Half Diallel Research Articles

Heterosis of seedling traits and their correlation to aphids infestation in chili pepper

Chili pepper is a vegetable plant in a group of horticulture plants. The seedling vigorous and their genetic potency to reduce the number of aphids infestation can encourage chili pepper productivity. The objective of this research was to study heterosis, heterobeltiosis, and correlation of seedling traits to aphids infestation from ten chili hybrid genotypes derived from five chili inbred lines through half diallel crosses. The experiment was conducted using a Randomized Complete Block Design (RCBD) with three replications at the IPB University experiment field and laboratory, Darmaga. Seedling traits and aphids infestation observed at 5 weeks after sowing. Two aphids were infested per plant and evaluated 12 days after infestation. Heterosis effects were predicted based on the average values of their parents whereas heterobeltiosis were predicted based on the average values of the best parents. Hybrid IPB C5 x IPB C4 had the highest heterosis and heterobeltiosis for all seedling traits. Hybrid IPB C3 x IPB C4, IPB C4 x IPB C313 and IPB C20 x IPB C313 had the highest heterosis and heterobeltiosis for reducing number aphids per leaf and aphids per plant. There was no correlation between seedling traits with aphids infestation.

Studies on heterosis for yield and yield attributing traits in American cotton (<em>Gossypium hirsutum</em> L.)

The present study was made in upland cotton with 10 x 10 half diallel to assess the extent of heterosis over standard check (LAHH 5) for seed cotton yield and its related traits at Regional Agricultural Research Station, Lam, Guntur. The highest heterotic effect were recorded in the hybrids SCS-1207 × GSHV-177, GSHV-177 × L1231 and SCS-1207 × PBH-13 were promising hybrids in this study over the standard check for seed cotton yield per plant and its most of the yield attributing traits. Those hybrids exhibiting high heterosis for seed cotton yield per plant also had high heterosis for yield attributing characters. The study reveals good scope for commercial exploitation of heterosis as well as isolation of pure lines among the progenies of other heterotic F1 hybrids.

Studies on heterosis and per se performance in early Segregant population of Urdbean (<em>Vigna mungo</em> L. Hepper)

The present investigation consisted of six Urdbean cultivars and fifteen crosses developed using half diallel mating design to study the mean performance of genotypes and heterosis among the crosses. The crosses (F2’s) along with the parental genotypes were grown in a randomized block design with three replications at Experimental Farm of the Department of Crop Improvement, CSK HPKV Palampur (H.P.) during Kharif, 2018. The data were recorded for yield and yield contributing traits. Mean performance and standard heterosis is studied over the check variety i.e. Palampur-93. Analysis of variance revealed that there was sufficient variability among the parental lines and cross combinations. Standard heterosis for seed yield per plant ranged from -36.25 per cent (IC-281994 X DU-1) to 34.55 per cent (HPBU-111× KU-553). Significant positive heterosis for seed yield was observed in only one cross HPBU-111× KU-553 (34.55%), whereas seven crosses were statistically at par with the check. Thirteen genotypes were recorded significantly superior to the check for mean value of seed yield per plant. Mean value for this trait ranged from 2.29 g to 3.45 g. On the basis of per se performance for physiological and yield related traits, three crosses viz., HPBU-111 × KU-553, Palampur-93 × IC-281994 and Him Mash × KU-553 were identified as best cross combinations. These crosses can be further evaluated at Multilocations for commercial exploitation.

Genetic analysis of spike traits in wheat (Triticum aestivum L.)

An 8×8 half diallel cross design was carried out by the Griffing method II of fixed model (I) in a Complete Randomized Block Design using Kouhdasht, Mehregan, Karim, Line17, N80-19, Atrak, N-92-9 and Ehsan cultivars in two replications at the research field of Gonbad Kavous University in 2017. In order to study the impact of general combining ability (GCA) and specific combining ability (SCA) of traits of wheat maturity including spike length, spike weight, number of grains per spike, grain weight per spike, awn length, and grain yield. The mean square of general combining ability (GCA) and specific combining ability (SCA) was significant for all traits at 1% probability level due to the importance of both additive gene action and non-additive gene action on the inheritance of the traits. The obtained results from the ratio of mean square of GCA to SCA indicated that the contribution of dominance was greater than the additive gene in controlling the spike weight and grain yield, while the additive gene effect played a decisive role in the number of grain per spike, length of awn, spike length and weight of spike grain due to the significant ratio of SCA to GCA. According to results number of grains per spike, length of awn, spike length and weight of spike seeds largely had the additive gene variance and had the ability of responsive selection.

