Combiners For Grain Yield Research Articles

COMBINING ABILITY ANALYSIS FOR DIFFERENT YIELD COMPONENTS IN MAIZE (Zea mays L.) INBRED LINES

The present study was carried out to determine the combining ability of yield and yield components by crossing six diverse maize inbred lines in a half diallel mating design. Fifteen F1 progenies along with their six parents were planted in randomized complete block design with three replications. GCA to SCA ratios were less than one for plant height, cob diameter, cob length and number of kernels row/cob indicating a preponderance of additive over non additive gene action. The crosses P1×P2, P3×P5 and P5×P6 were exhibited significant and positive SCA effects for yield and cob diameter, number of row/cob and number of grains/cob of yield contributing characters. The parents P1 (IL4), P3 (IL18)and P5 (IL23 were good general combiner for grain yield and yield attributing characters. It can be concluded that these parental lines can be desirable parents for hybrids as well as for inclusion in breeding program, since they may contribute favorable alleles in the synthesis of new varieties.

COMBINING ABILITY AND HETEROSIS STUDIES USING DIFFERENT CMS SOURCES IN HYBRID RICE BREEDING

this investigation was carried out during 2013 and 2014 rice growing seasons at the Experimental Farm of Agriculture Research Station, Sakha, Kafr El-Sheikh, Egypt, to study the magnitude of genotypic variation, the magnitude of both general and specific combining abilities (GCA & SCA) and their interaction with the two years as two different environmental conditions, estimation of the genetic parameters and broad and narrow senses heritability and the potentiality of heterosis expression for agronomic and yield and its components characters. Hybrids with a yield advantage of > 1.5t/ha over the highest yielding check variety Giza 178R were considered as promising. Among 12 hybrid combinations tested, six were most promising with mean performance of grain yield ranging from 11.62 t/ha for large stigma A/Giza 182R to 12.99 t/ha for G46A/Giza 178R. The yield over the best local inbred check, Giza 178 ranged from 1.10 to 2.47 ton ha-1. Among the four cytoplasmic male sterile (CMS) lines, G46A and IR 58025A were the best general combiners for grain yield. The restorer, Giza 178R was the best general combiner among testers for grain yield and most studied characters.

Genetics of Starch Content and its Correlations with Agro-morphological Traits in Sorghum

Sorghum can be an alternative to corn for industrial uses, especially in drought prone areas of the world. Sorghum cultivars with high potential of grain and starch yields are needed to continuously meet the industrial demands. We have studied the genetics of grain yield and starch content of sorghum to decide the breeding procedure to develop suitable cultivars for starch industry. The genetic material from 8 × 8 diallel (28 F1 and 8 parents) was grown in a randomized complete block design, with three replications at Directorate of Sorghum Research, Hyderabad, India. Observations were recorded on seven agro-morphological and two grain quality traits including grain yield and starch content. Correlation studies revealed that the grain hardness was negatively correlated to starch and positively correlated to grain yield, panicle weight and days to flowering. Variance due to specific combining ability effects was greater in magnitude for both starch content and grain yield. Bi-parental crossing in F2 will help in getting pure lines with high starch content and high grain yield. The parents chosen for breeding program need to be good combiners for starch and grain yields to obtain superior hybrid. One MS line, 422B was a good combiner for grain yield, high starch content and 100 grain weight, and had good per se performance.

Analysis of combining ability in white seeded genotypes of maize (Zea mays L.)

