Survey for the incidence of false smut of rice in different districts of Odisha

Introduction

Rice (Oryza sativa L.) is one of the most important cereal crops and belongs to family poaceae. It is a staple food crop of 60 percent of world's population. It is one of the important staple food crops of India, which stands second with regard to production amongst the rice growing countries in the world.. The major rice growing states in India are West Bengal, Bihar, Madhya Pradesh, Odisha, Andra Pradesh and Uttar Pradesh. Rice suffers from many fungal diseases such as blast of rice (Pyricularia grisea), sheath blight of rice (Rhizoctonia solani), brown spot of rice (Helmithosporium oryzae), baceterial diseases such as bacterial leaf blight of rice (Xanthomonas oryzae pv oryzae), bacterial leaf streak (Xanthomonas oryzae pv oryzicola), viral diseases such as rice tungro disease. False smut of rice, a fungal disease caused by Ustilaginoidea virens (Cooke) Takahashi. was first reported from Tirunelveli in Tamilnadu in 1978 by Cooke (Ou,1972) [5] . This disease was considered earlier as minor disease due to its sporadic nature. The disease is considered as a symbol of bumper harvest and regarded as Laxmi. False smut disease appears only after grain formation in the panicles where individual grains are transformed into large spore balls, which initially yellowish in colour, later turn to greening black as they mature. But now the disease is gaining importance due to its wide spread distribution and its destructiveness under favourable conditions. Since 2001 disease started occurring in severe form in majority of rice growing states of India (Mandhane et al., 2008; Ladhalakshmi et al., 2012) [4,3] . Yield loss due to false smut of rice was estimated to the extent of 50 percent. (Rashmi and Gokulapalan, 2014) [6] . On different varieties in different regions of India, yield loss due to false smut was estimated to the range of 0.2 to 49 percent (Singh et al., 1992 ; Biswas 2001) [8,2] . Only limited literature is available on the occurrence of false smut of rice in Odisha, hence survey for the incidence of false smut of rice is considered to be essential. This information would be useful for locating 'hot spots' and also for assessment of loss in yield.

In each field, five spots of one square meter area were selected randomly. Number of infected tillers and infected grains in the panicles were recorded. Survey was done for assessing percent disease incidence (PDI), average smutted balls per panicle and disease severity of false smut of rice. The disease parameters were worked out as per the following formula given by Singh and Dube (1978) [7] .

Number of infected tillers/m 2 Percent disease incidence (PDI) =

x 100 Total number of tillers/m 2 Total number of infected grains/ panicle Percent infected grains = X 100 Total number of grains /panicle Disease severity = Percent infected tillers X Percent infected grains

Results and Discussions

Roving method of survey was conducted during kharif, 2024 in six selected districts of Odisha viz., Bhadrak, Sundargarh, Sambalpur, Kendrapara, Ganjam and Balasore to know the incidence and severity of false smut disease in farmers' fields. The data pertaining to this study are given in Table 1. The survey indicated that, the disease incidence recorded in different localities was low to high level. The disease incidence was found to vary between 3.64% to 14.10% in different villages. Among eighteen villages surveyed, higher disease incidence (above 10%) was observed in Talanga (14.10%), Ambaroli (12.23%), Sundarpur (11.05%) villages under Bhadrak district, Tangarpali (10.14%) village under Sundargarh district. Moderate disease incidence (ranged between 7-10%) was noticed at Tudalaga (9.53%), Dandaharipur (8.12%), Balani (7.5%) localities and lower disease incidence (below 7%) was observed at Gurupali (3.64%),,Dhumkapada (3.7%), Kalamati (4.51%) and Naladhalia (4.6%), Deogaon (5.12%), Kakharuni (5.3%) villages. Maximum disease incidence was recorded in Bhadrak district (12.46%), followed by Sundargarh (9.05%), Balasore (7.08%), Ganjam (5.55%) and Kendrapara (5.33%) district. Highest smutted ball percentage was recorded in Bhadrak district (3.74%). Lowest smutted ball percentage was recorded in Sambalpur district (1.33%). Among eighteen villages surveyed, disease severity varied to the range of 4.11% to 50.90% in different localities. It was observed that disease severity was higher (above 30.96%) in Bhadrak district. The disease severity was moderate (ranged between 16.23-30.96%) in Sundargarh and Balasore districts. Disease severity was low (below 16.23%) in Ganjam, Kendrapara and Sambalpur district (Fig. 1). Baite et al., (2017) [1] had undertaken a survey to assess the disease incidence and severity of false smut of rice in the fields of Kisan nagar village and National Rice Research Institute, Cuttack in Odisha for 15 paddy varieties. They observed that mean disease incidence and severity of 15 rice varieties were 17.64% and 43.79%, respectively. Soodamani and Vaikuntavasan (2023) [9] conducted roving survey to assess disease incidence and severity of false smut of rice in Tamil Nadu. They recorded maximum disease incidence in Erode district (40%). Our survey data revealed that the incidence and severity of the disease varied from locality to locality which might be due to type of variety, inoculum load, environmental conditions and amount of fertilizers applied.

Conclusion

Roving method of survey was conducted in six districts of Odisha during Kharif, 2024 to know the disease incidence and severity of false smut of rice. The data revealed that disease was not severe in the districts surveyed except Bhadrak district. In the present study, survey was conducted only in six districts of Odisha. In future, more survey work may be undertaken in the remaining districts of Odisha to draw more precise conclusion about occurrence of false smut of rice in Odisha and for developing management strategies to combat the disease effectively.

References

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