Non-additive Gene Effects Research Articles

Inheritance of resistance traits to African stem borer in grain sorghum

The African stem borer (Busseola fusca [Fuller]) is an important insect pest of cereals, mainly maize, sorghum and millets. The pest causes up to 80% reduction in grain yield, depending on the pest population in the field, cultivar and the management practices employed. This reduction in yield translates into food insecurity, especially in semi-arid lands (ASALs) where sorghum is cultivated by small holder farmers. This study investigated the inheritance of resistance traits to the African stem borers in grain sorghum in Kenya. The experimental material consisted of seventeen sorghum lines with varying levels of resistance to the African stem borer. The mating design employed was North Calorina Design 2, where 15 sorghum lines were used as females on two males. The crosses were evaluated in two seasons at University of Embu farm in 2011/2012 short and long seasons replicated twice. Artificial infestation with African stem borer neonates was done 30 days after planting using a camel brush. Data collected included stem borer damage and agro-morphological traits. Genetic analyses were performed using a line x tester method using Genstat statistical software. It was found that both additive and non-additive gene effects were important in conditioning resistance traits to the African stem borer. This implies that expression of high leaf glossiness, plant vigour and bloom waxiness in F1 hybrids is conditioned by additive genes and these traits can be used as morphological markers to select for resistance to the borer in sorghum. ICSB 464 x ICSB 473 was the best combiner for stem borer resistance and grain yield. Parents ICSA 464, ICSB 464 and ICSB 474, were among the good combiners for resistance to the stem borer. These parents can be utilised in developing superior sorghum hybrids resistant to the insect pest.Key words: Gene action, heritability, Sorghum bicolor

Heterosis and combining ability in cytoplasmic male sterile and doubled haploid based Brassica oleracea progenies and prediction of heterosis using microsatellites.

In Brassica oleracea, heterosis is the most efficient tool providing impetus to hybrid vegetable industry. In this context, we presented the first report on identifying superior heterotic crosses for yield and commercial traits in cauliflower involving cytoplasmic male sterile (CMS) and doubled haploid (DH) lines as parents. We studied the suitability of genomic-SSRs and EST-SSRs based genetic distance (GD) and agronomic trait based phenotypic distance (PD) for predicting heterosis in F1 hybrids using CMS and DH based parents. 120 F1 hybrids derived from 20Ogura based CMS lines and 6 DH based testers were evaluated for 16 agronomic traits along with the 26 parental lines and 4 commercial standard checks. The genomic-SSRs and EST-SSRs based genetic structure analysis grouped the 26 parental lines into 4 distinct clusters. The CMS lines Ogu118-6A, Ogu33A, Ogu34-1A were good general combiner for developing early maturity hybrids. The SCA effects were significantly associated with heterosis suggesting non-additive gene effects for the heterotic response of hybrids. Less than unity value of σ2A/D coupled with σ2gca/σ2sca indicated the predominance of non-additive gene action in the expression of studied traits. The correlation analysis of genetic distance with heterosis for commercial traits suggested that microsatellites based genetic distance estimates can be helpful in heterosis prediction to some extent.

GENETIC ANALYSIS AND HETEROSIS FOR SOME QUANTITATIVE TRAITS IN TOMATO (SOLANUM LYCOPERSICUM L.)

