INTRODUCTION Gladiolus (Gladiolus hybridus Hort.) is a glamorous bulbous flower combining beauty and perfection. It is one of the most attractive and popular bulbous flowers much- acclaimed for its majestic spikes possessing attractive, elegant and delicate florets. It is said to be the ‘Queen of bulbous flower crops’ and is commonly called ‘Sword lily; It belongs to the family Iridaceae with its origin in South Africa. India, with its varied climatic conditions in different parts, offers the possibility of growing gladiolus round the year, in one or the other part of the country. However, phenotypic expression of a character is governed mainly by genetic makeup of the plant, the environment in which it grows and interaction between genotype and the environment. Genotype environmental interactions (GxE) pose a major problem in developing new cultivars and choosing suitable cultivars for any specific location, to identify the most desirable genotypes. Presence of a high (GxE) interaction complicates breeding work because it is difficult to predict how genotypes selected under a given Stability analysis for earliness and corm characters in gladiolus (Gladiolus hybridus Hort.) Naik Kirtimala, S.K. Nataraj, B.S. Kulkarni and B.S. Reddy Biotechnology Centre, P.B.7648, Hulimavu, B.G. Road, Bangalore-560 076, India E-mail: kirtiflori@gmail.com ABSTRACT A field study was conducted in gladiolus (Gladiolus hybridus Hort.) in the floriculture field of Department of Floriculture and Landscaping, KRCCH (University of Agricultural Sciences, Dharwad) during 2005-2006. Fourteen promising cultivars were planted under three environments, viz, shade-house, polyhouse and the open condition, and tested for various characters related to earliness. Genotypes x Environment interactions were significant for days to spike emergence and days from first floret to last floret opening. For days to corm sprouting, genotypes Sylvia (4.24), American Beauty (7.87), Candiman (9.6), White Prosperity and Priscilla (12.09) showed low mean values, i.e., early sprouting. For days taken from first to last floret opening, genotypes Eighth Wonder (15.87), Melody (14.51), Friendship (14.49), Pricilla (14.29), Pacifica (13.80), White Prosperity (13.80) and Vedanapoli (13.56) were stable, with high mean values. On the basis of mean performance, the genotype Vedanapoli was stable for number of daughter corms per plant (2.22). Genotypes Pacifica (6.13cm) and Eighth Wonder (6.09cm) were stable for corm diameter, with high mean values. Though ‘Vedanapoli’ showed unpredictable performance for average weight of corm, ten cormel weight and number of cormels per plant, it gave the highest corm yield per plant and showed predictable performance for corm diameter, exhibiting a great promise for hybridization with consistent corm yield outcome. Key words: Gladiolus, stability, environment set of conditions will perform under a different set of conditions (Ceccarelli, 1989). Stable genotypes are of great importance because environmental conditions may vary from season to season and year to year. Although a number of gladiolus varieties are recommended for cultivation, information on stability is lacking on flowering attributes, yield and quality parameters of corms and cormels which are a major source of propagation in this crop. Therefore, the present study was undertaken taking fourteen gladiolus genotypes under three different environments. MATERIAL AND METHODS The present experiment was laid out at the floricultural field of Department of Floriculture and Landscaping, Kittur Rani Channamma College of Horticulture (University of Agricultural Sciences, Dharwad) during 2005-2006. Fourteen promising cultivars, viz., American Beauty, Sylvia, Melody, Summer Sunshine, Vedanapoli, Magic, Copper King, Red Ginger, Candiman, Priscilla, Jester Yellow, White Friendship, White Prosperity, Eighth Wonder and Pacifica were planted under three environments, viz., shade-house, J. Hortl. Sci. Vol. 6(1):41-45, 2011 42 polyhouse and the open condition, and tested for various characters related to earliness. Corms of optimum size 4- 5cm dia were planted at 30x30cm spacing at a depth of 5- 6cm. Beds of 45cm height and 65cm width were prepared by thoroughly digging to 30cm depth. Well-decomposed FYM was applied @25 t ha-1 and mixed well into the soil. Recommended dose of NPK fertilizer @ 100:60:60kg ha-1 (Anony., 2002) was applied through urea, SSP and MOP, respectively. Fifty percent of nitrogen and the full dose of phosphorus and potash were applied as basal dose, and the remaining fifty per cent of nitrogen was applied 45 days after planting. Uniform cultural practices were imposed throughout