The present investigation consisted of 45 hybrids alongwith 18 parents and four checks viz., Arawali Makka-1, Mahi Kanchan, Navjot and PEHM-2 a total 67 entries was conduted during Kharif 2002 in Randomised Block Design having three replications. The data were recorded on fourteen traits to study general and specific combining ability effects. In general inbred lines L 1 , L 3 , L 11 and L 15 were considered good general combiner for yield and yield contributing traits as well as for quality traits. Among the testers, the tester T 2 was considered good general combiner for maturity traits, plant type traits, harvest index and starch content. Majority of the hybrids exhibited significant positive values for yield and yield contributing traits as well as quality traits. Thereby, indicating that for these traits the genes with positive effects were dominent. The variance due to lines was of greater magnitude than that of testers for most of the traits. The ratio of 6 2 sca/6 2 gca indicated prependerance of non-additive variance for most of the traits. Parental lines L 1 , L 3 , L 11 and L 15 were found to be good general combiners for grain yield per plant as well as for other traits. Hybrid L 12 x T 1 exhibited maximum significant positive sca effects for grain yield per plant. While the hybrid L 2 x T 1 exhibited highest estimates of significant positive sca effects for starch content. In general, there is a close association between sca effects, relative heterosis and per se performance for grain yield per plant was observed among the best hybrid identified on the basis of sca effects.

التحليل الوراثي لصفة الغلة و مكوناتها و بعض الصفات المورفوفيزيولوجية في هجن فردية و عكسية من الذرة الصفراء = Genetic Analysis for Yield and Its Components and Some Morpho-Physiological Traits in Single and Reciprocal Crosses of Maize Zea Mays L.

Complete diallel mating design experiment with reciprocal crosses was used to determine combining abilitiy and maternal effects of six maize inbred lines and their hybrid combinations with R.C.B.D. in three replications for grain yield, silking date, plant and ear height, shelling percentage, physiological maturity, ear length, ear diameter, during 2009-2010 season, at the Researches Center of Hama (G.C.S.A.R.). Crosses, general (GCA) and specific (SCA) combining ability mean squares were significant for all traits, while reciprocal crosses mean squares were non-significant for all traits except silking date and physiological maturity. Also, the maternal mean squares were non-significant for all traits except physiological maturity. The ratios σ2GCA/σ2SCA were detected for all traits and showed that non-additive gene action was more important than additive gene action in controlling of most traits except ear height and ear length. GCA effects showed that the lines P5 (IL.359-06) and P2 (IL.358-06) were good general combiners for grain yield. Also, SCA effects showed that five hybrids were the best F1 crosses combinations such as (IL.259-06 × IL.358-06) for grain yield. The results of means compared showed that the cross (IL.358-06 × IL.359-06) (13.478 Ton/h) and it's reciprocal cross (IL.359-06 × IL.358-06) (13.223 Ton/h) were the best hybrids compared with the two check varieties (Basel-1 and Ghota-82).

Inheritance of yield and quality component under two environments in barley (Hordeum vulgareL.)

Studies on combining ability effects were executed through line x tester analysis under normal and saline sodic soil conditions. The results indicated the predominance of non-additive gene action for all the traits. The desirable lines, viz. NDB-1245, NDB-1445, NDB-3, NDB-1276, NDB-1302, K-762, K-880, HUB-202, BH-910, RD-2035, RD-2640, PL-820, PL-826, BCU-546, RD-2552 and four tester's, viz. NDB-1173, Azad, Lakhan, and NDB-943 were chosen for experiment. It was observed that the entries NDB-1245, NDB-1445 and RD-2552 were proved to be good general combiners for grain yield and quality component characters. The crosses namely, NDB-1302 x Aazd, RD-2035 x NDB-1173, RD-2640 x NDB-1173, K-762 x Azad and NDB-3 x NDB-1173 in normal soil and BCU-546 x NDB-1173, NDB-1302 x Azad, NDB-3 x NDB-1173, K-880 x NDB-943 and RD-2035 x NDB-1173 in saline sodic soil while NDB-1302 x Azad, RD-2035 x NDB-1173 and NDB-3 x NDB-1173 in both environments exhibited highest SCA effects for grain yield and a few quality traits, showing their desirability to offer transgressive segregants in succeeding generations.

GENETIC BEHAVIOR OF MORPHOLOGY, YIELD, YIELD COMPONENTS AND GRAIN QUALITY IN RICE (Oryza sativa L.).