This study was conducted during three successive early summer seasons of 2016- 2018 at the experimental farm of both faculty of Agricultural, Menoufia University, Shebin El-Kom and Bahga Agricultural development company, Anshas, sharkia. The present investigation was aimed to obtain more information on combining ability and degree of heterosis for some plant and fruit characters. Four breeding lines and one cultivar of tomato (Solanum lycopersicum L.) and their ten F1's resulted from a half – diallel cross were evaluated and the component of genetic variance , combining ability and the extent of heterosis were determined for some tomato traits ,i.e., number of primary branches and leaves , early and total yield , average fruit weight and fruit firmness. The analysis of variance reflected significant differences among the studied genotypes for all the traits studied. Estimation of the magnitude of variance due to general and specific combining ability effects (s2 GCA & s2 SCA) showed that both additive and non-additive gene effects were significant and important in inheritance of all studied traits, except average fruit weight. However, the estimated genetic parameters revealed that the additive gene effects were more important and play the main role in the inheritance of early and total yield, average fruit weight and fruit firmness and could be improved by varietal breeding program. While, the non-additive genetic variance was found predominance for number of branches and leaves and improving these two traits could be occurred by heterosis breeding. The two lines MON-8 and MON-9 were considered as the best general combiner parents, since they recorded positive GCA effects for four traits.The cross combinations MON-8 x MON-9 and MON-9 x MON-15 were the best specific combinations, since they recorded significant SCA values for five and four traits.Relative heterosis (MPH%) was observed for all studied traits, except, average fruit weight, while heterobeltiosis (BPH%) was observed in some crosses for number of branches and leaves as well as early and total yield. Based on the standard heterosis (SH %) expressed by the hybrids MON-8 X MON-9 and MON-9 X MON-15 were found to be superior since significantly exceeded the commercial hybrid (control).

Combining capacity and heterosis in eggplant hybrids under high temperatures

ABSTRACT The objective of this work was to estimate the combinatorial capacity and heterosis of eggplant hybrids under high temperature conditions. Seven genitors, twelve hybrid combinations, originated from a partial diallel, and the Ciça F1 hybrid, as control, were evaluated. The experiment was conducted under greenhouse conditions in randomized block design with four replications, from April to December 2017. The assessed traits related to high temperatures were pollen viability (PV) and fruit fixation index (FFI); the morphoagronomic traits were number of fruits per plant (NFP), fruit weight (FWe), production per plant (PP), fruit length (FL), fruit width (FWi), fruit length/width ratio (FLWR) and plant height (PH). The variance analysis showed greater participation of the additive gene effects in relation to the non-additive gene effects in most traits, except for PV. The genitors CNPH 141, CNPH 135, CNPH 109 and CNPH 51 stood out with favorable gene effects to obtain genotypes tolerant to high temperatures, since they present good general combining ability (GCA) for the traits FFI, NFP and PP. The 1x4 and 3x4 hybrids presented positive estimates for both GCA and specific combining ability (SCA), demonstrating a greater potential to be used in breeding to increase the FFI, NFP and PP, under high temperatures. The 1x4, 1x5 and 1x6 hybrids expressed positive heterosis for most analyzed traits. The 1x4 hybrid stood out for the highest averages for PV, FFI, NFP and PP. For FWe, FL, FWi and FLWR, both positive and negative heterosis were observed, as consequence of the phenotypic variability of the genitors for these traits and suggests the possibility of selection for different sizes and formats.

Genetical studies of corn crop to exploit heterosis, proportional contribution and gene action at diverse water regimes

The study is based on mating fashion of line × tester and its relative analysis to exploit the heterosis, proportional contribution of diverse lines, testers, their interaction and gene action in cross combinations of different corn genotypes under different water regimes. Total 12 parents comprised of eight lines and four testers; crossed to produce 32F1 hybrids. Parents including their hybrids were evaluated in CRD with three water treatments under controlled conditions with three replications in two seasons. Heterosis, percent contribution of lines, testers and line × tester interaction and gene action were studied for the traits i.e. ear leaf area, number of kernel rows per ear, 100 grain weight, biological yield, vegetative dry matter and anthesis-silking interval. Variable heterosis both in magnitude and direction was observed. Both additive and non-additive gene effects have role in the control of anthesis-silking interval; whereas non-additive gene effects were observed for ear leaf area, number of kernel rows per ear, 100 grain weight, biological yield and vegetative dry matter. However100 seed weight was mainly affected by dominance effects under this study that helped for the selection of parents to be used for the development of synthetics and hybrids durable for different water regimes. Keywords: Additive; Hybrid; Line × tester; Susceptible; Water stress http://dx.doi.org/10.19045/bspab.2019.80077

