Identification of best heterotic crosses for yield and water use efficiency traits in groundnut (Arachis hypogaea L.)

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1 Journal of Plant Breeding and Crop Science Vol. 4(2), pp , 30 January, 2012 Available online at DOI: /JPBCS ISSN Academic Journals Full Length Research Paper Identification of best heterotic crosses for yield and water use efficiency traits in groundnut (Arachis hypogaea L.) K. John, P. Raghava Reddy, K. Hariprasad Reddy, P. Sudhakar and N. P. Eswar Reddy Regional Agricultural Research Station, Tirupati, S. V. Agricultural College Campus, Tirupati , Andhra Pradesh, India. Accepted 30 January, 2012 A set of 28 crosses involving 8 parents were studied to get the information on the extent of heterosis over mid parent, better parent and standard parent for yield and physiological attributes. The maximum better parent heterosis for pod yield was observed to be 92.73% and that of mid parent and standard parent was found to be and % respectively. TIR-25 x TCGS-647, TPT-4 x TIR-25, K-1375 x TCGS-647, ICGV x TCGS-647, TIR-25 x TCGS-647 and TIR-25 x ICGV hybrids were identified as promising for many desirable physiological traits and they may be useful in exploiting hybrid vigour in groundnut. Key words: Heterosis, water use efficiency, yield, groundnut. INTRODUCTION Groundnut is grown widely under rain-fed conditions in the semi-arid tropics, where, drought is a major constrain of groundnut productivity especially during the pod and seed forming stages that can greatly reduce pod yield (Songsri et al., 2008a). Drought resistant varieties have been used to stabilize groundnut productivity under drought conditions. Breeding for drought resistance has been an important stgy in alleviating the problem. Food productivity is decreasing due to detrimental effects of various biotic and abiotic stresses; therefore minimizing these losses is a major area of concern to ensure food security under changing climate. Environmental abiotic stresses, such as drought, extreme temperature, cold, heavy metals, or high salinity, severely impair plant growth and productivity worldwide. Drought, being the most important environmental stress, severely impairs plant growth and development, limits plant production and the performance of crop plants, more than any other environmental factor (Shao et al., 2009). Plant experiences drought stress either when the water supply to roots becomes difficult or when the transpiration becomes very high. *Corresponding author. johnlekhana@rediffmail.com. Most of the groundnut breeding programmes aimed at improving productivity have been directed towards hybridization followed by selection in segregating generation. Since groundnut is a predominately self pollinated crop and commercial product of F 1 seed is not currently feasible, it was felt that heterosis in groundnut is unstable, because tetraploid nature heterosis is unstable in groundnut. However, the magnitude of heterosis provide the basis of genetic diversity and a guide for choice of desirable parents for developing superior F 1 hybrids to exploit hybrid vigour and are building gene pool to be employed in breeding programme. Heterosis in F 1 generation expressed in terms of superiority over the better/mid-parent/standard parent is of direct relevance not only for developing hybrids in cross-pollinated crops, but also in