The present investigation was carried out at the Farm of Sakha Agricultural Research Station, during 2012 and 2013 summer seasons. Combining ability analysis was estimated in rice through a 6 x 6 diallel set analysis involving 6 diverse parents for grain yield and its components and grain quality. Eight yield and its component and eight grain quality characters were studied. Mean square values of parents and crosses and parents vs crosses were found to be highly significant for all characters. Both general and specific combining ability variances were found to be highly significant for all characters, indicating the importance of both additive and non-additive genetic variance in determining the performance of the studied sixteen characters. GCA/SCA ratios were found to be greater than unity for all characters studied except for panicle length, number of filled grains/panicle and gelatinization temperature, indicating that the additive and additive x additive types of gene action were of great importance in the inheritance of all the studied characters except for the three mentioned traits which were controlled by non-additive genetic variance. The genotypes GZ 1368, Sakha106, Sakha 102 and Sakha 103 were good general combiners for most studied characters. Cross combinations involving such parents were superior for most of studied characters. The promising combinations for grain yield along with at least two of yield component characters were GZ1368 x Giza 177, Sakha 106 x Giza 176, Sakha 102 x Giza 177, Sakha 102 x Sakha 106, GZ 1368 x Sakha 103 and Giza 176 x Giza 177. Four crosses Sakha106 x Giza 177, Sakha103 x Giza177, Sakha102 x Giza 176 and Sakha103 x Giza176 showed highly significant and positive SCA for most studied grain quality characters. A greater magnitude of heterosis ranged between 2.38 and 13.88% was observed in seven crosses i.e. Sakha 103 x Sakha 106, Sakha 103 x Giza 176, Sakha 103 x Giza 177, GZ1368 x Giza 177, Sakha 106 x Giza 176, GZ1368 x Sakha 103 and Sakha 102 x Sakha 106 for grain yield /plant and grain quality characters. The availability of sufficient hybrid vigor in several crosses in respect of grain yield suggests that a hybrid breeding program could profitably be undertaken using these materials. From the foregoing discussion, it may be concluded that the crosses,Sakha 103 x Sakha 106, Sakha 103 x Giza 176, Sakha 103 x Giza 177, GZ1368 x Giza 177, Sakha 106 X Giza 176, GZ1368 x Sakha 103 and Sakha 102 x Sakha 106 can be rated as the best crosses based on their heterosis in most of the studied traits including grain yield. Thus, it can be exploited in subsequent generations to improve most of the studied traits. Four crosses Sakha106 x Giza 177, Sakha 103 x Giza 177, Sakha 102 x Giza 176 and Sakha 103 x Giza 176 could be recommended for growing as hybrid rice.

Evaluation of genetic potential for various traits in maize hybrids (Zea mays L.) extracted from crosses with CIMMYT germplasm

Combining ability analysis for yield and related yield was performed with seven lines, four testers and the resulting 28 hybrids using Line x Tester analysis. The analysis of variance revealed significant differences among the hybrids for grain yield, 1000-grain weight, number of row per ear and harvest index. The interaction of Line x Tester was significant for grain yield, number of rows per ear and harvest index. The ratio of GCA to SCA variances was less than unity for all traits studied which indicates the predominant role of non additive gene action play in the inheritance of all the characters studied hybrids. Among the lines, L4 was found as the best general combiner for grain yield and 1000 grain yield traits. Considering the testers, T4 was found as the best general combiner for grain yield, 1000 grain yield and number of rows per ear traits. Among the crosses, the four crosses L7 x T2, L6 x T3, L3 x T2 and L4 x T4 were found to be the best specific combinations for most of the characters studied.

