Epidemiology and Management of Corm Rot of Saffron

Abstract

AbstractSaffron, a low volume high value crop, is obtained from the dried stigmas of Crocus sativus flowers. The major constituents of saffron are phytochemicals like crocin, picrocrocin, safranal and crocetin, which attribute to its broad spectrum medicinal properties, because of which it has attained the status of being one of the costliest dietary spices. Saffron is mainly being cultivated in Iran, India, Afghanistan, Greece, Italy, Spain, etc. Though limited to only four districts of the Union Territory of Jammu and Kashmir, India has the second largest area under saffron cultivation, after Iran. However, in India saffron productivity is very low (2.0–2.5 kg/ha) as compared to other countries. In the recent past its production has declined in several countries, due to the vegetatively propagated and labour intensive nature of the crop, genetic erosion, lack of modern cultivation practices and mechanization, urbanization of traditional saffron cultivation land, and prevalence of corm rot of saffron. Saffron has antioxidant, radical scavenging and anti-inflammatory properties, and acts as anti-arthritic agents reducing cholesterol and triglycerides. It acts against stress and anxiety and also helps in decreasing depressive conditions. Saffron has immunological effects and is effective against neurological diseases including Alzheimer and Parkinson-like behaviour. It also shows anti-cancer properties, and its extract reduces dental caries. Saffron has also been used to dye textiles and in human and animal histological staining. It is as well used in various cuisines, confectionaries and non-alcoholic beverages. Corm rot, prevalent in almost all the saffron growing areas, has emerged as one of the major limitations for the successful cultivation of saffron, globally. The disease is primarily noticed during flowering (October–November) and grubbing stages (May–July) and is manifested as symptoms like drooping, damping-off, yellowing, wilting of shoots, basal stem rot and corm rot. In Kashmir, 46% corm rot incidence has been reported with none of the saffron fields being free from the disease. The disease is also widespread in Kishtwar (up to 100%), with maximum incidence and severity in Lower Poochal (59.33 and 35.00%, respectively). Cultivation of saffron, a perennial crop with planting cycle of 5–17 years, is carried out without proper phyto-sanitary inspection; hence the infected and/or infested corms act as an important source of primary inoculum of corm rot. Plant pathogens such as Fusarium oxysporum f. sp. gladioli, Fusarium oxysporum, Rhizoctonia sp., Aspergillus sp., Penicillium sp. and Macrophomina sp. have been found associated with corm rot complex disease of saffron. Most of them survive in infected corms and soil as dormant structures. The association of multiple soil-borne pathogens shows synergism in the incidence of corm rot. Human mediated cultural operations, field implements, bullock carts or tractors used for field preparation and use of infected corms help in the dispersal of pathogens. Even the air currents carrying dust particles along with plant debris containing the inoculum assist in the dispersal of plant pathogens. Heavy rainfall also helps in the short-distance dispersal of plant pathogen. The presence of primary inoculum in the field, infestation of soil by plant parasitic nematodes/rodents, faulty agronomic practices, erratic rainfall and poorly drained fields are the pre-disposing factors for corm rot. The disease drastically reduces the saffron yield, corm development and production of cormlets. Thereby, contributing towards direct economic losses and fluctuations in saffron prices. Although chemical fungicides are very effective, yet growing concern about their deleterious impacts on the environment and human beings, along with pesticide residues in the produce, has resulted in exploring alternative eco-friendly and sustainable methods, for the management of corm rot. Beneficial microbes have proved effective in managing the disease because they compete for energy, food and ecological niche or substrate with the pathogen, and produce inhibitory allelo-chemicals and induce of systemic resistance in the plant. Bacillus spp., due to the advantage of it producing heat and desiccation resistant spores, significantly reduces the incidence of corm rot. Though carbendazim causes maximum disease suppression, yet Pseudomonas fluorescens, Trichoderma viride and Trichoderma harzianum are greatly effective against corm rot. Soil solarization for 4 and 6 weeks significantly reduces the corm rot incidence. Corm dip in mancozeb + carbendazim results in 85.49% reduction in corm rot. Field sanitation and proper drainage are equally important for the management of corm rot. Application of plant growth promoting fungi (PGPF) and plant growth promoting bacteria (PGPB) are also widely advocated in different crops to amelioration biotic and abiotic stresses and promote plant growth.KeywordsCorm rotEpidemiologyManagementSaffron