experimentation. Observations were recorded on number of days taken for corms to sprout, days taken to spike initiation, days taken for first floret opening, days taken from first floret to last floret opening, number of daughter- corms per plant, number of cormels per plant, diameter of daughter corms, and average weight of daughter-corms and cormels. Analysis was made following three replications and observations were recorded from five labeled plants. Stability was analyzed with SPAR package for analysis using Eberhart and Russell (1966) model, which provided three parameters of stability, i.e mean, regression co-efficient (b i ) computed using students t-test and deviation mean squares (S2d i ), computed using F-Test. RESULTS AND DISCUSSION Analysis of Variance (Table 1) for genotypes was highly significant for days to corm sprouting, spike emergence, days taken for spike initiation, days taken for first floret opening and days taken from first floret to last floret opening, indicating significant difference among genotypes. Such variation was also reported earlier by Arora and Sharma (1991) in gladiolus. Significant difference among environments was also observed for all characters, except days to spike emergence. Similar difference was also observed by Mishra and Gupta (2005) in carnation. Significant linear portion of environmental variance indicated considerable additive environmental variance. Environmental variance was observed to be of considerable magnitude as indicated by significance of environment (linear) component for number of cormels per plant and corm diameter. Similar results were obtained by Dhaduk et al (2004) in tomato. Genotype x Environment interaction was not significant for days taken to spike emergence and days taken for first floret opening. Hence, the genotypes are seen to be stable for these traits across environments. Genotype x Environment interaction and pooled deviation mean squares (non-linear) were found to be significant for all the corm characters, indicating contribution of both linear and non-linear components to GE interaction variance for these characters. Variance due to environment + (genotype x environment) and variance due to environment (linear) were highly significant for all characters, except days required for first flower opening. Significant pooled deviations were observed for all the characters indicating that this quantum of variance, which is unpredictable, formed a major part of the Genotype x Environment interaction among genotypes. The non-significant Genotype x Environment (linear) interactions for these characters and significant pooled Table 1. Pooled analysis of variance (mean square) for earliness and corm characters in gladiolus S.N Source of Df Days Days for Days Days from Number Number Corm Average variation for corm spike for first first to of corms of cormels diameter corm sprouting initiation floret last floret per plant per plant (cm) weight opening opening (g) 1 Genotype 13 68.52** 180.94** 179.56** 6.13 1.256** 4576.20* 2.14** 1310.8** 2 Environment 2 15.93** 11.17 14.95 19.38** 0.36 8726.34** 1.70** 770.75 3 Genotype x 26 0.46** 4.56 9.23 2.39** 0.154** 1103.96** 0.17** 206.01** Environment 4 Environment 28 1.56** 5.02* 9.6 3.60** 0.169** 1648.41** 0.28** 246.35** +(genotype x environment) 5 Environment 1 31.86** 22.34* 29.96 38.76** 0.73* 17452.7** 3.40** 1541.47* (linear) 6 Genotype x 13 0.59** 3.9 5.34 2.11 0.14 1426.32 0.18 92.50 environment (linear) 7 Pooled 14 0.31** 4.8* 12.18** 2.48** 0.15** 725.76** 0.15** 296.69** deviation 8 Pooled error 78 0.07 3.5 7.52 0.07 0.03 2 0.018 1.55 * and ** indicate significance at 5% and 1%, respectively, Df - Degree of freedom Naik Kirtimala et al J. Hortl. Sci. Vol. 6(1):41-45, 2011 43 deviation mean squares suggest a greater importance of non-linear component of the genotype-environment interaction and presence of both predictable and unpredictable components in the genotype x environment interaction. Such pooled deviations were also reported by Narayannakutty (2005) in snake gourd. Significant Genotype x Environment interaction leads to identification of stable genotypes. Stability parameters, viz., mean, regression co- efficient (b i ) and deviation from regression (S2d i ) were computed using Eberhart and Rusell model (1966) given in Table 2, 3 & 4. An ideal genotype, according to Eberhart and Russell (1966), would be one having high mean, unit regression co-efficient (b i =1) and low deviation mean squares (S2d i =0). If regression co-efficient (b i ) is greater than unity with high mean values, the genotype is considered to possess below-average stability and is highly sensitive to environments. Regression co-efficient (bi<1) with