General and Specific Combing Ability of Maize (<i>Zea mays</i> L.) Inbred Line for Grain Yield and Yield Related Traits Using 8×8 Diallel Crosses

Combining ability is the genotype's ability to pass the desired character to the offspring. Hence, combining ability information is needed to determine the crossed pairs in the formation of hybrid varieties. Therefore, this study was conducted to estimate general and specific combining ability effects of maize inbred lines for yield and yield-related traits. Eight maize inbred lines were mated through a half diallel mating design (Griffing’s Method IV, Model I). The resulting twenty-eight F1 hybrids for twenty one characters were evaluated using Alpha-Lattice Design with three replications during 2018 main cropping season at Haramaya University Research Site (Raare). Genetic analysis of variance due to mean squares revealed significant differences for general combining ability (gca) and specific combining ability (sca) effects indicated the presence of additive as well as non additive gene effects in governing the inheritance of these traits. These results confirm the possible involvement of both additive and non-additive gene actions in the inheritance of these characters and can be improved either by recurrent selection or even by heterosis breeding methods like production of hybrids, synthetics and composites. However, relative magnitude of these variances indicated that additive gene effects were more prominent for most of the characters studied since the ratio of GCA:SCA were more than unity in most of the traits. Parental line L3 and L8 were good general combiner for grain yield and L1, L2, L6 and L7 are desirable for earliness. The better performing four crosses L3×L6, L3×L8, L2×L5, and L6× L8 were good specific combiners for grain yield, which could be utilized for developing high yielding hybrid varieties as well as for exploiting hybrid vigor.

Evaluation of Some Maize Genotypes for Some Yield Components, High Protein and Amino Acids Content

The current filed experiments were conducted at Nubaria Region, El- Behira Governorate, Egypt during 2018 and 2019 seasons, to evaluate some maize genotypes for high protein and amino acids content. In this respect, in the first season, six maize single hybrids were planted in two group to granted flowering matching. The crossing had been done to get fifteen hybrids by half diallel design with enough grain for two years. Then, in the next season, the obtained hybrids grains were planted in blocks to determine the heterosis percentage (H %) based on mid and better parents for yield, yield components, protein and amino acids content. The results revealed that the 6 genotypes and 15 hybrid differed significantly in yield, its components, protein % and amino acids (%), where SC3062 X SC3737, SC444 X SC3737 recorded the highest values followed by (SC3062 X SC3737) and (SC3062 X SC444) then (SC2066 X SC3737) and (SC2066 X SC444). The results showed positive values of heterosis percentage between all the obtained hybrids that refer to the successful of hybridization. Amino acids values also showed significant variations between the maize hybrids.

Evaluation of Combining Ability for Second Fillial Populations in the Faba Bean (Vicia faba L.) Depends on Half Diallel Cross

Evaluation of Combining Ability for Second Fillial Populations in the Faba Bean (Vicia faba L.) Depends on Half Diallel Cross

Combining Ability Analysis of Ear Characteristics of Sweet Corn Hybrids Suitable for Organic Crop Production

Abstract Good knowledge of genetic merits governing the inheritance of economic traits is of paramount importance to plant breeders for crop improvement. Objectives of the study were to investigate the genetic nature of ear traits in sweet corn (Zea mays convar. saccharata var. rugosa) based on the general and specific combining ability (GCA and SCA) analysis, and to determine the breeding potential of eight promising inbred lines for the development of new hybrid cultivars well suited for organic production. Thirty-six genotypes (hybrid families) derived from a half diallel cross design were grown under organic crop management at three agro-ecological zones of the tropics. Although the genotypes varied significantly for all the observed ear traits, some of them showed clear inconsistencies in performing husked ear size (length, diameter, and weight), kernel row number, and kernel number per row across environments. The combining ability analysis showed that additive gene action was more preponderance than non-additive gene actions in governing the inheritance of the studied ear traits. The inbred lines: Caps 5, Caps 17A, Caps 17B, and Caps 22 showed their potential as good partners for the improvement of ear performances as to the development of superior sweet corn cultivars for organic production.

