7, L6, and L1 also showed the highest positive and most significant GCA effects for key yield traits, indicating their potential as parents in breeding programs. The crosses L-10×T-1 and L-6×T-2 were outstanding for their heterotic effects on earliness in days to tasseling and silking. Similarly, the crosses L-4×T-2 and L-1×T-1 excelled in plant and ear heights under both irrigation regimes. The hybrids L-1×T-2 and L-7×T-1 demonstrated superior heterosis for chlorophyll content, number of rows per ear, and overall grain yield. Additionally, hybrids L-11×T-1 and L-11×T-2 exhibited remarkable heterotic effects for the number of grains per row, number of rows per ear, 100-kernel weight, and grain yield, highlighting their potential in breeding for productivity. Based on drought tolerance indices and cluster analysis, the cross combinations L-11×T-1, L-11×T-2, L-7×T-1, and L-1×T-2 were classified as the most drought-tolerant crosses. The principal component analysis highlighted traits such as days to tasseling, days to silking, chlorophyll content, plant height, ear height, number of grains per row, number of rows per ear, and 100-kernel weight can be taken as selection criteria for improving grain yield in maize breeding programs under limited water conditions. Based on the summarized results, the identified genetic materials could be considered promising under both conditions and hold potential for future breeding programs.

Identification of heterosis and combining ability in the hybrids of male sterile and restorer sorghum [Sorghum bicolor (L.) Moench] lines.

In sorghum [Sorghum bicolor (L.) Moench], combining ability and heterosis analysis are commonly used to evaluate superior parental lines and to screen for strongly heterotic hybrids, which helps in sorghum variety selection and breeding. In this context, combining ability and heterosis analysis were assessed using 14 restorer lines and seven cytoplasmic male sterile (CMS) lines in 2019 and 2020. The analysis of variance of all cross combinations had highly significant differences for all characters studied, which indicated a wide variation across the parents, lines, testers, and crosses. Combining ability analysis showed that the general combining ability (GCA) and specific combining ability (SCA) of the different parents were differed significantly among different traits. Most combinations with high SCA also showed high GCA in their parent lines. The heritability in the narrow sense of grain weight per panicle and grain yield was relatively low, indicating that the ability of these traits to be directly inherited by offspring was weak, that they were greatly affected by the environment. The better-parent heterosis for plant height, grain weight per panicle, panicle length, and 1000-grain weight was consistent with the order of mid-parent heterosis from strong to weak. The GCA effects of two lines 10480A, 3765A and three testers 0-30R, R111, and JY15R were significant for the majority of the agronomic traits including grain yield and might be used for improving the yield of grains in sorghum as parents of excellent specific combining ability. Seven strongly heterotic F1 hybrids were screened; of these, hybrids 3765A × R111, 1102A × L2R, and 3765A × JY15R showed significant increases in seed iristectorigenin A content and will feature into the creation of new sorghum varieties rich in iristectorigenin A.

Exploration of Diallel Method for Assessing Heterosis and Combining Ability in Maize (Zea mays L.)

During the Kharif season of 2018 and Rabi season of 2018-19, an experimental study was conducted. The selection of seven maize genotypes was based on quantitative traits, growth duration, suitability for the Kharif season, and yield. These genotypes were then crossed in a half diallel mating design, resulting in the production of 21 single-cross hybrids. The cultivation of these hybrids, along with the seven parental inbred lines, totaling 28 genotypes, followed a randomized block design. Each plot had dimensions of 23.10m by 1.0m and maintained a plant density of 240 plants per plot. To assess the quantitative traits, observations were recorded from five randomly selected plants per plot. The analysis of variance indicated significant genetic variability among the genotypes, particularly in traits such as days to 50% germination, silking, maturity, plant height, number of leaves per plant, biological yield, cob ear weight, number of rows per cob, and number of seeds per cob. This variability was attributed to both additive and non-additive genetic components, as evident from significant variances due to general combining ability (GCA) and specific combining ability (SCA). The GCA/SCA ratio was less than unity for most traits. For most traits, parental lines P1, P2, and P4 exhibited high GCA effects. Additionally, F1 hybrids P4x P3, P3x P1, P5x P3, and P7 x P5 were found to be desirable in terms of yield and related traits. In terms of yield, seven crosses (P1 x P6, P2 x P7, P2x P5, P1 x P2, P3x P4, P5 x P7, and P3 x P5) outperformed the check hybrid, demonstrating their potential for future breeding programs aimed at enhancing maize yield.

