Correlation and path analysis of morpho-physiological and yield traits in boro rice (Oryza sativa L.)

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1 Agric. Sci. Digest., 35 (4) 2015: Print ISSN: X / Online ISSN: AGRICULTURAL RESEARCH COMMUNICATION CENTRE Correlation and path analysis of morpho-physiological and yield traits in boro rice (Oryza sativa L.) Shantanu Das* and Debojit Sarma Department of Plant Breeding and Genetics, Assam Agricultural University, Jorhat , Assam, India. Received: Accepted: DOI: /asd.v35i ABSTRACT Thirty rice genotypes of local and exotic origin were analyzed to ascertain the genotypic and phenotypic correlation among 21 morpho-physiological and yield traits and their direct/ indirect contribution to grain yield under boro season. The result revealed that grain yield per plant had significant positive correlation with biological yield (0.927**, 0.766**), harvest index (0.748**, 0.658**), days to first flowering (0.459*, 0.377*), panicle length (0.501**, 0.445*), grains per panicle (0.576**, 0.484**) and 1000 grain weight (0.573**, 0.460*) at both genotypic and phenotypic levels. Path coefficient analyses at both genotypic and phenotypic levels revealed high positive direct effect of biological yield (0.7181) and harvest index (0.6382) on grain yield per plant. Thus direct selection for grain yield per plant and indirect selection through these characters would be effective to improve yield in boro rice. Key words: Correlation, Direct effect, Grain yield, Indirect effect, Morpho-physiological traits. INTRODUCTION Rice is the world s most important and staple food crop for more than 60 per cent of the world s population. Meeting the food needs of Asia s population increase has become a staggering challenge to step up the rice production and productivity. It has therefore become urgent to breed high yielding rice varieties adaptive to various biotic and abiotic stress conditions. Assam produces million tonnes of rice from million ha yielding tonnes per ha in (Anonymous, 2012). Among various problems identified, low temperature induced injury and slow growth in the seedling stage are the most serious problems registered in boro rice of Assam. Improvement in rice grain yield per unit area is the only way to achieve increased rice production because of the reduction in area in recent times. Rice grain yield is a quantitative character governed by many genes (polygenes) and is highly influenced by environment too. Yield represents the ultimate product from the interaction of all the plant characters. However, certain plant characters could prove useful as selection criteria in breeding for high yield with tolerance to stress environment. Selection of parents based on yield alone is often misleading. It is, therefore, important to identify important morpho-physiological determinants influencing grain yield through estimation of correlation among the characters. Identifying the causal relationships *Corresponding author s shanubrdr.oryza@gmail.com. among the traits would help in identifying the contributing traits in a given environment. In the present investigation, 30 diverse genotypes were evaluated for important morpho-physiological and adaptive traits during the boro season with an aim to decipher the casual relationship among the characters under study. The study on associated traits with direct and indirect effect on grain yield of rice genotypes will help to formulate effective selection for the boro season. MATERIALS AND METHODS Plant materials and crop management: Thirty rice genotypes of indigenous and exotic origin including local cultivars, modern varieties and advance breeding lines obtained from Regional Agricultural Research Station (AAU), Karimganj were detailed in Table 1. One hundred seeds of each genotype were uniformly sown in trays each of the three replications in a net area of 50 cm x 30 cm per tray. Extra trays were transplanted to provide sufficient seedlings for planting in the main field. Randomized Block Design (RBD) was adopted in the nursery experiment. The boro crop in the experimental field was preceded by rice seedling nursery in Kharif 2012 followed by a period of fallow. The soils belong to the order Inceptisols and sandy loam texture with ph of 4.8. The field preparation and application of manures and fertilizers were done as per recommended Package of Practices for Kharif crops of

