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STUDIES ON DRY ROOT ROT [Rhizoctonia bataticola (Taub.) Butler] OF CHICKPEA (Cicer arietinum L.)

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Title STUDIES ON DRY ROOT ROT [Rhizoctonia bataticola (Taub.) Butler] OF CHICKPEA (Cicer arietinum L.)
 
Creator SRINIVAS, P
 
Contributor NARAYAN REDDY, P
 
Subject STUDIES, DRY ROOT, ROT, CHICKPEA
 
Description Dry root rot caused by Rhizoctonia bataticola (Taub.) Butler [Pycnidial stage: Macrophomina phaseolina (Tassi) Goid] is a soil borne fungal pathogen. Keeping in view the importance of the disease due to change in climatic conditions, studies were conducted on distribution of the disease, cultural, morphological, pathological and molecular diversity. Effect of temperature and moisture on the disease severity was studied. Various biochemical and physiological changes associated with the development of the disease in susceptible and moderately resistant genotypes under glass house conditions were conducted at ICRISAT, Hyderabad.
A survey was conducted in January, 2014 rabi cropping season in different chickpea growing locations of central (Madhya Pradesh and Maharashtra) and southern (Andhra Pradesh, Telangana and Karnataka) India. Due to diversified weather conditions and variation in sowing dates in different states, different crop growth stages i.e. from seedling (20 days old) to podding stage were observed and the disease was observed in all the stages. The maximum dry root rot incidence was observed in Telangana (18.28%) and the least in Maharashtra (5.38%). Disease occurrence was observed irrespective of cropping system, soil types and cultivars. Mostly the disease incidence was low in the irrigated fields compared to rainfed fields.
Disease severity rating of 2.5 to 9.0 was observed in the 68 isolates inoculated on BG 212 and their incubation period varied from 1.0 to 4.8 days. It was observed that with an increase in disease severity there was decrease in incubation period in all the isolates. Diversity in cultural characters viz., radial growth ranged from 17.7 mm to 80.0 mm at 72h after incubation; colony colour of black, black with grey aerial mycelium, dark brown and grey colour; colony texture of appressed, fluffy and velvety were observed.
The morphological characters such as hyphal cell size varied from 9.38 x 3.80 μm (Rb10) to 14.88 x 7.50 μm (Rb 63) and sclerotial size varied from 54.86 x 45.49 μm (Rb 46) to 216.08 x 181.09 μm (Rb 59). Ratio between length and width of sclerotia varied from 1.00 (Rb 5) to 1.64 (Rb 23). The isolates categorized into irregular, round and ovoid groups based on shape of sclerotia, rough and smooth groups based on texture of sclerotia. Isolates took 1.7 (Rb1) to 4.3 days (Rb4, Rb23 and Rb 28) for sclerotial initiation and their intensity per microscopic field (10x) varied from 11.67 (Rb 63) to 70.67 (Rb 56).
The similarity coefficient ranged from 0.63 to 0.92 indicating that no any two or more isolates were 100% similar. The highest similarity coefficient (0.92) was between isolates Rb 2 and Rb 4. The results of the present study also indicated that, all the isolates were not necessarily showing the geographical linearity.
Influence of different temperature, osmotic potential and pH were tested on growth of R. bataticola. The maximum mycelial growth was observed at 35ºC followed by 30 and 25ºC. Among different osmotic potential levels of NaCl, KCl and dextrose, maximum mean radial growth was observed at -0.5 MPa viz., 27.5 mm, 31.1 and 38.2 mm respectively while the minimum growth was observed in -1.0 (4.9 mm), -1.5 (2.1 mm) and -2.5MPa (10.7 mm) respectively. The growth was observed at all the levels of pH tested. Maximum radial growth was observed at pH 5.0 (67.3mm) followed by pH 6.0 (64.4) while the least was observed at pH 11.0 (14.6mm) followed by pH 10.0 (33.0mm).
The optimum temperature for dry root rot severity rating was at 35°C (8.5) followed by 30°C (7.9) followed by 25°C (7.0). In black soil, the disease severity rating was 9.0, 8.9, 8.1, 6.9, 5.3, 3.8 and 2.3 while in red soil, it was 9.0, 8.9, 8.7, 7.9, 6.5, 4.7 and 3.0 at 40, 50, 60, 70, 80, 90 and100% soil moisture, respectively. The disease severity decreased as the soil moisture increased in both the types of soil.
The susceptible genotype BG 212 was having fewer amounts of total sugars compared to moderately resistant genotypes viz., ICCV 5530 and ICCV 8305. The total sugar was more in the control plants as compared to plants in sick soil, while in the sick soil, the amount of increase was more in 100% as compared to 60% soil moisture condition. Similar results were present in reducing and non reducing sugars.
Total phenol, Phenylalanine Ammonia Lyase, Polyphenol oxidase and Peroxidase were maximum at 30DAS in sick soil with 60% soil moisture in all the three genotypes. The amount of increase was more in the inoculated plants grown at 60% compared to 100% soil moisture condition. The amount of phenol and enzymes were more in the moderately resistant genotypes (ICCV 5530 and ICCV 8305) compared to susceptible genotype (BG 212)
Among the genotypes, the dry weight of the genotypes was more in the 100% soil moisture as compared to 60% moisture. With respect to the sick and control soil, it was observed that, severe disease in the sick soil made the disintegration of the roots and there by losing the weight of plants in sick soil at 60% compared to control.
Genotypes grown in 100% moisture in control soil had more transpiration and stomatal conductance while the least was noticed in sick soil at 60% soil moisture in contrast, leaf temperature was more in the genotypes grown in sick soil at 60% moisture and the least was noticed in control soil with 100% soil moisture.
Overall results showed that dry root rot present in all the locations of central and southern India and may become severe disease due to change in climate. The determination of changes in biochemical and physiology of the genotypes help in screening the resistant genotypes and also early detection of the disease in fields.
 
Date 2016-12-27T11:33:05Z
2016-12-27T11:33:05Z
2016
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/93135
 
Language en
 
Relation D9895;
 
Format application/pdf
 
Publisher PROFESSOR JAYASHANKAR TELANGANA STATE AGRICULTURAL UNIVERSITY