A novel open pollinated seed production strategy to exploit both additive and non-additive genetic effects in Eucalyptus dunnii

Eucalyptus dunnii, an important plantation species, is deployed either as clones or open-pollinated (OP) seed. OP seed lots are mainly sourced from seed orchards, where the mothers are known and the pollen is an uncontrolled mix of orchard genotypes. Seed Energy’s current E. dunnii clonal seed orchards have been established using genotypes selected for their general combining ability (GCA), an approach that exploits additive genetic effects. OP progeny trials of the seed orchard parents have been used to increase genetic gain deployed via backward selection. The best parents have demonstrated growth gains of up to 19.3% over unimproved native forest collections. Evaluation of control pollinated (CP) progeny trials, established from crosses of the best seed orchard parents, have shown growth traits to be under a degree of non-additive genetic control. The presence of non-additive variance in these traits suggests that additional genetic gain can be made by specific combinations of mother and pollen parent, known as specific combining ability (SCA). Capturing and deploying the gains from GCA and SCA effects into plantations at commercial scale currently require capital intensive clonal propagation programmes. Here we present a new strategy to exploit both additive and non-additive genetic effects through a novel open-pollinated seed orchard design called micro-orchards. This strategy aims to increase the frequency of the best performing combinations of mother and pollen in an OP environment. These orchards are structured with a central mother genotype tree initially surrounded by ten pollen parent genotypes, which is replicated in a repeated block design. The pollen parents are culled over several years to retain only the best specific combinations with the mother genotype. The culling of pollen parents is based on the results of iterative genetic evaluations of data from the CP trials, which contain families of the mother-pollen combinations present in the micro-orchards. The number of pollen parents culled increases with trial assessment age, concluding with a cull utilising age 6 trial data. The cost and productivity of this strategy allow gains from GCA and SCA effects to be accessible to a significant portion of the Uruguayan market at lower costs and complexity than operating a clonal propagation program.

The combining ability of extra-early maturing quality protein maize (Zea mays) inbred lines and the performance of their hybrids in Striga-infested and low-nitrogen environments

Maize production in sub-Saharan Africa (SSA) faces challenges due to the damage caused by the parasitic weed, Striga hermonthica (Del.) Benths and low soil nitrogen. To address these constraints and improve food security and nutrition, this study assessed the combining ability of 47 inbred lines and four testers, grouped them into heterotic groups, identified effective testers, and determined the stability of the lines in hybrid combinations under contrasting research conditions. The study was conducted at Mokwa and Abuja during the 2019 and 2020 growing seasons. One hundred and ninety-six hybrids comprising 188 testcrosses, 6 hybrids derived by intermating the four testers, and two commercial checks were evaluated using a 14 × 14 lattice design with two replicates. Results revealed that under Striga infestation, the best quality protein maize (QPM) hybrid, TZEEQI 468 × TZEEQI 321, outyielded the best check, TZEEQI 342 × TZEEQI 7, by 24%. Under low-N, QPM hybrid, TZEEQI 515 × TZEEQI 321 outyielded the best check, TZEEQI 507 × TZEEQI 7 by 11% while under optimal conditions the best QPM hybrid, TZEEQI 506 × TZEEQI 321 outyielded the best check, TZEEQI 342 × TZEEQI 7 by 2%. General combining ability (GCA) and specific combining ability (SCA) significantly influenced grain yield and other measured traits across the test environments. These indicated the importance of both additive and non-additive genetic variances in trait inheritance. GCA was more important than SCA for grain yield and most traits in contrasting environments. Four inbred lines had significant and positive GCA effects for grain yield under Striga-infested conditions, while three lines had similar GCA effects under low-nitrogen conditions. These lines demonstrated outstanding potential for developing Striga-resistant and low-nitrogen-tolerant hybrids. The study identified four heterotic groups using the heterotic grouping method based on the general combining ability of multiple traits (HGCMAT). Inbred lines TZEEQI 490 and TZEEQI 460 were identified as testers. The QPM hybrid TZEEQI 515 × TZEEQI 321 exhibited outstanding yield and stability across contrasting environments, highlighting the need for extensive on-farm trials to confirm its superiority and potential for commercialization in SSA.

