MOLECULAR CHARACTERIZATION AND MANAGEMENT OF WHITE RUST OF CHRYSANTHEMUM CAUSED BY Pucciniahoriana P. Hennings
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Date
2018-06
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University of Horticultural Sciences, Bagalkot. (College of Horticulture, Bengaluru)
Abstract
Chrysanthemum (Dendranthema x grandiflorum Tzvelev) is one of the most important and widely cultivated commercial flower crops in South India. The crop is prone to be affected by several diseases. Among them, white rust of chrysanthemum caused by Puccinia horiana P. Hennings is a serious fungal disease, which is regarded as a quarantine pest in many countries. The symptoms of the disease include occurrence of numerous, light green to yellowish spots on the upper surface of leaves and pinkish coloured, buff, waxy raised pustules on the corresponding lower surface of infected leaves. Later, the raised pustules get matured and finally infected leaves become necrotic, distorted, coalesce and fall off. The pathogen upon artificial inoculation yielded the characteristic symptoms on 16th day after inoculation with the production of telia in later stage. It is obligate, microcyclic rust which produces pale yellowish, pedicellate up to 40 μm long, bicelled teliospores produced in telium and the dimensions ranged from 20-40 x 10-18 μm and upon germination, it produced hyaline basidiospores. Further, the identity of pathogen was confirmed by PCR amplification of rDNA gene using specific primers: Ph-F1/ Ph-R1 and Ph-F2/ Ph-R1, which yielded an amplicon size of 340 and 240 bp respectively. The maximum disease intensity 21.32 per cent was observed in the crop planted in the month of August-2017. Among the four cultivars used for biochemical studies, Arka pink star and Arka chandrakanth had not expressed any symptoms. While, Arka chandrika and Rajat was found to be susceptible by producing symptoms on 14th day after inoculation. The Phenylalanine Ammonia-Lyase (PAL), Peroxidase (POD) and PolyPhenol Oxidase (PPO) and phenol activities were more in resistant than susceptible cultivars and these defensive enzymes were closely associated with resistance to Puccinia horiana. The Thiophanate methyl (T7) @ 0.1 per cent followed by Propiconazole (T4) @ 0.1 per cent and Azoxystrobin (T8) @ 0.1 per cent was found to be very effective for the management of the disease.