Combining ability analysis for identifying elite parents for heterotic rice hybrids

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1 Academia Journal of Agricultural Research 3(5): , May 2015 DOI: /ajar ISSN: Academia Publishing Research Paper Combining ability analysis for identifying elite parents for heterotic rice hybrids MJ Hasan 1 *, MU Kulsum 1, Emran Hossain 1, M Manzur Hossain 2, M Mustafizur Rahman 3 and Niaz M Farhat Rahmat 4 1 Hybrid Rice Division, Bangladesh Rice Research Institute (BRRI), Gazipur-1701, 2 Agriculture Information Service, Khamarbari, Farmgate, Dhaka-1215, 3 BARC, Farmgate, Dhaka-1215, 4 Agril. Statistics Division, Bangladesh Rice Research Institute, Gazipur-1701, *Corresponding author: jamilbrri@yahoo.com; Tel: Accepted 9 th April, 2015 ABSTRACT Twenty hybrids developed from five CMS lines and four restorers along with parents were evaluated for nine quantitative traits to elucidate the nature of gene action present in the inheritance of important quantitative traits. Preponderance of non additive gene action was observed for all the characters studied. BRRI7A and IR75608A among the lines and BasmatiR, BRRI26R and BRRI31R among the testers were found to be good general combiners as they could contribute alleles with positive effect for improving the important quantitative traits. IR79156A BRRI26R, IR79156A BRRI20R, IR75608A BasmatiR and BRRI7A BRRI31R were identified as the most promising. Key words: L T analysis, GCA, SCA, hybrid rice. INTRODUCTION Rice is the staple food for half of the world s population, of which more than 90% of the rice consumers inhabit in Asia. Therefore, rice plays an important role in ensuring food security and contributing to poverty and malnutrition alleviation in Asia and the world. As the world s population continues to increase, there will be further demand on rice supply to meet additional consumption requirement. Since the rice lands have been decreased due to expansion of urban areas and industrialization or agricultural diversification, the increase of rice production in the future would primarily rely on the increase of productivity. Nevertheless, it is recorded that the growth of rice productivity has declined in recent years due to minor improvement in the rice yield potential. To overcome this challenge, the adoption of hybrid rice technology as experienced in China would offer an alternative to raise further the rice yield potential by exploiting the genetic expression of heterosis or hybrid vigor (FAORAP and APSA, 2014). To develop improved heterotic rice hybrids, we need to adopt new strategies by enhancing the frequency of occurrence of maintainers and restorers that ensures a constant and steady supply of genetically diverse parental lines. Hence, study of maintainers and restorers in large numbers will provide opportunity to breeders for their exploitation in hybrid breeding program. Combining ability analysis seems to be the most reliable and quickest method of understanding the genetic nature of quantitatively inherited characteristics. The successful development of rice hybrids by utilizing the cytoplasmic-genetic male sterility and fertility restoration system mainly depends upon the availability of stable male sterile lines and commercially feasible hybrid seed production technology. The success can further be hastened by choice of suitable outstanding adaptable parents with excellent out-crossing which would give heterotic hybrids. The combining ability analysis of parents and their crosses generates information on the components of variance viz., additive and dominance variance or their interaction, which are utmost important to decide upon the parents and crosses to be selected for eventual success and also the appropriate breeding procedure. The knowledge of combining ability is useful to assess nicking ability in self pollinated crops and an insight into nature and relative magnitude of gene actions involved (Peng and Virmani, 1990). It provides the breeders an insight into nature and relative magnitude of fixable and non-fixable genetic variances (Cockerham, 1961; Pradhan et al., 2006). Therefore, present investigation was carried out to estimate combining ability effects for yield and its components involving CMS and restorer lines to identify

