Positive GCA Effects Research Articles

Combining ability of yield attributes traits, oil and protein contents in oil seed rape (Brassica napus) under normal and restricted nitrogen application

Combining ability of yield associated traits has been studied quite frequently in oilseed rape (Brassica napus L.) but it was hardly ever studied based on nitrogen levels variations. Six parents along with their 15 F2 half diallel crosses were evaluated in two nitrogen (N) levels including N0 and N+. Analysis of variance revealed significant mean squares of general and specific combining abilities (GCA and SCA) for all the traits studied. The high narrow-sense heritability estimates were found for seed yield and harvest index, implying the more importance of additive genetic effects for and consequently high selection efficiency for improving these traits. Due to low narrow-sense heritability estimates for oil and protein contents and therefore more importance of non-additive genetic effects, selection for improving these traits should be done in later segregating generations. The GCA × N level interaction was significant only for oil content which is indicating of more differences of GCA effect of this trait at two nitrogen levels. Significant N × SCA effect mean squares for harvest index and oil content, revealed significant variation of SCA effects of these traits in nitrogen levels application. Most of the crosses with high seed yield at N0 and N+ had at least one parent with positive GCA effect at both N levels. Among the six parents, PF7045/91 appeared to be the best combiner for seed yield at the N0. This variety also showed high GCA at the N+ but its low oil content at the N+ is certainly disadvantageous as the quality of the hybrid is often intermediate between the two parents.

Combining Ability Analysis of Some of Grain Yield Stress Indices in Rapeseed (Brassica Napus L.) Varieties

Although most of investigations showed that nitrogen fertilizers gave substantial rapeseed yield increases even in diverse and contradicting conditions but in a few studies were focused on genetic parameters of nitrogen stress effects. Combining ability of some of important grain yield stress indices based on application and non application of nitrogen (N+ and N0) was studied using half diallel of six spring rapeseed varieties and their 15 F2 progenies. Significant mean squares of general and specific combining abilities (GCA and SCA) were observed for potential yield(Yp), Stress yield(Ys), mean productivity (MP), geometric mean productivity (GMP), tolerance index (TOL), stress tolerance index (STI) and stress susceptibility index (SSI), indicating importance of additive and non-additive genetic effects for them. Non significant ratio of GCA to SCA mean square and low narrow-sense heritability estimates were detected for all the indices, indicating the prime importance of non-additive genetic effects. Significant positive GCA effect of Yp, Ys, MP, GMP and STI for PF7045/91 and significant negative GCA effects of them for Option500, indicated the same direction of GCA effects of these indices and GCA effects of Yp and Ys. On compare to SCA effects, most of crosses had significant high parent heterosis for Yp, Ys and and all the stress indices, therefore selection the better combinations based on heterosis will be more effective than SCA effect.

English

The present study was carried out to investigate the diallel analysis in upland cotton (Gossypium hirsutum L.) by involving seven parents and their 42 cross combinations. All the characters were predominantly controlled by additive gene action except number of sympodial branches, single plant yield and bundle strength. Non additive gene action was controlled for the characters sympodial branches, single plant yield and bundle strength. The parent BW4-1 had superior per se performance for single plant yield, boll weight, lint index, number of bolls per plant, seed index, and micronaire followed by MCU 13 which had recorded high per se for single plant yield, lint index, seed index and number of sympodial branches. The parent TCH 1726 exhibited positive and significant gca effect for single plant yield, ginning percent, number of sympodial branches, boll weight and plant height. Based on high per se performance and high gca effect, the parent MCU 13 was considered as best general combiner as it had significantly greater values for single plant yield, number of sympodial branches, lint index and seed index. The hybrids KC 2 × TCH 1726 and TCH 1705 × MCU 3 had recorded high per se for single plant yield, number of bolls per plant and number of sympodial branches. Based on sca effects, KC 2 × TCH 1726 showed significant sca effects for single plant yield and number of sympodial branches.   Key words: Cotton, Combining ability, gca, fibre quality traits, sca, single plant yield.

ESTIMATION OF GENE ACTION, COMBINING ABILITY, HETEROSIS AND HERITABILITY IN MAIZE BY USING LINE × TESTER METHOD UNDER TWO OF NITROGEN LEVELS.

