Effect of soil temperature at different depths of soil on incidence of wilt in selected lentil genotypes

Introduction

Lens culinaris Medik is the botanical name of lentil, which is the oldest crops among legumes and belongs to the leguminousae family. It is originated from the Near East and Egypt at the Center and Southern Europe, the Mediterranean basin, Ethiopia, Afghanistan, India, Pakistan, China and later spread to Latin America (Cubero 1981) [5] . India is one of the prime pulse producing countries in the world. In India the total area under lentil was 13.00 lakh ha with a total production of 11.00 lakh tonnes and its average productivity was 847 kg/ha. The major lentil producing states in the country are Madhya Pradesh, Uttar Pradesh, Bihar, Uttarakhand and Bengal. In Madhya Pradesh lentil is grown in 3.79 lakh ha with a total production of 2.94 lakh tonnes with 777 kg/ha productivity (Anon., 2020) [1] . Lentil is grown as a Rabi crop or winter crop in India and sown in between months of October and November. Lentil is adapted in semi-arid environments, where it is usually grown in rotations. It is usually cultivated in all continents except Antarctica. Lentil is known by various names in different regions and languages like adas (Arabic), mercimek (Turkey), messer (Ethiopia), masoor (India), and heramme (Japanese) (Muehlbauer and McPhee., 2005) [8] . It can be cultivated on a wide range of soil from light loam to black cotton soils and it can also stand in less fertile moderately alkaline soils and even in rainfed conditions. The crop matures in arounds 90 to 120 days. Lentil is among the first crops domesticated globally and it has become a prime food legume crop in the farming and food systems in many countries. It is a rich source of protein, minerals, and vitamins and plays an important role in human nutrition. The straw of lentils are pretty much valued animal feed and its ability in nitrogen fixation and carbon sequestration improves the nutrient status of soil, which in turn gives sustainability in production system (Sarker and Erskine, 2006) [9] . Lentil crop is at risk to a various diseases caused by fungi, viruses, nematodes, insect pests, parasitic plants and abiotic stress. The most significant and serious soil-borne disease among them is Fusarium wilt. In many countries like in India, Algeria, Syria and Iran the pathogen of lentils showed high levels of phenotypic and genotypic diversity. The disease develops at the temperature of 22-25 °C and affects lentil either at seedling and vegetative or at the reproductive stages (Tiwari et al., 2018) [11] . In India lentil wilt caused by Fusarium oxysporum f. sp. lentis is the major disease in lentil growing regions. The disease was first reported in Hungary but in India, it was first observed in 1941 in Delhi and Karnal. The annual yield losses are 10-15 per cent due to this disease alone which valued approximately Rs. 2000-2500 crores (Chaudhary and Amarjit, 2002) [4] . If infection takes place in early stage of the plant then it does not produces seeds and if infection occurrs at later stage than only few number of seeds are formed. Wilt causes more damage during flowering and pod formation stage of the crop. The Fusarium wilt pathogen that primarily infects lentils, F. oxysporum f. sp. lentis (Vasudeva and Srinavasan 1952) [12] is present in many countries in Asia, Europe, Africa and America. Frequently the fungus spreads through the plant debris and soil contamination and it infects the plant through the root system. There is also an evidence of dissemination of fungus through seeds (Bayaa et al., 1990) [2] . Temperature and soil moisture are the most important factors in determining symptoms expression and fungal growth rates (Saxena and Khare, 1988) [10] .

Materials and Methods

Experimental site

Effect of soil temperature at different depths of soil on incidence of wilt at weekly intervals

Influence of soil temperature at different soil depths (5 cm, 10 cm and 20 cm) on wilt incidence was examined in selected susceptible lentil genotypes L 9-12, Sehore 74-3, DPL-62 grown in factorial RBD design. Percent wilting was calculated by the following formula:

The absolute disease intensity was calculated as the difference between two successive observations of wilt incidence and correlation coefficient ('r') was computed between the absolute disease intensity and meteorological factors like soil temperature at different depths (5 cm, 10 cm and 20 cm). The significance of correlation coefficient was judged by 't' test as per standard statistical methods.