2 Academia Journal of Agricultural Research; Hasan et al. 071 parental lines for heterotic rice hybrids. MATERIALS AND METHODS Plant materials Five CMS lines (BRRI7A, IR75608A, IR79156A, BRRI33A and BRRI28A) were used as lines (female) of which three were developed by Bangladesh Rice Research Institute (BRRI) and two were collected from International Rice Research Institute (IRRI). Four testers (male parents), BRRI20R, BRRI26R, BRRI31R and BasmatiR of which BasmatiR is collected from India. Site and soil The experimental site was a sub-tropical zone situated at N latitude and E longitude with an elevation of 8.4 m from the sea level. The site is characterized by high rainfall, cloudy sky to clear sunshine day and moderate to high temperature in the earlier part of the year with low temperature at the later part of the year. The soil of the experimental field was clay loam in texture having ph of 6.2. It belongs to the Chitra soil series of red brown terrace of Field experiment The experiment was conducted at the experimental farm of Bangladesh Rice Research Institute (BRRI) during T. Aman season of 2012 and Boro season of The pregerminated seeds of selected five CMS and four restorers (pollen parent) lines were sown separately during T. Aman season of 2012, in a staggered way so as to get synchronization in flowering to facilitate easy hybridization in a line (CMS line) tester (restorer) fashion to obtain 20 hybrids. Seedlings of each of these lines were raised in bed and 21 days old seedlings were transplanted in single plant/hill in the experimental plots in three different blocks. The plots were 2.5 m in length containing five rows. The plant spacing provided was 20 cm between rows and 15 cm between plants of the same row. In flowering stage spikelets of CMS lines were clipped off and pollinated with restorer lines. There were 5 CMS and 4 restorer lines which gave 20 F 1 hybrids in line x tester combinations. To produce sufficient amount of seeds 8 plants from each CMS lines crossed with each restorer lines. Twenty hybrids along with their corresponding parents and check varieties was grown in Boro season with three replications. Individual plot size was 2 m 2 containing 50 plants in each entry with a spacing of 15 cm between plants and 20 cm between rows. Soil fertility was ensured by applying appropriate doses of fertilizer according to seasons and necessary inter culture operations and irrigation were made whenever required. Ten sample plants were randomly selected from each plot excluding the border plants and the following data were recorded: Plant height, growth duration, panicle length, panicle weight, number of panicles/m 2, number of spikelet/panicle, spikelet fertility, thousand grain weight and grain yield/plot. Statistical analysis Collected data were subjected to statistical analysis using line x tester analysis by Kempthorne (1957) and genetic components of each parameter following Singh and Chaudhary (1979). RESULTS AND DISCUSSION Analysis of variance for yield and different yield contributing characters revealed significant variations for all the characters (Table 1). The crosses also exhibited significant variations among all these characters but both the cases panicle length was significant at 5% level of probability. Similar trend of variations were observed for parents. Variance due to interaction effect of parents and crosses were highly significant for all the traits except thousand grain weight. The variances due to restorer lines (tester) were found significant for plant height, growth duration, panicle length, number of spikelet/panicle and thousand grain weight but insignificant for panicle weight, number of panicle/m 2, spikelet fertility and grain yield. Opposite trend of variation for number of panicles/m 2 and number of spikelets/panicle was noticed among CMS lines. The magnitudes of sca variances were higher for all the characters indicated the predominance of non-additive gene actions for the characters studied. The heterosis breeding could be a better option for improving these traits. The ratio of gca to sca variances ranged from 0.00 to These results indicated that the non-additive gene actions predominated over the additive gene actions for all the characters. Predominance of non additive gene action for grain yield and its components was also reported by many other workers (Satyanarayana et al., 2000; Rita and Motiramani, 2005; Singh et al., 2005; Venkatesan et al., 2007; Dalvi and Patel, 2009). The proportional contribution of lines, testers and their interaction to the total variance are presented in Table 2. It is evident from the table that testers played important role towards panicle length (38.01%), number of spikelets/panicle (46.92%) and thousand grain weight (62.92%) indicating predominant of paternal influence for these traits. On the contrary, maternal lines contributed most for plant height (42.75%), growth duration (57.52%) and number of panicles/m 2. The contribution of maternal and paternal interactions (line x tester) were found vital for

