d(GC) - Association of Biotechnology and Pharmacy
d(GC) - Association of Biotechnology and Pharmacy
d(GC) - Association of Biotechnology and Pharmacy
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Current Trends in <strong>Biotechnology</strong> <strong>and</strong> <strong>Pharmacy</strong><br />
Vol. 6 (2) 173-182 April 2012, ISSN 0973-8916 (Print), 2230-7303 (Online)<br />
Genetic frequency for heterozygsity in the<br />
population was analyzed using Hardy-Weinberg<br />
equilibrium it was revealed that few<br />
heterozygote’s was observed indicating<br />
inbreeding pattern in the population this may be<br />
due to the most <strong>of</strong> the isolates collected from<br />
same region while MGM - 2, MGM - 5 <strong>and</strong> MGM<br />
– 24 primers showed significant observed<br />
heterozygosity (Table 2) indicating that MGM<br />
primers are the right choice to analyze the<br />
Magnaporthe grisea genetic diversity compared<br />
to other conventional primers, Similarly using<br />
Hardy–Weinberg equilibrium Li et al., (29) was<br />
observed no deviations between any pair <strong>of</strong> loci,<br />
suggesting that null alleles at all the loci are rare<br />
in M. grisea. However, we observed great extent<br />
<strong>of</strong> variation among the isolates collected from<br />
different endemic areas. For instance, the<br />
isolates collected from Mareturu (SP 25 <strong>and</strong> SP<br />
26), Assam (SP 3 <strong>and</strong> SP 4), Almora (SP 1 <strong>and</strong><br />
SP 2) <strong>and</strong> Nellore grouped in the same cluster<br />
but they share only 35 % similarity. Another 9<br />
isolates two each from Ranchi (SP 33 <strong>and</strong> SP<br />
34), Jagityal (SP 20 <strong>and</strong> SP 21), Karjat (SP 22<br />
<strong>and</strong> SP 23) <strong>and</strong> 3 isolates from DRR (SP 12, SP<br />
10 <strong>and</strong> SP 19) also grouped in the first major<br />
cluster they were out grouped with two sub<br />
clusters by showing 75 % dissimilarity to the<br />
isolates in the first major cluster. We also<br />
observed some exceptions like isolates collected<br />
from coastal Andhra Pradesh (Mareturu <strong>and</strong><br />
Nellore) shares the high similarity <strong>of</strong> 64 % with<br />
Assam isolates (SP 3 <strong>and</strong> SP 4). High similarities<br />
between isolates collected from various endemic<br />
areas <strong>of</strong> India like Uttaranchal, Himachal Pradesh<br />
those <strong>of</strong> Madhya Pradesh <strong>and</strong> Karnataka was<br />
reported earlier by Chadha et al., (30) with RAPD<br />
markers contributing to the possibility <strong>of</strong> seedborne<br />
transmission <strong>of</strong> the pathogen. Therefore<br />
it is expected that, the migration <strong>of</strong> the pathogen<br />
to a newer location operates. Due to extensive<br />
gene flow among the isolates genetic variability<br />
may arise that was evident from the presence <strong>of</strong><br />
high variation among the isolates collected from<br />
different endemic areas. Kumar et al., (23) also<br />
179<br />
concluded the migration <strong>of</strong> the pathogen that<br />
results in to the wide distribution <strong>of</strong> lineages in<br />
the Indo-Gangetic Plains <strong>of</strong> India. Nguyen et al.,<br />
(31) also observed the significant gene flow<br />
between P. oryzae isolates <strong>of</strong> indica populations<br />
collected from North Vietnam.<br />
The clustering analysis revealed the grouping<br />
<strong>of</strong> the isolates collected over differentials with the<br />
isolates collected from the susceptible cultivars<br />
<strong>of</strong> blast endemic areas. Based on these<br />
clustering <strong>and</strong> similarity values, a prediction <strong>of</strong><br />
AVR/avr genes was done. The isolate (SP 14)<br />
which was virulent on differential variety i.e.,<br />
Kanto51 (which has Pi-k gene) shares 43 %<br />
similarity with the isolates (SP 29 <strong>and</strong> SP 30)<br />
collected from Nellore. Hence, we presumed that<br />
in Nellore region the fungal population may have<br />
avr Pi-k gene, hence deployment <strong>of</strong> varieties<br />
having Pi-k gene may not <strong>of</strong>fer resistance to this<br />
prevalent race in that region. Interestingly, many<br />
present day ruling varieties (NLR 145) in this<br />
region have developed using Tetep (which has<br />
Pi-Kh ) as a resistance source (32, 33). It is also<br />
predicted that there will be many alleles exist in<br />
avr Pi-k cluster in Magnaporthe grisea as like Pik<br />
cluster in rice It has also been reported that<br />
the Pi-k locus is actually a cluster <strong>of</strong> genes<br />
including Pik-p, Pik-m, Pik-s <strong>and</strong> Pik-h present<br />
on rice chromosome 11 (34). Similarly, the isolate<br />
(SP 24) collected from endemic area <strong>of</strong> South<br />
India (M<strong>and</strong>ya- Karnataka) showed 70 %<br />
similarity with the isolate (SP 17) which is<br />
collected on IR50 variety as well as 40 % with<br />
the isolate (SP 9) which is collected on BL-245<br />
variety which is known to contain a combination<br />
<strong>of</strong> Pi-2 <strong>and</strong> Pi-4 genes. Hence the fungal<br />
population <strong>of</strong> M<strong>and</strong>ya region might be having<br />
both or either <strong>of</strong> avr Pi-2 <strong>and</strong> avr Pi-4 genes.<br />
Assam fungal population might be having avr<br />
Pi-ks gene since these isolates collected from<br />
these regions showed 64 % <strong>of</strong> similarity to the<br />
isolate collected from a differential variety<br />
(Calaro) which contains Pi-ks gene. On the other<br />
h<strong>and</strong>, tightly linked blast resistance genes at the<br />
Pik locus were presumed to have evolved from<br />
Analysis <strong>of</strong> Population Structure <strong>of</strong> Magnaporthe grisea