2 TABLE 1: Details of genotypes used in the present investigation Volume 35 Issue 4 (2015) 257 GENOTYPE PEDIGREE ORIGIN Agni Sail LAND VARIETY ASSAM, INDIA CU 11 RATNA/LENG KWANG INDIA Himdhan R 575/TN 1 HIMACHAL PRADESH, INDIA Kala Boro LAND VARIETY ASSAM, INDIA Madhav Boro LAND VARIETY ASSAM, INDIA Rata Boro LAND VARIETY ASSAM, INDIA Tepi Boro SELECTION FROM LAND VARIETY ASSAM, INDIA Jhum Mycin LAND VARIETY (JHUM RICE) ASSAM, INDIA Jhum Kamrung LAND VARIETY (JHUM RICE) ASSAM, INDIA B 2983B-SR SIRENDAH MERAH/IR INDONESIA IR B IR //DOBONGBYEO/MOROBEREKAN IRRI, PHILIPPINES IR IR /IR IRRI, PHILIPPINES IR B-3 ABHAYA/IR PMI SRN 1-1//CN IRRI, PHILIPPINES IR SR18977-TB-4/JINMIBYEO IRRI, PHILIPPINES Kmj 13 A MAHSURI/LUIT ASSAM, INDIA Kmj 13B MAHSURI/LUIT ASSAM, INDIA Kmj 13A MAHSURI/LUIT ASSAM, INDIA Kmj 13A MAHSURI/LUIT ASSAM, INDIA Tamdao INTRODUCTION VIETNAM TN 1 DEE-GEO-WOO-GEN/TSAI-YUAN-CHUNG TAIWAN Luit HEERA/ANNADA ASSAM, INDIA Boro 1 SELECTION FROM LAND VARIETY ASSAM, INDIA Joymoti JAYA/MAHSURI ASSAM, INDIA Kanaklata JAYA/MAHSURI ASSAM, INDIA Dinanath IR /MAHSURI ASSAM, INDIA Swarnabh TAINUNG SEN GLUTINOUS 2/MAHSURI ASSAM, INDIA Gautam RASI MUTANT BIHAR, INDIA IR 64 IR /IR IRRI, PHILIPPINES IR 68 IR /IR //IR 54 IRRI, PHILIPPINES IR 72 IR /IR //IR IRRI, PHILIPPINES Assam (Anonymous, 2009). Forty-two days old seedlings were transplanted in the main field with single seedling per hill on January 25, 2013 having a spacing of 15 x 15cm. The experiment was laid out in Randomized Complete Block Design (RCBD) with three replications. Each genotype per replication was allotted a gross plot of size 2.25 m x 0.45 m accommodating three rows. Evaluation of the genotypes at different growth stages: In the nursery seedling emergence was recorded at 7, 10, 13, 16 and 21 days after sowing (DAS) and the established seedlings were counted finally after 21 days from sowing. The specific method with or without modification was followed for taking observations at different stages of the crop. Altogether 26 characters were observed from germination to maturity stage. Germination percentage (GP) and Seedling emergence (SE) were recorded at 7 and 13 DAS respectively. Speed of emergence was calculated by following the method of Dadlani and Sleshu (1990) with modification as the ratio of number of seeds emerged at 10 DAS and total number of seeds emerged at 16 DAS in percentage. Seedling establishment (SEs) at 21 DAS was obtained by following the method of Yamauchi and Winn (1996). Seedling height (SH) was observed at 30 DAS. Seedling vigour index (SVI) was calculated by following the method of Perry (1978) with modification as seedling height (cm) at 30 DAS multiplied by germination percentage. Recovery percentage after transplanting (RAT) was recorded at 30 DAT. Days to first (DF) and 50 per cent flowering (DFF), booting to heading duration (BHD) as the number of days from first appearance of pregnant stage to the day of 50 per cent flowering in a plot, days to maturity (DM), plant height (PH), culm length (CL), panicle exertion percentage (PE) (Virmani et al., 1997), Panicle length (PL), grains per panicle (GPP), spikelet fertility percentage (SF), 1000 grain weight (TGW), effective tillers per plant (ET), grain yield per plant (GY), biological yield per plant (BY), harvest index (HI) were recorded at flowering and maturity stages. Statistical analysis: In order to assess the correlation among the characters under study at both phenotypic and genotypic level for all the possible comparisons were computed as per

