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 This research was aimed to study combining ability for growth, kernel yield, and its components, for maze (Zea mays L.) inbred lines, which evaluated in 8×8 diallel crosses. At two locations, Dukan and Qlyasan, at the Sulaimani region.  Significant genetic variability was found in all genotypes for all characters except no. of ears/plant. Highest significant general and specific combining ability were observed for most characters, revealing the importance of both additive and non-additive gene action, at the same time a low ratio of Ϭ2GCA/ Ϭ2SCA was recorded for all traits at both locations vice versa the average degree of dominance was more than one, this indicates to the high contribution of a non-additive gene effect. Heritability in broad sense was found to be high, while a narrow sense, it was low for all traits at both locations. Significant differences were noticed between both locations for kernel yield and most of its components, confirming the exceeding Dukan location.

Phosphorus is a non-renewable natural resource that will run out of reserves in the upcoming decades, making it essential to understanding the inheritance of nutrient use efficiency for selecting superior genotypes. This study investigated the additive and non-additive effects of commercially relevant traits for the popcorn crop (grain yield—GY, popping expansion—PE, and expanded popcorn volume per hectare—PV) in different conditions of phosphorus (P) availability in two locations in Rio de Janeiro State, Brazil. Six S7 lines previously selected for P use—L59, L70, and P7, efficient and responsive; and L54, L75, and L80, inefficient and non-responsive—were used as testers in crosses with 15 progenies from the fifth cycle of intrapopulation recurrent selection of UENF-14, with adaptation to the North and Northwest regions of Rio de Janeiro State. Using the Griffing diallel analysis, P use efficiency was predominantly additive in the expression of PE, and non-additive effects were prominent for GY and PV. For obtaining genotypes that are efficient for phosphorus use, it is recommended that heterosis with parents that provide additive gene accumulation for PE be explored.

Combining ability is referred to as the hybridization value of the parental genotypes involved in the crossing to develop hybrids. The best parents are selected through combining ability methods and subsequently used to produce high yielding and resistant hybrids. Thus, the objectives of this study were to (i) understand the nature and action of genes controlling water deficit tolerance, and (ii) identify superior genotypes from the genetic breadth provided by hybridization in cowpea. Twenty-four genotypes were subjected to normal irrigation and water deficit condition to examine combining ability, genotypic and phenotypic correlations for traits directly related to water deficit (proline and chlorophylls), grain yield and yield components. The results showed the presence of the action of additive and non-additive genes under both water regime conditions. However, there was the predominance of the action of additive genes for most of the traits studied under both conditions. The parents KVX61-1, IT06K242-3, IT07K-211–1-8, Kpodjiguèguè, IT99K-573–1-1, Tawa and IT97K-206–1-1 were observed to be good general combiners for proline content, chlorophyll content and traits associated with yield, while KVX61-1 × KVX396-18, IT06K242-3 × KVX396-18, IT07K-211–1-1 × KVX396-18, Kpodjiguèguè x KVX396-18, KVX61 -1 × IT97K-206–1-1, IT06K242-3 × IT97K-206–1-1, IT07K-211–1-1 × IT97K-206–1-1 and Kpodjiguèguè x IT97K-206–1-1 were proven to be the best specific combiners for traits directly related to water deficit tolerance and yield. It should be noted that number of days to pod maturity, pod length, number of pods per plant and weight of hundred seeds were highly heritable traits in this study.

Understanding the inheritance of maize (Zea mays L.) kernel weight (KW) under contrasting nitrogen (N) supply is crucial for obtaining high KW across diverse N conditions. This work evaluated broad‐sense heritability (H2), general combining ability (GCA), and specific combining ability (SCA) under contrasting N levels for (i) KW and kernel number per plant and (ii) grain‐filling traits represented by the duration of lag and effective filling phases, kernel growth and desiccation rates, maximum water content and volume, and moisture content at physiological maturity. A six‐parent full diallel cross generated via Griffing's method 3 was tested under high (N200) and low (N0) N supply in 2 years (Y). For the various traits: (i) F1 hybrid, and F1 by Y and/or N interactions were significant (p < 0.05); (ii) GCA was significant at both N levels and affected (p < 0.05) by the Y effect; (iii) SCA was important (p < 0.05) only at N200; and (iv) GCA sum of squares was higher than those of SCA (except for KW). For KW and grain‐filling traits, H2 and GCA/SCA ratios were higher at N0 than at N200, suggesting low‐N environments would be more advantageous for developing genetic selection. Lag‐phase duration (LPD), kernel desiccation rate (KDR), and kernel maximum water content (KWCMAX) had higher H2 (≥0.70) and GCA/SCA ratio than KW, particularly under N0. Thus, the highest KW hybrid (LP2×LP662) was composed of inbreds with high GCA for LPD, KDR and KWCMAX, revealing superior KW hybrids could be selected from the GCA of mentioned traits. Core Ideas General surpassed specific combining ability for most evaluated traits, mostly at low nitrogen level. Specific combining ability effects were important only at high nitrogen supply. Heritability and GCA/SCA ratio of kernel weight and grain‐filling traits were increased at low nitrogen level. Kernel number per plant surpassed kernel weight in heritability estimates and GCA/SCA ratio. Lag‐phase duration, kernel maximum water content, and desiccation rate had the highest heritability and GCA effects.