Fertility restoration, combining ability effects and heterosis in sunflower (Helianthus annuus L.) using different CMS sources

Combining ability studies were made in sunflower (Helianthus annuus L.) using line x tester analysis with two diverse CMS lines PET-1 and ARG-1 and 12 testers. Analysis of variance revealed significant differences among the genotypes i.e., parents and hybrids. Non-additive type of gene action was found important for expression of all the charactersstudied. Studies on identification of effective restorer linesrevealed that out of 12 inbreds,fourturned out to be restorers for both PET-1 and ARG-1, while eight behaved as maintainers. Among the lines, PET-1 was found to be good general combiner forseed yield and oil content. Testers HAM-161, RHA-273 and HAM-174 have also exhibited desirable general combining ability effect for seed yield and several other characters. The cross combination ARG-1 x RHA-273 and ARG-1 x RHA-274 were found to be promising for most ofthe characterssuch as seed yield, plant height, number of leaves, capitulum diameter, stem girth and 100-seed weight. Besides PET-1source, other source viz., ARG-1 used in the present investigation was equally efficient in expressing their fullest potential of yield and yield contributing characters. Most of the crosses involving high x low general combining parents, exhibited high sca effects for various traits.

Heterosis and combining ability estimates for okra (&lt;i&gt;Abelmoschus esculentus&lt;/i&gt; L. Moench) varieties for yield attributing characters in Sudan savanna of Nigeria

Two location trials were conducted at the Teaching and Research Farm of the University of Maiduguri and screen house of the Faculty of Agriculture during 2018/2019 dry season to estimate the combining ability variance, general combining ability (GCA) effects of parents and specific combining ability (SCA) effects of crosses with six okra genotypes. They include: three improved varieties NHAe 47-4, LD-88, Clemson spineless and three locals, Chalawa, Syria and Sola, crossed in a 3 x 3 line x tester mating design to generate nine F1 hybrids. All the F1s along with their parents were evaluated in a Randomized Complete Block Design (RCBD) and Completely Randomise Design (CRD), with 3 replications. Positive heterosis were observed for number of fruits per plant in the crosses Chalawa x NHAe47-4, Chalawa x Clemson Spineless, this directly indicated their important contributions toward total fruit yield in okra. The variance of GCA and SCA revealed that both additive and non-additive gene actions were important in the control of most agronomic.The ratio of GCA/ SCA indicates greater preponderance of non-additive gene action for the characters in all the traits except number of leaves per plant and days to 50% flowering which were controlled by additive gene actions. The parent Syria was the overall best general combiner among the lines for all characters in the field and Chalawa was the overall best general combiner for all characters measured among lines in the screen house. LD88 recorded the highest GCA effects for all of the characters among testers in both experiments. Similarly, in the field, the hybrid Sola x NHAe47-4 recorded the maximum SCA effect for all characters except days to 50% flowering; Syria x NHAe47-4 was the best SCA for most characters except plant height and also the cross between Syria x Clemson Spineless was the best SCA for most characters except number of fruits per plant. In the screen house, the cross between Chalawa x NHAe47-4, showed superior SCA for all characters measured. Appreciable level of heterosis was observed for most of the characters studied, the overall maximum positive significant heterosis for total fruit yield (kg/ha) was observed in crosses Syria x LD88 (52.80) and Chalawa x NHAe47-4(123.30) over better parents. The preponderance of non-additive genetic effect and the tremendous level of heterosis observed among the characters in the parents and their crosses studied would be great asset in choosing the okra varieties for intercrossing and development of hybrids varieties for commercial production of okra.