3 Academia Journal of Agricultural Research; Hasan et al. 072 Table 1. Analysis of variance for yield and different yield contributing characters in rice under line tester method. Sources of variation df PH GD PL PW PPM SPP SF TGW GY Replication * 5.05 ** 1.60 * 0.25 * ** ** Treatment ** ** 5.15 * 1.82 ** ** ** ** ** ** Parents ** ** 7.58 * 2.06 ** ** ** ** ** ** Parents vs. Crosses ** ** * ** ** ** ** ** Crosses ** ** 3.75 * 0.72 ** ** ** ** ** 8.61 ** Lines ** ** 6.31 * * ** 3.18 Testers ** ** 9.03 ** ** ** 3.86 Lines Testers ** ** 1.58 * 0.75 ** ** ** ** 4.01 ** ** Error σ 2 gca σ 2 sca σ 2 gca/σ 2 sca *and ** significant at p=0.05 and p=0.01 level, based on t-test, respectively. PH=Plant height (cm), GD=Growth duration, PL=Panicle length (cm), PW=Panicle weight (g), PPM=Number of panicle/m 2, SPP=Number of spikelets/panicle, SF= Spikelet fertility (%), TGW= 1000 grain weight (g), GY= grain yield (t/ha). Table 2. Proportional contribution of line, tester and their interaction to total variance for different characters in rice. Proportional contribution PH GD PL PW PPM SPP SF TGW GY Lines Tester Line tester PH=Plant height (cm), GD=Growth duration, PL=Panicle length (cm), PW=Panicle weight (g), PPM=Number of panicle/m 2, SPP=Number of spikelets/panicle, SF= Spikelet fertility (%), TGW= 1000 grain weight (g), GY= grain yield (t/ha). panicle weight (65.48%), spikelet fertility (59.13%), and grain yield (85.14%). General combining ability (GCA) effects are presented in Table 3. The selection of parents with good general combining ability (gca) effects is a prime requisite for a successful breeding program especially hybrid breeding. Estimates of gca effects showed that it was difficult to choose a good combiner for all the traits, as the combining ability effects were not consistent for all the yield and yield contributing traits simultaneously. It might be possible due to low negative association of different traits. The character wise estimation of gca effects of lines and testers revealed that the parents BRRI28A, BRRI33A, BasmatiR, BRRI31R and BRRI26R were good general combiners for dwarfness while, the parents IR75608A, IR79156A, BRRI7A and BRRI20R appeared to be good general combiner for tall plants. The parents BRRI28A, BRRI33A and BasmatiR were good general combiner for short growth duration while BRRI7A, IR79156A, BRRI26R and BRRI31R were good general combiner for late maturity. The parental lines IR75608A and BRRI20R had the highest gca effects for panicle length while IR75608A and BasmatiR for panicle weight. In respect of number of panicles/m 2 IR79156A, BRRI33A, BRRI20R and BRRI26R exhibited significant positive gca effects while the parents IR75608A, BRRI28A, BRRI7A, BasmatiR and BRRI31R exhibited significant negative gca effects. Based on gca effects the parents BRRI7A, IR75608A, BRRI20R and BRRI31R expressed superior significant positive gca effects for number of spikelets/panicle while BRRI28A, BasmatiR and BRRI26R showed significant negative gca effect for this trait. In case of spikelet fertility, the parental lines IR79156A, BRRI33A and BasmatiR exhibited superior positive significant gca effects while, BRRI7A, IR75608A and BRRI20R expressed significant negative gca effects. CMS lines are male sterile. So, it could not give yield data. Maintainer or B line is the isogeneic line or genetically identical line of CMS line. So, counterpart B line yield data is mentioned here. The parents IR75608A, BRRI7A, BRRI28A and BasmatiR were considered as the best general combiner for thousand grain weight. For grain yield the parents IR79156A and BasmatiR had the highest significant gca effects and considered as the best general combiner for grain yield. Similar findings were also reported by Singh and Kumar (2004), Rosamma and Vijayakumar (2005), Richharia and Singh (1983) and Sarker (2001) in rice. Specific combining ability effects of the crosses are presented in Table 4. In case of plant height, out of 20 crosses, 7 crosses exhibited significant sca effects for plant

4 Academia Journal of Agricultural Research; Hasan et al. 073 Table 3. Estimate of general combining ability (gca) effects of parents for different traits in rice. Designation PH GD PL PW PPM SPP SF TGW GY A Line BRRI7A 2.67 ** 4.18 ** 0.44 ** ** ** ** 0.71 ** IR75608A 4.97 ** 0.43 ** 0.82 ** 0.33 ** ** ** ** 1.62 ** IR79156A 3.18 ** 2.85 ** ** ** ** 0.91 ** BRRI33A ** ** ** ** ** ** BRRI28A ** ** ** ** ** ** SE(gi) SE(gi-gj) R Line BRRI31R ** 1.42 ** ** * 7.84 ** * * BRRI20R 8.01 ** ** ** ** ** ** BRRI26R ** 2.22 ** * ** ** ** ** * BasmatiR ** ** ** ** ** 8.05 ** 3.33 ** 0.74 ** SE (gi) SE (gi-gj) *and ** significant at p=0.05 and p=0.01 level, based on t-test respectively. PH=Plant height (cm), GD=Growth duration, PL=Panicle length (cm), PW=Panicle weight (g), PPM=Number of panicle/m 2, SPP=Number of spikelets/panicle, SF= Spikelet fertility (%), TGW= 1000 grain weight (g), GY= grain yield (t/ha). Table 4. Estimate of specific combining ability (sca) effects of hybrids for different traits in rice. Designation PH GD PL PW PPM SPP SF TGW GY BRRI7A/BRRI31R ** ** * ** 9.37 ** ** 2.43 ** BRRI7A /BRRI20R ** ** * BRRI7A /BRRI26R ** ** ** ** ** BRRI7A /BamatiR ** 1.02 ** ** 9.99 ** 2.14 ** 0.65 * IR75608A/BRRI31R * ** IR75608A/BRRI20R ** ** ** ** IR75608A/BRRI26R ** ** ** IR75608A/BamatiR ** ** IR79156A/BRRI31R 4.85 ** 1.42 ** ** IR79156A/BRRI20R ** ** ** IR79156A /BRRI26R ** ** ** IR79156A /BamatiR ** ** ** ** ** BRRI33A/BRRI31R ** 1.83 ** ** ** BRRI33A /BRRI20R ** ** * ** ** BRRI33A /BRRI26R ** ** * 1.03 ** ** BRRI33A /BamatiR 4.99 ** 1.77 ** ** ** 0.43 BRRI28A/BRRI31R * ** * 1.50 ** ** BRRI28A /BRRI20R ** * ** * 1.05 ** BRRI28A /BRRI26R * 2.70 ** 1.02 ** ** * 0.79 ** BRRI28A /BamatiR ** ** 0.77 * ** ** SE (sij) SE (sij-skl) *and ** significant at p=0.05 and p=0.01 level, based on t-test respectively. PH=Plant height (cm), GD=Growth duration, PL=Panicle length (cm), PW=Panicle weight (g), PPM=Number of panicle/m 2, SPP=Number of spikelets/panicle, SF= Spikelet fertility (%), TGW= 1000 grain weight (g), GY= grain yield (t/ha).

5 Academia Journal of Agricultural Research; Hasan et al. 074 Table 5. Per se performance, sca effects and standard heterosis of F1 hybrids and gca estimates of the parents in rice. Cross combination Mean performance Standard heterosis (%) BRRI dhan28 BRRI dhan29 sca effect gca female gca male BRRI7A/BRRI31R ** * BRRI7A /BamatiR ** ** IR75608A/BRRI31R ** * IR75608A/BRRI26R ** * IR75608A/BamatiR ** ** IR79156A/BRRI20R ** 0.91 ** IR79156A /BRRI26R ** 0.91 ** BRRI33A /BRRI20R ** BRRI33A /BamatiR ** ** BRRI28A /BRRI20R ** BRRI28A /BRRI20R ** * BRRI dhan BRRI dhan height. The hybrids BRRI33A/BRRI31R, BRRI7A/BasmatiR, IR79156A/BasmatiR and BRRI28A/BRRI26R exhibited highly significant and negative sca effects for plant height indicating them as good specific combiner crosses for short plant stature while the crosses BRRI28A/BasmatiR, BRRI33A/BasmatiR and IR79156A/BRRI31R exhibited highest positive significant sca effect and considered as the best specific combiners for taller plants. The cross BRRI7A/BRRI31R had the highest significant negative sca effect for growth duration and considered as the earliest variety followed by BRRI33A/BRRI20R, IR79156A/BRRI26R and IR75608A/BasmatiR. Under stress, early maturing hybrids are desirable as they are more efficient in partitioning carbohydrate to the panicle and producing more yields per day (Atlin and Lafitte, 2002). On the other hand, BRRI28A/BRRI26R and IR75608A/BRRI20R had the highest positive sca effects for growth duration and considered as most delayed maturing varieties. For panicle length, only four crosses showed significant effects of which both negative and positive significant effects shared equally. The cross BRRI28A/BRRI26R exhibited the highest significant positive effects and the highest significant negative effects by BRRI28A/BRRI31R. The best specific combiners for panicle weight were BRRI7A/BRRI31R, IR75608A/BRRI26R and IR79156A/BRRI20R while, IR75608A/BRRI20R, BRRI7A/BRRI26R and IR79156A/BasmatiR expressed negative significant sca effects for this trait. It was observed that a total of ten crosses out of twenty crosses exhibited significant sca effects for number of panicles/m 2 of which negative and positive significant effects were similar in number. Highest significant positive effects were observed in IR79156A/BRRI26R while highest significant negative effects were observed in IR79156A/BasmatiR. Out of 20 crosses only four crosses showed significant effects for number of spikelets/panicle. For spikelet fertility majority of the crosses exhibited significant effects. The cross IR79156A/BRRI20R showed high significant sca effects for spikelet fertility evolved from high low parental gca effects indicating the involvement of additive dominance genetic interaction. Similar results were also reported by Peng and Virmani (1990) and Maurya and Singh (1997). The crosses expressed high significant positive and negative sca effects for thousand grain weight were BRRI7A/BasmatiR and BRRI28A/BasmatiR evolved from high high parental gca effects suggesting additive additive type of gene action. Sandhyakishore et al. (2011) also reported interaction between positive and positive alleles in crosses involving high high combiners which can be fixed in subsequent generations if no repulsion phase linkages are involved. Yield is a cumulative function of various components; the contribution of components for yield is through component compensation mechanism. It was proved in some of the crosses which were characterized by significant positive sca effect for grain yield also exhibit significant positive sca effects for some of the major yield components. For example, the cross combination BRRI7A BRRI31R showed significant positive sca effects for grain yield along with panicle weight, number of panicles/m 2, number of spikelets/panicle and spikelet fertility. This indicates that the crosses, which are best for yield contributing traits like panicle weight, number of panicles/m 2, number of spikelets/panicle, spikelet fertility and 1000 grain weight would also perform well for yield. The per se performance, sca effects of crosses, gca effects of parents and standard heterosis in superior hybrid combinations are presented in Table 5. The cross combinations which recorded significant heterosis over the best yielding inbred checks i.e., BRRI dhan28 and BRRI dhan29 also exhibited significant sca effects, as

6 Academia Journal of Agricultural Research; Hasan et al. 075 confirmed earlier by Sreeramachandra et al. (2000). The significant differences among the lines, testers and lines x testers indicated that the treatments had wide genetic diversity among themselves. Also, significant variances due to line tester s interaction for all the characters suggested the presence of sca variances among hybrids. Presence of highly significant gca and sca variances for almost all the characters indicated the importance of both additive and non-additive gene in the expression of the characters. The ratio of σ2gca / σ2sca was less than unity for all the characters also suggested pre-ponderence of non-additive genetic variance. It indicated greater importance of non-additive gene action in their expression and indicated very good prospect for the exploitation of non- additive genetic variation for grain and its component characters through hybrid breeding. Importance of non-additive gene expression for different traits has also been reported by Thirumeni et al. (2000), Bansal et al. (2000) and Ganesan and Rangaswamy (1998). Among the male parents, BasmatiR, BRRI26R, and BRRI31R were found to be good general combiner for grain yield. These parents can be used in the hybridization program to extract more heterosis. Among the female parents IR79156A and IBRRI28A were found to be good general combiner for grain yield. All varieties were not good general combiners for the component traits. Restorers like BasmatiR, BRRI31R and BRRI26R was good combiner for short plant height. For earliness, BasmatiR exhibited good general combining ability while for CMS lines BRRI28A and BRRI33A showed earliness. Therefore, It is suggested the importance of multiple crosses or recurrent selection allowing random mating facilitated by CMS system. BRRI7A/BRRI31R, IR79156A/BRRI26R, BRRI33A/BRRI20R, IR75608A/BasmatiR, IR79156A/BRRI20R and BRRI28A/ BRRI20R were good cross combinations with high sca for grain yield. Some of these crosses were involved with high/low or average/low parental gca combinations indicating additive dominance type of gene interactions for expression of traits. But very few crosses showing low/ low general combiners showed high sca, suggesting the epistatic gene action may be due to genetic diversity in the form of heterozygous loci. Thus, in majority of the crosses, high SCA for grain yield were attributed to dominance and epitasis gene action. Similar results have also been reported by Shrivastava and Seshu (1983), Dwivedi et al. (1999). CONCLUSIONS All these hybrids possessed morphological characters of modern plant type rice inherited from their male parents thereby offering good scope for developing superior rice hybrids with increased yield potential. IR79156A BRRI26R, IR79156A BRRI20R, IR75608A BasmatiR and BRRI7A BRRI31R were identified as the most promising. The present study has helped in identifying and understand- ing the gene action in inter-sub specific hybrids throwing light on the extent of heterosis and combining ability effects. REFERENCES Atlin GN, Lafitte HR (2002). Developing and testing rice varieties for watersaving systems in the tropics. In: Water Wise Rice Production. Proceedings of the International Workshop on Water-wise Rice Production, 8-11 April (Eds. Bouman, B.A.M., H. Hengsdijk, B. Hardy, P.S. Bindraban, J.P. Twong and J.K. Ladha), IRRI, Los Banos, Philippines, pp Bansal UK, Saini RG, Rani NS (2000). Heterosis and combining ability for yield, its components and quality traits in some scented rice. Tropical Agril. 77: Cockerham CC (1961). Implication of genetic variances in hybrid breeding programme. Crop Sci. 8: Dalvi VV, Patel DU (2009). 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