The experiment was carried out at the field of College of Agriculture at the University of Duhok during the spring season of 2010. Eleven inbred lines of maize, had been selected, eight of them were used as a line (males), (ZP 204, ZP 301, ZP 595, ZP 670, ZP 430, ZP 505, un 44652, ZP 735) and the reminder used as testers (females), (ZP 197, ZP 607 and ZP 707) to estimate gene action, specific and general combining ability, heterosis and heritability for yield and its components under two nitrogen fertilizer levels (135 and 275 Kg N/ha). The results showed significant positive heterosis for most studied characters of hybrids under two nitrogen levels. The better hybrids for grain yield were (ZP 607 × ZP 505) and (ZP 707 × ZP 204). The line ZP 505 showed the heights positive GCA effect of grain yield. Heritability in broad sense was high for all studied characters while heritability in narrow sense was high for ear height under both nitrogen levels and number of rows / ear under value nitrogen level only. The additive variance was more than dominance variance for all characters except 100 grain weight (g) and ear length (cm) under (135 Kg N). The average degree of dominance was greater than one for all characters. The results of this study can enhance the use of promising inbred lines in a programme focused on developing hybrid that efficiently can take up and use nitrogen.

Studies on Recombinational Variability for Combining Ability Among F4 Barbadense Lines

The present study was aimed at evaluating recombinational variability for combining ability in F4 generation. To assess variability for combining ability, twenty eight F4 (Gossypium barbadense L.) lines were crossed with four common diverse testers (Gossypium hirsutum L.) viz., DH 98-27 (T1), ZCH8 (T2), 178-24 (T3) and DH 18-31 (T4) for use in assessing the variability for combining ability. The entire experimental material was planted on a medium black soil at College of Agriculture, Dharwad under irrigated condition. All the 53 F5 (included Suvin variety as check) barbadense lines, four hirsutum testers and derived F1 crosses along with the straight crosses (Bench Mark Crosses (BMC)) and ruling commercial checks (MRC 6918 Bt check and DCH 32 non Bt check) were sown during kharif 2011 in a Randomized Block Design with two replications and a spacing of 90 cm between rows and 60 cm between the plants within a row. Among the barbadense lines (males), the mean sum of squares (MSS) were not significant for all the characters except mean boll weight, reproductive points on sympodia and seed cotton yield which showed highly significant differences, while number of bolls per plant and ginning outturn exhibited significant differences. Among the hirsutum testers (females) exhibited not significant difference for all the characters except number of bolls per plant and seed cotton yield which recorded highly significant differences, while mean boll weight and transpiration rate showed significant differences. Line x Tester interaction were highly significant differences for number of monopodia per plant, number of bolls per plant, mean boll weight, reproductive points on sympodia, seed index, lint index, photosynthetic rate, stomatal conductance and transpiration rate, while seed cotton yield had significant differences. The estimates of variance due to general combining ability (GCA), variance due to specific combining ability (SCA), the magnitude of SCA variances were greater than GCA variance for all 14 characters and the variance ratio was less than half in these traits, indicating that dominance variance was more than additive variance for these characters. For seed cotton yield, eight lines recorded significant gca effects, of which five lines exhibited positive significant gca effects. The highest gca effect was found by the line DB 533 x DB 534 F4 IPS 8 (363.15). Among the testers, the tester DH 98-27 had positive significant gca effect (94.65) and the tester DH 18-31 showed positive gca effect (35.44), while 178-24 (-77.43) recorded negative significant gca effect. Two crosses manifested positive significant sca effects, of which the cross DH 98-27 X (DB 534 x DB 533 F4 IPS 22) (680.34) recorded the highest positive sca effect. Based on weighted gca method ,the most potential combiners were found to be the lines DB 533 x DB 534 F4 IPS 26, DB 533 x DB 534 F4 IPS 17, DB 533 x DB 534 F4 IPS 8 and DB 533 x DB 534 F4 IPS 32 . Among the testers, the tester DH 18-31 based on weighted gca method is the most potential parent Key word: Recombinational variability, F4 barbadense lines, hirsutum testers, gca, sca

