PhD

ABSTRACT
Marigold (Tagetes spp.), one of the commercially grown flower crops in India, is of multipurpose uses in floriculture, pharmaceutical, cosmetic and dye industries. The present investigation entitled “Standardization of production technology for African marigold (Tagetes erecta L.) was undertaken in the Department of Floriculture and Landscaping, during the year 2018-2020. The research programme consisted of five experiments. The first experiment was ‘Performance evaluation of African marigold and evaluation of other Tagetes spp. against bacterial wilt’. Thirty two marigold genotypes from three different species of Tagetes viz., T. erecta, T. patula and T. tenuifolia were evaluated in a wilt sick plot, for assessing bacterial wilt incidence during rainy (June-September) and winter (October–January) seasons. Genotypes of T. erecta M-1 and M-2 did not show bacterial wilt incidence during both seasons and these genotypes were categorised as completely resistant to bacterial wilt. Wilt incidence in other genotypes ranged from 4.16 per cent to 87.50 per cent during rainy season while during winter, it ranged from 27.7 per cent to 100.00 per cent. Compared to rainy season (43.00%), bacterial wilt incidence was more severe during winter season (70.00%). Days to wilt was also very early during winter (26.00 days) than rainy season (71.00 days). Significant negative correlation was observed between flavonoid content (leaves and petals) and bacterial wilt incidence. The causal organism of marigold wilt was characterized and identified as Enterobacter cloacae and this is first report of the bacterium in marigold. The 16SrDNA sequence data were deposited in NCBI (MT649902 and MT649903). From the performance evaluation, it could be observed that the genotypes viz., Bhagwati, Royal Orange, Maria-91, Rupa and P-4 were superior with respect to morphological characters. These F1 hybrids also recorded greater flower weight as well as petal weight. Genotypes P-4, Maria 91 and Bhagwati recorded significantly greater number of flowers per plant (59.10, 52.07, 51.23, respectively), and yield per plant (476.80g, 355.17g, 319.73g respectively). The highest carotenoid content was recorded in the genotype Bhagwati (0.105 mg/g).
In the second experiment, twelve genotypes which were categorized as resistant as well as moderately resistant during field evaluation, were subjected to artificial inoculation studies. The genotypes M-1 and M-2 were found to be completely wilt resistant in artificial screening. Among other genotypes, Bhagwati showed a lower bacterial wilt incidence of 26.00 per cent. The third experiment was conducted with the objective to evaluate rootstocks for T. erecta. Two resistant genotypes viz., M-1 and M-2 were used as rootstocks for grafting nine susceptible genotypes which consisted five F1 hybrids (Bhagwati, Maria 91, Sakuara 031, Suvarna Orange and Suvarna Yellow) and four varieties (Pusa Narangi Gainda, Pusa Basanti Gainda, Double orange and Double Yellow). F1 hybrids recorded better graft survival compared to varieties. Significantly greater graft survival was recorded in Bhagwati and Maria 91, grafted on M-1 rootstock (60% and 54%, respectively) and M-2 rootstock (54% and 50%, respectively). The fourth experiment was conducted during rainy, winter and summer seasons under precision farming system using two selected genotypes viz., Bhagwati and M-1. Irrigation was given @ 75 and 100 per cent Epan and fertigation was given at 75, 100 and 125 per cent of IIHR recommendation (90:90:75 kg/ha) for marigold. During rainy season, fertigation @ 75 per cent RDF (F1) recorded a yield of 35.00 t/ha for Bhagwati and 13.00 t/ha for M-1 which were double the yield in the control treatments of respective genotypes. During winter and summer seasons, irrigation @ 100 per cent Epan along with fertigation @ 125 per cent RDF (I2F3) recorded the greatest yield of 12.50 and 10.00 t/ha respectively in Bhagwati. WUE was the highest in the treatment I2F3 for Bhagwati and M-1 during winter (10.92 kg/ha mm-1, 10.11 kg/ha mm-1) and summer (6.79 kg/ha mm-1, 7.02 kg/ha mm-1) seasons. The fifth experiment was conducted to study the effect of growth regulators on plant growth and yield by using F1 hybrid Bhagwati during rainy and winter season. Spraying growth retardant CCC @ 1000 mg/L during rainy season at 30 and 45 days after transplanting (DAT), was proved to be the best treatment for reducing the plant height (24%) and improvement of yield (14%). CCC @ 1000 mg/L delayed flowering by 12 days compared to control. During winter, spraying growth promoter GA3 @ 300
mg/ L (30 and 45 DAT) was the best for enhancing vegetative growth and yield (28.00%) over control. The study could identify a new wilt causal organism of bacterial wilt in marigold and it was identified as Enterobacter cloacae. Among the thirty two genotypes evaluated, two genotypes viz., M-1 and M-2 were identified as bacterial wilt resistant types. With regard to Tagetes erecta, among the F1 hybrids, Bhagwati, Maria- 91, P-4, Sakura 031 showed better performance in terms of flower yield whereas among the varieties, Double Orange, and Arka Agni and Arka Bangara-2 showed better performance with respect to floral parameters and flower yield. F1 hybrids with good yield but highly susceptible to bacterial wilt can be grafted on resistant rootstock genotypes. F1 hybrids showed better graft survival compared to varieties. Greater graft survival (60%) was recorded for Bhagwati on M-1 rootstock. During rainy season 75 % RDF (90:90:75) was the best with respect to the yield and quality parameters. During winter and summer I2F3 (100% Epan along with 125% RDF) was performing best. Hybrid Bhagwati was performing well during all the seasons studied, with the highest B:C ratio. Genotype M-1 can be suggested as an alternate variety during winter season. During rainy season spraying CCC @ 1000 mg/L (30 and 45 DAT) was found the best treatment for reduction in plant height (24%) and increased yield (14%) over control. CCC @ 1000 mg/L can also be used for delaying flowering in marigold. During winter, spraying GA3 @ 300 mg/L or 200 mg/L (30 and 45 DAT) enhanced the plant height (15%, 11% respectively) and yield per plant (28%, 22% respectively) over control.