English

Maize is staple cereal crop in Ethiopia despite the fact that its production is constrained by nitrogen deficiency due to the high cost of fertilizer, and risks of drought. Therefore, development of maize varieties for low nitrogen might be one of the options to overcome the problem. The objective of this study was to estimate combining ability of highland maize inbred lines for yield and yield related traits under low nitrogen (low N) stress and non-stress conditions. Twenty-six inbred lines (two heterotic testers and twenty-four lines) were crossed using line × tester mating design, which generated 48 F1 hybrids and along with two hybrid checks (AMH853 and AMH 851) that were evaluated using alpha lattice design with two replications for grain yield and yield related traits within 2017 cropping season at Ambo under low and optimum nitrogen. Analyses of variances showed significant mean squares due to crosses for all traits under both low N stress and non-stress conditions, except for ear per plant under low N stress condition. The mean squares for general (GCA) and specific (SCA) combining abilities were significant for most of the traits under both conditions. Generally, the study indicated the importance of both additive and non-additive gene effects in most cases, while non-additive gene effects are less important under low-N stress. Inbred lines L1, L2, L9 and L20 were found as good combiners for grain yield at optimum N environment, whereas L5 and L14 were good general combiners under low N stress condition. L20 were good combiner for grain yield in combine analysis across environments and hence were promising parents for hybrid cultivars development. Based on SCA effects and per se performance, L5×T2 and L7×T2 were identified as promising hybrids for majority of traits studied in combined analysis across environments. Key words: General combining ability, gene action, heterotic group, specific combining ability.

Inheritance pattern of genes for morpho-physiological and yield traits in wheat (Triticum aestivumL.)

In order to study the inheritance pattern of morpho-physiological traits in bread wheat, a 10×10 diallel cross, excluding reciprocals was made and grown in a randomized complete block design (RCBD) with three replications. Observations were recorded on Days to 75% flowering (DF), Days to maturity (DM), Duration of reproductive phase (DRP), Plant height (cm) (PH), Effective tiller/plant (TLS), No. of spikelets per spike (SLS), No. of grains per spike (GS), Grain weight per spike (g) (GW), Spike length (cm) (SL), Biological yield per plant (g) (BY), Harvest index (%) (HI), 1000-Grain weight (g) (TGW), Spike density (SD), Canopy temperature depression (°C) (CTD), Chlorophyll intensity (%) (CI), Chlorophyll fluorescence (Fv/Fm) (CF), Protein content (%) (PC), Grain yield per plant (g) (GY). Highly significant differences were observed among the genotypes for all traits. The resulted 45 F1s and their F2s used for study the nature of gene for grain yield and its contributing traits in bread wheat. The result indicated that considerable gene action and average degree of dominance respond to achieving significant result for grain yield and its component traits. In both the generations F1s and F2s, grain yield per plant (g) was governed by non-additive gene action based on combining ability analysis, (σ2 g/σ2 s)0.5 [GCA and SCA variance ratio] and (H1/D)0.5 [Degree of dominance] were exhibited over dominance type average degree of dominance for grain yield and its component traits in both generations. Genetic analyses of the traits confirm the involvement of both additive and non-additive gene effects in governing the inheritance.

Genetic variability analyses for yield and physiological traits in groundnut (Arachis hypogaea L.) genotypes