Genetic analysis in maize (Zea maysL.) under moisture stress conditions

The present study was undertaken to assess combining ability, heterosis and association among morphophysiological traits of maize under stress and optimum conditions. Elite maize inbred lines with known performance under drought were crossed in half diallel fashion. The resulting hybrids and their parents were evaluated under managed drought and optimum conditions. CI 4, Hyd Sel 4 and KDMI 15 recorded high mean grain yield and significant positive gca effects under stress where as CML 446 and NEI 9208B recorded high mean grain yield with significant positive gca effects under optimum conditions. CI 4 and NEI 9202B were identified as good combiners for grain yield. Among the 66 hybrids, 15 under optimum conditions and 21 under stress recorded significant positive heterosis over mid parent.Three hybrids viz., KDMI 15 x NEI 9202B, Hyd Sel 4 x NEI 9202B and NEI 9208B x Hyd Sel 15 were identified as high grain yielding under stress and optimum conditions. The hybrids viz., Hyd Sel 15 x Hyd Sel 17 (4.18 t ha–1), KDMI 15 x NEI 9202B (4.01 t ha–1), NEI 9208B x Hyd Sel 15 (3.96 t ha–1), CM 111 x CI 4 (3.96.5 t ha–1) and KDMI 15 x Hyd Sel 15 (3.88 t ha–1) recorded good grain yield under stress.

Heterosis of Single Cross Sweet Corn Hybrids Developed with Inbreds of Domestic Genepool

The sweet corn hybrids synthesized with inbreds of domestic gene pool were studied for heterosis, combining ability effects and nature of gene action involved in the expression of green cob yield and quality traits in a Line x Tester design involving eighteen lines and four testers. Totally twelve quantitative and six qualitative traits were considered in the study. Combining ability indicated the predominance of non-additive gene action for all the characters and the contribution of lines was greater than the testers for all the traits studied. Since non-additive gene action was predominant, heterosis breeding was suggested for the improvement of green cob yield as well as quality traits. Among the lines, B.No. 1421-5-1, SC 8324 -3, SC 7855-3-1 USC 10-3-2-3 and USC 10-2-2 and among testers USC 3-1-2-1 and USC 4 were identified as superior ones, as they possessed higher per se and significantly positive gca effects for green cob yield coupled with desirable percentage of total sugar and starch. Therefore, these parents may be utilized for development of heterotic sweet corn hybrids with enhanced green cob yield and total sugar

Combining ability of nitrogen deficiency stress indices for plant height in rapeseed varieties

Although an average plant height is more preferable in most of agronomic crops, less reduction of this trait in stress condition makes yield components and seed yield sustainable in rapeseed varieties. Combining ability, heterosis and heritability of plant height at application and non-application of nitrogen environments (Hp and Hs, respectively) and its related stress tolerance indices were detected in half F2 diallel crosses of six spring rapeseed varieties. Significant mean squares of general and specific combining abilities (GCA and SCA) were detected for Hp, Hs, mean productivity (MP), geometric mean productivity (GMP) and stress tolerance index (STI), indicating the importance of additive and non-additive genetic effects for them. A high narrow-sense heritability estimate was exhibited for STI, emphasizing the prime importance of additive genetic effects for this stress tolerance index. A significant correlation among Hp, Hs, MP, GMP and STI showed the efficiency of these stress indices for improving plant height in plant breeding programme. In comparison to SCA effects, most of the crosses had significant high parent heterosis for Hp, Hs and all the stress indices. RGS003 with a significant positive GCA effect of Hs was considered as a suitable parent for improving this trait and most of the combinations of this genotype had significant negative SCA effects.

Combining Ability and Heterosis Studies inAvena sativaL. For Green Fodder Yield and Component Traits

Forty F1 hybrids, obtained by crossing eight lines and five testers selected from oat germplasm available at Forage Research farm, PAU, Ludhiana were evaluated along with parents in RBD during Rabi 2010–11. Analysis revealed significant gca and sca mean squares for most of the traits. Among female parents OL 1696 showed positive gca effects for green fodder yield, number of leaves, number of tillers, stem girth and number of leaves on main shoot. The male parent JHO2009-1 was best general combiner for green fodder yield whereas SKO 117 was good general combiner for green fodder yield, number of leaves, leaf length number of tillers, flag leaf length and number of leaves on main shoot. The best specific combinations were OL 1696 x JHO-2009-1, OL 1680 x UPO-09-2, OL 1696 x UPO-09-2 Kent x JO-03-93, OL 1690 x UPO-09-2 and OL 1696 x SKO 117 for different traits. Highest significant and positive heterosis for green fodder yield (1506.1%) was shown by F1 OL 1696 x JHO-2009-1 followed by OL 1696 x SKO 117.