DIALLEL CROSSES FOR ESTIMATION OF COMBINING ABILITY FOR YIELD AND AGRONOMIC ATTRIBUTES IN MAIZE

The present study was carried out to estimate combining ability of 36 hybrids generated by crossing 9 new maize inbred lines in a half diallel model in 2013 season at two locations of Sids and Gemmeiza Agric. Res. Stns. The experiment was laid out in a randomized complete block design with four replications. Number of days to 50 % silking, plant height, ear height, ear length, ear diameter and grain yield (Ard / Fed) were determined. The mean squares, due to general combining ability (GCA) and specific combining ability (SCA) were highly significant for all studied traits. There was preponderance of additive gene action for all studied traits. Estimates of GCA and SCA effects showed that parental lines P6 and P8 were generally good combiners for earliness, shortness and lower ear placement, while, P2, P3 and P9 were good combiner for grain yield and can be included in future improvement maize breeding programs. Two crosses exhibited desirable SCA effects for grain yield, four hybrids significantly out yielded the highest yielding check hybrids SC. 162, and twelve hybrids did not differ significantly than the check. These hybrids may be released as commercial hybrids after further testing and evaluation. It could be concluded that P2, P3 and P9 was found to be a good GCA can be used in synthetic variety and hybrids ( P1 x P2 ) and ( P7 x P8 ) was found to be a good combiner and can use as a potential single cross hybrid combination and tester further.

Identification of good combiners in early maturing × high yielding cultivars of Indica Rice (Oryza sativa L.)

Line × tester analysis involving seven early maturing lines and four high yielding testers, made to produce 28 F1s hybrids. The F1 data revealed that both additive and non-additive gene were important in controlling yield contribution in Indica rice. Variances were significant for GCA and SCA effects for all the characters indicating the significance of both additive and non-additive genes. There was high proportion of non-additive genes for the expression of different traits. Cultivars Anjali, MTU-7029 and BPT-5204 were identified as best general combiners for yield and yield traits among the parents. The most promising specific combiners for grain yield and its contributing traits were Govind × HUR 105, NDR 97 × HUR 4-3, Anjali × HUR 4-3, NDR 97 × MTU 7029, Vandana × BPT 5204, Shanthi × HUR 105, Anjali × MTU 7029 and Shanthi × BPT 5204. DOI: http://dx.doi.org/10.3329/bjb.v42i2.18026 Bangladesh J. Bot. 42(2): 247-255, 2013 (December)

Combining Ability Analysis for Yield and its Related Traits in Pearl Millet

A 10 × 10 half diallel excluding reciprocals was evaluated in 3 environments to study the combing ability and gene action involved in respect of yield and its attributers in pearl millet. The environment wise combining ability analysis revealed significant differences for GCA (general combining ability) and SCA (specific combining ability) variances for characters viz. days to 50% flowering, days to maturity, productive tillers/plant, plant height, panicle length, panicle girth, biological yield/plant, dry fodder yield/plant, grain yield/plant, harvest index, test weight and protein content in all the three environments, except GCA for productive tillers per plant in E2 and panicle girth in E3 and SCA for panicle girth in E3, indicating the importance of both additive and non-additive gene effects for the genetic control of all the characters studied. The estimates of GCA effects indicated that the parents 71–75 and 76–80 emerged as good general combiners for grain yield and its components in the entire environment. Out of 45 crosses combinations only seven combinations such as 26–30 x 71–75, 26–30 × RIB-135-144, 31–40 × 76–80, 31–40 × RIB-135-144, 31–40 × 101–105, 41–50 × RIB-20 and RIB-20 × 71–75 showed significant and positive SCA effects in all the three environment for grain yield and other yield attributing characters. These parents and crosses have immense potential for pearl millet improvement and may be utilized in multiple crossing programme.