self pollinated crops because heterotic crosses help the breeder to select appropriate crosses which would lead to desirable transgressive segregants in advanced generations (Arunachalam et al., 1982). Study of heterosis together with inbreeding depression has a direct effect what on the breeding methodology, to be followed in varietal improvement. Promising F 1 s with desirable traits may advance further to obtained transgressive segregants. Besides that, it should be possible through selection to fix heterosis if it is due to epistatic gene action or due to repulsive phase linkage of loci

2 18 J. Plant Breed. Crop Sci. Table 1. Analysis of variance (Mean squares) for yield and water use efficiency traits in groundnut. Character Replications (d.f. = 2) Treatments (d.f. = 35) Error (d.f. = 70) Days to 50% flowering ** Days to maturity ** SPAD chlorophyll meter reading * area ** weight ** Leaf area index ** Transpiration * Photosynthetic ** Stomatal conductance * Water use efficiency * Dry haulm weight per plant ** Harvest index ** Kernel yield per plant ** Pod yield per plant ** *Significant at 5% level, **Significant at 1% level. exhibiting partial or complete dominance. Therefore, with present study, the magnitude of heterosis for pod yield and other physiological traits were studied in 28 groundnut crosses in F 1 generation. MATERIALS AND METHODS Twenty eight F 1s were obtained by crossing eight parental genotypes viz; TPT-4, TIR-25, ICGV-91114, TCGS-584, JL-220, ICGV-99029, K-1375 and TCGS-647 in a diallel manner without reciprocals. The eight parents and their resultant 28 F 1s were grown in a randomized block design with three replications during kharif 2009 at RARS, Tirupati. F 1 hybrids were grown in plots consisting of single row of 5 m length having a spacing of cm and parental genotypes had three rows. In parents and F 1 hybrids, ten plants per replication per genotype and in F 1 crosses 20 plants per replication per cross were sampled for recording observation. Data were recorded on fourteen characters. viz., days to 50% flowering, days to maturity, SPAD Chlorophyll Meter Reading, specific leaf area (cm 2 g -1 ), specific leaf weight (g cm -2 ), leaf area index, transpiration (mmol H 2O m -2 s -1 ), photosynthetic (µmol co 2 m -2 s -1 ), stomatal conductance (mol H 2O m -2 s -1 ), water use efficiency (WUE) (%), dry haulms yield per plant (g plant -1 ), harvest index (%), kernel yield per plant (g plant -1 ) and pod yield per plant (g plant -1 ). The water use efficieny traits viz., SPAD chlorophyll meter reading (SCMR) was measured on all four-leaflets of third leaf from the top on main axis at 60 DAS under normal sunlight using SPAD meter of Minolta Company, NJ, USA (SPAD-502). area (SLA) was recorded at 60 days after sowing. Ten leaves (3 rd fully expanded leaf from the top on the main axis) were collected from each treatment in each replication for calculating SLA. These leaves were cleaned and their leaf area was estimated using a leaf area meter (LICOR model-3100). They were dried in a hot air oven at 80 C and dry weight recorded. The formula used was: Leaf area (cm 2 ) SLA = Leaf dry weight (g) The specific leaf weight (SLW) was recorded at 60 days after sowing as follows: Total dry weight (g) SLW = Leaf area (cm 2 ) Leaf area index (LAI) Total leaf area (cm 2 ) LAI = Unit ground area Transpiration, photosynthetic, stomatal conductance