Development of Heterotic Groups (<i>G. hirsutum</i> vs <i>G. barbadense</i>) Based on Combining Ability and Inter Specific Hybrids Performance for Yield and Fiber Quality Traits

Utilization of heterosis depends on genetic diversity existing between the parents, magnitude of dominance at the yield influencing loci and the genetic distance between the chosen parental genotypes. It is possible to maximize heterosis by enhancing genetic distance between two chosen parental populations. The main objective of the Line x Tester study was to determine the combining ability status of the barbadense and hirsutum lines included in the heterotic box. These lines were compared with other barbadense and hirsutum lines. For the pattern of combining ability and the potentiality of the interspecific hybrids developed based on them. The efforts on creating recombinational variability have begun with two barbadense lines. However to compare the potentiality of the 8 hybrids with other potential hybrids developed over years at Dharwad centre and best commercial hybrids ( Bt and non Bt ), a separate evaluation of these hybrids was taken up. Realizing the need for developing potential interspecific ( G. hirsutum x G. barbadense ) hybrids, a detailed study was initiated at UAS Dharwad to identify hirsutum and barbadense genotypes capable of giving potential interspecific hybrids. Based on this study done during earlier years in 2009-2010 two barbadense DB 533 and DB 534 and four hirsutum DH 98-27 (T 1 ), ZCH 8 (T 2 ), 178-24 (T 3 ) and DH 18-31 (T 4 ) lines giving best hybrids (H x B) combinations between them were selected. Among four barbadense lines positive gca effects for seed cotton yield was recorded by DB 533 and DB 534 confiriming the potential of these barbadense lines in developing productive interspecific hybrids. Among 23 hirsutum testers, four testers DH 18-31, ZCH 8, DH 98-27 and 178-24 exhibited good positive values of gca effects for seed cotton yield and were located among top ten testers ranks 2, 8, 1 and 7 respectively when compared to other hirsutum testers. The potential of 8 bench mark crosses of heterotic box ZCH 8 x DB 533, DH 98-27 x DB 534, DH 18-31 x DB 533, ZCH 8 x DB 534, 178-24 x DB 533, DH 98-27 x DB 533, DH 18-31 x DB 534 and 178-24 x DB 534 recorded higher per se performance for seed cotton yield ranking 1, 2, 4, 6, 8, 10, 11 and 14 out of 49 crosses. These crosses also recorded superior value for yield attributing characters like number of bolls and mean boll weight. The mean performance of these crosses associated with this heterotic box was found to be 2174 kg/ha as compared to the overall mean of best HB interspecific hybrids which was 1921 kg/ha.

Combining Ability for Yield and Yield Attributing Characters in Line x Tester Inter Specific Hybrids (<i>G. hirsutum</i> × <i>G. barbadense</i>) for Confirmation of Heterotic Groups

The prime objective of cotton breeders is to develop new varieties with high yield and yield components. Present study aims to estimate general combining ability of the parents and specific combining ability of hybrids for yield and yield components. The term heterotic group refers to a group of related or unrelated genotypes from the same or different populations, which display similar combining ability and heterotic response when crossed with genotypes from other genetically distinct germplasm groups. If two lines A and B are found to give potential crosses with testers T 1 and T 2 , it is possible to increase the genetic distance between these opposite pairs A, B vs, T 1 and T 2 by following population improvement scheme for improving combining ability defined in cross pollinated crops by introducing suitable changes to match the crossing system seen in self pollinated crops. The Line x Tester study was planned to assess the relative potential of the barbadense and hirsutum in developing interspecific hybrid combinations. The objective of this study was to determine the relative the 4 barbadense and 23 hirsutum lines. Barbadense were used as lines and hirsutum were used as testers. The ongoing study at Agricultural Research Station, Dharwad on evaluation of interspecific hybrids led to formation of a heterotic box of two barbadense lines DB 533 and DB 534 and hirsutum testers DH 98-27 (T 1 ), ZCH 8 (T 2 ), 178-24 (T 3 ) and DH 18-31(T 4 ). Among four barbadense lines positive gca effects for seed cotton yield was recorded by DB 533 and DB 534 confiriming the potential of these barbadense lines in developing productive interspecific hybrids. Among 23 hirsutum testers, four testers DH 18-31, ZCH 8, DH 98-27 and 178-24 exhibited good positive values of gca effects for seed cotton yield and were located among top ten testers ranks 2, 8, 1 and 7 respectively when compared to other hirsutum testers.

