RÉSUMÉ
Aims: Owing to its export value in flower trade elsewhere in the world, Rose is the key commercial flower crop and the area under rose cultivation is ever increasing and the end-users always prefer new color variations. Hence, evolving new cultivars with novel color characteristics is the need of the hour, for which understanding genetic variation in the available cultivars is very much needed. Study Design: This investigation was conducted to analyze the genetic diversity of 11 elite and commonly cultivated rose accessions in South India by using randomly amplified polymorphic DNA (RAPD) markers.Place and Duration of Study: Department of Floriculture and Landscape Architecture, Horticultural College and Research Institute, TNAU, Coimbatore.Methodology: A total of 10 RAPD primers were employed, which was sufficient to distinguish the investigated rose cultivars.Results: Among the 44 PCR products produced by these markers, 39 (88.64%) were found to be polymorphic bands. The number of amplified products per RAPD primer varied from 3 to 8 with a mean of 4.4 bands per primer. The Un weighted paired group of arithmetic means (UPGMA) dendrogram distinguished the rose accessions into two major clusters suggesting that the accessions were different from each other. The genetic similarity coefficients were determined with this RAPD data, and they were ranged from 0.59 to 0.89.Conclusion: Molecular profiling data of this study have contributed to characterize and catalogue the rose germplasm data, which will be useful to identify the diverse rose lines for further breeding program that have the potential to improve the color variations.
RÉSUMÉ
Crepe jasmine or East Indian rosebay or pinwheel flower, Tabernaemontana divaricata originated from India is a popular large shrub or a small tree grown in tropical and sub-tropical gardens for its beautiful glossy foliage and mild fragrant waxy white, ornamental flowers. It produces flowers throughout the year, except in winter but profusely during summer season. Rather than the opened flowers, the unopened flower buds are commonly used as an alternate to Jasminum sambac buds in off-season. The present investigation was carried out at the Department of Floriculture and Landscape Architecture, Horticulture college and Research Institute, Tamil Nadu agriculture university, Coimbatore during 2022-2023. Randomized Block Design was used with three replications with the objective of investigating promising genotypes of Tabernaemontana divaricata, collected based on the type of petals from different locations for loose flower production. In the study totally 12 accessions were collected and named from Acc. No. 1 to 12. They are evaluated for their vegetative and floral parameters such as plant height, leaf length, leaf width, no. of branches, plant spread in EW & NS direction. Floral parameters include bud length, bud diameter, stalk length and no. of petals/flower. Out of the collected accessions, Acc. No. 2 & 5 are suitable for veni arrangement and Acc. No.10 & 11 are suitable for garland making. Buds of acc. No.4 & 6 are similar to Jasminum sambac and J. auriculatum buds.
RÉSUMÉ
Yellow leaf disease of sugarcane (Saccharum spp.) caused by the Sugarcane yellow leaf virus (SCYLV), vectored by aphids has attained epidemic proportions causing severe yield losses, ranging from 20 to 40 % in susceptible varieties. Yellow leaf spread by aphids depends on cultivar susceptibility as well as weather parameters and thus the present studies were conceptualized. The observations on meteorological parameters were taken from the observatory at the station. The data on incidence of vector(aphids) and yellow leaf disease were recorded at weekly interval during the entire crop growth period on three sugarcane varieties viz., 2005 A 128, 2001 A 63 and 2003 V 46. The data on vector and disease incidence was correlated with weather parameters. The aphid incidence on 2005 A 128 initiated (4.6 per leaf) at 30 SMW and gradually increased to 19.1 per leaf at 40 SMW. In the variety 2001 A 63, the aphid incidence was first observed (2.2 per leaf) at 27 SMW and reached the peak population of 19.1 per leaf at 38 SMW. The aphid incidence on 2003 V 46 initiated (2.1 per leaf) at 29 SMW and gradually increased to 18.1 per leaf at 42 SMW. With regard to yellow leaf disease the incidence was first observed (1.0 per cent) at 26 SMW and reached the peak (28.7 per cent) at 37 SMW in the variety 2005 A 128. In the variety 2001 A 63, the incidence of yellow leaf disease was 1.8 per cent at 26 SMW which later on increased up to 29.4 per cent by 46 SMW. The incidence of yellow leaf disease was 3.5 per cent at 28 SMW which later on increased up to 27.6 per cent by 44 SMW in the variety 2003 V 46.The observations on incidence of aphids and YLD in susceptible varieties revealed that aphids contribute significantly to the initial spread of YLD, from initial incidence of aphids and YLD in 29-30 SW up to 42-44 SMW when the aphids reach peak incidence and YLD also leaps to above 25 per cent. The aphid population exhibited positive correlation with maximum temperature (r2=0.62), minimum temperature (r2=0.55) and relative humidity I (r2=0.65), whereas, negative correlation with rainfall (r2=-0.63). The yellow leaf disease exhibited positive correlation with minimum temperature (r2=0.75) and relative humidity I (r2=0.67), whereas, negative correlation with rainfall (r2=-0.63). The leaf and aphid samples were collected at peak incidence of Yellow leaf disease and were tested and found positive for presence of virus using ELISA reader at 405 nm.