Diallel analysis for yield and component traits in maize (Zea mays) under infestation and non-infestation with pink stem borer (Sesamia cretica)

A half diallel cross between nine yellow inbred lines of maize (Zea mays L.) was evaluated under two environments, viz. borer artificial infestation conditions and normal conditions in RCBD with three replications in 2015 to estimate general and specific combining ability effects and identify superior genotypes resistant to Sesamia cretica. Highly significant cross mean squares were detected for all the studied traits indicating the wide diversity in the parental materials used in this study. General and specific combining ability (GCA and SCA) were significant for all the studied traits except SCA for number of rows/ear in normal condition revealing that both additive and non-additive gene effects were involved in determining the performance of the single cross progeny. The parental inbred line P6, P8 and P9 can be considered as good combiners for grain yield and some of its component traits under infestation and non-infestation conditions as well as the combined over them. Six crosses (P1×P6, P1×P7, P2×P4, P3×P5, P5×P7, and P8×P9) selected based on desirable SCA effects also had high mean performance for grain yield and out-yielded the check hybrid SC 166. Therefore, these crosses could be utilized for future breeding work as well as for direct release after confirming the stability of their performance across different environments. The information from this study may be useful for researchers who would like to develop high yielding hybrids of maize tolerant to borer attack.

PERFORMANCE AND GENE ACTION FOR EARLINESS, YIELD AND CHOCOLATE SPOT DISEASE OF FABA BEAN

In order to determine performance, gene action and heritability for earliness, yield and chocolate spot disease of faba bean, a half diallel crosses among six parental genotypes were evaluated under control and artificial infection by chocolate spot disease (Botrytis fabae sard). The results indicated highly significant differences among faba bean genotypes for all the studied characters under these conditions. All faba bean genotypes under study appeared to be high resistant or resistant for chocolate spot disease with a few exception under different conditions. Whereas, genotypes Misr 3, Wadi 1, Sakha 4 x Misr 3, Sakha 4 x Nubaria 1, and Misr 3 x Wadi 1 under the natural infection conditions. However, Sakha 4, Nubaria 1, NA 112, Sakha 4 x Misr 3, Sakha 4 x NA 112, Misr 3 x Wadi 1, Nubaria 1 x T.W, Wadi 1 x NA 112 and T.W x NA 112 under the artificial infection were less resistant or susceptible to chocolate spot disease. The results revealed that additive (D) and dominance (H1 and H2) appeared to be significant for days to flowering and maturity, chlorophyll content (SPAD), seed weight/plant and resistance to chocolate spot under both conditions. The additive genetic component was higher in its magnitude as compared to the dominance ones for resistance to chocolate spot under the natural infection condition, resulting in average degree of dominance (H1/D)0.5 less than the unity. Whereas, dominance component (H1 and H2) made up the most part of the total genetic variation as it was larger in its magnitude than the corresponding additive one for earliness characters, chlorophyll content and seed weight/plant under both conditions and resistance to chocolate spot under the artificial infection only. Thus, the average degree (H1/D) 0.5 was more than the unity for these characters. Narrow sense heritability (h2n) was moderate (39.1%) to low (20.4%) for seed weight/plant and high (65.1%) to moderate (45.0%) for chocolate spot disease under control, natural infection and artificial infection of chocolate spot disease, respectively.

MORPHOLOGICAL IDENTIFICATION AND EVALUATE THE COMBINING ABILITY AND HETEROSIS OF SOME INBRED LINES OF MAIZE AND ITS CROSSES

In 2016 five maize inbred lines were crossed in all possible combinations without reciprocals by using a half diallel crosses mating design to obtain 10 single crosses. Parental inbred lines and their F1 single crosses were evaluated through 2017 season to evaluate the role of general and specific combining ability, heterosis and the morphological characteristics. A randomized complete block design with three replicates was used. Results showed that mean squares of genotypes, general combining ability (GCA) and specific combining ability (SCA) were highly significant for all studied yield traits. The GCA/SCA ratio was less than unity for all studied traits, this means that these traits are predominantly controlled by non-additive gene action. Positive significant GCA effects were found for all studied traits. Based on GCA estimates, it could be concluded that the best combiners were Inb 209 and Inb 239 for most of studied traits. This result indicated that these inbred lines could be considered as good combiners for improving yield and its attributes. Positive significant SCA effects were found for all studied traits. Based on SCA effects, the best crosses for ear diameter, 100-kernel weigh and kernel number/row was C1; for ear length was C10 and for ear weight/plant, grain weight/plant and shelling percentage was C8. Results showed positive significant heterosis values for all studied yield traits. The best crosses over both their mid-parents and better-parents for ear diameter and 100-kernel weigh was C2; for ear length and kernel number/row was C5; for ear weight/plant and grain weight/plant was C9 and for shelling percentage was C8.