Combining ability analysis and gene effects in maize (Zea maysL.) using line × tester crosses

Determination of gene effects and combining abilities is a critical stage in maize hybrid breeding. In the present study, eight lines as female and two inbred lines (K3615.2 and A679) as tester were crossed and the resulting test cross progenies were evaluated in a randomized complete block design with three replications in 2011. During the growing period, several agronomic characters including grain yield were measured. Effects of lines and testers were significant on all the characters except for the grain yield, grains per row and days to maturity. This indicated the importance of additive gene effect in controlling most of the traits under investigation. Inbred lines L5, L10 and L14 were identified as good general combiners for grain yield because they showed significant positive GCA for this trait. L14 was superior compared with L1 and L5 because of significant positive GCA for most of the agronomic characters. These lines, especially L14, have potential additive gene effects to be utilized in the breeding programmes. T3 tester showed favourable additive gene effects for forage yield, its components, early maturity and shorter stature. Promising crosses were selected based on per se performance, standard heterosis and sca effects. The highest grain yield (107.313) belonged to L6 × A679 combination. The superiority of L6 × A679 hybrid can be attributed to its days to physiological maturity and more ears per plant. Higher grain yield and sca for forage yield were also observed in L7 × A679 and L14 × K3615.2. The cross L14 × K3615.2 had also large positive sca for grain rows per cob. Furthermore, negative sca of ear height, number of leaves above ear and grains per row were observed for L6 × A679, while positive sca of these characters was determined for L7 × A679. However, none of the scas for these combinations was significant. On the basis of grain yield, the genotypes L6 × A679, L7 × A679 and L14 × K3615.2 may be regarded as promising hybrids and should be evaluated further for grain yield and other desirable characters.

Test Cross Mean Performance and Combining Ability Study of Elite Lowland Maize (Zea mays L.) Inbred Lines at Melkassa, Ethiopia

In Ethiopia, there are several maize production constraints, among which shortage of improved varieties is the major one. The objective of this study was to observe the mean performance of crosses and estimate combining abilities for grain yield and other agronomic traits in thirty six maize inbred lines using Line x Tester mating design. Seventy-two lines x test crosses (L1xT1, L1xT2, L2xT1, L2xT2… L36xT1 and L36xT2) and three standard checks were evaluated for 11 traits in alpha lattice design at Melkassa, Ethiopia. Analyses of variances showed significant mean squares due to crosses for all traits. Among the crosses, L34xT2, L36xT2, L30xT1, L19xT1 and L33xT2 crosses were the top five highest grain yield mean performance. While L35xT1, L23xT1, L13xT1, L24xT2 and L15xT1 crosses were lowest mean grain yield performance. GCA Mean squares were significant, but SCA mean squares were non-significant for all traits. The ratio of GCA/SCA mean square was high which exhibited the preponderance of additive gene effects in the inheritance of all traits. Furthermore, the GCA sum of square component was greater than the SCA sum of square for all traits, supported that variation among crosses was mainly due to additive rather than non-additive gene effect. Inbred lines L15, L25, L27, L33, L34 and L35 were the best general combiners for grain yield, and hence were promising parents for hybrids as well as for inclusion in breeding programmes for yield improvements. Inbred lines L2, L3, L4, L6, L10, L27, L30, L31 and L32 had negative and significant GCA effects for the days to anthesis, indicating that the lines had gene combinations that can enhance early maturity.

Exploitation of Heterosis and Combining ability for Yield and its Contributing traits in Crosses of Two-row and Six-row barley (Hordeum vulgareL.) under Rainfed Environment.

Combining ability for grain yield and its components in barley was studied in a set of four females (Testers 6 rowed), six males (lines 2 rowed) and their resultant F1’s with standard check k-603. Twenty two crosses, excluding BCU -4925 x K-603 and BCU-4922 x Karan-16, showed significant positive economic heterosis for grain yield per plant. Analysis for variance for combining ability analysis revealed that the variance due to General Combining Ability (GCA) and Specific Combing Ability (SCA) were highly significant for most of the traits studied. The estimated value of σ2A was higher than its σ2D for plant height and thousand seed weight which indicated the predominance of additive gene action as the ratio of σ2A/σ2D was more than unity, while rest of the traits showed preponderance of non-additive gene action. The value of average degree of dominance for plant height and thousand seed weight indicated partial dominance while rest of the traits viz., chlorophyll content, spike length, awn length, number of effective tillers, number of grains per spike, harvest index and grain yield per plant showed over-dominance. Two male parents (BCU-4925 and BCU-4927) and one male parent (Lakhan) had significant and positive effect for grain yield per plant. Five crosses were found to be good specific combiners for grain yield with maximum SCA effect in cross BCU-4922 x Lakhan.

