Variability in Ustilaginoidea virens (Cke.) Tak. causing false smut of rice and identification of resistance sources
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Date
2014
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PAU
Abstract
False smut of rice (Ustilaginoidea virens) has become an important disease causing significant yield losses in major rice producing states of India including Punjab. Thirty five isolates of U. virens were differentiated on the basis of their morphological, physiological, pathological and molecular characteristics. All the isolates produced well defined colonies on potato sucrose agar (PSA) medium with colony diameter ranging from 26.0 to 90.0 mm after 2 weeks of incubation. Colony color in most of the isolates was initially white which changed to yellow and finally became green. The conidia were spherical, hyaline and warty and size ranged from 4.05-4.94 to 6.10-6.36μm. The isolates also differed in the growth pattern from appressed, fluffy, less fluffy to raised. Sectoring in mycelial growth was observed in five isolates (Uv25, Uv26, Uv27, Uv28 and Uv29). Mycelial growth of representative isolates (Uv1, Uv4, Uv9, Uv13, Uv21, Uv28) of U. virens grown on Czapek‘s dox agar as basal medium was highly variable when supplemented with different carbon and nitrogen sources with maximum utilization of sucrose and sodium nitrate, respectively; consequently resulting in highest growth. Maximum growth was produced when isolates were incubated at 25 ± 2°C (average dry weight = 57.74mg) followed by 30 ± 2°C (56.84mg). Sucrose (2 and 1%) was found superior in inducing spore germination than dextrose. Potato sucrose broth was the best medium for supporting maximum mycelial growth (104.80mg) and sporulation. Maximum colony diameter and sporulation was also observed on PSA (68.74mm) followed by potato dextrose agar (59.26mm). Maximum sporulation was produced on natural substrate medium based on barley seeds (5.54 X 105 conidia/ ml). Among all the isolates, Uv1 was found more aggressive on both the cultivars. Rest of the isolates varied in their virulence/ aggressiveness behavior on tested cultivars and two isolates viz. Uv17, Uv26 and Uv28 failed to produce disease on PR 114. The genetic variation among 35 isolates of U. virens by PCR amplification using ten random operon decamer primers showed polymorphism. Similarity coefficient values among U. virens isolates ranged from 0.56 to 0.97. Of 31 elite germplasm lines three viz. PAU-3965-11-4-1-4-2, PAU-3965-11-4-1-1-2, PR118 were highly resistant while PR122 and PR114 were resistant. Disease incidence, infected panicle and number of balls/plant were increased with increased nitrogen level on rice cultivars viz. PR114 and PR116.
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Keywords
diseases, rice, biological development, biological phenomena, application methods, nitrogen, fungi, developmental stages, planting, potatoes