Estimation of Combining Ability for Flowering and Yield Attributes in Bhendi (Abelmoschus esculentus (L.) Moench)

The present study on general combining ability effects and specific combining ability effects involves seven parents viz., G1 (Arka Anamika), G2 (Aruna), G3 (Varsha Uphar), G4 (Pusa-5), G5 (MDU-1), G6 (Kashi Kranti), G7 (Ankur-41) with their 21 F1 hybrids through half-diallel mating system. The present investigation was undertaken using Randomized Block Design with three replications. The combining ability effects were estimated for seven characters viz., days to first flowering, days to first fruit harvest, fruit length, fruit girth, fruit weight, number of immature seeds per fruit and fruit yield per plant. The results showed that gca effects of parents and sca effect of hybrids were significantly differed. The SCA variance was higher than the GCA variance that indicates the presence of preponderance of non-additive gene action for all the seven traits i.e., presence of preponderance of non-additive gene action for all characters except number of nodes per plant. Among the parents, G3 was found to be a good general combiner based on the per se performance and gca effects for its flowering and yield traits. Among the 21 F1 hybrids, the crosses G3 x G5 and G4 x G6 were superior on the basis of per se performance and sca effect for flowering and yield attributes. Hence, these hybrids were used for further exploitation of heterosis.

Genetic variation among cocoa (Theobroma cacao L.) families for resistance to black pod disease under field and laboratory conditions

The laboratory detached black pod test method has been suggested as the most economical and effective screening procedure to complement field black disease resistance selection. General combining ability and association between black pod disease incidence under field and laboratory conditions among 24 cocoa F1 families were investigated over a 7-year period. The 24 F1 families were derived by crossing three seed garden parental clones with eight GU clones as males in a 3 x 8 North Carolina II (NC II) mating design. The 24 families together with four standard varieties planted in a randomized complete-block design with four replicates of 25 trees per plot were monitored for percentage black pod disease incidence (PBDI). Selfed pods from the 24 NC families and four standard varieties were arranged in a completely randomized design with four replicates of five pods each in the laboratory and subsequently inoculated with Phytophthora megakarya isolates. Percentage detached pod disease incidence (PDDI) was determined after seven days of incubation. Family effects was significant (p < .01) for PBDI and PDDI, and the association between them was positively and moderately correlated (r = 0.71; p < .01). Broad-sense heritability was high but narrow-sense heritability was low for both traits. General combining ability effects of eight of the 11 parental clones and specific combining ability effects of 17 of the 24 crosses were consistent (positive or negative) for PDDI and PBDI. Results from the study indicate that there is a considerable association between both traits, and clones GU 125/C and GU 255/V and their corresponding crosses PA 150 × GU 255/V, T60/887 × GU 125/C, and PA7/808 × GU 255/V had favorable effects for resistance to black pod disease expression. It is concluded that the detached black pod test represents a suitable method to support the field selection of black pod-resistant cocoa varieties.

EVALUATING COMBINING ABILITIES AND HETEROTIC EFFECTS FOR ENHANCED COTTON YIELD

The present research was conducted to evaluate heterosis in diallel crosses, determining general and specific combining abilities for yield-related traits and identifying top-performing genotypes for future breeding programs. A field experiment was conducted using selected genotypes (CIM-599, CIM-602, Shahkar, and NS-181) to produce F1 hybrids through frequent pollinations in a diallel fashion. Twelve F1 hybrids and their four parental genotypes were cultivated in a randomized complete block design with two replications. Yield-related traits including plant height, branches per plant, bolls per plant, lint percentage, boll weight, seed cotton yield, seed index, and lint index were recorded. Analysis of variance and combining ability effects analysis were performed to assess the significance of the genotypes and their interactions. Significant variability among parental genotypes was observed for yield-related traits, indicating genetic variation in the breeding material. Combining ability analysis revealed the predominance of non-additive gene action. General combining ability (GCA) effects were significant for most traits, with CIM-599 exhibiting the highest GCA effects. Specific combining ability (SCA) and reciprocal combining ability (RCA) effects were significant for various traits and hybrid combinations, indicating their potential for trait improvement. Notably, the hybrid combination CIM-599 x Shahkar exhibited substantial mid-parent heterosis for seed cotton yield, boll weight, and lint percentage. This cross also displayed notable SCA effects, indicating its importance for hybrid breeding. These findings highlight the potential of hybrid breeding for trait enhancement. Future breeding programs could leverage the insights gained here to create improved cotton varieties with enhanced yield.