and water use efficieny (WUE) were measured on all four-leaflets of third leaf from the top on main axis at 60 DAS using artificial sunlight (1000 µeim m -2 s -1 ) with portable photosynthetic meter with light control (Licor company, LI 6400). Heterosis over mid parent (>MP), better parent (>BP) and standard parent (> SP) in F 1 generation was estimated for fourteen characters using standard formulae. RESULTS AND DISCUSSION The mean sum of squares due to genotypes was highly significant for all the characters indicating the diversity of parents (Table 1). There is no ANOVA table which shows that the results are significant. The range of heterosis over mid parent, better parent and standard parent for 14 characters have been presented in Table 2. Relative heterosis for days to 50% flowering ranged from (ICGV x TCGS-647) to (TIR-25 x TCGS- 584). Significant negative heterosis over mid-parent was observed in all the F 1 s except one F 1 that is, TIR-25 x TCGS-584. The minimum and maximum heterosis for days to 50% flowering over better parent was observed in F 1 s ICGV x TCGS-647 (-16.28) and K-1375 x TCGS-

3 John et al. 19 Table 2. Range of heterosis for yield and water use efficiency traits in groundnut. Character Mid parent Better parent Standard parent Days to 50% flowering to to to Days to maturity to to to 0.63 SPAD chlorophyll meter reading to to to area to to to weight to to to Leaf area index to to to Transpiration to to to Photosynthetic to to to Stomatal conductance to to to Water use efficiency to to to Dry haulms yield per plant to to to Harvest index to to to Kernel yield per plant to to to Pod yield per plant to to to (-0.00). Twenty two F 1 s exhibited significant negative heterosis over better parent. Standard heterosis ranged from (Tirupati-4 x TCGS-584) to (TIR-25 x TCGS-584 and TCGS-584 x TCGS-647). Positive and significant heterosis was noticed in thirteen F 1 s. Significant and negative heterosis over standard parent was observed in nine F 1 s (Tables 3 to 5). For days to maturity the relative heterosis ranged from (TIR-25 x TCGS-647) to 5.78 (TIR-25 x ICGV ). Two F 1 s exhibited positive significant relative heterosis. Significant negative heterosis over mid-parent was observed in twenty F 1 s. The minimum and maximum heterosis for days to maturity over better parent was observed in F 1 s Tirupati-4 x TIR-25 (-10.06) and ICGV x TCGS-584 (1.65) respectively. Positive and significant heterosis was noticed in only one F 1. Twenty seven F 1 s exhibited significant negative heterosis over better parent. Standard heterosis ranged from 5.02 (Tirupati-4 x TCGS-584) to 0.63 (K-1375 x TCGS-647). Significant and negative heterosis over standard parent was observed in twenty two F 1 s. For SCMR in most of the F 1 s positive heterosis was observed over mid-parent, better parent and standard parent. The F 1, K-1375 x TCGS-647 exhibited the highest significant and positive heterosis over mid-parent (8.30%) and standard parent (13.84%). These results are in agreement with those reported by Seethala (2004). For SLA the range of heterosis over mid-parent varied from (Tirupati-4 x TCGS-647) to (TCGS-584 x ICGV-99029). Out of twenty eight F 1 s, five F 1 s recorded significant positive heterosis over mid-parent. Significant negative heterosis was noticed in only nine F 1 s. Heterobeltiosis ranged from (Tirupati-4 x TCGS- 647) to (Tirupati-4 x