Okra [Abelmoschus esculentus (L.) Moench.] is a warm-season, traditional fruit- vegetable crop commercially grown in both tropical and subtropical parts of the world. Globally, India is the largest producer, where okra is grown in an area of 4.32 lakh hectares with annual production of 45.28 lakh tonnes and a productivity of 10.5 MT/ha (Vigneshwara Varmudy, 2011). It is a potential export revenue earner, accounting for 60% of all fresh vegetables exported (Sharma and Arora, 1993). In India, commercial production of F 1 hybrid in okra is done by hand emasculation and hand pollination which is a tedious process that takes 70 % of the time and labour in cultivation. Geneic Male Sterile (GMS) line MS-1 identified by the Division of Vegetable Crops, Indian Institute of Horticultural Research (IIHR), is being used for development of a commercial F 1 hybrid. Male sterility in okra is controlled by a pair of single, recessive genes and can be utilized by hybrid seed production. Genetically Controlled male sterility (MS1) is an important trait for the production of F 1 hybrid seeds in several crops (Kaul, 1998). Some male sterile systems have been reported in Brassica campestris var. Japonica (Kato and Tokumasu, 1984). In okra, male sterility has not been observed in nature, but, has been induced by gamma radiation Studies on inheritance of Geneic Male Sterility (GMS) and hybrid seed production in okra [Abelmoschus esculentus (L.) Moench.] M. Pitchaimuthu, O.P. Dutta and K.R.M. Swamy Indian Institute of Horticultural Research, Bangalore Karnataka - 560 089, India E-mail: muthu@iihr.ernet.in ABSTRACT Inheritance of geneic male sterility in GMS line MS-1 of okra [Abelmoschus esculentus (L.) Moench.] was studied using F 1 , F 2 and test-cross generations of crosses between GMS line MS-1 and normal fertile genotypes, and the varieties Arka Anamika, Parbhani Kranti, Arka Abhay, IIHR-108-1-31, IIHR-109-20-6, IIHR-116-23-6, IIHR- 180-6-3, IIHR-161-10-1 and IIHR-130-2-10. All the F 1 were found fertile. Segregation of pollen fertility in F 2 and test - cross generations involving ms1 was segregated in the ratio 1 fertile: 1 sterile, respectively. This indicated that GMS trait in the line is controlled by a single recessive gene (ms1ms1). Large-scale F 1 hybrid seed production in okra becomes rather slow due to the tedious hand-emasculation, followed by hand-pollination, incurring additional labour and cost of F 1 seed production. In comparison to fertile lines, this saves approximately 70% time and manual labour. Use of Geneic Male Sterile (GMS) line MS-1 can make F 1 hybrid seed production in okra easy and more economical compared to hand-emasculation. Key words: Abelmoschus esculentus, Geneic Male Sterility (GMS), back cross, generations, recessive allele Short communication J. Hortl. Sci. Vol. 7(2):199-202, 2012 (Dutta, 1971). Male sterility in okra was seen to be a controlled by a single recessive gene (ms1) when present in the homozygous (ms1ms1) condition. The symbol ms1 was proposed for this gene (Dutta, 1980). The gene was stable, not being influenced by environmental factors. Anthesis was normal but anther dehiscence was partial. Microsporogeneisis was normal upto the tetrad stage. Hence, a great future for hybrid seed production is envisaged in a heterosis breeding programme. Studies were conducted at IIHR during 2002-2003. IIHR-MS-1 was crossed with ten fertile parents, namely, Arka Anamika, Parbhani Kranti, Arka Abhay, IIHR-108-1- 31-1, IIHR-109-1-20-6, IIHR-120-11-8-1, IIHR-116-12-23- 6, IIHR-180-6-3, IIHR-161-10-1, IIHR-130-2-10. A Series of crosses were made to determine the genotype of F 1 progenies by selfing and backcrossing randomly for selected F 1 individuals from each progeny to their respective male fertile (Fig. 1) and male sterile parent (Fig. 2). Data were collected in respect of F 2 and BC 1 for all the ten segregating progenies (Tables 1 & 2). Segregation ratio of the male- sterile character was subjected to Chi-square test. Test on goodness of fit between expected and observed segregation ratio was calculated as per Snedecor and Cochran (1967). 