COMBING ABILITY OF CMS AND RESTORERS IN RICE (O. sativa L.)

General and specific combining ability effects were estimated from a 5 line × 8 tester crosses to explore the genetic behavior of CMS and restorers in rice. The variance for GCA and SCA showed predominance of non-additive gene action for all the ten morpho-physiological traits. The estimates of GCA effects revealed that none of the parent was general combiner for all the traits in desired direction. Gan46A and BR827R were good general combiners for higher grain yield coupled with earliness, and IR46R and BR168R was good general combiner for grain yield and lateness in maturity. Good x poor general combiners (Gan46A × Gui99R) for grain yield produced the best specific cross for higher grain yield coupled with earliness, longer panicle, panicles/plant, filled grains/panicle and less sterility (%). Additive × additive, additive × dominance and dominance × dominance gene interactions were involved in deriving good specific cross for grain yield.DOI: http://dx.doi.org/10.3329/bjpbg.v20i1.17013

The Effect of Environment on Combining Ability and Heterosis in Hybrid Rice

Study was undertaken to estimate the combining ability and heterosis for yield and yield contributing characters over environments. Environment, Crosses, GCA and SCA, and their various interactions with environment were significant suggesting that the hybrids did not have the same relative performances among environments. An evaluation of combining ability across the environment indicated that both general and specific combining ability effects are important but predominance of non-additive genetic variance indicated the presence of heterozygosity in the population. As such this type of genetic variance is non-fixable hence; heterosis breeding is effective for crop improvement. Line IR-79156A, IR-68897 and tester R-51 during both the seasons and testers R-47, R-48, R-49, R-52, IR-64 and IR-10198 during kharif and line R-42, IR-66, R-43, R-46, R-56 and IR-13419 during rabi were the promising general combiners for grain yield per plant and other traits. These parents used as testers and lines in the cross combinations would be able to realize good hybrids. Considering high physical grain quality parameters as well as per se performance, sca effects (High x high or high x low gca effects of each cross) and standard heterosis, hybrids viz., IR-80555A x R-51 and IR-79156A x R-44 during kharif and IR-79156A x R-43, IR-68897A x R-51 and IR-68897A x R52 during rabi have been identified as promising rice hybrids.

Combining ability and heterosis for grain yield and its components in maize inbreds over environments (Zea mays L.)

Twelve inbred lines were crossed with each of five testers in a line × tester design to evaluate combining ability and heterosis to identify promising hybrids of maize for various characters like, 50% tasseling, 50% silking, 75% dry husk, ear length, ear diameter, kernels per ear, kernel rows per ear, 1000 kernel weight and grain yield. The resulting F1s along with three checks and the parents were evaluated in two environments duringkharif 2010 and rabi 2010 to 2011. Pooled analysis of variance revealed highly significant differences among the genotypes. Crosses excelled their perspective parents in performance for most of the traits studied. L9among the parental lines and T2 among the testers were identified as the best general combiner for grain yield. Whereas among the hybrids, (L6 × T5) was identified as a potential cross combination for grain yield while the cross (L9 × T2) recorded highest magnitude of economic heterosis of 84.60% over the best standard check (Vivek hybrid-9). So the crosses (L6 × T5) and (L9 × T2) can be utilized for developing high yielding hybrid varieties as well as for exploiting hybrid vigor. Key words: Combining ability analysis, heterosis, line × tester, maize (Zea mays L.).