Half-diallel analysis of Fusarium head blight resistance in bread wheat (Triticum aestivum L.)

TO CHARACTERIZE FHB resistance, a set of 48 advanced inbred lines (AILs) along with two Egyptian cultivars (Sakha-93 and Giza-168) were evaluated for their resistance to the FHB during 2015/2016 and 2016/2017 under both greenhouse and field conditions. We identified some resistant AILs to the FHB including 37, 35 and 22 based on percentages of diseased spikelets under both greenhouse and field conditions and free phenolic compounds along with grain yield (GY) under the field condition. While most of the AILs were susceptible to the FHB. Three resistant AILs, three susceptible AILs and an Egyptian susceptible cultivar were crossed in a half–diallel mating system. The parents and the non–reciprocal F1 crosses were evaluated for their response to the FHB under infected conditions in both greenhouse and field conditions. Both general combining ability (GCA) and specific combining ability (SCA) were significant for all studied traits. Both additive and non–additive describes for resistance to the FHB; however, different calculations supported that additive gene action is the preponderant constituent. The moderately high estimates of narrow–sense heritability values implied that further improvement of the FHB resistance could be accomplished through selection. We found that AILs 22, 35 and 37 were good combiners and successfully conveyed their resistant genes to their offspring based on the SCA. These resistant AILs could be integrated in wheat breeding programs using bi-parental or multi-parental populations to develop new resistant varieties to FHB. In addition, they can be exploited to improve existing cultivars using backcrossing approach.

Diallel analysis of cowpea [<i>Vigna unguiculata</i> (L.) Walp.] for seed size, and resistance to <i>Alectra vogelii</i> Benth.

Cowpea production is hampered by several abiotic and biotic constraints. Parasitic weed Alectra vogelii is a formidable biotic constraint in cowpea production. This study was implemented to determine gene actions involved in cowpea seed size and its resistance to Alectra in order to determine the appropriate breeding approach to develop resistant cowpea varieties to Alectra vogelii. For this purpose, a half diallel of 9 parents was developed at Kamboinse in 2016. The F1 and their parents were screened in screen house with Alectra vogelii seed collected from Alectra infested field in Koupela in centre east Burkina Faso. Data were collected on dates to cowpea flowering, cowpea hundred seeds weight and the severity of Alectra 70 days after planting and analysed with Diall 98 software. Both additive and non-additive gene actions were operative for the investigated characters. Additive gene effects were more important, resulting in high narrow sense heritability, inferring that breeding progress can be achieved through backcross or single seed descent method.Keywords: additive, Burkina Faso, dominance, general combining ability, gene action, heritability.

Combining ability estimates in 6 x 6 half diallel crosses of bread wheat (Triticum aestivium L.)

Combining ability estimates in 6 x 6 half diallel crosses of bread wheat (Triticum aestivium L.)

Amylose content and grain appearance traits in rice genotypes

Amylose content (AC) and grain appearance traits of rice (Oryza sativa L.) represent a major problem of rice marketing in many rice producing areas in the world. In Uganda, cooking, eating and appearance qualities remain undefined in the rice breeding programme. The objective this study was to determine amylose content of rice genotypes, and its relationship with grain appearance traits; and mode of its inheritance in selected rice genotypes. Forty genotypes were planted in two seasons (2015B and 2016A), in alpha lattice design at National Crop Resource Research Institute in Uganda. Seven parents, involving 3 low and 4 intermediate amylose content genotypes selected in 2015B season,were crossed in a half diallel,and the F1 were advanced to F2 generation, which together with parents were planted in the field. Amylose content (AC), kernel width (KW) and kernel length (K/L) to width ratio were affected by both genetic effects and genotype by season (G x S) interactions; while kernel length was mainly affected by genetic factors. Genotypes were grouped into low, intermediate and high amylose content categories depending on the environment where the genotypes were grown. Three genotypes (Namche 1, P62H17 and 1190) had no significant responsesin amylose content in different growing seasons, suggesting that these genotypes were stable. Amylose content correlated weakly and negatively with physical appearance quality traits of the grain; implying that improvement in amylose content would not affect grain size and shape.There were significant differences (P<0.001) among parents for general combining ability (GCA) and among crosses for specific combining ability (SCA) (P<0.5) for amylose content; indicating that both additive and non-additive gene actions were responsible for the inheritance of AC. However, the variance component of GCA was larger than for the SCA, implying that the inheritance of amylose content was more conditioned by the additive gene effect.Key words: Combining ability, Oryza sativa, Uganda

