Characterization of spot blotch of wheat pathogen and defining their mechanism of resistance or susceptibility in wheat
Loading...
Date
2023-12-20
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Plant Pathology, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, Nadia – 741252
Abstract
Wheat (Triticum aestivum L.) is a dominant staple crop cultivated in an area of
around 215 million hectares, across wide range of latitudes covering around 89 countries
of the world. Out of the total global area under wheat cover, an estimated 25 million ha
is infected by spot blotch disease of which 40% is India’s share. Considering the
importance of the pathogen under West Bengal conditions, the following objectives for
the research work was formulated: 1) Identification and characterization of fungi
associated with spot blotch of wheat and their pathogenecity assessment on host 2)
Determination and correlation of ecological and phenological factors responsible for
occurrence and host preference of spot blotch pathogen and 3) Determination of
resistance in different wheat varieties and relative susceptibility to spot blotch disease.
The roving survey conducted in Nadia and Murshidabad revealed that the disease severity
ranged from 44.03% to 81.48% and the highest disease severity (DLA%) was observed
in Domkol-Taraf (81.48%), while the lowest value was observed in Ghaat more,
Krishnanagar - Karimpur route (44.03%). Among the twelve isolates of Bipolaris
sorokiniana collected from the locations, BSC11 was found to be most aggressive, based
on Percent Disease Index, Incubation Period, Latent Period and Lesion size. The disease
severity, observed in spot blotch susceptible genotype K 1317, was positively correlated
with number of spores, growth rate of mycelium and lesion size, whereas, length of the
spore, incubation period, latent period were negatively correlated with disease severity.
The molecular characterization of the twelve isolates with ITS1/ITS4 primer pair
produced amplified product at ~600bp. For assessment of ecological and phenological
factors responsible for occurrence and host preference of spot blotch pathogen, leaf tip
necrosis (LTN), lesion mimic (Lm), lesion size (LS), lesion type (LT), leaf angle (LA)
and chlorophyll content was evaluated on fifty wheat genotypes during the rabi season
of 2020-21, 2021-22 and 2022-23. It was observed that with increase in Lm, LT, LS and
LA, there is a significant increase in Disease Leaf Area, whereas with increase in LTN
and Area Under SPAD value Decline Curve, Disease Leaf Area was significantly
decreased. It indicated that Plants with leaf tip necrosis, higher chlorophyll, erect leaves,
without lesion mimic, and smaller lesion lesion size might be chosen for tolerance to spot
blotch. Field screening of wheat genotypes conducted during the rabi season of 2020-21,
2021-22 and 2022-23 revealed that the genotypes DBW 252, DBW 386, PBW 899, PBW
897, HI 1612, HI 1653, HD 3086, HD 3293, DBW 187 showed resistant reaction.
Whereas, the genotypes DBW 303, PBW 644, PBW 771, PBW 872, PBW 887, PBW
891, PBW 893, HI 1654, HI 1674, HI 1675, HD 2932, HD 2967, HD 3369, HD 3385,
HD 3470, HD 3471, GW 538, GW 542, WH 1402, CG 1036, UP 3102, MACS 4100,
MACS 6814, NIAW 3170, JKW 261, MP 3557 showed moderately resistant reaction.
Similarly, the genotypes DBW 380, GW 322, GW 547, WH 1311, CG 1040, recorded
moderately susceptible disease reaction and DBW 398, PBW 889, GW 513, GW 543,
UP 3111, UAS 3080, LOK 79, K 1317, Raj 4083 recorded susceptible reaction among
the 50 genotypes screened. The analysis of yield attributes revealed that Maximum
Panicle Length was obtained in PBW 897, PBW 899, PBW 889, HD 3293,GW 513,
NIAW 3170, whereas, minimum value was observed in Raj 4083, followed by HD 3471.
Maximum number of grains per panicle was noticed in PBW 897, HI 1653, HD 3086,
DBW 252, and minimum in Raj 4083, followed by MACS 6814 and WH 1311.
Maximum Thousand Grain Weight was noticed in DBW 252, PBW 893, HI 1653,
whereas minimum thousand grain weight was recorded in GW 543, HD 3086 and HD
3293. Biochemical characterization was conducted considering total phenol content,
Polyphenol oxidase activity and Phenylalanine ammonia lyase activity at different
intervals. A significant negative correlation was observed between Diseased Leaf Area
with Phenol content at 24 hours after inoculation (hai), Phenol content at 48 hai, Phenol
at 72 hai, PPO activity at 7 days after inoculation (dai), PPO activity at 15 dai,
Phenylalanine Ammonia Lyase activity at 0, 24, 48 and 72 hai. Molecular
characterization of nineteen genotypes was done from the fifty genotypes collected.
Twelve SSR primers were taken for assessment, out of which six primers, i.e., Xgwm148
(200bp), Xgwm374 (200 bp), Xgwm295 (220 bp), XWGGC7412 (70 bp), Wmc335 (140
bp) and Xgwm425 (100 bp), exhibited polymorphism. Among the genotypes, PBW 897
exhibited resistance reaction as well as positive reaction with the primers, except primer
Xgwm 425. Among the primers, three primers Xgwm374, Xgwm295 and Xgwm425
exhibited signification reaction when assessed in the genotypes on the basis of Diseased
Leaf Area (DLA%). The isolates of Bipolaris sorokiniana collected in this study can be
further subjected to diversity analysis using specific SSR markers. The outcome of the
present investigation may be utilised further for selection of genotypes for resistance
breeding against spot blotch of wheat at field as well as molecular levels.