Developing high-yielding cultivars requires understanding genetic variation in yield and its components. The study aimed to investigate the genetic structure and inheritance of key traits to identify suitable parents and promising hybrid combinations across F 1 –F 4 generations, using a randomized complete block design with three replications (2019–2023). Data analysis included Griffing Method I, Model 1, general combining ability (GCA) and specific combining ability (SCA) analysis, full diallel variance analysis, Jinks-Hayman diallel hybrid analysis, and heterosis-heterobeltiosis ratios. The Arcanda cultivar showed strong general combining ability, while the Arcanda/Asparuh and Alena/Asparuh hybrid combinations exhibited significant specific combining ability. In the F 1 –F 4 evaluations, Arcanda × Asparuh achieved the highest yields (30.43 g plant −1 ; 340.40 g 1 m⁻ 1 ; 8500.0 and 9151.0 kg ha⁻ 1 ), with mean heterosis and heterobeltiosis values of 37.32% and 23.07%, respectively. Alena × Asparuh also performed strongly, particularly in F 3 (8459.0 kg ha⁻ 1 ), and exhibited high heterosis in F 1 . High heterosis and heterobeltiosis values, especially for grain yield and thousand kernel weight indicate substantial potential for genetic improvement. To assess the kinship of the parental lines, iPBS-retrotransposon primers were used. The Alena and Arcanda cultivars showed 78% similarity, while the Asparuh cultivar showed 71% similarity to the other parents. In conclusion, Arcanda × Asparuh and Alena × Asparuh consistently combined high yield with genetic stability, making them strong candidates for breeding high-performing barley cultivars. Delaying selection to the later F 3 –F 4 generations increases the accuracy of identifying and stabilizing superior hybrids, thereby maximizing genetic potential and enhancing agricultural productivity.

Geraniums (Pelargonium spp.) are ornamental plants that are widely popular because of their abundant flowering, color variability, different flower patterns, and ease of cultivation. Genetic breeding of this species aims to reduce the plant size and flower color. The objective of this study was to carry out morphoagronomic characterization of parents and F1 hybrids and to estimate the combined capacity and hybrid performance in the circulating diallel in F2 geranium (Pelargonium sp.). We obtained 18 and 275 plants from the F1 and F2 generations, respectively. Characterization of the parental genotypes and F1 and F2 hybrids was performed based on the descriptors for Pelargonium. Parents and F1 hybrids were grouped using the Tocher and UPGMA methods and diallel analyses in the F2 generation. The F1 hybrids G8, G11, and G17 exhibited color combinations suitable for commercialization and are promising for inclusion in breeding programs. The effects of general combining ability (GCA) and specific combining ability (SCA) were significant for these traits were also significant. The results showed the presence of both additive and non-additive genes. However, non-additive and dominant genes were predominant in most characteristics studied. Diallel analysis of the F2 hybrids revealed that the best hybrid combinations for reducing plant height were 14 × 11, 14 × 13, and 15 × 12. Therefore, the implementation and use of diallel analysis were efficient in selecting superior parental genotypes and producing hybrids with high yields.

The presence of variability in phenotypic traits is of less significance in vegetable breeding including okra. Meanwhile, the development of hybrids offers an opportunity to enhance productivity and introduce desired characteristics through variation. A diallel analysis was conducted on five advanced breeding lines (Parents—F 8 ) during Rabi [monsoon] 2020, to assess the combining ability and ascertain the magnitude of heterosis for yield and its attributes. The seeds of parents (P1, P2, P3, P4 and P5), 20 hybrids and a commercial check were sown in Kharif [winter] 2021 for evaluation. Statistical analysis was performed to determine the extent of heterosis, general combining ability (GCA) and specific combining ability (SCA). The results illustrated that parent 1 (P1) and parent 3 (P3) were better combiners for key yield characters, while crosses P1 × P2, P2 × P3, P4 × P3, P3 × P1, P3 × P2, P4 × P1, P1 × P4 and P5 × P2 exhibited as desirable specific combiners for yield attributes. The combining ability outcomes disclosed that GCA variances remained lesser than SCA, indicating non-additive gene action. The cross combinations with better heterosis over standard cultivars can be tested for superior and stable performance across different environments. In addition, the study highlights the importance of considering diverse parents and their gene effects in hybrid development. Graphical Abstract