Twenty different groundnut genotypes were evaluated in a randomized block design with three replications during kharif 2012 to study the variability parameters, heritability, genetic advance, correlation coefficient and path analysis for ten characters. Analysis of variance revealed highly significant differences among genotypes for all the traits except stability of soil plant analytical development (SPAD) and Chlorophyll Meter Reading 45 days after sowing indicating that adequate variability was found in the genotypes studied for most of the characters. The characters like 100 kernel weight, SPAD Chlorophyll Meter Reading 75 days after sowing, specific leaf area 75 days after sowing and rust resistance had high heritability with high genetic advance as per cent of mean and medium genotypic coefficient of variation indicating greater role of additive gene effects on these traits. While pod yield had moderate genotypic coefficient of variation and heritability along with high genetic advance as per cent of mean revealed that this character is also governed by additive gene effects and selection would be effective even in the early generation. Days to maturity, shelling outturn and specific leaf area 45 days after sowing had moderate heritability accompanied with low genotypic coefficient of variation and genetic advance indicating these traits are governed by non-additive gene effects. Selection may be practiced in later generations for improving these traits. The results on genotypic correlation coefficients revealed that pod yield had significant highly positive correlation with days to maturity, 100-kernel weight, and SPAD Chlorophyll Meter Reading 45 days after sowing while it was negative and significant for days to flower initiation and rust disease. SPAD Chlorophyll Meter Reading 45 days after sowing and SPAD Chlorophyll Meter Reading 75 days after sowing had highly significant negative correlation with specific leaf area 45 days after sowing and specific leaf area 75 days after sowing. Specific leaf area 45 days after sowing had highly significant negative correlation with rust. Therefore, SPAD Chlorophyll Meter Reading value could be used to identify genotypes with low specific leaf area and rust resistance. Path analysis indicated that 100-kernel weight had high positive direct effect with highly significant positive correlation with pod yield. Hence, this character may be effective for selection of high pod yield.

Evaluating Genetic Parameters and Combining Ability of Starch Viscosity Parameters in Rice Cultivars (Oryza sativa L.)

This study was undertaken to assess the combining ability of 6 rice varieties, for viscosity parameters and determining gene action controlling Rapid Visco Analyser (RVA) characters. F2 progenies derived from a 6×6 half diallel mating design with their parents were grown in a randomized complete block design with three replications at the research farm of Rice Research Institute of Iran (RRII) in 2015. The diallel analysis by Griffing`s method indicated the involvement of additive and non-additive gene actions controlling RVA traits. For traits PV and FV RI18447-2 and IR50 were the best combiners for increasing and decreasing, respectively. Deylamani and IR50 were the best combiners for increasing and decreasing BV, respectively. Beside, due to more portion of non-additive gene action in controlling trait SV, The Gilaneh × RI18430-46, and Deylamani × RI18430-46 crosses were the best for increasing and decreasing SV, respectively. The high estimates of broad sense heritability and narrow sense heritability for BV and FV, indicated the importance of additive effects in expression of these traits. Therefore, selection base breeding methods will be useful to improve these traits and selection in the early generations could be done to fix the favourable genes. Low estimate of narrow sense heritability for SV revealed that non-additive gene effects play important role in controlling setback viscosity. So, hybrid base breeding methods will be useful to improve this trait.

Inheritance and combining ability of grain yield in half diallel barley population

Studies on the genetic control of grain yield are of great importance for devising effective breeding programmes for yield gain in barley. Hence, inheritance of grain yield, heterosis and combining ability was investigated in barley population obtained from half-diallel crossing among 7 parental lines. The analysis of variance revealed that mean squares due to genotypes were highly significant for grain yield indicating wide diversity among the parental materials usedin the study. Mean squares of general combining ability (GCA) and specific combining ability (SCA), the ratio of GCA to SCA mean squares and portion of additive and dominance variances showed, the importance of both additive and non-additive gene effects for grain yield. The non-significant ratio of GCA to SCA mean square highlighted that non-additive gene effects were more important than additive effects. Distribution of dominant and recessive alleles in parentswas asymmetrical and parents possess the majority of recessive alleles. Since an average degree of dominance has values greater than 1, which indicated the over-dominance type of gene action in the inheritance of the grain yield. The parent BHS400 was considered suitable according to its yield capacities and general combining ability effects. Only 2 crosses viz., BHS400 X RD2660 and BHS400 X RD2552 had significantly higher grain yield than that of the check variety (BHS400), high significant SCA values and high significant useful heterosis values. Considering average narrow-sense heritability and over-dominant effects in the genetic control of grain yield it is better to postpone selection for this trait until advanced breeding generations. Doi.org/ 10.25174/2249-4065/2018/83278