Combining Ability and Heterosis among Bottle Gourd [Lagenaria siceraria (Molina) Standl.] Selections for Yield and Related Traits under Drought-Stressed and Non-Stressed Conditions

Bottle gourd [Lagenaria siceraria (Molina) Standl.] is cultivated for multiple utilities, including as a leafy vegetable, for fresh and dried fruits and seeds. It is an under-researched and -utilized crop, and modern varieties are yet to be developed and deployed in sub-Saharan Africa (SSA). There is a dire need for pre-breeding and breeding of bottle gourds for commercialization in SSA. Therefore, this study aimed to determine the combining ability and heterosis among selected genotypes of bottle gourd for fruit yield and related traits under drought-stressed and non-stressed conditions to select the best parents and hybrids. Eight preliminarily selected and contrasting parents with drought tolerance were crossed using a half-diallel mating design. The 8 parents and 28 crosses were evaluated under non-stressed (NS) and drought-stressed (DS) conditions across two growing seasons (2020/21 and 2021/22) using a 6 × 6 alpha lattice design with three replicates. Data were collected on fruit yield and related traits and subjected to analysis of variance, combining ability and heterosis analyses. Significant (p &lt; 0.05) specific combining ability (SCA) and general combining ability (GCA) effects were computed for fruit yield per plant (FYPP). The SCA × environment and GCA × environment interaction effects were highly significant (p &lt; 0.001) for FYPP and SYPP. The results suggest that genetic effects were affected by the test environment. Parental genotypes BG-58 and GC recorded positive and significant GCA effects for FYPP under the DS condition, whereas GC recorded positive and significant GCA effects for FYPP under the NS condition. The two genotypes are ideal breeding parents for population development to select genotypes with high fruit and seed yields. Crosses BG-27 × BG-79, BG-79 × BG-52, BG-79 × BG-70, BG-80 × BG-70, BG-80 × GC, and BG-70 × GC recorded high and positive SCA effects for FYPP and SYPP under DS condition. Crosses BG-81 × BG-52, BG-81 × GC, BG-27 × BG-79, BG-27 × GC, BG-79 × GC, BG-80 × BG-70, BG-81 × BG-58, BG-27 × BG-80, BG-27 × BG-58, BG-79 × BG-52, BG-52 × BG-58, BG-80 × BG-58, and BG-58 × BG-70 recorded high and positive SCA effects for FYPP and SYPP under NS condition. Crosses BG-80 × BG-58, BG-27 × BG-79, BG-79 × BG-52, BG-27 × BG-52, and BG-52 × BG-80 showed high and positive mid- and better-parent heterosis under DS condition for FYPP and SYPP. Crosses BG-27 × GC, BG-79 × GC, BG-27 × BG-58, and BG-27 × BG-79 showed high and positive mid- and better parent heterosis under NS condition for FYPP and SYPP. The newly selected families are recommended for multi-environment evaluation forrelease and commercialization in South Africa or similar agroecologies.

Combining Ability Analysis of Yield-Related Traits of Two Elite Rice Restorer Lines in Chinese Hybrid Rice.

Hybrid rice breeding is an important strategy for enhancing grain yield. Breeding high-performance parental lines and identifying combining abilities is a top priority for hybrid breeding. Yuenongsimiao (YNSM) and its derivative variety Yuehesimiao (YHSM) are elite restorer lines with a high ability of fertility restoration, from which 67 derived hybrid combinations have been authorized to different degrees in more than 110 instances in China. In this study, we found that YNSM and YHSM contained three candidate restorer-of-fertility (Rf) genes, Rf3, Rf4, and Rf5/Rf1a, that might confer their restoration ability. Subsequently, we investigated heterosis and combining ability of YNSM and YHSM using 50 F1 hybrids from a 5 × 10 incomplete diallelic mating design. Our results indicated that hybrid combinations exhibited significant genetic differences, and the additive effects of the parental genes played a preponderant role in the inheritance of observed traits. The metrics of plant height (PH), 1000-grain weight (TGW), panicle length (PL), and the number of spikelets per panicle (NSP) were mainly affected by genetic inheritance with higher heritability. Notably, the general combining ability (GCA) of YHSM exhibited the largest positive effect on the number of grains per panicle (NGP), NSP, PL, and TGW. Thus, YHSM had the largest GCA effect on yield per plant (YPP). In addition, the GCA of YNSM exhibited a positive impact on YPP, mainly due to the critical contribution of seed setting percentage (SSP). Moreover, YNSM and YHSM exhibited negative GCA effects on PH, implying that YNSM and YHSM could effectively enhance plant lodging resistance by reducing the plant height of the derived hybrids. Remarkably, among the hybrids, Yuanxiang A/YNSM (YXA/YNSM), Shen 08S/Yuemeizhan (S08S/YMZ), and Quan 9311A/YHSM (Q9311A/YHSM) represent promising new combinations with a higher specific combining ability (SCA) effect value on YPP with a value more than 3.50. Our research thus highlights the promising application for the rational utilization of YNSM and YHSM in hybrid rice breeding.