Morpho-chemical quality improvement in tomato (Solanum lycopersicum) through heterosis breeding

The demand of tomato (Solanum lycopersicum L.) and its products continue to rise due to its excellent source of antioxidants including lycopene, total carotenoids, ascorbic acid and total soluble solids. The present experiment was carried out during the autumn-winter season of 2014–2016. The seven parents were crossed in half diallel fashion and the resultant 21 F1 hybrids along with their parents and one hybrid check (BSS - 488) were evaluated in randomized complete block design with three replications for eight morpho-chemical quality component traits in tomato. The highest standard heterosis were observed in the cross Selection-12 × Pusa-120 (12.16%) for pericarp thickness, Pusa Rohini × Selection-12 (25.95%) for total soluble solids, H-86 × Pusa Rohini (23.53) for ascorbic acid, Selection-12 × CLNB (38.79) for total phenolics, Arka Alok × CLNB (46.49) for total antioxidant capacity, Pusa Rohini × Arka Alok (25.95) for lycopene and total carotenoids (29.53). Among the crosses Pusa Rohini × CLNR, Arka Alok × CLNB, H-86 × Pusa-120 and H-86 × CLNR were found to be better for most of the quality traits and these crosses could be considered as most promising specific combiners. Among the parents, Selection-12, CLNB, Pusa Rohini and Arka Alok were identified as most promising general combiners for quality traits and these may be used as valuable donors in the hybridization programme for producing promising varieties.

Molecular genetic studies on abiotic stress resistance in sorghum entries through using half diallel analysis and inter-simple sequence repeat (ISSR) markers

BackgroundWater deficit stress is considered as one of the most important environmental stresses which is more harmful to strategic crops, as it reduces the final crop yield by up to 40%. Therefore, the aim of this research is to evaluate some promising and superior sorghum entries for water stress tolerance and determine the most agro-morphological parameters and reasons responsible for drought tolerance in this regard.ResultsFifteenth sorghum genotypes (five parents and their ten F1 crosses resulting from half diallel analysis) were used in this investigation under two levels of irrigation (normal and drought experiment). The recent genotypes were estimated through some physiological parameters related to water stress tolerance in sorghum; besides that, eight inter-simple sequence repeat (ISSR) primers were used to identify among the five sorghum parents and the highest five crosses resistance to water deficit conditions depending on the data calculated from all studied traits under both conditions. The following genotypes P1, P2, P3, P1 × P2, P1 × P3, P2 × P3, P2 × P4, and P3 × P4 confirmed high resistance to water deficit conditions under the drought treatment compared with the control. This high resistance was affirmed through the calculated data for all studied traits. The ISSR profile analysis showed 151 fragments as taxonomic divisions among the ten sorghum genotypes (38 of them were monomorphic and 113 polymorphic with 74.83% polymorphism).ConclusionThe entries (P1, P2, P3, P1 × P2, P1 × P3, P2 × P3, P2 × P4, and P3 × P4) were succeeded in achieving the highest concept of water deficit resistance under both conditions. Therefore, this work will be the nucleus for producing resistant sorghum varieties for drought stress in the future.

Genetic analysis of four main flavonoids in barley grain

Genetic analysis of 4 major flavonoids in barley interspecific hybrids which were used as parents for half diallel crossingwas carried out. Compared with seven parents, the highest general combining ability of catechin content was Clipper barley, the higest general combining ability (GCA) of myricetin content were Schooner barley and Huangchangguang barley, the highest general combining ability of quercetin content were Ziguangmang barley and Kuanying barley, the highest general combining ability of kaempferol content were Ziguangmang barley and Schooner barley, the highest general combining ability of flavonoids are Schooner barley and Huangchangguang barley. The hybrid combination of a good matching were Clipper barley, Schooner barley, Ziguangmang barley and Kuanying barley, as a comprehensive general combining ability, specific combining ability, and combinations of which can be used as flavonoids in barley breeding.