Changes in heterosis of maize (Zea mays L.) varietal cross hybrids after four cycles of reciprocal recurrent selection

Two improved tropical maize composites, TZL COMP3 and TZL COMP4; representing complementary heterotic pools have been subjected to four cycles of reciprocal recurrent selection (RRS) for two decades to enhance varietal cross performance. The objectives of this study were to evaluate the effect of selection on genetic gain in heterosis for grain yield and other agronomic traits of these composites. Ten parental populations representing the C0 to C4 of each composite and their crosses plus a varietal check were evaluated in a trial at eight environments in Nigeria. Grain yield of the varietal crosses increased with selection by 3.1% cycle–1. Mean grain yields of the C4 × C4 varietal cross exceeded that of a popular improved reference variety by 23%. Selection also reduced anthesis-silking interval, improved ear characteristics, phenotypic appeal and resistance to foliar diseases. Mid-parent heterosis (MPH) increased from 4% at C0 × C0 to 24% at C4 × C4. The average rate of genetic gain in heterosis for grain yield in population crosses was 3.1% possibly because of presence of non-additive gene effects. The results of our study present the potential usefulness of the advanced selection cycle as sources of diverse inbred lines with improved combining ability as well as improved varietal crosses that can be multiplied and deployed in areas with limited market access.

Combining Ability Analysis of Late Leaf Spot Resistance and Other Agronomic Traits in Nine Groundnut Genotypes

Late leaf spot (LLS) Phaeoisariopsis personata (Berk. and Curtis) Deighton is one of the most important foliar diseases of groundnut worldwide including Nigeria. The genotypes were used to estimate the general combining ability (GCA) and specific combining ability (SCA) for yield components and late leaf spot (LLS) resistance. Four susceptible genotypes (SAMNUT 23, SAMNUT 24, SAMNUT 25 and SAMNUT 26) were used as females and five resistant genotypes (ICGV 12991, ICGV 7878, FDR-F7 82, FDR-F7 67 and FDR-F7 61) were used as males using line x tester mating design with three replications. The parents and progenies were evaluated for late leaf spot resistance. Highly significant negative general combing ability (GCA) effects were recorded for disease incidence in SAMNUT 25 (-0.05), indicating the genotype is a good general combiner for late leaf spot (LLS) and SAMNUT 26 (-5.90) is a good general combiner for LLS disease severity. ICGV 12991 (-12.00), FDR-F7 67 (-.68) and FDR-F7 61 (-2.23) genotypes are good general combiner for late leaf spot (LLS) disease resistance (disease incidence and severity), among the crosses, significant and negative SCA effects were obtained for most of the crosses i.e SAMNUT 24 x FDR-F7 67 and SAMNUT 24 x FDR-F7 61 for late leaf spot (LLS) resistance indicating that they are good specific combiners for late leaf spot (LLS) resistance. The ratio of the general combining ability (GCA) and specific combing ability (SCA) variances indicated the preponderance of specific combining ability (SCA) variance over general combining ability (GCA) variance for disease incidence and severity, indicating the role of non-additive gene effect and it may be due to difference in genotypes used as parents.

Genetic architecture of yield and quality traits in wheat (Triticum aestivum L.)

The aim of this study was to investigate gene effects and genetic variability by generation mean analysis for some yield and quality traits in three diverse crosses of wheat (JW 3288 × HD 8864, MP 3269 x GW 173 andJW 3020 × GW 366). The parents P1 and P1 and F1 , F2 , BC1 and BC2 populations were grown in a randomized complete block design with three replications during 2017-2018 crop seasons. Both additive and non-additive gene effects were involved in the expression of days to ear emergence, plant height, days to maturity, number of grains per spike, grain yield, flour recovery, husk content, protein content, lysine content and amylose content. The epistatic interaction was observed for all the ten traits in said crosses. In general, magnitude of dominance effect (h) has a greater value than additive effect (d) in all the traits. Digenic interaction indicated complex nature of inheritance means non-additive gene action. The improvement by selection in early generation could be advisable.

