Heterobeltiosis in French Marigold (Tagetes patula L.)

The studies on heterosis were carried with four male sterile lines namely; ms7, ms8, ms9, ms10 and 18 diverse pollinators as tester by using line × tester crossing programme. The 72 F1 hybrids were produced and evaluated along with 22 parental lines during summer 2009 and rainy season 2009 in Randomized Block Design. Observations were recorded on nine quantitative traits during both the seasons. Highly significant variances for all the traits indicated the sufficient variability in the parental material for all the characters under study. The performance of F1 hybrids was much better than the mean performance of parents during both the crop seasons. Appreciable heterosis was observed in all the characters, except flower weight in summer and plant height in rainy season.


Introduction
Marigold (Tagetes spp.) is one of the major loose flower crop among ornamentals, and grown commercially in all states of India.It gained popularity among crops due to its easy culture and wider adaptability.It is commonly grown as loose flowers and highly suitable for cultivation under different agro-climatic conditions.Marigold is especially used for festive occasions, marriages, religious ceremonies, social function and in landscape plans due to its wide range of attractive colour, shape, size and having good keeping quality.Besides this, its leaves and flowers are equally important for medicinal value (Tripathy et al., 1991).Now a day, marigold is used as a source of pigment for poultry feed.Carotenoids are used as poultry feed mix and food colourant (Sreekala et al., 2002).In recent years, Exploitation of heterosis proved to be most viable and successful technology in increasing productivity and the production.The hybrids have various advantages over open pollinated varieties like; earliness, profuse and uniform flowering, increased flower weight, large flower size, elongated flower stalk, longer flower duration etc. Apetalous and double-flowered (Goldsmith, 1963) are two kinds of male sterility found in marigold and with the availability of male sterile line, hybridization becomes economically viable and commercially feasible.

Material and Methods
The field experiment were carried out at the experimental farm of the Department of Floriculture and Landscaping, University of Horticulture and Forestry, Nauni, Solan (H.P.) during summer and rainy season (2009).The parental material used for present studies consisted of four male sterile lines namely; ms 7 , ms 8 , ms 9 and ms 10 .A set of 18 diverse testers/ pollinators were used for crossing with each four male sterile lines.
Seeds of all the parental materials viz male sterile lines and testers were sown during summer and rainy season in the nursery to raise the seedlings.Transplanting of these seedlings was carried out after one month of sowing of the seeds in the nursery.The experiment was laid in polyhouse.The seedlings were planted at a spacing of 30 × 30 cm and the standard cultural practices were followed as per the requirement of the crop.Buds of male sterile lines were bagged before anthesis to avoid contamination from unwanted pollens.The testers were also bagged to avoid cross pollination and to ensure their progenies.For producing F 1 hybrids, 4 male sterile lines were crossed with 18 testers in line × tester fashion (Kempthorne, 1957), resulting into 72 F 1 hybrid combinations at a stage when the flowers of male sterile lines were fully opened.Crossing was done from 9:30 AM to 1.30 PM and was repeated for three consecutive days to ensure good seed set.These crossed flowers were again bagged and labeled.The resulting seeds from all the 72 hybrid combinations were harvested and kept separately in plastic moisture proof seed jars.
The 72 cross combinations made during 2008 were raised during March-July (summer) and July-November (rainy) 2009, respectively, along with parents comprising lines and testers in-order to judge their performance for biochemical and commercial traits.The experiment was laid out in Completely Randomized Block Design with three replications in both the seasons.The data recorded on 72 crosses along with 18 testers and 4 lines was used to estimate heterosis over better parent using appropriate formulae and statistical package SPAR 2.0.The ANOVA for randomized block design in the present study was calculated (Tables 5 and 6) according to the model suggested by Panse and Sukhatme (1967).Heterosis was calculated as deviation of the F 1 mean from the better parent (BP) (Hayes et al., 1955).

Results and Discussion
Exploitation of heterosis proved to be most viable and successful technology of increasing productivity and the production.Success achieved in production and cultivation of F 1 hybrids in maize, sorghum and pearl millet, encouraged the application of this technique even in self-pollinated crops like cotton (Basu et al., 1995) and rice (Paroda, 1995).In vegetables crops, production of F 1 hybrids are being increasingly adopted (Kalloo, 1996).However in ornamentals plants, this technique is to be fully exploited (Swarup, 1995).Line × testers is very helpful in selecting the lines on the basis of their combining ability.The significant means sum of square due to parents vs. crosses in both the seasons for most of the traits suggested sufficient diversity among the parental material (lines and testers) and the crosses.Further, the significant sum of square for all the traits during both the seasons reflected a wide range of diverse hybrids generated as given in Tables 3 and 4. The 72 F 1 hybrids were produced and evaluated along with 22 parental lines during summer 2009 and rainy season 2009 in Randomized Block Design.Thus, these hybrids could be selected for some particular desirable traits based on their performance for these characters.

Early Flowering
During summer and rainy season, among male sterile line ms 9 (53.27days) and ms 10 (48.07 days) were found significantly early in flowering.However, tester Spray Boy (54.33 days) and French Bonita-6 (45.53 days) were earliest to flower.Among hybrids, ms 10 × Single Petal Red (48.13) days was earliest in flowering during summer and ms 7 × Nana Jambo Bicolour (45.33 days) during rainy season.It revealed the non additive gene action.The selection at later stages might be useful.

Plant Height
Minimum height is consider in French marigold as it can be grown as potted plant and in turn increase the yield.Hybrid ms 7 × Single Petal Red showed minimum plant height (21.40 cm) while its parent ms 7 × Single Petal Red had higher plant heights in summer season while in rainy season ms 7 × Sunkist had minimum plant height (33.60 cm) while its parent ms 7 (99.37 cm) and Sunkist (32.53 cm) both were taller which clearly showed that genes controlling the plant height in parent were showing non additive gene action in hybrids.Thus, it would be advisable to delay the selection at later generation in order to improve the plant height

Plant Spread
In the summer, maximum plant spread was exhibited by ms 9 (34.87 cm) and ms 7 (39.10 cm) during rainy season.The testers, Spray Mix-1 showed maximum plant spread (32.70 cm) during both the seasons.In both season, male sterile line ms 7 flowered for longest duration.Within the set of hybrids, ms 9 × Single Petal Red (39.97 cm) revealed maximum plant spread during summer and ms 10 × Spray Mix-1 (48.37cm) during rainy season.Plant spread and plant height is interrelated.It was found that for plant spread male sterile lines as well as testers had lower values for the traits during both the season in comparison to hybrids, thus suggesting the presence of divergent gene in the parents which helped in heterotic with more plant spread.

Flowering Duration
Among testers, Cupidon Orange (51.87 days) and French Bonita 6 remained in flowering for maximum duration (56.47 days) during summer and rainy season.The best hybrid ms 10 × Safari Queen flowered for the longest duration (53.40 days) in summer season and ms 10 × Spray mix-1 flowered for the maximum duration (74.47 days) in rainy season.

Number of Flowers per Plant
The most important characters which contributes towards the production, is the number of flowers per plant.Hybrid values were higher for number of flowers per plant than those of the parents during both the seasons which indicated that, for this trait widely diversed genes were present in both the parents which lead to heterotic hybrids in both the seasons.Among hybrids, ms 9 × Single Petal Red produced maximum number of flowers per plant (104.33)during summer and in rainy season ms 9 × French Bonita-2 produced maximum number of flowers per plant (96.47).

Flower Size
Flower size is another desirable character as flowers of marigold are being used for making garland and other decorative and religious purposes.FM-786 produced maximum number of flowers per plant (56.60 flowers) during summer and Nana Jambo Bicolour (49.27) during rainy season.Among the 72 hybrids ms 7 × Cupidon Yellow produced largest flower in both seasons.The remarkable increase in flower size indicated the presence of non additive gene action for the traits and selection at later stages would be useful.

Flower Weight
ms 8 (1.90 g) and ms 10 (2.00 g) among lines and Cupidon Yellow (3.06 g) and Cupidon Orange (1.47 g) among testers, were found maximum flower weight during respective season.Within different hybrid combinations, ms 8 × Hero B recorded highest flower weight (2.05 g) during summer and Cupidon Orange registered maximum flower weight (1.47 g) during rainy season as indicated in fig.Thus, it was clearly evident that the non additive gene action leads to the production of hybrid with very higher flower weight surpassing the range of both the parents.In this case, selection at later stages would be adopted.

Flower Yield
The most important character which contributes towards the more number of flowers and more flower weight is the flower yield.The means of flower yield per plant of hybrids was higher than the mean flower yield per plant of parents during both crop seasons.In summer season, hybrid ms 8 × FM-786 gave highest flower yield of 145.91 g, while the flower yield of parents were 27.12 g and 92.67 g, respectively.In rainy season, hybrid ms 10 × French Bonita-1 yielded 155.73 g flowers and its parents produced 73.67 g and 37.22 g flowers, respectively, proving that the highly divergent genes are present in these parents when brought together in hybrid combination and produced the F 1 hybrids with exceptionally high heterosis.

Carotene Content
Out of various hybrids combinations, ms 7 × Single Petal Red (771.00 g) and ms 10 × French Bonita-4 recorded maximum carotenes content (1084.00g) during respective seasons.The highest heterosis was obtained in carotene content which was 45.96%.duringsummer crop and 193.85%.duringrainy crop.
Appreciable heterosis was observed in all the characters during summer and rainy season except flower weight and plant height, respectively.The highest heterosis was obtained in flower yield which was 148.28% during summer crop (Table 1) and 220.94% (Table 2) during rainy crop.During summer season, significantly positive heterobeltiosis was observed in 2 hybrids and 32 hybrids during rainy season out of 72 hybrids.During summer, hybrid ms 7 × French Bonita-2 (148.28%) and during rainy season ms 8 × French Bonita-6 (220.94%)recorded highest percentage of heterosis.During summer season, significantly positive heterobeltiosis was observed in 8 hybrids and 11 hybrids during rainy season out of 72 hybrids.During summer, hybrid ms 9 × Sunkist (45.96%) and during rainy season ms 8 × Safari Queen (193.85%)recorded highest percentage of heterosis.The highest heterosis observed in other traits was -13.33% days taken to flowering, -26.64% for plant height, 37.09% for plant spread, 23.60% for duration of flowering, 141.49% for number of flowers per plant, 48.68% for flower size during summer season.During rainy crop, the highest heterosis observed in other traits was -15.54% days taken to flowering, 36.42% for plant spread, 49.79% for duration of flowering, 205.92% for number of flowers per plant, 48.62% for flower size and flower weight 93.48%. in all the characters, the best performing F1 was better than the better parent.

Table 1 .
Heterosis per cent of hybrids over better parent during summer season 2009 *: Significance at 5% of level of significance.

Table 2 .
Heterosis percentage of hybrid over better parent during rainy season 2009 *: Significance at 5% of level of significance.

Table 3 .
Mean performance of parents and hybrids during summer season 2009

Table 4 .
Mean performance of parents and hybrids during rainy season 2009

Table 5 .
Analysis of variance for Line × Tester including parents during summer season 2009Note.*: Significance at 5% of level of significance.

Table 6 .
Analysis of variance for Line × Tester including parents during rainy season 2009