Combining Ability for Yield and Yield Attributing Characters in Line×Tester Interspecific Hybrids (<i>G. hirsutum</i>×<i>G. barbadense</i>) for Confirmation of Heterotic Groups

The prime objective of cotton breeders is to develop new varieties with high yield and yield components. Present study aims to estimate general combining ability of the parents and specific combining ability of hybrids for yield and yield components. The term heterotic group refers to a group of related or unrelated genotypes from the same or different populations, which display similar combining ability and heterotic response when crossed with genotypes from other genetically distinct germplasm groups. If two lines A and B are found to give potential crosses with testers T 1 and T 2 , it is possible to increase the genetic distance between these opposite pairs A, B vs, T 1 and T 2 by following population improvement scheme for improving combining ability defined in cross pollinated crops by introducing suitable changes to match the crossing system seen in self pollinated crops. The Line Normal 0 7.8 pt 0 2 false false false EN-US ZH-CN X-NONE × /* Style Definitions */ table.MsoNormalTable {mso-style-name:Table Normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:none; font-size:11.0pt; font-family:Calibri,sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-fareast-language:EN-US;} Tester study was planned to assess the relative potential of the barbadense and hirsutum in developing interspecific hybrid combinations. The objective of this study was to determine the relative the 4 barbadense and 23 hirsutum lines. Barbadense were used as lines and hirsutum were used as testers. The ongoing study at Agricultural Research Station, Dharwad on evaluation of interspecific hybrids led to formation of a heterotic box of two barbadense lines DB 533 and DB 534 and hirsutum testers DH 98-27 (T 1 ), ZCH 8 (T 2 ), 178-24 (T 3 ) and DH 18-31(T 4 ). Among four barbadense lines positive gca effects for seed cotton yield was recorded by DB 533 and DB 534 confiriming the potential of these barbadense lines in developing productive interspecific hybrids. Among 23 hirsutum testers, four testers DH 18-31, ZCH 8, DH 98-27 and 178-24 exhibited good positive values of gca effects for seed cotton yield and were located among top ten testers ranks 2, 8, 1 and 7 respectively when compared to other hirsutum testers.

Genetic analysis of seed yield and oil content in safflower using F1 and F2 progenies of diallel crosses

Improvement of seed yield and oil content in safflower (Carthamus tinctorius L.) as an oilseed crop is the main objective of its breeding programs. However, little genetic information is available for these traits. The main objective of this study was to estimate genetic parameters for seed yield and oil content. Six safflower lines each derived from different Iranian local populations and Saffire as a foreign cultivar were crossed in all combination as a diallel set without their reciprocals. Crosses were selfed to obtain seeds of F2 progenies. F1 and F2 progenies along with their parents were evaluated in two separate experiments to do F1 and F2 diallel analysis. The GCA mean squares were significant for all traits including seed yield per plant, heads per plant, seeds per head, 100-seed weight, days to flowering, plant height and oil content. In both analyses, positive GCA effects for seed yield were found for parental lines IUTE1449 and IUTH13, indicates that progeny with those genotypes as parents showed seed yields that were greater than the average of all crosses. The parental line IUTKH211 was the best combiner for developing genotypes with high oil content. For achieving genotypes with short time to flowering and plant height, Saffire was the best parent. GCA/SCA ratio indicated there were large additive effects for all the traits, except for seed yield per plant. Narrowsense heritability for seed yield per plant and oil content was 9.3 and 23.5%, receptively. However, seeds per head, 100-seed weight, days to flowering and plant height had moderate to high narrowsense heritability (79.8, 55.4, 65.6 and 89.4%, respectively). There was reasonable consistency for estimating genetic parameters from analysis of F1 and F2 progenies.