Quantitative genetic analysis of water deficit tolerance in coriander through physiological traits

AbstractDrought stress restricts the production of agricultural crops through morphological, physiological and biochemical changes in plants. This study explored the genetic control of physiological traits related to drought in coriander. In a diallel analysis, all six parents, their 15 F1hybrids and 15 F2populations were subjected to different irrigation regimes including well-watered, mild and severe water deficit stress. Drought stress decreased the relative chlorophyll content (RCC), the relative water content (RWC), chlorophyll a (Chla), chlorophyll b (Chlb), total chlorophyll (TChl) content, carotenoids (Car) and essential oil yield (EOY) in F1and F2generations. General combining ability (GCA) and specific combining ability effects were highly significant for all traits in F1and F2generations. Additive gene action was predominant for Chla, Chlb, TChl and Car under well-watered condition while non-additive gene effects were more important under mild and severe water deficit stresses in F1and F2generations for the above traits. Additive gene effects were more important for RCC, RWC and electrolyte leakage (EL) traits in both F1and F2generations under mild and severe water deficit stresses. In conclusion, the high narrow-sense heritability and significant genetic correlations between EOY and RCC, RWC and EL suggest that these traits can be used as surrogates to identify superior genotypes for arid and semi-arid regions. Also, the parental lines, P4and P6had the best GCA for RCC, RWC, Chla, Chlb, TChl, Car, essential oil content and EOY.

Line × tester analyses for anther culture response of bread wheat (Triticum aestivum L.)

The aim of this study was to investigate the gene effects that play a role in the inheritance of the anther culture response of the F1 and F2 populations obtained from the hybridization between the seven doubled haploid (DH) wheat line and four bread wheat cultivar using line × tester method as well as, to determine suitable parents and promising hybrids. Eleven parents and their twenty-eight hybrid combinations were examined for androgenic properties related to anther culture response such as the number of callus, green, albino, haploid, spontaneous DH and fertile plants. The obtained data were evaluated by the combining ability analysis calculated using the line × tester method and by estimating the heritability degrees. According to the results, for all traits examined, the non-additive gene effects were found as significant and narrow sense heritability at a low level. Significant combining ability effects have been identified for some parents and hybrids regarding traits examined. DH19, DH22, and Harmankaya-99 have been identified as suitable parents to develop the androgenic traits, while crosses formed between them have been determined as promising. A total of 444 plants (142 F1, 302 F2) were transferred to the greenhouse from the plants obtained from the anther culture, and 205 (68 in F1, 137 in F2) were fertile. Ninety-three of the fertile plants were obtained from the parents. The seeds of 112 DH plants obtained from hybrids were replicated to be used in breeding programs.

Heterosis and combining ability in bitter gourd (Momordica charantia L.)

Ten parents of bitter gourd viz., Solan Hara, Pusa Do-Mousmi, BG-14, Green Long, MDU-1, IC-85605, IC-45346, IC-68272-1, IC-68237 and Solan Collection and their forty five crosses (using half diallelic system) along with check viz., Jhalri, US-6214 and US-6203 were evaluated in field trials in two locations Udaipur and Chittaurgarh in two different seasons which consists four environments. Economical heterobeltiosis for yield per vine (kg) were recorded in IC 85605 x IC 45346 (38.94%) and MDU 1 x IC 85605 (34.98%) over the environments. Good general combiners for various economic traits IC-68237 for number of primary branches per vine (0.09), fruit length (0.52), fruit diameter (0.17) & number of fruits per vine (0.22) over the pooled environments. SCA (Specific Combining Ability) for economic traits were observed in Solan Collection x IC 68237 (1.24) for number of fruits per vine, IC 68237 x MDU-1 for fruit length (1.82) and fruit weight (7.81). These results indicate that both additive and non-additive gene effects are involved in the inheritance of the studied traits. The additive gene action was more important than the non-additive ones in the genetics of most studied traits.