The data on wilt intensity were plotted against soil temperature at different depths to predict the correlation between wilt and soil temperature. Regressions equations were also computed and scatter diagrams were drawn.

Data on soil temperature at different depths during the period were obtained from Agro-meteorological section, at R.A.K. College of Agriculture, Sehore. (Table -1).

Statistical Analysis

The data obtained in all the experiments was subjected to the statistical analysis (Panse and Sukhatme, 1978) [7] . The

3) Correlation coefficient

Correlation per cent disease index and per cent seed infection were worked out as per method suggested by Chandel (1991) [3] .

Were, r (x y) = correlation coefficient between character x and y. COV (x y) = covariance between character x and y.

V(x) = variance of x character. V(y) = variance of y character.

Results and Discussion

Effect of soil temperature at different depths of soil on incidence of wilt in selected susceptible lentil genotypes.

Soil temperature and incidence of wilt in L 9-12 lentil cultivar

Wilt incidence in L 9-12 lentil genotype was studied in relation to soil temperature at different depths. The wilt incidence and temperatures were recorded every week and correlated. Correlation coefficient (r) andt statistic was computed at each depth level i.e. 5 cm, 10 cm and 20 cm for is given in (Table 2.) To quantify the effect of soil temperature depth levels the linear regression equation was also worked out (Table 3). Wilt susceptible L 9-12 lentil genotype did not show significant correlation at 5 cm soil depth the observed correlation coeficient (r) was 0.568 the regression equation of L 9-12 lentil genotype showed that wilt incidence of lentil increased by 0.0412% with the increase of 1 0 C of the soil temperature at 5 cm depth. (Fig. 1). Soil temperatures at 10 cm and 20 cm depths of soil were found to have significant positive correlation (at 5% level of significance) with lentil wilt, the observed correlation coeficient (r) 0.700 and 0.702 with wilt incidence in L 9-12 lentil genotype, respectively (Table 5). The regression equation showed that wilt incidence of lentil increased by 0.603% and 0.06% with the increase of 1 0 C of the soil temperature at 10 cm and 20 cm depth. (Fig. 2 and3). 4). To quantify the effect of soil temperature depth levels the linear regression equation was also worked out (Table 5). The Sehore74-3 lentil genotype did not show significant correlation at 5 cm depth of soil, the observed correlation coeficient (r) was 0.558 The regression equation of Sehore 74-3 genotype showed that wilt incidence of lentil increased by 0.0517% with the increase of 1 0 C of the soil temperature at 5 cm depth. (Fig. 4).

Temperatures at 10 cm and 20 cm depth of soil had significant positive correlation (at 5% level of significance) with lentil wilt, the observed correlation coeficient (r) 0.691 and 0.692. The regression equation of Sehore 74-3 lentil genotype showed that wilt incidence of lentil increased by 0.0661% and 0.0755% with the increase of 1 0 C of the soil temperature at 10 cm and 20 cm depth. (Fig. 5 and6). The wilt incidence and temperatures were recorded every week and correlated. Correlation coefficient (r) andt statistic was computed at each depth level i.e. 5 cm, 10 cm and 20 cm (Table 6). To quantify the effect of soil temperature at different depth levels the linear regression equation was also worked out (Table 10).

The DPL-62 lentil genotype was found to have a significant positive correlation(at 5% level of significance) at 5 cm depth of soil, the observed correlation coeficient (r) was 0.672).The regression equation of DPL-62 genotype showed that wilt incidence of lentil increased by 0.0759% with the increase of 1 0 C of the soil temperature at 5 cm depth. (Fig. 7). Temperatures at 10 cm and 20 cm depth of soil was found to have significant positive correlation (at 1% level of significance) with lentil wilt, the observed correlation coeficient (r) 0781 and 0.770. The regression equation of DPL-62 genotype showed that wilt incidence of lentil increased by 0.01047% and 0.1024% with the increase of 1 0 C of soil temperature at 10 cm and 20 cm depth. (Fig. 8 and9).

References

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