​Effect of Nutrients on Wilt in Chickpea

Chickpea is the third most important grain legume after common bean and pea (Anwar et al., 2009). Asia covers 89.7 per cent of the area in chickpea cultivation followed by 4.3 per cent in Africa, 2.6 per cent in Oceania, 2.9 per cent in America and 0.4 per cent in Europe (Gaur et al., 2010). India ranks first in terms of chickpea production and consumption in the world. About 65 per cent of the global area with 68 per cent of global production is contributed by India (Reddy and Mishra, 2006). It accounts for 70 per cent of the cultivated rabi pulses in India. The major chickpea growing states in India are Madhya Pradesh, Rajasthan, Andhra Pradesh, Bihar, Uttar Pradesh, Maharashtra, Haryana and Karnataka. The total area under chickpea cultivation in India is about 9.93 million hectare with an annual production of 9.53 million tonnes. The average productivity of chickpea is 960 kg/ha (Anonymous, 2015).
 
Among the fungal diseases, chickpea wilt caused by Fusarium oxysporum f. sp. ciceri is widespread in several countries of the world like India, Iran, Pakistan, Nepal, Burma, Spain, Mexico, Peru, Syria and USA (Nene et al., 1989; Jalali and Chand, 1992). It is one of the important limiting factors of chickpea production in India. The disease causes substantial yield losses which may reach even 100 per cent under favorable weather conditions (Nene 1980, Jalali and Chand, 1992). Characteristic symptoms of wilt are sudden drooping of leaves and petioles, no external rotting of roots and black internal discoloration involving xylem and pith (Dubey and Singh, 2004). The disease is characterized by two syndromes, namely vascular wilt and yellowing that can be distinguished by both symptomlogical and chronological development.

Pot culture experiments were carried out during 2014-15 and 2015-16 were carried out to study the effect of macro and micro nutrients on the wilt disease of chickpea. The experimental soil was loamy sand, neutral in reaction, low in nitrogen and medium in phosphorus and potash. The pH, electric conductivity (EC) and organic carbon were being 8.2, 0.15 dsm^-1 and 0.15 per cent, respectively. Soil mixed with Fusarium oxysporum f.sp. ciceri inoculums multiplied on maize-meal-sand medium at the rate of 10 per cent (w/w) was filled in earthen pots of 30 cm diameter after lining the pots with polyethylene sheet of 40 µm gauge. Four nitrogen levels viz., 0, 15, 20 and 25 kg/ha and four levels of phosphorus viz., 0, 30, 40 and 50 kg/ha were tried in sixteen different combinations. Required quantity of urea and single super phosphate were added in soil in order to achieve the desired levels of nitrogen and phosphorus, respectively. In each pot 7 kg sterilized soil was filled. Quantity of each fertilizer in each pot (7 kg soil) was calculated on the basis of weight of the soil, 0, 105.91, 141.19, 176.59 mg of urea and 0, 595.59, 795.34 and 994.31 mg SSP were added to supply the above-mentioned levels of N and P, respectively. Four replications (4 pots) in each combination treatment were maintained. Fifteen surface sterilized seeds of chickpea cultivar L-550 were sown in each pot. After sowing, 400 ml water was supplied to each pot, thereafter watering was done at an interval of 6 days. Disease incidence was recorded periodically commencing after 15 days of sowing and was continued up to 55 days. The pathogen population was also determined in terms of mycelia spores per gram of soil.

For study of micro-nutrients, plastic pots of 10 cm diameter were used. Seven micro-nutrients viz., zinc, manganese, calcium, copper, cobalt, iron and nickel were tried. Each element at the rate of 10 mg kg^-1 of soil was applied in Fusarium oxysporum f. sp. Cicero inoculated soil. Nitrogen and phosphorus were applied at 20 kg N and 40 kg P₂O₅/ha as a general dose in all the treatments. Five surface sterilized seeds of chickpea cultivar L-550 were sown in each pot. Each treatment was replicated eight times. After sowing 25 ml water was supplied to each pot thereafter, watering was done at an interval of 6 day. Disease incidence was recorded 7 days after sowing and continued till 55 days. Pathogen population and incubation period were also recorded. Micronutrients were supplied in the form of chemicals as given below.