Combining ability effects and heterotic grouping in newly developed early maturing yellow maize (Zea mays L.) inbreds under sub-tropical conditions

A field experiment was conducted at Experimental Farm, Shivalik Agricultural Research and Extension Centre, Kangra representing subtropical conditions of north western Himalayasecology during Kharif 2017 to estimate combining ability of newly developed early maturing yellow maize inbred lines. Twenty two crosses were generated by crossing 11 new developed yellow maize inbreds with 2 diverse testers using Line x Tester mating design. The experiment was conducted using randomized block design with two replications. The mean square due to genotypes, parents and parents v/s crosses were significant for all the traits, except for days to 50 per cent silking due to genotypes, kernel rows, days to 50 per cent tasseling and days to 50 per cent silking due to parents. This revealed presence of appreciable amount of genetic variability in the experimental material of the present investigation. The ratio of σ2gca / σ2sca for all the studied traits indicated the preponderance of non-additive gene effects in the inheritance of these traits. Among female inbred lines, L9 had significant GCA effects for grain yield per plant (21.64) and yield component traits like shelling percentage (3.24) , ear length(2.37), ear diameter(1.07), number of kernels/row(3.84) and 1000- kerenel weight (8.68) , indicated that best general combiner for these traits, while in male parent T2 was the best general combiner for yield contributing traits viz., ear length (0.47), ear diamter (0.19), number of kernel rows per ear (0.59), number of kernels/row (1.02) and 1000-kernel weight (10.05). On the basis of mean grain yield and SCA effects, three test crosses, viz., L9xT2, L5xT1, and L1xT1 were identified most promising and may be further tested at multi environments for use as single cross hybrids. L9xT2 manifested highest mean grain yield (102.17g/plant) and significant positive specific combining ability effect (15.93). Based on the SCA effect for grain yield, the newly developed inbreds were classified into two heterotic groups. The lines L1, L2, L4, L5 and L6 belonged to tester group CM-212, while L3, L9, and L11 belonged to heterotic group of HKI-1105. Inbred lines assigned into two opposite heterotic groups could be used as parents to develop hybrids and inbred lines with same heterotic group with positive GCA may be used for synthetic variety development.

Performance and Combining Ability of Some Agronomic Traits of Bread Wheat Under Normal and Water Stress Conditions

The present investigation was carried out during 2015/2016 and 2016/2017 seasons at the Experimental Research Station, Faculty of Agriculture, Assiut University. The objectives of this investigation were to obtain information about the performance and genetic components of parental wheat genotypes and their F1s under normal and water stress conditions. The performance of all genotypes under water stress condition was lower than its performance under normal condition. The parent 6 (P6) was the earliest flowering under both conditions and the parent P5 under water stress condition (85.70 day), while the parents P1, P2,P4 andP6 gave the tallest spike under both of normal and water stress conditions. While, P1 and P2 gave the tallest spike under water stress condition. The hybrids (P4 × P5) and (P1 × P6) were the earliest among F1- hybrids under normal and water stress conditions, respectively. Furthermore, the hybrids (P1 × P3) and (P1× P4) gave the tallest spike under normal and water stress conditions, respectively. The mean of grain yield /plant for all genotypes was 32.70 g and 24.96 g under normal and water stress condition, respectively. The P6 gave the highest grain yield/ plant compared with other parental genotypes under both conditions. On the other hand, the highest grain yield /plant was obtained from the hybrids (P4 × P5) under both conditions. The results showed that the magnitude of SCA exceeded GCA ones for days from planting to 50 % heading trait, which indicating that the major portion of genetic variance was due to the non-additive gene effects. The ratio of GCA/SCA was noticed to be low for days from planting to 50 % heading trait, indicated the specific combining ability was more important than general combining ability variance. The ratio of GCA/SCA was low for Plant height except SCA under irrigation in the F1- hybrids. The ratio of GCA/SCA was 1.08 and 0.80 in the F1-hybrids under normal and water stress conditions, respectively. The good genotypes for plant height in the F1- hybrid under both environments were Entry 21 and Entry 20. While, the ratio of GCA/SCA was noticed to be low for spike length, indicated the specific combining ability was more important than general combining ability variance, which indicating that the major portion of genetic variance was due to the non-additive gene effects. The results showed that the magnitude GCA/SCA ratio for number of kernel/spike was 0.31 and 0.20 in the F1-hybrids under normal and water stress conditions, respectively, indicating that the non-additive were larger than additive effects in the inheritance of number of kernel/spike and both were highly significant. The ratios of GCA/SCA were less than the unity for grain yield/plant under both environments indicating that the non-additive gene action controlled the inheritance of grain yield/plant. The GCA/SCA ratio was 0.14 and 0.48 for 100-grain weight in the F1-hybrids under normal and water stress conditions, respectively, indicating predominance of non-additive gene effect in the inheritance of 100- grain weight

