INCIDENCE AND VARIABILITY OF SCLEROTIUM ROLFSII CAUSING COLLAR ROT OF CHICKPEA (Cicer arietinum L.)
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Date
2023-08-09
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Department of Plant Pathology, College of Agriculture Banda University of Agriculture & Technology, Banda-210001
Abstract
Chickpea (Cicer arietinum L.) is an important and oldest pulse crop. Collar rot caused
by Sclerotium rolfsii is an important disease of Chickpea. An intensive roving survey was
conducted in 2021-2022 for the assessing prevalence and incidence of collar rot in seven
growing districts (Banda, Hamirpur, Mahoba, Chitrakoot, Jhansi, Jalaun, and Lalitpur) of
Bundelkhand region of Uttar Pradesh. A total of 63 locations were surveyed and observed that
the disease was prevalent at all the locations. The collar rot incidence ranged from 4.0 to 17.0%.
The highest disease incidence (17.0%) was recorded from Lodhipur village of Muskara
block in Hamirpur district and the lowest collar rot incidence (4.0%) was recorded from
Chakrauli village of Karwi block in Chitrakoot district. In order to diversity study of collar rot
pathogen a total of twenty nine isolates of Sclerotium rolfsii were isolated from diseased plant
samples collected from surveyed locations. It was observed in diversity study of pathogen that
all the isolates of the Sclerotium rolfsii highly diverse in mycelial and sclerotial morphological
traits on PDA medium. Among the mycelial traits significant variations were recorded in colony
diameter, colony colour, type and appearance of colony growth on PDA medium after 72 hrs of
incubation at 27 °C. ‘Most of the isolates were medium growth rate which recorded 50 to 80
mm colony diameter and fast growing isolates which recorded 80.33 to 90.00 mm colony
diameter after 72 hrs of incubation’. Based on the colony appearance seven isolates were
showed fluffy, sixteen isolates showed dense and remaining six isolates were showed the sparse
mycelial growth on PDA medium. Variation among the isolates on the basis of colony colour
was also recorded, that the isolates were produced white, extra white and dull white colour
colonies on PDA medium.The variability in sclerotial traits of isolates was recorded
significantly. The numbers of sclerotia were highly varied among the isolates and ranged from
106.33 to 1005.33 per plate (90 mm). The isolates also showed variation in test weight (weight
of 100 sclerotia) of sclerotia, ranged from 68.66 mg to 538.33 mg per hundred sclerotia. The size
of sclerotia also varied in different isolates and ranged from 0.93 mm to 1.59 mm in diameter.
The colour of sclerotia was mostly brown, light brown and dark brown at maturity. Shape of
sclerotia was also varied among the isolates and most of the isolates were produced spherical to
oval shape sclerotia. The sclerotia in most of the isolates were distributed in scattered to
peripheral manner over the PDA plates. In order to determination of mycelial compatibility
groups (MCG) among the isolates were paired to each other on PDA plates and the isolates also
paired themselves to ensure self-compatibility. There were 435 combinations of twenty nine
isolates, out of which only 211 combinations showed compatible reactions while remaining 224
combinations showed incompatible reaction. Based on compatible and incompatible reaction
three MCGs were distinguished among twenty nine isolates. In case of pathogenic variability,
isolates from different locations showed difference in their virulence on different variety.
Among the all isolates the isolates SRC22, SRC25, SRC27 and SRC28 considered as most
virulent as it causes highest diseases incidence in all selected variety of chickpea. The
physiological requirement of pathogen for maximum mycelial growth of different isolates of
S. rolfsii was observed on Czapek’s dextrose agar and Potato dextrose agar medium and
maximum sclerotia production on Potato dextrose agar medium while, on 25 ℃ temperature
and pH level 7.0 observed maximum mycelial growth and sclerotia production. Genetic
similarities were analyzed through the data obtained on the basis of 10 RAPD primers from
the 29 isolates of the Sclerotium rolfsii and presented varying degree of genetic relatedness.
Jaccard’s similarity coefficient ranged from 0.05 to 1.01. The highest similarity 1.0 was
observed between genotypes SRC-11 and SRC-29. The lowest similarities were revealed
between the isolates SRC-5 and SRC-25, SRC-13 and SRC7, SRC-18 and SRC8, SRC-25
and SRC-18 registered the minimum similarity value (0.0) indicating the maximum genetic
distance between them. Among the different type of soil the maximum collar rot disease
incidence was recorded in black soil (66.02%), followed by light brown soil with (61.13%)
incidence.
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ARVIND KUMAR (2024). INCIDENCE AND VARIABILITY OF SCLEROTIUM ROLFSII CAUSING COLLAR ROT OF CHICKPEA (Cicer arietinum L.) Thesis, Ph.D. Department of Plant Pathology, College of Agriculture Banda University of Agriculture & Technology, Banda-210001