DETERMINATION HETEROSIS AND COMBINING ABILITY FOR TRAITS YIELD AND YIELD COMPONENTS IN THE FABA BEAN (VICIA FABA L.)

Study was conducted genotypes of faba bean half diallel crosses were done in winter season 2016. All genotypes (parents and hybrids) were planted in winter season 2017, in one of the agricultural fields in the Al-Sufiya region at latitude 33.28? north and longitude 43.33? east of Anbar province, using R.C.B.D. design with three replicates. Studied traits were pod length, number of pods per plant ,number of seeds per pod, seeds100 weight and seed yield. Results showed significant differences between the mean of parents and the mean of their hybrids for all studied traits. The parent (Spanish) was superior and had the highest mean of the pod length 16.610 cm, number of pod plant 15.493 pod plant-1, number of seeds pod 5.873 seed pod-1 and seed yield 124.110 g plant-1. While the parent (Dutch) recorded the highest mean for trait seed100bweight reached 142.580g. As for the means of the hybrids, hybrids (Spanish×Dutch) showed the highest mean significant for traits the pod length 24.120 cm, number of pod plant 20.420 pod plant-1 and the seed yield 212.330 g.plant-1. While the hybrid (Iraqi×Italian) gave the highest significant mean of the number of seeds pod 6.267 seed pod-1 and non-significantly from the hybrid (Spanish×Dutch). Hybrids (Iraqi×Turkish) showed the highest mean for trait seeds100 weight 176.340 g. Hybrid (Turkish×American) was superior and had the highest value of heterosis in number of pods plant 39.560%. While hybrid (Iraqi×Italian) recorded the highest value of the heterosis number of seeds pod reached 69.83% , The highest value of the heterosis in two trait seed100 weighed and seed yield was by the hybrid (Iraqi×Turkish) gave 30.820% and 78.238% sequentially. And that the variance components of the general ability to the specific ability components were less than one for all traits. This indicates the type of gene action for dominance genes in the control of the heritability of these traits.

DETERMINATION HETEROSIS AND COMBINING ABILITY FOR TRAITS YIELD AND YIELD COMPONENTS IN THE FABA BEAN (VICIA FABA L.)

Study was conducted genotypes of faba bean half diallel crosses were done in winter season 2016. All genotypes (parents and hybrids) were planted in winter season 2017, in one of the agricultural fields in the Al-Sufiya region at latitude 33.28? north and longitude 43.33? east of Anbar province, using R.C.B.D. design with three replicates. Studied traits were pod length, number of pods per plant ,number of seeds per pod, seeds100 weight and seed yield. Results showed significant differences between the mean of parents and the mean of their hybrids for all studied traits. The parent (Spanish) was superior and had the highest mean of the pod length 16.610 cm, number of pod plant 15.493 pod plant-1, number of seeds pod 5.873 seed pod-1 and seed yield 124.110 g plant-1. While the parent (Dutch) recorded the highest mean for trait seed100bweight reached 142.580g. As for the means of the hybrids, hybrids (Spanish×Dutch) showed the highest mean significant for traits the pod length 24.120 cm, number of pod plant 20.420 pod plant-1 and the seed yield 212.330 g.plant-1. While the hybrid (Iraqi×Italian) gave the highest significant mean of the number of seeds pod 6.267 seed pod-1 and non-significantly from the hybrid (Spanish×Dutch). Hybrids (Iraqi×Turkish) showed the highest mean for trait seeds100 weight 176.340 g. Hybrid (Turkish×American) was superior and had the highest value of heterosis in number of pods plant 39.560%. While hybrid (Iraqi×Italian) recorded the highest value of the heterosis number of seeds pod reached 69.83% , The highest value of the heterosis in two trait seed100 weighed and seed yield was by the hybrid (Iraqi×Turkish) gave 30.820% and 78.238% sequentially. And that the variance components of the general ability to the specific ability components were less than one for all traits. This indicates the type of gene action for dominance genes in the control of the heritability of these traits.