JL-220). Significant and positive heterosis was observed in eleven F 1 s. Significant negative heterosis was noticed in only seventeen F 1 s. Standard heterosis ranged from (Tirupati-4 x TCGS-647) to (TCGS-584 x ICGV-99029). Out of twenty eight F 1 s, four F 1 s recorded significant positive heterosis over standard parent. Significant negative heterosis was noticed in eleven F 1 s. Peanut genotypes with low SLA had more photosynthetic machinery and the potential for greater assimilation per unit leaf area and large genotypic differences in the of light satud photosynthesis per unit area was reported by Wright and Bell (1992). Heterosis for SLA in groundnut was reported earlier by Pallas and Samish (1974). For specific leaf weight the range of heterosis over midparent varied from (JL-220 x K-1375) to (TPT-4 x TCGS-647). Out of twenty eight F 1 s, seven F 1 s recorded significant positive heterosis over mid-parent. Heterobeltiosis ranged from (JL-220 x K-1375) to (Tirupati-4 x TCGS-647). Significant and positive heterosis was observed in twelve F 1 s. Standard heterosis ranged from (ICGV x TCGS-647 to (TPT-4 x TCGS-647). Out of twenty eight F 1 s, eleven F 1 s recorded significant positive heterosis over standard parent. The F 1, TPT-4 x TCGS-647 recorded the highest significant positive heterosis over mid-parent (38.15%), better parent (37.62) and standard parent (38.68) respectively. Significant positive relative heterosis for leaf area index was observed in eleven F 1 s, heterobeltiosis in fifteen F 1 s, and standard heterosis in eight F 1 s. The F 1, TPT-4 x ICGV recorded the highest significant positive relative heterosis (40.40%), heterobeltiosis (32.28%) by TPT-4 x K-1375 and standard heterosis (37.17%) by JL-220 x ICGV Out of twenty eight F 1 s, eleven, fifteen and eight F 1 s showed significant positive heterosis for transpiration over mid-parent, better parent and standard parent. The F 1, TIR-25 x TCGS-647 exhibited the highest significant and positive relative heterosis (28.50%), heterobeltiosis (25.68%) and standard heterosis (31.38%). For photosynthetic,

4 Days to 50% flowering Days to physiological maturity SPAD chlorophyll meter reading area weight Leaf area index Transpiration Photosynthetic Stomatal conductance Water use efficiency Dry haulms yield per plant Harvest index Kernel yield per plant Pod yield per plant 20 J. Plant Breed. Crop Sci. Table 3. Mid parent heterosis for yield and water use efficiency traits in groundnut. Crosses TPT-4 x TPT ** -7.46** ** ** 41.77* * 37.32* TPT-4 x ICGV ** * ** 47.55** TPT-4 x TCGS ** -2.57** * ** ** 51.18* * 48.15** TPT-4 x JL ** -3.65** ** 20.39** * ** 59.55** TPT-4 x ICGV ** -6.71** -7.12** ** ** ** 70.55** TPT-4 x K ** -3.75** * ** 33.05** ** 40.44** TPT-4 x TCGS ** -4.00** ** 38.15** * 18.35** ** ** 72.49** TIR-25 x ICGV ** -2.66** * TIR-25 x TCGS ** ** * 41.91** 41.67** TIR-25 x JL ** -4.00** ** 17.47** ** 18.87** * TIR-25 x ICGV ** 5.78** * ** ** ** 86.69** TIR-25 x K * -6.22** -9.08** * 18.45** * ** * ** TIR-25 x TCGS ** -7.62** * ** ** ** ** ICGV X TCGS ** 1.99** ** 18.97** * ** ** ** ** ** ** ** ICGV X ICGV ** -3.13** * * * 87.56** * 53.52** ICGV X K ** * ** ** 56.11** 62.99** ** -3.16** ** ** * 72.63** ** ** TCGS-584 X JL ** ** * ** * * TCGS-584 X ICGV ** -3.44** ** * 38.80** ** * 45.24** ** 75.90** TCGS-584 X K ** ** ** * 19.22* TCGS-584 X TCGS ** ** 21.67** * ** -2.00** * ** ** ** ** ** 88.49** JL-220 