Genetic Potential of Tropically Adapted Exotic Maize (Zea mays L.) Heat-Tolerant Donor Lines in Sub-Tropical Breeding Programs

Breeding for heat stress tolerance became a priority in sub-Saharan Africa (SSA), as projections are showing an increase in frequency, duration, and severity. In this study, 14 heat stress tolerant-donor lines (HSTDLs) sourced from CIMMYT-India (males) were crossed with 15 locally adapted elite lines (females) developed within the CIMMYT-Zimbabwe maize-breeding program using the North Carolina Design II mating scheme. The resultant 175 single crosses were evaluated alongside five commercial hybrids and adjacent to the trial of parental lines used in the crosses across two locations representing heat stress and optimal environments in Zimbabwe. The design II analysis showed significant (p &lt; 0.01) general combining ability (GCA) effects for exotic heat donor lines and specific combining ability (SCA) effects on grain yield under heat stress, optimal conditions, and across locations; demonstrating additive and non-additive genetic inheritance of grain yield. High Baker’s ratios observed in this study indicate predominance of additive over non-additive gene effects. Three exotic HSTDLs, namely CAL14138, CAL152, and CAL1440, exhibited significant (p &lt; 0.001) and positive GCA effects under heat stress conditions. The results imply that these exotic lines could serve as valuable genetic resources for introgression of heat tolerant alleles into local maize populations for accelerated yield genetic gains. Single crosses, DJ265-15 × VL1018816 and DJ267-9 × CAL1440, exhibited positive and significant (p &lt; 0.01) and (p &lt; 0.05) SCA effects for grain yield under heat stress conditions, respectively. These crosses can be used for further breeding and can contribute to grain yield performance under heat stress conditions. The exotic HSTDLs, CAL14138, CAL152, and VL109126 showed superior per se performance under heat, optimal conditions, and across environments. Overall data demonstrate the potential of exotic HSTDLs for improving the adaptation of maize to heat stress in sub-tropical breeding programs.

Combining ability of experimental maize lines for yield and aflatoxin in the southeastern United States

AbstractAflatoxin contamination of maize (Zea mays L.) grain presents risks to animal and human health and causes economic losses for growers, particularly in the southeastern United States. Development of hybrids with genetic resistance to aflatoxin contamination by Aspergillus flavus will reduce these risks. Two factorial crossing experiments were conducted to evaluate yield, agronomic traits, and aflatoxin in maize hybrids. In Experiment 1, 18 aflatoxin‐resistant (GT) lines were each crossed to six testers. In Experiment 2, 13 of the same lines were each crossed to 10 different testers. Each experiment was conducted for 2 years at Tifton, GA, and commercial check hybrids were included for comparison. Ears were inoculated with A. flavus isolate NRRL 3357 using the side‐needle technique 14 days after silking. Aflatoxin was quantified after harvest. Broad sense heritability for aflatoxin was low in Experiment 1 (H2 = 0.09) but was higher in Experiment 2 (H2 = 0.27). Heritability was moderate to high for plant height (H2 = 0.49–0.51) and days to silking (H2 = 0.54–0.72). Among experimental lines, GT1209 and GT1309 had consistent positive general combining ability (GCA) for yield, whereas GT1203 and GT1204 had consistent negative (favorable) GCA for aflatoxin. Significant GCA effects, both positive and negative, for aflatoxin were also observed among testers in both experiments. Some experimental hybrids had yields that were comparable to commercial checks while also having lower aflatoxin, demonstrating the progress made in improvement of both traits in maize hybrids adapted to the Southern United States.

Efficient Genomic Prediction of Yield and Dry Matter in Hybrid Potato.