COMBINING ABILITY FOR SOME YELLOW MAIZE INBRED LINES BY DIALLEL CROSSES

Eight yellow maize inbred lines (L 730, L 731, L 739, L 743, L 744, L 745, L 746 and L 749) were planted at Gemmeiza Research Station, and were crossed in a diallel cross system during the growing season 2009. The 28 crosses and two check hybrids (SC 162 and SC 166) were evaluated at Gemmeiza and Sids Agricultural Research Stations during 2010 growing season. Data were collected on number of days to 50% silking (day), plant and ear heights (cm), resistance to late wilt disease and grain yield ( ton/ha) and analyzed according to Griffing (1956) method-4 model-1fixed modelfor each location and their combined performance. Locations mean squares were significant for all studied traits, except for number of days to 50% silking. Variations of genotypes (G) and their partitions; crosses (Cr), checks (Ch) and Cr vs Ch were significant for most traits, except some partitions for all the studied traits under the two locations and their combined performance, as well as their interactions with locations were significant for mean squares of most partitions. These results indicated that the genotypes and their different partitions differed in their performances from location to another for all the studied traits. GCA and SCA mean squares for each location and their combined were significant for all the studied traits, except for plant height and SCA for ear height under Gemmeiza and resistance to late wilt disease under the two locations and their combined performance. Moreover, interactions GCA and SCA with locations were significant for all the studied traits, except for resistance to late wilt disease under the combined performance only, indicating that additive and non-additive effects were important in the inheritance of the studied traits. On the other hand, the ratio of δ2 GCA / δ2 SCA was greater than unity for most studied traits, indicating an importance of additive gene effects in the inheritance of studied traits. While, the ratio δ2GCA x loc/δ2SCA x loc indicated an important both additive and non-additive effects in the expression of these studied traits, Moreover, the additive and non-additive effects were more interacted by environmental conditions ( locations) under this study . The inbred line L 743 seemed to be a good combiner for earliness, inbred line L 749 was the best combiner for shorter plants and lower ear placement, inbred line L 730 exhibited desirable GCA effects for resistance to late wilt and grain yield, also the inbred line L739 gave positive and desirable GCA effects for grain yield (ton/ha). Three crosses i.e. 1x8, 1x4 and 3x5 (10.21, 10.11 and 9.91 ton/ha) significantly out-yielded the check hybrid SC162 9.12 ton/ha by (11.95, 10.90 and 8.70 %, respectively). These crosses are considered promising comparing with the check hybrid SC162 under this study.

LINE X TESTER ANALYSIS FOR SOME ECONOMICAL USEFUL CHARACTERS IN KENAF (Hibiscus cannabinus L.)

This study was conducted with the objective of estimating combining ability and gene action for some economical useful traits in kenaf. This was achieved via evaluating 15 progenies of the line x tester analysis consisting of five females (P1=S,13, P2= S.114, P3= S.119, P4= S.98/205 and P5= S.38) and three males (P6=Giza3, P7=S.105/2, and P8=S.112). In 2010, the eight parents and their 15 F1 ,s progenies were evaluated in a randomized complete block design with four replications at Ismailia Agric. Res. Station Farm, Ismailia Governorate, Egypt. The predominant role of additive gene action was involved in the expression of all studied characters except for each of plant height, technical stem length and fiber length. Therefore, selection can be performed followed in the F2 and subsequent generations for all studied characters, except for the previous three traits. P3 and P7 exhibited significant and positive GCA effects for green weight and most of its components as well as P6 for three important components (green weight/plant, fiber weight/plant and fiber percentage), indicating that the use of these parents in kenaf breeding programs could increase green weight and consequently increasing fiber yield. Concerning, seed weight per plant results indicated that the P7 followed by P3 and P5 exhibited high best combiners for seed weight. The cross P3P7 exhibited significant positive SCA effects for green weight and most components ( plant height, technical stem length, fiber length, fiber weight and seed weight per plant). This cross involved high x high general combiners for these traits. Also, P4P6 (high x high) for fiber percentage. Whereas, P4P6 exhibited significant positive SCA effects as well as high x low general combiner parents for green weight/plant and most important components. Phenotypic (rp) and genotypic (rg) correlation coefficients concluded that the green stalk weight, plant height, technical stem length, fiber percentage and fiber length are the major components contributing to fiber weight/plant in kenaf. Therefore, selection for these traits will improve the fiber yield in kenaf.