X K ** -2.69** 5.15* 19.09** ** ** 11.37** * * JL-220 X TCGS ** -3.27** ** * ICGV x K ** -5.78** -8.59** * 31.90* * ICGV x TCGS ** -5.09** ** 21.78** 32.71** ** * 51.65* 69.34** K-1375 x TCGS ** -1.53* 8.30** ** 14.95* ** ** * 54.16** 56.47** S.E *,**Significant at 5 and 1% level of probability respectively. significant positive relative heterosis was observed in ten F 1 s, heterobeltiosis in eleven F 1 s, and standard heterosis in seven F 1 s. The F 1, K x TCGS-647 recorded the highest significant positive relative heterosis (24.44%) and heterobeltiosis (20.45%). ICGV x TCGs-584

5 Days to 50% flowering Days to physiological maturity SPAD chlorophyll meter reading area weight Leaf area index Transpiration Photosynthetic Stomatal conductance Water use efficiency Dry haulms yield per plant Harvest index Kernel yield per plant Pod yield per plant John et al. 21 Table 4. Better parent heterosis for yield and water use efficiency traits in groundnut. Crosses TPT-4 x TPT ** ** -0.66** ** -2.39** 19.66** 0.85** -6.43** ** 20.67** ** 27.30** TPT-4 x ICGV ** -3.76** -3.83** 1.71** -3.57** 11.39** 0.40** -3.24** 16.51** 12.42** 24.91** ** 37.97** TPT-4 x TCGS ** -5.02** -5.08** 9.87** ** 13.28** -9.58** 4.85** 7.45** 17.47** ** 39.24** TPT-4 x JL ** -4.70** -3.02** 17.69** 19.66** ** 2.43** -3.52** ** -5.79** 37.91** ** 57.28** TPT-4 x ICGV ** -9.20** -9.95** 1.47** -9.21** 20.37** 2.84** -3.04** 37.52** -6.63** ** 65.48** TPT-4 x K ** -4.05** -8.81** 6.05** ** 32.28** 6.45** ** -5.03** ** 24.88** TPT-4 x TCGS ** -5.74** -3.02** ** 37.62** 15.15** 16.51** 13.66** -0.42** -2.28** 13.13** ** 54.75** TIR-25 x ICGV ** -0.07** -4.17** ** 9.23** -2.96** -8.95** ** ** 3.58** ** 3.78** TIR-25 x TCGS ** 3.47** 2.47** ** 22.57** 7.19** ** ** ** 2.54** ** 24.05** TIR-25 x JL ** -7.69** 0.81** ** 8.14** ** 17.54** -6.31** ** ** -1.34** ** 18.11** TIR-25 x ICGV ** -5.92** -6.84** ** -9.74** 7.90** 1.55** -7.06** ** * ** ** ** 78.11** TIR-25 x K ** ** -2.36** -2.41** 15.54** 14.90** ** ** ** ** 36.21** TIR-25 x TCGS ** -8.58** 3.77** 3.79** ** 6.77** 25.68** ** ** ** *10.90** ** 9.73** ICGV X TCGS ** 1.65** -0.94** ** 17.15** ** 11.21** -6.19** ** ** ** ** 20.14** -8.45** -1.92** -3.54** -4.43** 2.42** ** 1.90** 14.21** ** 5.54** 36.92** 19.89** 25.24** 51.79** ICGV X ICGV ** -8.31** 0.35** ** 5.37** ** 9.55** -3.04** ** ** ** 43.81** 39.58** ICGV X K ** -2.80** -7.83** ** -1.48** ** 4.29** -4.22** ** ** 16.64** ** 36.70** -8.45** -7.55** -2.60** 1.77** -7.79** -1.51** 8.50** -1.97** ** ** ** 92.73** TCGS-584 X JL ** -0.96** 1.25** 14.52** ** ** 6.29** 11.40** ** -0.71** ** ** ** TCGS-584 X ICGV ** -8.31** -4.56** 12.34** ** 20.46** -1.88** 0.14** ** 10.11** ** 47.49** 60.71** TCGS-584 X K ** -7.24** ** 1.53** ** ** 5.52** ** 9.13** 1.08** ** ** TCGS-584 X TCGS ** -4.53** 0.52** ** 19.41** 4.77** -3.94** 3.67** ** -9.13** ** 31.30** -5.19** -5.64** -2.21** ** 9.24** 2.83** ** ** ** ** ** 80.36** JL-220 X K ** -4.05** -0.85** 9.67** ** ** 14.65** 6.71** ** ** ** 10.12** ** ** JL-220 X TCGS ** -6.04** 3.31** -5.25** 2.89** ** 0.55** 0.00** ** -9.34** ** 25.08** ICGV x K ** ** -8.10** ** ** 5.37** 4.01** 19.46** -5.64** ** ** ** ICGV x TCGS ** -5.93** -5.67** ** 16.36** 14.28** 1.46** 10.08** -4.55** 0.00** ** 47.92** K-1375 x TCGS ** -3.02** 0.91** ** 4.57** ** 4.45** 20.45** ** 11.49** ** 26.60** S.E correct *,**Significant at 5 and 1% level of probability respectively.