high mean values indicates above-average stability and can adapt to poor environments. If regression co-efficient (b i ) is equal to unity (b i =1) with high mean values, this indicates average sensitivity to environmental changes and adaptation to various environments. Stable genotypes are those that interact less with the environment, giving consistent performance across environments. An ideal genotype, according to Eberhart and Russell (1966), is one that interacts less with the environment with high mean values, regression coefficient (b i =1) close to unity and (S2d i =0) not deviating significantly from zero. For days to corm sprouting (Table 2), genotypes Sylvia (4.24), American Beauty (7.87), Candiman (9.6), WhiteProsperity and Priscilla (12.09) showed low mean values, which is advantageous for earliness and regression coefficient around unity, with non-significant deviation from regression. Hence, these genotypes were stable and predicable. Genotype x Environment interactions were significant for days taken to corm sprouting and days from first floret to last floret opening, suggesting variable performance of cultivars under different environments. Variance due to environment + (genotypex environment) and variance due to environment (linear) were highly significant for all characters except for day taken for first floret opening. Genotype x Environment interaction was not significant for days taken for spike emergence and days taken for first floret opening and, hence, the genotypes were stable for these traits across environments. Therefore, stability for these characters has not been tabulated for days taken from first to last floret opening (Table 1). Genotypes Eighth Wonder (15.87), Melody (14.51), Friendship (14.49), Priscilla (14.29), Pacifica (13.80), White Prosperity (13.80) and Vedanapoli (13.56) were stable, with high mean values and regression coefficient around unity but were unpredictable, as observed by their significant deviation from regression coefficient. Such varied responsiveness of genotypes in changing environments has been earlier reported by Deshraj and Mishra (1998) in gladiolus for the same traits. This parameter is an important estimate for determining self-life of gladiolus. But, due to the influence of environment on genotype, it is unpredictable. Therefore, flowering duration is seen to ultimately depend on the season and the environment. On the basis of mean performance, genotype Vedanapoli was stable for the number of daughter-corms per plant (2.22) (Table 3). Genotypes Sylvia, Priscilla, American Beauty and Copper King showed high mean values, with (b i =1), but were not predictable as these showed significant deviation from the regression slope. Genotype Melody produced the maximum number of cormels (170.96) Table 2. Stability parameters for corm sprouting and days from first to last floret opening Variety Number of Days taken from days required first to last floret for sprouting opening Mean b i S2d I Mean b i S2d I American 7.87 0.29 0.04 12.33 -0.04 0.51** Beauty Sylvia 4.24 0.95 -0.02 10.09 0.68 3.60** Melody 9.29 1.09 0.46** 14.51 2.16 4.20** Summer 14.42 1.27 0.04 12.44 2.68 6.85** Sunshine Vedanapoli 18.62 1.36 0.00 13.56 -0.20 2.98** Copper King 18.53 1.32 1.13** 12.78 0.69 4.47** Red Ginger 6.22 0.40 0.10* 12.25 1.75 0.17** Candiman 9.60 0.37 -0.01 12.80 0.16 0.77** Priscilla 12.09 0.52 -0.02 14.29 0.95 7.17** Jester 15.04 1.21 1.31** 11.73 0.95 0.46** Yellow White 13.60 0.38 0.47** 14.49 0.67 1.16** Friendship White 10.56 1.67 0.06 12.91 2.14 0.62** Prosperity Eighth 20.24 1.66 0.45** 15.87 0.43 0.28** Wonder Pacifica 12.96 1.52 -0.02 13.80 0.98 1.19** Mean 12.38 13.13 SEm± 0.39 0.36 1.11 0.94 *, ** - Deviation from regression differed significantly from zero at p = 0.05 and p = 0.01, respectively Stability analysis in gladiolus J. Hortl. Sci. Vol. 6(1):41-45, 2011 44 and was seen to be stable for this trait, whereas, the other genotypes showed unpredictable performance for number of cormels due to their significant deviation from the regression slope. Varied response for yield of rhizomes was earlier reported (Khar et al, 2005) in ginger grown under different environments. Genotypes Pacifica (6.13cm) and Eighth Wonder (6.09cm) were stable for corm diameter, with high mean values (Table 4). Genotypes Summer Sunshine, Candiman, Jester Yellow and White Prosperity showed high mean values, but were linearly not predictable. Such response of genotypes in changing environments was reported earlier by Ibrahim and George (1985) for tuber diameter in the sweet potato. Genotypes Summer Sunshine, Copper King, Red Ginger, Candiman and White Friendship were stable, with high mean values