Effect of macro-nutrients during 2014-15
 
The increasing levels of nitrogen increased the mean disease incidence successively. Minimum disease incidence of 39.19 and 40.06 per cent was recorded when no (zero) nitrogen was applied to the plants in the years 2014-15 and 2015-16, respectively. Whereas, the incidence of the disease was maximum 65.99% and 65.91 when chickpea plants were supplied with the highest dose of nitrogen 25 kg ha^-1 during 2014-15 and 2015-16, respectively.
 
A reverse trend was noticed in case of phosphorus. Incidence of wilt of chickpea was decreased with the increasing levels of phosphorus. Minimum wilt incidence of 43.13 and 44.01 per cent was recorded when the highest dose of phosphorus, 50 kg ha^-1 was applied during 2014-15 and 2015-16, respectively.
 
Interactions between nitrogen and phosphorus levels were found to be significant with the highest dose of phosphorus (50 kg ha^-1) and zero application of nitrogen and exhibited the lowest disease incidence of 33.58 per cent (Table 1). Interactions between nitrogen and phosphorus were found significant. The minimum disease incidence of 34.13 per cent was recorded when zero level of nitrogen and 50 kg phosphorus was applied, as against 68.80 per cent in plants supplied with 25 kg N and 0 level of P per hectare (Table 2).




 
Effect of macro-nutrients during 2015-16
 
Increased levels of nitrogen resulted in increase in wilt disease incidence. However when phosphorus levels were increased from 0 to 50 kg/ha disease incidence had gone down in general, it has been observed that when nitrogen and phosphorus were applied in combinations. The effect of nitrogen was suppressed by increasing levels of phosphorus. Similar observations have been recorded by Singh et al., (2002), Bharathi and Rao (2009) and Harchand and Khirbat (2009) who observed that the development of wilt is favoured by increase in nitrogen.
 
Effect of micro-nutrients
 
Application of zinc and calcium reduced the wilt incidence significantly over check. Zinc was found to be most effective in minimizing the disease with incidence of 41.68 and 43.43 per cent in the year 2014-15 and 2015-16, respectively. This treatment was closely followed by calcium and found statistically at par with the disease incidence of 43.68 per cent during 2014-15. However, it was significantly super to zinc application in the year 2015-16 (Table 3). All the micronutrient applied significantly reduced the disease incidence over control. However, the application of copper, iron, manganese, cobalt and nickel were less effective as compared to zinc and calcium. Lowest pathogen population was observed at 1.6 x 103 spores/g of soil when the soil was amended with zinc followed by calcium having pathogen population of 1.80 x 103 spores g^-1 of soil. The highest pathogen population of 2.2 x 103 spores was observed when the soil was amended with nickel (Table 3).


 
Soil application of zinc and calcium reduced the wilt disease incidence. Similarly, a marked reduction in pathogen population of Fusarium oxysporum f.sp. ciceri was also observed when soil was amended by zinc and calcium. On the contrary increase in disease incidence as well as pathogen population were noted when the soil was amended by nikel. Application of zinc is reported to control Fusarium wilt in some crops. These results are consistent with the findings of Sanjeev and Eswaran (2008) who studied the efficacy of micro nutrient viz., calcium nitrate, ammonium sulphate, copper sulphate, potassium chloride, sodium chloride, borax, ferrous sulphate and zinc sulphate against Fusarium oxysporium f.sp. cubence (Panama wilt of banana) and found that among the micro nutrients used borax @500 and 750 ppm completely inhibited the mycelial growth of Fusarium oxysporium f.sp. cubence fallowed by zinc sulphate (100, 250, 500 and 750 ppm).