There is an ongoing endeavor within the potato breeding sector to rapidly adapt potato from a clonal polyploid crop to a diploid hybrid potato crop. While hybrid breeding allows for the efficient generation and selection of parental lines, it also increases breeding program complexity and results in longer breeding cycles. Over the past two decades, genomic prediction has revolutionized hybrid crop breeding through shorter breeding cycles, lower phenotyping costs, and better population improvement, resulting in increased genetic gains for genetically complex traits. In order to accelerate the genetic gains in hybrid potato, the proper implementation of genomic prediction is a crucial milestone in the rapid improvement of this crop. The authors of this paper set out to test genomic prediction in hybrid potato using current genotyped material with two alternative models: one model that predicts the general combining ability effects (GCA) and another which predicts both the general and specific combining ability effects (GCA+SCA). Using a training set comprising 769 hybrids and 456 genotyped parental lines, we found that reasonable a prediction accuracy could be achieved for most phenotypes with both zero common parents (ρ=0.36-0.61) and one (ρ=0.50-0.68) common parent between the training and test sets. There was no benefit with the inclusion of non-additive genetic effects in the GCA+SCA model despite SCA variance contributing between 9% and 19% of the total genetic variance. Genotype-by-environment interactions, while present, did not appear to affect the prediction accuracy, though prediction errors did vary across the trial's targets. These results suggest that genomically estimated breeding values on parental lines are sufficient for hybrid yield prediction.

Heterosis and Combining ability analysis in F1 hybrids of bread wheat

Bread wheat (Triticum aestivum L.) is the most auspicious cereal food crop with regard to production, consumption, nutritional value, storage space, quality, adaptability and transportation. The all 15 F1 cross combinations and their parents were planted in a randomized block design (RBD) with three replications. Out of 15 cross combinations, only 10 show significant heterobeltiosis for early maturity over the standard check-in desirable direction. Five cross combinations PBW 343 x PBW 65, RAJ 2184 x PBW 65, PBW 343 x RAJ 2184, CPAN 3004 x RAJ 2184, HD 1981 x PBW 154 show significant positive heterobeltiosis whereas two cross combinations HD 1981 x PBW 154 and PBW 343 x PBW 65 show significant positive heterosis over commercial check for seed yield. The GCA (General combining ability) effects of the parent PBW343 showed significant positive effect for most of all the traits followed by CPAN3004, PBW154 and PBW65. Out of fifteen, two cross crosses, namely PBW 343 x PBW 65 and CPAN 3004 x RAJ 2184 showed a significant positive SCA (specific combining ability) effect for grain yield.

INHERITANCE OF MORPHO-ECONOMIC TRAITS AND COMBINING ABILITY ANALYSIS IN INTRASPECIFIC HYBRIDS OF GOSSYPIUM BARBADENSE L.

In intraspecific F1 diallel hybrids of Gossypium barbadense L., the inheritance study of traits plant height, boll weight, plant productivity, and 1000-seed weight, with combining ability analysis took place in 2020–2022 at the Institute of Genetics and Plant Experimental Biology, Academy of Sciences, Uzbekistan. These polygenic traits’ inheritance showed different ways in the fine-fiber cotton F1 hybrids. The plant height trait’s inheritance with overdominance and intermediate level of the high/low-performance cultivars. The boll weight trait was mainly in negative overdominance with incomplete dominance of the low-performance cultivar. The inheritance of seed cotton yield had the positive overdominance main control, while the 1000-seed weight had negative and positive overdominance. According to combining ability analysis, the highest positive general combining ability effects resulted in fine-fiber cotton cultivars Surkhan-14 (ĝi = 8.71) and Bo'ston (ĝi =1.86) for plant height, Guzor (ĝi = 0.12) for boll weight, in genotypes Marvarid (ĝi = 2.44) and Surkhan-14 (ĝi = 2.95) for plant productivity, and in cultivars Marvarid (ĝi = 2.3) and Guzor (ĝi = 2.8) for 1000-seed weight. The F1 hybrids Guzor × Surkhan-14, Marvarid × Bo'ston, and Bo'ston × Surkhan-14 showed the highest positive and desirable specific combining ability effects for 1000-seed weight and seed cotton yield. Results concluded that fine-fiber cotton cultivars Marvarid, Surkhan-14, and Guzor can benefit as initial breeding material in selecting high-yielding cotton cultivars.