200 Pitchaimuthu et al Fig 2. Male-sterile plant showing no pollen grainsFig 1. Male-fertile plant showing yellow colored pollen Table 1. Behaviour of F 2 families in some crosses involving IIHR-MS-1 and testers during Rabi-Summer 2002-03 Cross combination of (F 2 ) IIHR-MS-1 No. of plants observed No. of plants expected fertile sterile fertile sterile Total χ2(3:1) P value IIHR-MS-1 X Arka Anamika 56 27 63.75 21.25 65 2.80 0.20-0.10 IIHR-MS-1 X Parbhani Kranti 50 25 56.25 18.75 75 2.77 0.10-0.05 IIHR-MS-1 X Arka Abhay 68 27 71.25 23.75 95 0.59 0.50-0.30 IIHR-MS-1 X IIHR-108-1-31-1 70 26 73.50 24.50 96 0.67 0.50-0.30 IIHR-MS-1 X IIHR-109-1-20-6 61 29 67.50 22.50 90 2.51 0.20-0.10 IIHR-MS-1 X IIHR-120-11-8-1 69 21 67.50 22.50 90 0.07 0.80-0.70 IIHR-MS-1 X IIHR-116-12-23-6 66 29 71.25 23.75 95 1.55 0.3.-0.20 IIHR-MS-1 X IIHR-180-6-3 77 21 73.50 24.50 98 0.67 0.50-0.30 IIHR-MS-1 X IIHR-161-10-1 65 13 58.50 19.50 78 2.59 0.10-0.05 IIHR-MS-1 X IIHR-130-2-10 70 18 66.00 22.00 88 0.97 0.50-0.30 Total 654 238 669 223 892 14.77 0.22-0.10 Pooled Chi-square values - - - - - 1.35 0.33-0.20 Heterogeneity - - - - - 13.42 0.20-0.10 Homogeneity - - - - - 12.88 0.20-0.10 Table 2. Segregation in BC 1 generation of IIHR-MS-1 (Male sterile) X F 1 s in okra during Rabi season 2002 Cross combination (BC 1 ) IIHR-MS-1 No. of plants observed No. of plants expected fertile sterile fertile sterile Total χ2(3:1) P value IIHR-MS-1 X Arka Anamika 56 27 63.75 21.25 65 2.80 0.20-0.10 IIHR-MS-1 X Arka Anamika 48 31 35.5 35.5 71 1.1 0.30-0.20 IIHR-MS-1 X Parbhani Kranti 41 29 35 35 70 2.06 0.20-0.10 IIHR-MS-1 X Arka Abhay 35 38 36.5 36.5 73 0.12 0.30-0.70 IIHR-MS-1 X IIHR-108-1-31-1 34 41 37.5 37.5 75 0.66 0.50-0.30 IIHR-MS-1 X IIHR-109-1-20-6 40 32 36 36 72 0.68 0.50-0.30 IIHR-MS-1 X IIHR-120-11-8-1 37 41 39 39 78 0.20 0.70-0.50 IIHR-MS-1 X IIHR-116-12-23-6 30 35 32.5 38.5 65 0.36 0.70-0.50 IIHR-MS-1 X IIHR-180-6-3 38 30 34 34 68 0.94 0.50-0.30 IIHR-MS-1 X IIHR-161-10-1 43 35 39 39 78 0.82 0.50-0.30 IIHR-MS-1 X IIHR-130-2-10 25 35 30 36 66 1.66 0.20-0.10 Total 363 347 355 355 710 9.13 0.70-0.50 Pooled Chi-square values - - - - - 0.36 0.70-0.50 Heterogenity - - - - - 8.77 0.50-0.30 Homogenity - - - - - 8.56 0.50-0.30 J. Hortl. Sci. Vol. 7(2):199-202, 2012 201 In male sterile plants, anthesis was normal but anther dehiscence was partial, showing a small, longitudinal slit without pollen shed. All the F 1 plants obtained from hybridization between ms and the other ten cultivars (Arka Anamika, Parbhani Kranti, Arka Abhay, IIHR-108-1-31-1, IIHR-109-1-20-6, IIHR-120-11-8-1, IIHR-116-12-23-6, IIHR-180-6-3, IIHR-161-10-1, IIHR-130-2-10) were fertile. However, F 2 in all the crosses confirmed 3 fertile: 1 sterile ratio (Table 1), further confirmed by segregation behavior (1fertile: 1 sterile) in BC 1 population (Table 2). Segregation pattern in the crosses indicated that GMS trait of IIHR- MS-1 was controlled by a single recessive gene. Chi-square test, when applied to the ten individual F 2 progenies, indicated good fit for the expected ratio. Test for heterogenity indicated that there classes could be pooled; the total segregating progenies agreed and were quite close to the expected ratio of 3:1 (p=0.30, 0.20). The chi-square test for heterogenity for testing agreement of the progenies gave a chi-square value of 12.88, indicating that the progenies are non significant at 5% level. The 10 F 1 progenies, when backcrossed to their respective fertile parent produced only fertile backcross progenies. The test for heterogeneity gave Chi-square value of 8.77 at 9 df, Which was non-significant at 5% level, indicating that, the progenies agreed with 1:1 ratio of male fertile to male sterile, and could be pooled. Chi-square test of the pooled data gave a