Studies on Corm Rot of Saffron (Crocus sativus L.)

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Date
2004
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SKUAST Kashmir
Abstract
A major bottleneck in the successful cultivation of saffron (Crocus sativus L.) in Kashmir has been the wide spread occurrence of corm rot. The incidence and intensity of the disease ranged from 4.00 to 40.00 per cent and 0.80 to 16.93 per cent, respectively in 1999 and, 4.66 to 42.00 and 1.33 to 17.46 per cent in 2000 in surveyed saffron growing fields. Collectively the corm rot severity was more in district Pulwama than in Budgam and Anantnag districts. Maximum corm rot infestation during both the years was observed in the corms collected at digging state. The disease in the field is characterized by wilting and drooping of saffron plants, having yellow dull foliage and tip burn symptoms. On digging out 25 the infected corms showed dark brown sunken, irregular lesions, frequently on buds which generally coalesce. The affected plants had less number and undersized daughter corms and flowers besides reduction in the flowering period. Three Fusarium spp. viz. F. solani, F. moniliforme and F. oxysporum have been found associated with the disease and their pathogenicity was also established. However, F. solani was most prevalent and destructive and was regarded as the principal pathogen. This was the only species isolated from the infected corms collected at digging and harvesting stages. While other two species isolated only from infected corms collected at storage stage but there too F. solani was the most predominant. Association of nematodes with Fusarium propagules was invariably encountered in the corm rhizopheres in all the saffron growing fields. The saffron fields of Pulwama district had higher population count of both nematodes and Fusarium spp. as compared to Budgam and Anantnag districts. Simultaneous rhizosphere inoculation of nematodes and F. solani produced the maximum corm rot infestation and significantly reduced the saffron yield as compared to un-inoculated check or inoculation of either nematode or fungal pathogen. Three non-chemical disease management approaches involving the use of bioagents, organic amendments and soil solarization were investigated in polyethylene bag. All resident bioagents viz. Trichoderma viride, Trichoderma harzianum, Gliocladium virens and Asperigillus niger in in vitro ,inhibited the growth of pathogen to varying degrees but T. viride exhibited highest antagonistic affect and showed strong volatile and non-volatile inhibition activity as compared to other bioagents. However, T. viride and G. virens were equally effective in reducing the 26 corm rot to appreciable levels when tested as soil treatment. Among the various organic amendments, decomposed FYM, poultry manure and mushroom compost suppressed corm rot and enhanced the yield of saffron. These organic amendments in general enhanced soil fungal population and reduced the population of pathogenic fungi with maximum effect due to FYM and poultry manure (4:1 w/w) amendments. Amendments in general, exhibited stronger protection at higher level (4:1 w/w) then at lower dosages (5:1 w/w). Soil solarization for 6 weeks during mid June to July increased the soil temperature in sick soil at 5 cm depth by 8.4 and 8.90C during 2000 and 2001, respectively. While as for 4 weeks, the rise in temperature during corresponding period was 6.5 and 6.40C. The corm rot intensity in such plots was significantly suppressed during both the years of experimentation. Among the solarized treatments, highest disease reduction was achieved with 6 weeks solarization after irrigation and amending the soil with FYM in the ratio of 4:1 w/w (soil: FYM).
Description
PhD Thesis submitted to SKUAST Kashmir
Keywords
Plant Pathology, Corm Rot, Saffron, Crocus sativus L.
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