HEAT TOLERANCE IN SOME BREAD WHEAT GENOTYPES UNDER TWO SOWING DATES

A 7x7 half diallel cross along with their parental wheat cultivars were evaluated under two sowing dates (19th Nov. and 17th Dec.).The results revealed that mean squares due to sowing dates, genotypes and genotypes x sowing dates interaction were significant for most of the studied traits. Delaying sowing date to Dec. reduced all studied characters compared to the normal sowing date except electrolyte leakage which increased by delaying sowing date. Heterosis over better parents showed that, the best hybrids under stress condition were Misr 2 X Giza 168 and Sids 1 X Giza 168 for grain yield / plant and some of other studied traits. General and specific combining ability mean squares indicated the importance of both additive and non-additive gene effects in the inheritance of the studied traits with few exceptions. However, the additive effect was more important than the non-additive effects in the inheritance of days to 50% heading, plant height, No. of spikes/ plant,No. of kernels / spike and 1000-kernel weight while, the non-additive effects were more important than the additive effects in the inheritance of electrolyte leakage and flag leaf area. The best general combiner parents for grain yield / plant and some of other studied traits were Gemmeiza 11 and Giza 168under stress condition. The best hybrids for SCA effects were Sakha 93 X Sids 1, Gemmeiza 11 X Giza 168, Misr 2 X Giza 168 and Sids 1 X Giza 168 under stress condition for grain yield / plant and some of other studied traits. The crosses Gemmeiza 11 X Giza 168 (HSI 0.36), Gemmeiza 7 X Giza 168 (HSI 0.58) and Sakha 93 X Giza 168 (HSI 0.60) have recorded the lowest values of heat susceptibility index (HSI), indicating their tolerance to heat stress (late sowing date).

English

For the estimation of genetic parameters (such as heterosis effect, potence ratio, combining ability and reciprocal effects) of five fruit traits, in order to suggest breeding strategies in Citrullus mucosospermus (Fursa), a field trial was carried out at Kononfla city in Western Cote d’Ivoire using 4x4 full diallel. All 12 F1 hybrids and their parents were planted in a randomized complete block design with three replications. A positive heterosis effect relative to mid-parental values was observed to hybrids having one parent Bebu for characters’ fruit weight, fruit diameter and fruit volume. Variances due to general (GCA) and specific (SCA) combining abilities were significant (PE‚0.001) for all studied traits, indicating the involvement of both additive and non-additive gene actions in the inheritance of these traits. Non-additive gene effects were predominant for all studied traits. Bebu was the best general combiner for all traits except fruit number which the best combiners were three morphotypes of Wss. For NF, Wss1×Wss2 and Wss2×Wss3 recorded the highest positive SCA values. Crosses involving Bebu as one parent, presented the best SCA values for other traits. Key words: Bebu, Wlewle small seeds, heterosis, potence ratio, combining ability.