COMBINING ABILITY FOR GRAIN YIELD AND SOME RELATED TRAITS OF NEWLY YELLOW MAIZE (Zea mays L.) INBRED LINES

Nine S5 newly yellow maize inbred lines were developed from segregated generation of different Hungarian sources were topcrossed with two testers i.e., inbred line Giza (Gz)-656 and single cross SC-166 at Ismailia Agricultural Research Station during 2009 growing season. In 2010 summer season, the 18 topcrosses and two yellow commercial check hybrids; SC-162 and TWC-352 were evaluated on two locations; Sakha and Ismailia Agricultural Research Stations. The studied traits were grain yield (GY ard/fed), ear length (EL cm), ear diameter (ED cm), No. of rows ear-1 (RE-1), days to 50% silking (SD day) and plant height (PH cm). Results showed that the differences between two locations were significant for all studied traits, indicating that environmental conditions were different at both locations. The crosses and their partionining to lines were significant for all studied traits except RE-1 trait for lines. Mean squares due to (L x Loc) were significant for RE-1, SD and PH traits. On the other hand, the interaction of (T x Loc) and (L x T x Loc) were insignificant for all studied traits except GY and PH traits for (L x T x Loc) interaction which were significant. The topcrosses (L1 x T1) (36.37 ard/fed), (L2 x T1)(36.80 ard/fed) were significantly out yielded the check hybrid SC-162 (32.40 ard/fed). Meanwhile, the topcrosses L1 x T1 (36.37 a ard/fed), L2 x T1 (36.80 ard/fed), L7 x T1 (35.53 ard/fed), L2 x T2 (34.32 ard/fed) and L7 x T2 (33.50 ard/fed) were highly significant compared with the check hybrid TWC-352 (30.20 ard/fed). The inbred lines L1, L2 and L7 have desirable GCA effects for GY and some yield components. Also, the inbred lines L3 and L8 exhibited desirable negative GCA effects for earliness and shorter plants. The relative relationship between GY GCA effects and the yield component traits (YCTs) GCA effects suggested that the direction of grain yield GCA effects (i.e., positive or negative) was largely determined by the number of YCTs GCA effects in the same direction. That is, if a line had significantly positive GY GCA effects, it usually had more YCTs with significantly positive GCA effects, and if as line had significantly negative GY GCA effect, it generally had a greater number of YCT s showing significantly negative GCA effects. The additive genetic effects (σ2GCA) seemed to have played an important role than non additive genetic effects (σ2SCA) in the expression of grain yield, ear length, ear diameter and silking date traits, while the σ2SCA played the major role in the inheritance of No. of rows ear-1 and plant height traits.

Combining ability among male sterile two-type and restorer lines of Zinnia elegans and implications for the breeding of this ornamental species

Nineteen parental lines including five male sterile A-lines (AH002A, AH003A, AH209A, S5001A, J16A) and fourteen restorers (A1-GH, A3, S5, J6, J7N, J7J, J8, J9, J10, J11, J12, J13, J14, J17) were crossed using the North Carolina II statistical method. Studies of combining ability and heritability were conducted on selected parents along with their seventy F 1 hybrids for main ornamental traits. Plant height, crown size and length of node had obvious additive genetic effects, high (>0.50) broad sense heritability and high narrow sense heritability (length of node was medium). Pedicel length showed approximately equivalent maternal and paternal additive genetic effects, high broad sense heritability and medium (0.30–0.50) narrow sense heritability. Number of whorls of ray florets across capitulum and number of branches were able to take advantage of heterosis. The relationship between general combining ability and specific combining ability in Zinnia elegans depended on materials and traits. Male sterile two-type line was pivotal in the hybridization breeding of Z. elegans. S5001A, AH002A and A1-GH, A3, J14 which performed high negative GCA effects in PH, PL, LN and type I in PH, PL, NW, LN were ideal female and male parents of potted flowering plants; AH209A, J16A and S5, J10, J17 which displayed positive GCA effects and almost type I in PH, PL, LN were ideal female and male parents of cut flowers, respectively. For potted flowering plants, AH002A × J17, AH209A × A1-GH and S5001A × J6 with high negative SCA effects in PH, PL and LN were the most promising combinations, AH002A × S5, AH003A × A3 and J16A × J6 were the subprime combinations; for cut flowers, AH209A × S5, AH209A × J17 and J16A × J17 with high positive SCA effects in PH, PL and LN were the primary combinations, AH209A × J9 and S5001A × J10 were the secondary combinations.