6 Days to 50% flowering Days to physiological maturity SPAD chlorophyll meter reading area weight Leaf area index Transpiration Photosynthetic Stomatal conductance Water use efficiency Dry haulms yield per plant Harvest index Kernel yield per plant Pod yield per plant 22 J. Plant Breed. Crop Sci. Table 5. Standard parent heterosis for yield and water use efficiency traits in groundnut. Crosses TPT-4 x TPT * -4.70** * 14.64* 19.66* * ** 64.37** ** 49.05** TPT-4 x ICGV ** -3.76** ** 16.00* * ** 37.97* TPT-4 x TCGS ** -5.02** * * 51.77* * TPT-4 x JL ** -4.70** ** 19.66** * ** 57.28** TPT-4 x ICGV * -4.08** * * ** * * 81.40** 75.95** TPT-4 x K ** -3.45** ** * ** 60.44** TPT-4 x TCGS * -2.19** ** 38.68** * 13.66** ** 54.75** TIR-25 x ICGV ** ** TIR-25 x TCGS ** -219** * 17.21** * 45.25** TIR-25 x JL ** -2.19** ** 27.01** ** 9.10* * 38.29* TIR-25 x ICGV ** * ** ** ** ** TIR-25 x K ** -3.13** ** 20.02** ** * 49.12** 75.00** TIR-25 x TCGS * -3.13** ** ** ICGV X TCGS * -3.45** ** 22.61** ** ** ** ** 19.24** * 16.18** ** ICGV X ICGV ** 6.84* ** * ** ** 41.20* 48.42** ICGV X K * -2.19** ** 21.17** ** * ** 75.63** ** ** * ** ** 67.72** TCGS-584 X JL ** ** * * TCGS-584 X ICGV ** -3.13** ** ** 16.98* ** ** 44.82** 70.89** TCGS-584 X K * ** 24.87** ** TCGS-584 X TCGS ** ** 24.97** * ** ** ** * * ** ** 71.93** 91.77** JL-220 X K ** 11.85** 11.53* * JL-220 X TCGS * -2.51** * * * * ICGV x K * -2.82** * 10.57** 62.19** ** ** ICGV x TCGS ** ** 17.26** ** ** ** ** K-1375 x TCGS ** ** ** 28.61** ** ** ** 62.66** S.E correct *,**Significant at 5 and 1% level of probability respectively.

7 John et al. 23 Table 6. List of best heterotic crosses for yield and water use efficiency traits in groundnut. Character Days to 50% flowering Best heterotic crosses-based on Relative heterosis Heterobeltiosis Standard heterosis TPT-4 X TCGS-54 ICGV X K-1375 TIR-25 X K-1375 Days to maturity TPT-4 X TIR-25 TPT-4 X TIR-25 TIR-25 X K-1375 TIR-25 X JL-220 TPT-4 X JL-220 SPAD chlorophyll meter reading JL-220 X K-1375 TIR-25 X TCGS-54 JL-220 X TCGS-647 JL-220 X K-1375 ICGV X ICGV area TCGS-54 X TCGS-647 TIR-25 X JL-220 weight TCGS-54 X TCGS-647 TPT-4 X JL-220 TCGS-54 X TCGS-647 TPT-4 X TCGS647 K-1375 X TCGS647 TIT25 X JL-220 Leaf area index TCGS-584 X ICGV TPT-4 X K-1375 TIR-25 X TCGS-584 TCGS-584 X ICGV TPT-4 X K-1375 Transpiration TIR-25 X JL-220 TIR-25 X K-1375 TIR-25 X JL-220 ICGV X TCGS- 584ICGV X ICGV Photosynthetic Stomatal conductance ICGV X K-1375 ICGV X K-1375 Water use efficiency TIPT-4 X TIR-25 TCGS-584 X K-1375 TPT-4 X TIR-25 TPT-4 X TIR-25 Dry haulm weight per plant ICGV-9114 X ICGV ICGV X ICGV Harvest index ICGV X TCGS-584 ICGV X TCGS-584 JL-220 X K-1375 ICGV X TCGS-584 Kernel yield per plant Pod yield per plant ICGV X K-1375

8 24 J. Plant Breed. Crop Sci. registered the highest standard heterosis (37.17%). Significant positive relative heterosis for stomatal conductance was observed in two F 1 s, heterobeltiosis in four F 1 s, and standard heterosis in three F 1 s. The F 1, TPT-4 x ICGV recorded the highest significant positive relative heterosis (44.17%) and heterobeltiosis (37.52%). Most of the F 1 s showed significant negative heterosis over mid-parent, better parent and standard parent. For water use efficiency four F 1 s expressed significant positive heterosis over their respective midparent, eight F 1 s exceeded over better parent and two F1s over standard parental values in desirable direction. Most of the F 1 s expressed significant negative heterosis over mid-parent, better parent and standard parent. For dry haulms yield per