good fit for 1:1 segregation g ratio (P=0.70-0.50). Chi-square test for homogenity was not significant suggesting that the progenies agreed with one another in whatever ratio obtained. F 1 s of all the cross were fertile this indicating that geneic male sterility is governed by recessive genes and fertility restoration male in fertile genotype is controlled by the dominant gene MS . Data on sterile and fertile plants obtained in each test cross combination with Chi-square, e are presented in Table 2. Segregation in the F 2 and backcross populations of the crosses - (MS-1 X 130-2-10 and MS-1 X 116-12-23-6)- involving one GMS line and several tester parents, confirmed 3:1 and 1:1 ratio, respectively. These results were similar to those observed in okra by Dutta (1971) and by Thombre and Deshmukh (2006) in okra GMS line mutant. Latha et al (2003) corroborated single recessive gene control of TGMS in rice and geneic ms in Brassica campestris L. (Borkato and Virmani (1996). The recessive nature of GMS mutants facilitates their deployment in hybrid breeding programme, because any pollen - fertile line can be used as the male parent to develop a commercial okra hybrid. Single gene control of the trait also facilitates its transfer from one genotype to another. This geneic male sterility has been transferred to other commercial varieties like Arka Anamika, Arka Abhay, Parbhani Kranti and other multi- ribbed variety like Bo-13. Use of male sterility in hybrid seed production in okra Geneic Male Sterile line of okra was identified by Division of Vegetable Crops , Indian Institute of Horticultural Research (IIHR), and is being utilized for development of commercial F1 hybrid. Male sterility in okra is controlled by a pair of single, recessive genes and can be utilized for hybrid seed production. Field designs for maximizing hybrid seed yield using male sterile lines under natural cross – pollination have been standardized , and combining ability of the parents using male sterile lines has been worked out (Pitchaimuthu and Dutta, 2002) A field design where alternate planting of two rows of the male sterile plants and one row of fertile plants was done keeping a ratio of 2:1 and maintaining a plant population of 4,166 male sterile plants per hectare, which gave hybrid seed yield of 5.66 quintals per hectare, which was 52.56% higher seed yield in comparison with the fertile control (Dutta, 1980). Using male sterile plants and hand pollination, it takes 3 h to pollinate 274 flowers enough to produce 1 kg of seed. By hand – emasculation and pollinating of 274 perfect flowers takes over 9 h (Dutta, 1980). Thus, approximately 70% saving in time and manual labour is achieved for producing 1 kg of hybrid seeds using male sterile lines in okra. ACKNOWLEDGEMENT We appreciate the technical help provided by Mr. S.K. Ramakrishna Rao (Technical Officer), Ms. D. Vimala (Field Technician) and Mr. Basanna (Mali). REFERENCES Borkato, R.P. and Vimani, S.S. 1996. Genetics of thermosensitive geneic male sterility in rice. Euphyt., 88:1-7 Dutta, O.P. 1971. Effect of gamma irradiation on germination plant growth, floral biology and fruit production in Abelmoschus esculentus. Third International Symp. Trop. Hort., IIHR, Bangalore, India, pp. 141- 156 Dutta, O.P. 1980. Male sterility in okra [Abelmoschus esculentus (L.) Moench.] and bottle gourd [Lagenaria siceraria (Mol.) Standl.] and utilization in hybrid seed production. Ph.D. thesis, UAS, Bangalore Geneic Male Sterility and hybrid seed production in okra J. Hortl. Sci. Vol. 7(2):199-202, 2012 202 Kaul, M.L.H. 1988. Male sterility in higher plants monographs. Theoretical and applied Genetics, Springer- Verlag, New York Kato, M. and Tokumasu, S. 1984. Male sterility in Brassica japonica. 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Genet., 66:353- 354 (MS Received 28 December 2011, Revised 18 June 2012) Pitchaimuthu et al J. Hortl. Sci. Vol. 7(2):199-202, 2012