and non-significant regression co- efficient, but were linearly unpredictable for weight of 10 cormels per plant. Genotypes Melody, Priscilla and White Prosperity were stable but showed low mean values and, hence, were poorly adapted to different environments. Genotypes Summer Sunshine, Vedanapoli, Candiman, Priscilla and Jester Yellow showed high mean values, but were linearly unpredictable for average weight of corms. Genotypes White Friendship, White Prosperity and Pacifica Table 4. Stability parameters for average corm weight per plant and corm diameter as influenced by variety and environment in gladiolus Variety Average corm weight (g) Corm diameter (cm) Mean b i S2d i Mean b I S2d i American 51.34 -0.47 56.53** 5.42 0.40 0.56** Beauty Sylvia 29.33 0.77 15.76** 4.30 0.53 0.37** Melody 40.70 0.81 93.87** 5.12 1.72 -0.01 Summer 98.25 3.00 2138.94** 7.16 3.32 0.17** Sunshine Vedanapoli 55.80 0.53 340.51** 5.69 0.17 0.00 Copper King 41.98 0.65 16.26** 5.04 0.55 0.05** Red Ginger 47.44 1.26 208.86** 5.81 1.20 -0.01 Candiman 97.33 1.71 840.02** 7.65 1.61 0.05** Priscilla 65.56 1.06 111.94** 5.88 0.28 0.30** Jester 71.32 2.28 162.81** 6.50 0.72 0.11** Yellow White 47.61 0.93 0.38 5.74 1.22 0.12** Friendship White 39.85 1.15 -0.42 5.97 1.27 0.41** Prosperity Eighth 49.64 -0.41 160.26** 6.09 -0.10 0.00 Wonder Pacifica 39.97 0.72 0.28 6.12 1.11 -0.01 Mean 55.43 5.89 12.17 1.64 0.28 0.80 * - Deviation from regression differed significantly from zero at p = 0.05 ** - Deviation from regression differed significantly from zero at p = 0.01 Table 3. Stability parameters for number of corms and cormels per plant as influenced by varieties and environment in gladiolus Variety No. of corms per plant No. of cormels per plant Mean b i S2d i Mean b i S2d i American 2.18 2.68 0.63** 62.13 -0.01 1919.58** Beauty Sylvia 3.44 2.63 0.06** 104.64 2.09 364.42** Melody 1.33 -0.70 -0.01 170.96 1.56 -0.33 Summer 1.53 0.87 0.06** 42.27 0.19 1211.73** Sunshine Vedanapoli 2.22 1.02 0.04 118.81 3.91 1547.87** Copper King 2.02 2.62 0.93** 25.11 0.16 156.24** Red Ginger 1.53 2.25 0.00 74.60 0.85 447.94** Candiman 1.82 0.78 0.00 35.98 -0.10 75.19** Priscilla 2.76 3.76 0.18** 88.04 1.17 194.85** Jester 1.09 0.15 -0.01 51.58 0.23 556.27** Yellow White 1.60 0.99 0.11** 76.51 0.39 2417.17** Friendship White 1.40 -2.10 0.00 40.44 0.78 563.57** Prosperity Eighth 1.42 -0.48 0.02 95.73 1.31 657.82** Wonder Pacifica 1.29 -0.48 0.02 91.89 1.44 39.03** Mean 1.83 77.05 0.27 1.72 10.76 0.76 ** - Deviation from regression differed significantly from zero at p = 0.01 were stable and predictable, but showed lower mean values and were, hence, poorly adapted to different environments. The present study demonstrates that excepting time taken from first to last floret opening, all the other characters studied are not influenced by environment to any great extent. In view of improvement in flowering habit, there is a further need for studies on this aspect. As corms are the main source of propagation in gladiolus, genotypes showing high yields with stables performance across environments should be selected. Hence for mass production of corms, Vedanapoli and Melody can be considered as ideal genotypes. REFERENCES Anonymous. 2002. Package of Practices for Horticultural Crops. UAS, Dharwad Arora, J.S. and Sharma, S.C. 1991. Genotype x Environment interaction of some quantitative traits in gladiolus. Ind. J. Hort., 48:83-86 Ceccarelli, S. 1989. Wide adaptation: How wide? Euphytica, 40:197-205 Deshraj, A. and Mishra, R.L. 1998. Stability analysis in Naik Kirtimala et al J. Hortl. Sci. Vol. 6(1):41-45, 2011 45 gladiolus-II: floral characters. J. Orn. Horti., 1: 13-16 Dhaduk, L.K., Mehta, D.R. and Pandya, H.M. 2004. Phenotypic stability analysis in tomato (Lycopersicone sculentum Mill). Veg. Sci., 31: 60-62 Eberhart, S.A. and Russell, N.A. 1966. Stability parameters for comparing varieties. Crop Sci., 6:36-40 Ibrahim, K.K. and George, K. 1985. Stability parameters association in sweet potato [Ipomea batataus (L.) Lam.] and their implications in breeding strategies. (MS Received 22 September 2010, Revised 7 April 2011) South Ind. Horti., 4:83-90 Khar, A., Asha Devi, A., Mahajan, V. and Lawande, K.E. 2005. Genotype x environment interactions and stability analysis in elite lines of garlic (Allium sativum L.). J. Spices & Aromatic Crops., 14:21-27 Mishra, S. and Gupta, Y.C. 2005. Stability analysis in carnation. Progressive Horti., 37:406-411 Narayanankutty, C., Jaikumaran, U. and Karuppaiyan, R. 2005. Genotype x Environment interaction and stability analysis in snake gourd (Trichosanthes anguina). Ind. J. Agril. Sci., 75:763-765 Stability analysis in gladiolus J. Hortl. Sci. Vol. 6(1):41-45, 2011