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EPIDEMIOLOGY, VIRULENCE DIVERSITY AND HOST-PLANT RESISTANCE IN BLAST [Magnaporthe grisea (Hebert) Barr.] OF FINGER MILLET [Eleusine coracana (L.) Gaertn.]

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Title EPIDEMIOLOGY, VIRULENCE DIVERSITY AND HOST-PLANT RESISTANCE IN BLAST [Magnaporthe grisea (Hebert) Barr.] OF FINGER MILLET [Eleusine coracana (L.) Gaertn.]
 
Creator KIRAN BABU, T
 
Contributor NARAYAN REDDY, P
 
Subject millets, diseases, biological phenomena, developmental stages, planting, fungi, pathogens, rice, land resources, application methods
 
Description Studies were conducted on blast disease of finger millet that included cultural,
morphological, pathological and molecular diversity, epidemiology and identification of host-
plant resistance at International Crops Research Institute for the Semi-Arid Tropics
(ICRISAT), Patancheru, India and field trials were conducted at ICRISAT; ARS,
Vizianagaram; RARS, Nandyal; ZARS, Mandya and OFRS, Naganahalli. A total of 125 blast
disease specimens from finger millet, 6 from foxtail millet, 3 from rice and 5 from pearl millet
were collected from major crop growing areas of India during 2008-2010. From these
samples, a total of 70 monoconidial isolates of Magnaporthe grisea, 56 from finger millet, 6
from foxtail millet, 3 from rice and 5 from pearl millet were obtained. Of the 70 isolates, 15
each were from Patancheru and Vizianagaram, 13 from Nandyal, 14 from Mandya, 8 from
Naganahalli and one each from Dholi, Aurangabad, Hissar, Jaipur and Solan.
In pathogenicity studies, considerable variation was found among the isolates from
finger millet for leaf blast however, no significant differences were found among the isolates
from foxtail millet and pearl millet. In cross-inoculation tests M. grisea isolates from finger
millet failed to infect foxtail millet and pearl millet, and vice versa.
Diversity in cultural characters, such as colony colour, texture and growth pattern
were noticed among the isolates, but no clear-cut groupings were observed between isolates
from different hosts. The isolates that were grayish-green and sector-forming produced more
spores than those having cottony and submerged growth. Variations in morphological
characters, such as colony growth, size of the conidia and sporulation were observed.
Variations in sporulation capacity were noticed within and between the isolates from the same
location.
Sixteen finger millet mini-core accessions developed varying reaction types for leaf,
neck and finger infection over 2 years of evaluation at five locations. Five selected
representative isolates (one isolate/location) were evaluated for pathogenicity (leaf blast) on
Finger Millet Blast Resistance Stability Nursery (FMBRSN) consisting of 28 accessions and
were found highly variable for virulence, disease severity and disease reaction. Among five
isolates, the isolate FMNg55 was found highly virulent and FMP1 the weakly virulent. A set
of 10 putative host differentials were identified based on field evaluation of FMBRSN
accessions over 2 years at five locations and greenhouse screening. Twenty isolates (4
isolates/location) evaluated for pathogenicity on 10 host differentials, and one resistant and
one susceptible check were found highly variable for virulence, disease severity and disease
reaction. Among these, the isolates FMP5, FMV23, FMNg54 and FMNg55 were found highly
virulent and FMV14 the weakly virulent. Based on leaf blast severity, M. grisea isolates were
classified into four pathotype groups.
High degree of polymorphism was detected among the isolates from finger millet and
foxtail millet using SSR analysis with 17 markers. The isolates were grouped on the basis of
their host origins however, two isolates from finger millet and one from foxtail millet were
grouped together indicating the occurrence of some genetic drift between the two populations.
Based on similarity coefficient, the isolates from finger millet were classified into nine
groups. The isolates from different plant parts (leaf and neck) were randomly distributed in
the dendrogram. In contrast, the isolates from neck and finger samples from the same
genotype/plant were clustered in one group at 90% similarity matrix. No correlation was
observed between pathogenicity data and SSR data of 25 M. grisea isolates. Model-based
population structure analysis revealed three distinct populations based on their host origin
with varying levels of ancestral admixtures among the 65 isolates.
Epidemiological studies showed maximum disease development after 48 h of leaf
wetness with 1×105 and 1×106 conidia ml-1 inoculum concentration. Influence of temperature
on sporulation showed that 27°C was optimum for sporulation of M. grisea lesions in finger
millet. Maximum growth and sporulation of finger millet isolates occurred at 25°C and those
of pearl millet at 30°C whereas, maximum growth of foxtail millet isolates occurred at 25°C
and sporulation at 30°C.
Effective greenhouse and field screening techniques, and rating scales for neck blast
(1–5 scale) and finger blast severity (%) were developed. From the resistance evaluation of
622 finger millet core collection, 402 accessions were found resistant to neck blast, 436
resistant to finger blast and 372 had combined resistance to both neck and finger blast in field
under artificial inoculation at ICRISAT during the rainy season (kharif) 2009. Of the mini-
core, 68 had combined resistance to all the three phases of blast in field during 2009 and 2010
at ICRISAT. A significant weak to moderate correlations were found between leaf blast with
neck blast and finger blast whereas, significant strong positive correlation was found between
neck and finger blast ratings. Of the mini-core, 58 accessions were found resistant to leaf blast
in greenhouse to Patancheru isolate. These represented five basic races of finger millet that
originated from 13 countries and exhibited considerable diversity for agronomic traits.
Of the mini-core, 68 accessions were resistant to both neck and finger blast at
Patancheru, 57 at Vizianagaram, 56 at Naganahalli, 11 at Naganahalli and 10 at Mandya
during 2009 field screening. Among the mini-core, 7 accessions were resistant to both neck
and finger blast across the 5 locations during 2009. Differential reactions across the locations
was evident in 60 accessions that were categorized into seven groups. The FMBRSN-2010
comprising of 28 accessions including resistant and susceptible checks was constituted and
evaluated at five locations during the kharif 2010. Of these, 17 were resistant to all the three
phases of blast at Patancheru; 11 at Naganahalli; 10 at Vizianagaram; 8 at Mandya and 7 at
Nandyal. Of the 7 resistant accessions during 2009, two were found susceptible to neck and
finger blast in 2010 screening.
Analysis of weather data from five locations over two years and neck, and finger blast
severity on three highly susceptible accessions did not show any significant association
between blast severity and weather variables (temperature and relative humidity) however,
positive association was observed with amount and frequency of rainfall.
Analysis of resistance stability (2009 and 2010) using relative variation and GGE
biplot technique showed that, five accessions (IE 2589, -2911, -4497, -6337 and -7018) were
most resistant to all the three phases of blast across the five locations over two years. Of the
five accessions, IE 2911 was found resistant to all three phases of blast against five isolates
(one representative isolate/location) under greenhouse conditions and thus appears to be the
best source of stable resistance.
 
Date 2016-06-08T10:05:08Z
2016-06-08T10:05:08Z
2011
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/66990
 
Language en
 
Relation D9093;
 
Format application/pdf
 
Publisher ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY