MSc

The present investigation entitled “Evaluation of African marigold (Tagetes erecta L.) hybrids/varieties for yield and resistance to bacterial wilt” was undertaken at Agricultural Research Station, Mannuthy during the year 2016-17. Performance of eight African marigold genotypes (5 F1 hybrids, 2 varieties and 1 local collection) was evaluated under five experiments viz., field evaluation for yield and bacterial wilt resistance, screening against bacterial wilt through artificial inoculation, field screening against bacterial wilt through spot planting technique, grafting studies and post-harvest studies.

Field evaluation of genotypes showed wide variation for characters studied. Plant height was significantly more in genotype Royal Orange, P-4 and Maria 91 whereas plant spread was high for P-4, Royal Orange, Maria 91 and M-1. Stem girth did not differ significantly among genotypes. Number of primary branches was more in all genotypes except the IIHR varieties. Maximum leaf area was observed in the genotype M-1 (68.75 cm2). All the genotypes had green coloured petiole. Except M-1, all the genotypes took period ranging from 28 to 31 days to initiate flower buds whereas M-1 was very late (50.62). However, days to flower opening was almost similar for all the genotypes. The genotypes P-4 and Rupa recorded largest flowers (9.08 cm and 9.06 cm, respectively). Flowers with longer stalk were observed in Royal Orange, P-4, Arka Agni and Arka Bangara 2. Fresh flower weight and petal yield per flower were very high for Rupa (23.36 g and 18.16 g) and P-4 (22.66 g and 16.56 g). The genotype P-4 recorded the maximum number of flowers (116.91) and yield per plant (1.034 kg). Number of harvests was more for genotypes Rupa, Royal Orange, P-4, Arka Agni and Arka Bangara 2. Carotenoid content did not vary among the genotypes. The genotype M-1 was observed as 100 per cent resistant to bacterial wilt whereas Sakura 031 was found to be highly susceptible, expressing disease incidence at vegetative stage itself.

Under artificial inoculation also, the genotype M-1 was found to be resistant to bacterial wilt and Sakura 031 was highly susceptible (100 per cent incidence). All the three inoculation methods viz., root dip, media drenching and stem injection recorded


the same efficacy in inducing the disease. Under spot planting technique also, M-1 spot planted with Sakura 031 showed no wilt incidence. Disease incidence in check genotype Sakura 031 ranged from 83.33 to 100 per cent whereas the disease incidence in genotypes spot planted with Sakura 031 ranged from 0 to 100 per cent.

For grafting studies, the genotype M-1 was used as rootstock for the other genotypes. Bacterial wilt incidence was not observed in grafted plants of all the genotypes. However in non-grafts the disease incidence ranged from 55.05 to 77.77 per cent. Maximum field survival of the grafts was recorded in P-4 (94.44 %). Irrespective of the genotypes, grafted plants showed significantly higher plant height and leaf area when compared to non-grafted plants. There were no significant differences observed in plant spread and number of branches between grafted and non-grafted plants. Grafted plants were significantly earlier to initiate flower buds (28.43 days) compared to non-grafted plants (29.36 days). However for flower opening, grafted plants took more days (10.37) compared to non-grafted plants (9.19). There was no significant difference observed between grafted and non-grafted plants with respect to flower diameter, stalk length, flower weight and petal yield per flower. Irrespective of the genotypes, grafted plants showed significantly higher number of flowers, yield per plant and more number of harvests.

Among the genotypes studied, shelf life of flowers ranged from 3 to 5 days under ambient storage condition. All the genotypes showed an accelerated loss in weight of flowers after three days of storage.

The study clearly showed that the genotype P-4 was found to be promising with high yield, large sized flowers and moderate susceptibility to bacterial wilt. The genotype M-1 was 100 per cent wilt resistant whereas Sakura 031 was found to be 100 per cent susceptible to bacterial wilt. The genotype M-1 can be used as rootstock for grafting susceptible genotypes. Grafting the susceptible genotypes on resistant rootstock was found to be an effective tool to combat the bacterial wilt. In general grafted plants of all genotypes produced more yield.