ICRISAT Archival Report 2006 - The seedlings of success in the ...

studied. Percentage of micro-conidia was significantly more than macro-conidia in all isolates. Highest percentage
of micro conidia (81.4%) in FOC 4 and lowest (51.6) in R4 was recorded. Largest micro-conidia (10.1x 5.5 μ m)
were observed in FOC 38, and smallest (7.7 x 4.8 μ m) in FOC 8. Macro-conidia were larger (22.1 x 5.8 μ m) in the
isolate R4, while they were smaller (14.9 x 5.5 μ m) in FOC 32. Mean number of cells in macro-conidia were 3.1
in FOC 10 and 4.6 in FOC 41.
Characterization of variability of Ascochyta rabiei : Differential reaction of cultivars to AB at different locations
in India indicated the probable existence of races/pathotypes in the pathogen, A. rabiei. Hence, we initiated a
systematic research to characterize races/pathotypes in A. rabiei. The A. rabiei infected chickpea plants were
collected from 14 locations in different agroclimatic regions in India. Isolations were made from these infected
plants and pure cultures of single spore isolates of A. rabie were obtained.
Morphological and cultural variation: Seven single spore isolates representing different agroclimatic zones were
selected for studying morphological, cultural, and pathogenic characters. Five mm diameter discs from actively
growing cultures of A. rabiei were placed at the center of 90 mm diameter petri plates containing CDA, and
inoculated at 20 0 C. Colony color, intensity of the mycelium, colony diameter, number of conidiomata, and conidia
were recorded. The A. rabiei isolates differed in morphology, colony color, colony size, pycnidial color (brown to
slate grey), number of conidioamata (42.3 to 90.7 cm- 2 ), number of conidia (0.55 to 3.01 conidia 10 3 cm- 2 ), and
conidial size (10.7 x 4.6 to 14 x 6.2 μm).
Pathogenic variation: All the 14 isolates were used for inoculation on 180 germplasm and advanced breeding lines
under controlled environment conditions. All the 14 isolates of A. rabiei differed in their virulence pattern against
180 lines with AB 13 having maximum virulence index of 7.9 and AB 6 with a minimum index of 5.4 (Fig. 1). None
of the lines were asymptomatic to any of the test isolates. Of the 180 lines, 10 lines to AB 6 and seven lines to AB
27 showed a resistant reaction. None of the entries were resistant to five isolates (AB 4, AB 17, AB 26, AB 1, and
AB 13), whereas only one entry showed resistant reaction to four isolates (AB 8, AB 15, AB 3, and AB 18). Of the
180 entries, 15 entries (ICC 12, ICC 607, ICC 2165, ICC 3918, ICC 4200, ICC 4475, ICC 5124, ICC 6306, ICC
7002, ICC 13754, ICC 14911, ICCX 810800, ICCX 910028-39ABR-BP-10, ABR-BR, ILC 3870, and FLIP 82-258)
differed significantly in their reaction to different isolates of A. rabiei, and hence were selected as differentials.
Characterization of variability of Botrytis cinerea: Thirty-two isolates of B. cinerea infecting chickpea, lentil, and
marigold were collected from different locations to determine the variability of the fungus. Of the 32 isolates, 23
were collected from chickpea, 5 from lentil, 2 from marigold, 1 from Dahlia and 1 from grasspea. All the isolates
were purified using BGM specific medium containing tannic acid. Preliminary analysis of eight Indian isolates
using 20 RAPD primers (decamers) categorized them into two distinct groups. Detailed molecular analysis will be
followed during 2007-08 season.
Fig. 1. Dendrogram showing the clustering of the single
spore isolates of A. rabiei based on AFLP analysis;
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