Combining Ability and Heterosis for Yield and Yield Components in Sunflower

Field experiments were carried out during 2005-2007 in order to study the genetic structure of a hybrid sunflower population, to identify the parents and crosses showing superior general and specific combining ability and finally to evaluate F1 hybrid vigour. Six artificial hybrids were created using 3 CMS and 2 restorer lines in sunflower (Helianthus annus L.) According to the results, the ratios of GCA:SCA variance were lower than 1 for plant height and head diameter in the both years; for number of seeds per head and 1000 seed weight in 2007 and for seed yield in 2006. For all these characters, non-additive effects were more effective than the other types of polygenetic effects. The additive gene actions were significant for 1000 seed weight and number of seeds per head in 2006 and for plant height and seed yield in 2007, since the ratios of GCA:SCA variances for these characters were greater than 1. The parental lines CMS 10 and RHA 10 proved to be good combiners having the highest positive GCA effect in yield and certain yield components. The crosses CMS 10 x RHA 03, CMS 01 x RHA 10, CMS 10 x RHA 10 and CMS 23 x RHA 10 might be considered as promising hybrid combinations in terms of seed yield . The values of heterosis and heterobeltiosis values ranged from 109.8 to 218.3% for seed yield. All of the tested hybrids showed positive and significant heterobeltiosis for seed yield.

Combining ability in medium-maturity maize genotypes adapted to mid-altitude and lowland tropical environments

Maize (Zea mays L.) is grown in different agro-ecological zones in the semi-arid tropical regions. Breeding for high production requires information on the combining ability and the magnitude of useful genetic variances among adapted genotypes. This study was conducted to determine the combining ability among tropical lowland and mid-altitude medium-maturity maize genotypes, provide information to clarify the relationship among them and identify suitable lines for distribution to growers. Six mid-altitude adapted maize inbred lines and six lowland adapted maize inbred lines were crossed in a full diallel mating system. The resulting 132 crosses, excluding the parental lines were evaluatedin four environments for grain yield, days to silking, plant height, ear height, ear weight and grain moisture at harvest. The subdivision of treatment effects in the general (GCA) and specific (SCA) combining ability were performed according to Griffing’s diallel analysis method 3, model 2. Both GCA and SCA were significant for all traits. The reciprocal meansquares were significant for ear height, ear weight, grain moisture and grain yield. Both additive and nonadditive gene effects were involved in combining ability between maize germplasm from different ecologies. Additive genetic effects were more important than nonadditive effects in controlling expression of the various traits evaluated. Positive GCAeffects for yield were observed with the lines EXP124, NCREGP1103, NCREGP28, and TZUT57 among the lowland and the lines TZMI308, 87036 among the mid-altitude lines. Crosses involving parents of different adaptation ecologies yielded hybrids with good agronomic performances and high estimates of SCA for all assessed traits. Crosses with atleast one mid-altitude female parent were better than lowland x lowland and mid-altitude x mid-altitude crosses in all environments. Mid-altitude maize germplasm may hold potential for use as source populations for both mid-altitude and lowland ecologies. These results emphasize the need to exploit the full potential of interpopulation crosses ofmaize genotypes.

Combining ability and heterosis of sorghum germplasm for stem sugar traits under off-season conditions in tropical lowland environments

Bioethanol production from sweet sorghum entails expansion and intensive production of the crop, which may include off-season production in the warm tropical lowlands. However, suitable cultivars are currently not available for this environment, especially in southern Africa. Hybrid cultivars were long ago demonstrated to be more productive than pure line varieties. Therefore a study was conducted to determine heterosis of experimental hybrids, and combining ability of parental lines for stem sugar traits. Sixty-four hybrids were generated among 16 lines in accordance with North Carolina design II mating scheme. Eight parents were cytoplasmic male sterile lines which were designated as females and were crossed with eight male fertile lines. The hybrids were evaluated at two sites in Mozambique and South Africa under off-season production conditions. Row-column alpha designs with three replications were used and standard agronomic practices were followed at both sites. Data were analysed in GenStat computer package. There was significant ( P = 0.05) variation among genotypes for stem °brix and associated traits. The top 20 stem °brix performers were constituted by 17 hybrids, exhibiting heterosis of up to 112%, and three parents. General and specific combining ability effects were significant for stem °brix and associated traits implying that both additive and non-additive gene action, respectively, were important for controlling the traits. The lines ZLR1 and ICSVP3046 displayed significant and positive GCA effects for stem °brix, while 13 crosses showed positive and significant SCA effects. These lines and the crosses ISCVP3046 × ICSA4, ICSV700 × ICSA731, ICSR165 × ICSA307, ZLR1 × ICSA474 and ICSR57 × ICSA479, which combined high mean performance with positive SCA effects, would be recommended for use in breeding new varieties for tropical lowland environments.