Nitrogen‐use efficient and leaf‐disease resistant corn (Zea mays L.) cultivars are important to reduce costs and increase sustainability in farming. Studies have shown that non‐additive genes may enhance nutrient‐use efficiency and disease resistance in corn crops. This work aimed to analyze the responses of popcorn hybrids to northern leaf blight (NLB) under contrasting nitrogen availability. We evaluated NLB incidence and severity in 28 diallel hybrids and their parental lines. Competition trials were set in a randomized block design and arranged in a 6 × 6 lattice. The trials were conducted in four environments: two sites and two nitrogen availability conditions per site (ideal [IN] and low [LN]). The area under the progress curve of NLB incidence and severity was estimated for each genotype. To reduce the disease in multiple environments, general combining ability (GCA) of parentals is more important than specific combining ability (SCA) of hybrid combinations. The interactions between SCA and environment were significant for the disease resistance. Therefore, the best combinations should be identified for each environment so that NLB resistance could be enhanced. Low nitrogen availability enhanced the ability of parents to reduce NLB incidence and severity. Hybrid development is an efficient strategy to attain genetic gains in NLB resistance in multiple environments, regardless of N availability. The exploitation of additive gene effects may assist plant breeders in obtaining promising parents for the development of resistant hybrids in multiple locations.

Improving maize (Zea mays L.) genotypes for higher productivity and tolerance to drought stress depends mainly on physiological and molecular markers. Therefore, this study aims at breeding maize for drought tolerance and high potentiality by selection based on molecular markers, photosynthetic parameters; and easy graphic methods that help in selecting elite genotypes across diverse environments. An 8 × 8 half diallel analysis was used at two locations involving drought and normal irrigation treatments to study parental genetic diversity (GD) and combining ability (general combing ability [GCA] and specific combining ability [SCA]) in F1 of maize. Fingerprinting of parents was made using simple sequence repeat (SSR) markers. Fifty‐eight alleles were ranged from two to five alleles per locus with an average of 0.63 alleles per locus. The average of polymorphic information content (PIC) was 0.63. Cuvette temperature (oc) was lowest by the cross L14 × L36. The cross L8 × L34 expresses the highest value for Quantum sensor (μmol m–2 s–1), net CO2 assimilation rate and chlorophyll content. As for leaf diffusive resistance (LDR) four crosses exhibited significant desirable LDR values. Concerning rate of leaf transpiration (LTR) (μg cm−2 S−1) the cross (L5 × L104) gave the lowest value. Most hybrids exhibited desirable values for drought susceptibility index. For grain yield plant–1, five F1 crosses, that is, L5 × L34, L8 × L14, L8 × L14, L30 × L104, and L36 × L104 expressed the most desirable SCA effects. These crosses are promising in maize breeding programs. Based on GGE biplot analysis, genotype nos. 8 and 10 exhibited the highest grain yield plant−1 and ranked the first across all environments. Core Ideas Five new maize hybrids with higher yield potentiality and tolerance to drought were developed. Crucial metabolic functions related to yield productivity of maize were identified. The polymorphic information content and gene diversity of 40 SSR markers associated with drought tolerance were investigated.

ABSTRACT The objectives were to estimate the potential of S2 corn progenies for forage-related traits, and use of AMMI analysis to evaluate topcrosses compared to the classic analyzes. Progenies were crosses with four different testers: LG 6030, 2B688, 9.H3.33 and 53F.P37. Topcross hybrids were evaluated in four 9 x 9 simple square lattice design, during the 2017/18 season at Maringa, Parana State. Grain yield, forage fresh matter yield, and forage dry matter yield were measured. Classical approach was composed by variance components, general and specific combining ability, whereas AMMI analysis was performed for progenies x testers interaction, considering additive main effects and multiplicative effects. Considering the classical approach, testers LG 6030 and 2B688 better expressed the genetic variability between progenies for grain yield. AMMI analysis allowed the partitioning of the sum of squares in additive main effects and multiplicative effects, being a complementary result for the classical approach. Progeny 14 was selected due to higher general combining ability for grain yield, forage fresh matter and forage dry matter yield. Topcrosses 14x9.H3.33 and 14x2B688 were selected due to their higher specific combining ability, additive and multiplicative effects. The AMMI analysis was effective and helped in the interpretation of the results.