Combining ability analysis using CMS breeding system for developing hybrids in rice (Oriza sativa)

Using line x tester mating design with three CMS lines and seven elite testers, the general combining ability (GCA) of parents and specific combining ability (SCA) of crosses were carried out for grain yield and its attributes. The SCA variance was greater than the GCA variance for grain yield and yield components, suggesting the preponderance of dominance and epistatic gene action in expression of these traits. The line CRMS 31 A and IR 79156 A were recorded as good combiners for head rice recovery percent. The tester NPT 80-1 was good general combiner for grain yield per plant and TOX 981-11-2-3 for both grain yield per plant and head rice recovery percent. The cross combinations APMS 6 A/ET 1-13, CRMS 31 A/ET 1-12, and IR 79156 A/ NP T 80-1 were found to be outstanding with respect to grain yield per plant, head rice recovery percent, and spikelets per panicle. The cross APMS 6 A/NPT 2-2-694- 1 was good combiner for head rice recovery percent. These promising lines, testers, and crosses revealed wide scope for enhancing the grain yield in the CMS line or three line breeding system based rice improvement programme to develop rice hybrids. DOI: http://dx.doi.org/10.3329/bjar.v37i4.14376 Bangladesh J. Agril. Res. 37(4): 583-592, December 2012

English

The genetics of resistance to grey leaf spot (GLS) disease, grain yield and selected agronomic traits was studied in 42 F1 progenies from a full diallel cross among seven maize inbred lines. These 42 F1 progenies and seven parents were evaluated at three locations; Kenya Agricultural Research Institute (KARI), Kiboko, KARI Kakamega and University of Nairobi (Field station) during the period June 2006 to April 2008. The experiments were laid out in a randomized complete block design with three replicates. Combining ability analyses were conducted on the across site data of grey leaf spot disease, grain yield and selected agronomic traits using Griffing’s method one, model one in the SAS program. Additive gene action played a greater role than non-additive gene action in the inheritance of resistance to grey leaf spot disease whereas the non additive effects were more important in the inheritance of grain yield. Reciprocal effects were not significant for GLS disease resistance and grain yield indicating absence of maternal effects for these traits. The inbred lines, CML 384 and CML 373 were the best combiners for grain yield with general combining ability (GCA) effects of 0.79 and 0.56 respectively while TZMI 711 and CML 373 were the best combiners for GLS resistance with highest negative values for GCA of -0.51 and -0.398, respectively. The local maize breeders could now incorporate the genes for GLS resistance in CML 373 and TZMI 711 and the grain yield genes in CML 384 into elite lines using recurrent and backcross methods, respectively in order to increase maize production and productivity in Kenya. Key words: Maize, Zea mays, grey leaf spot, grain yield, combining ability

Heterosis and combining ability in a diallel among elite inbred lines of maize<br>(Zea mays L.)

Heterosis and combining ability was studied for grain yield, days to tasseling, days to silking, plant height and ear height in a diallel cross involving seven elite maize inbred lines. Variance due to GCA and SCA were highly significant for the characters studied, indicating both additive and non-additive type of gene action were important for controlling the traits. Predominance of non-additive gene action was observed for all the traits. Standard heterosis for grain yield ranged from -17.60 to 9.71%. For other traits, desirable heterosis varied from -0.10 to -4.42%; -0.03 to -4.20%; -2.44 to -42.11% and -1.33 to -21.87% for days to tasseling, days to silking, plant height and ear height, respectively. Parent Q7 was the best general combiner for higher grain yield coupled with dwarfness, and Q1 was also good general combiner for grain yield and lateness in maturity. For other traits, parent Q2, Q3 and Q4 were found suitable both for days to tasseling and silking and Q4, Q5 and Q7 for both plant and ear height showing desirable significant negative GCA effects and simultaneously possessed desirable high mean values, indicating that per se performance of the parents could prove as an useful index for combining ability. Additive × additive, additive × dominance and dominance × dominance gene interactions were involved in deriving good specific cross for yield. The cross combinations Q1 × Q7, Q2 × Q3, Q4 × Q6 and Q6 × Q7 possessing significant desirable SCA effects and high heterotic values might be used for obtaining high yielding hybrids.