3 258 AGRICULTURAL SCIENCE DIGEST - A Research Journal the formula suggested by Al-Jibouri et al. (1958) and these estimates were used for path coefficient analysis using formula given by Dewey and Lu (1959). RESULTS AND DISCUSSION The analysis of variance revealed highly significant differences among the genotypes for all the characters studied, indicating the existence of considerable genetic variation in the rice genotypes under study. Correlation analysis: The significant correlation estimates at phenotypic (30 cases) and genotypic (56 cases) were moderate to strong in magnitude (Table 2). The magnitude of genotypic correlation coefficients was higher than their respective phenotypic counterpart in majority of the cases, which indicated the masking effect of environment on the phenotypic correlations among the characters. The significant genotypic correlations were found to have close agreement with phenotypic correlations in most of cases with a few differing in magnitude, indicating reliability of these associations for breeding programme. The correlation analysis revealed that grain yield per plant had significant positive correlation with biological yield, harvest index, days to first flowering, panicle length, grains per panicle and 1000 grain weight at both genotypic and phenotypic level. All these characters except harvest index exhibited moderate to high heritability estimates. Thus direct selection for grain yield per plant and indirect selection through the aforesaid characters would be very effective in yield improvement of rice. The correlation of grain yield per plant with biological yield was strong at both genotypic and phenotypic levels. Thus, indirect selection for biological yield would be expected to offer greater scope for yield gain. Developmental characters like days to first flowering, days to 50 per cent flowering, booting to heading duration, days to maturity and plant height showed moderate to strong association among them at both genotypic and phenotypic levels. Plant height was strongly associated with culm length, which in turn had moderate correlation with effective tillers. Days to first and 50 per cent flowering exhibited moderate to strong association with panicle length, indicating that long panicle would take more time for flowering in boro season. Likewise the correlations among panicle length, grains per panicle, 1000 grain weight and biological yield were moderate at both genotypic and phenotypic levels. Similar correlations of grain number per panicle with panicle length and grain weight at both the levels were also reported by Machunde (2013). Thousand grain weights were moderately correlated with harvest index at genotypic and phenotypic levels. Similarly, the associations with panicle length with grains per panicle and biological yield were moderate at both genotypic and phenotypic levels. Grains per panicle had moderate positive correlation with grain fertility at both the levels. These correlations assumed importance because of moderate to high heritability estimates noted for these characters, the exception being harvest index. The phenotypic and genotypic correlation coefficients among germination and seedling characters were found to be moderate to strong at both genotypic and phenotypic levels. Of particular importance were the strong positive correlations of seedling emergence with seedling establishment and seedling height with seedling vigour index at both genotypic and phenotypic level. Thus, these characters could be considered for selection at seedling stage for cold tolerance in boro rice. Seedling emergence and vigour would also contribute to recovery per cent after transplanting as evident from its moderate positive correlation with seedling emergence, seedling establishment and seedling height at both genotypic and phenotypic levels. Considering these associations breeding high yielding varieties for boro season would necessitate a compromise among the yield component characters to get maximum yield gain in the comparatively risk free boro season of Assam. An early maturing (165 days) genotype with high germination and seedling emergence, quick seedling growth, leaf greenness, semi dwarf stature, moderate tillering, intermediate panicle, high biological yield with high number of filled grains on the panicles would be better suited to boro season of the state. Path coefficient analysis: Path coefficient analyses at both genotypic (Table 3) and phenotypic level (Table 4) revealed high positive direct effect of biological yield and harvest index on grain yield per plant. The positive direct effects of days to maturity, effective tillers, panicle length, culm length and seedling establishment were also high at genotypic level. The heritability estimates for panicle length, culm length and seedling establishment were found to be high, and for grain yield, biological yield and effective tillers the estimate was moderate. Thus, selection for high seedling establishment, long panicles, increased culm length, more number of effective tillers and high biological yield would be effective to get desirable improvement in boro rice. Harvest index had the high positive indirect effect on grain yield via 1000 grain weight, grains per panicle and panicle length. Indirect selection for harvest index was nullified by its low heritability estimate. The residual effects of genotypic and phenotypic paths were 5.24 and per cent respectively, indicating major contribution of the characters under study toward the causal relationships, and hence most of the variation in yield.

4 Volume 35 Issue 4 (2015) 259 TABLE 2: Genotypic (above diagonal) and phenotypic (below diagonal) correlation coefficients among the characters in 30 rice genotypes, boro Character Germination Seedling Speed of Seedling Seedling Seedling Recovery after Days to Days to Booting to (%) emergence emergence establishment height vigour transplanting first 50% heading (%) (%) (%) (cm) index (%) flowering flowering duration GP 0.472** 0.379* 0.576** ** SE 0.476** ** 0.461* 0.542** 0.481** * SpE SEs 0.589** 0.884** * 0.590** 0.488** SH * * 0.900** 0.404* SVI 0.633** 0.519** ** 0.891** RAT ** DF ** DFF ** 0.501** BHD DM * PH CL ET PL ** 0.633** 0.373* GPP * SF TGW GY * BY HI h 2 (%) bs *, ** Significant at P=0.05 and 0.01, respectively. Table 2: contd...