plant, eight F 1 s expressed significant heterosis over their respective mid-parents, nine F 1 s exceeded over their corresponding better parental values and eighteen F 1 s recorded higher standard parental values in desirable direction. Earlier, Vinit and Sharma (2001) reported for dry haulms yield per plant. Significant positive relative heterosis for harvest index was observed in ten F 1 s, heterobeltiosis in two F 1 s (ICGV x JL-220 and JL-220 x K01375) and standard heterosis only in one F 1 (ICGV x Jl-220). The F 1, ICGV x JL-220 recorded the highest significant positive relative heterosis (27.35%), heterobeltiosis (19.89%) and standard heterosis (16.18%). The findings corrobo with the results of Suresh (1993) and Nisar (1995). Kernel yield per plant registered significant positive relative heterosis, heterobeltiosis and standard heterosis in seventeen, twenty three and sixteen F 1 s out of twenty eight F 1 s, respectively. Among twenty eight F 1 s studied the cross, TIR-25 x ICGV recorded the highest significant positive relative heterosis (120.18%), heterobeltiosis (104.83%) and standard heterosis (133.71%). Heterobeltiosis for pod yield per plant ranged from to The highest heterosis was observed in F 1, ICGV x TCGS-647. The lowest heterosis was noticed in JL-220 x K Twenty four F 1 s recorded significant positive heterosis. Relative heterosis ranged from (JL-2200 x K-1375) to (ICGV x TCGS-647). Twenty F 1 s recorded significant positive heterosis. Standard heterosis ranged from 3.80 (JL-220 x K-1375) to (TIR-25 x ICGV-99029). Nineteen F 1 s recorded significant heterosis over standard parent. Significant positive heterosis over mid-parent, better parent and standard parent for pod yield per plant was registered in twenty, twenty three and nineteen F 1 s respectively. Among twenty eight F 1 s studied, the cross, ICGV x TCGS-647 recorded the highest significant relative heterosis (101.52%) and heterobeltiosis (92.73%). Earlier, Arunachalam et al. (1982), Jayalakshmi et al. (2000), Jayalakshmi and Reddy (2005), John and Vasanthi (2006), Jivani et al. (2008) and Jivani et al. (2009) also reported positive heterosis for pod and kernel yields in groundnut. From the forgoing discussion it can be concluded that crosses ICGV x TCGS-647 and TCGS-584 x K with high relative heterosis and better parent heterosis for pod yield per plant. Thus, the mid-parent heterosis and better parent heterosis for pod yield can mainly be attributed to the manifestation of heterosis in component and associated characters. However, some of the crosses recorded significant standard heterosis for certain physiological traits, JL-220 x ICGV for leaf area index, TIR-25 x TCGS-647 for transpiration, ICGV x JL-220 for photosynthetic, ICGV x K-1375 for stomatal conductance and TPT-4 x TIR-25 for water use efficiency (Table 6). In all the previous cross combinations that showed high heterosis involved one good general combiner and one poor combiner thereby indicating the roll of inter-allelic interactions. Therefore, for exploitation of such heterosis in future breeding programmes either recurrent selection or diallel selective mating system is to be examined in these crosses. REFERENCES Arunachalam V, Bandopadhyay A, Nigam, SN, Gibbons RW (1982). Heterotic potential of single cross in groundnut (Arachis hypogaea L.) Oleagineux, 37: Jayalakshmi V, Reddy GL (2005). Heterosis and inbreeding depression for yield and physiological attributes in groundnut (Arachis hypogaea L). Indian J. Agric. 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