5 260 AGRICULTURAL SCIENCE DIGEST - A Research Journal Character Days to Plant Culm Effective Panicle Grains/ Spikelet 1000 grain Grain yield Biological Harvest maturity height (cm) length (cm) tillers/plant length (cm) panicle fertility (%) weight (g) /plant (g) yield (g) index GP SE ** SpE SEs ** SH ** * SVI * RAT ** ** DF 0.575** ** * ** DFF 0.711** ** * ** BHD 0.747** ** ** DM 0.434* ** ** PH ** * 0.531** CL ** * 0.414* * ET * PL ** ** ** 0.536** GPP * 0.512** ** ** SF * TGW ** 0.410* 0.677** GY * 0.484** * 0.927** 0.748** BY * 0.406* ** 0.446* HI * * 0.658** h 2 (%) bs

6 Volume 35 Issue 4 (2015) 261 TABLE 3: Direct (diagonal) and indirect effect of 11 characters on grain yield at genotypic level, boro Character Germination Seedling Days to Days to Culm Effective Panicle Grains 1000 grain Biological Harvest (%) establishment 50% maturity length tillers length /panicle weight Yield index (%) flowering (cm) /plant (cm) (g) (g) GP SEs DF * DM CL ET PL ** GPP ** TGW ** BY ** HI ** R = TABLE 4: Direct (diagonal) and indirect effect of 11 characters on grain yield at phenotypic level, boro Character Germination Seedling Days to Days Culm Effective Panicle Grains 1000 grain Biological Harvest (%) establishment 50% to length tillers/ length /panicle weight yield index (%) flowering maturity (cm) plant (cm) (g) (g) GP SEs DF DM CL ET PL * GPP ** TGW * BY ** HI ** R =

7 262 AGRICULTURAL SCIENCE DIGEST - A Research Journal CONCLUSION The results from the present correlation and path coefficient analysis indicated that harvest index and biological yield were the major yield contributing characters among the rice genotypes studied, as these characters not only showed positive and significant association with grain yield/plant, but also had high positive direct effect at both genotypic and phenotypic levels. The positive direct effect of effective tillers, panicle length, culm length and seedling establishment were also high at genotypic level. Thus, selection for high seedling establishment, long panicles, increased culm length, more number of effective tillers and high biological yield would be effective to get desirable improvement in boro rice. ACKNOWLEDGEMENT This work was supported by the Assam Agricultural University fund for the post graduate research programme under the Directorate of Post Graduate Studies, AAU, Jorhat REFERENCES Al-Jibouri, N.A., Miller, P.A. and Robinson, H.P. (1958). Genotypic and environmental variances, covariances in upland cotton cross of inter-specific region. Agron J. 50: Anonymous. (2012). Economic survey of Assam, , Government of Assam. Anonymous. (2009). Package of Practices for Kharif Crops, Assam Agricultural University and Department of Agriculture, Government of Assam. Dadlani, M. and Sleshu, D.V. (1990). Effect of wet and dry heat treatments on rice seed germination and seedling vigour. International Rice Res Newsl. 15: Dewey, D.R. and K.H. Lu. (1959). A correlation and path coefficient analysis of components of crested wheat grass seed production. Agron J. 51: Machunde, Z.A. (2013). Variation and interrelationships among yield and yield components in lowland rice genotypes (Oryza sativa L.) in Mwanza Region. M. Sc. Dissertation, Sokoine University of Agriculture. Morogoro, Tanzania. Perry, D.A. (1978). Handbook of Vigour Test Methods. International Seed testing Association, Zurich. Virmani, S.S., B.C. Viraktamath, C.L. Casal, R.S. Toledo, M.T. Lopes and J.O. Manalo. (1997). Hybrid Rice Breeding Manual. International Rice Research Institute. Los Banos, Laguna, Philippines. Pp1. Yamauchi, M. and Winn, T.. (1996). Rice seed vigour and seedling establishment in anaerobic soil. Crop Sci. 36: