STUDIES ON VIRULENCE AND HOST RESISTANCE IN OAT- Blumeria graminis f. sp. avenae PATHOSYSTEM
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Date
2020-07-16
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CSKHPKV. Palampur
Abstract
The investigation entitled “Studies on virulence and host resistance in Oat- Blumeria graminis f. sp.
avenae pathosystem” was conducted at Department of Plant Pathology, CSKHPKV Palampur during
2016-2020. Powdery mildew of oat caused by Blumeria graminis D.C. (Speer) f. sp. avenae Em.
Marchal is the most deleterious foliar disease of cultivated oat and severe losses of green fodder and
grain yield has been reported in North Western Himalayas. Total 24 isolates of B. graminis f. sp.
avenae causing powdery mildew were collected from 6 districts belonging to different zones of
Himachal Pradesh. On the basis of symptomatology, the disease was identified as powdery mildew
of oat and on the basis of morphological & molecular characterization, the pathogen causing
powdery mildew of oat was identified as Blumaria graminis f. sp. avenae. To identify the resistant
sources, 303 oat germplasm lines were evaluated under field conditions for 3 years and 11 lines viz.,
JPO-40, OS-10, OG-77, PLP-1, OL-1847, OL-1869, OL-1689, OL-1689-AVTSC, HFO-864, HFO125 and OL-6 were found resistant. Among 19 accessions belonging to 12 species of Avena also
evaluated under field conditions and none of the accessions of any species was found highly
resistant, however, OG-77 (A. sativa) and HFO-864-16 (A. byzantina) were found resistant against
powdery mildew pathogen. The cultivars IG-03-203, JPO-20 and KRR-AK-06 were identified as
slow mildewers on the basis of low values of AUDPC, high incubation and latent period, smaller
size of colonies, less sporulation as represented by number of „conidiophores bearing conidia‟ per
colony as compared to highly susceptible check HJ-8. Differential set of 11 lines viz., ADG-96,
HFO-102, IG-03-213, JPO-40, OL-1847, OG-77, PLP-1, JO-11, OL-1867, UPO-212 and susceptible
check HJ-8 was developed to study the pathogenic variability of B. graminis f. sp. avenae causing
oat powdery mildew. Study of pathogenic variability on developed differential set grouped 24
isolates into 14 pathotypes (OMP-1 to OMP-14) and the isolates were grouped in different
pathotypes as per their geographical locations. The OMP-2, OMP-7 and OMP-13 were highly
virulent among all the pathotypes, which gave susceptible reaction on 9 out of 11 differential lines.
Analysis of genetic diversity of 22 isolates of B. graminis f. sp. avenae using 4 polymorphic ISSR
markers formed 12 groups at 98 per cent similarity coefficient indicating high genetic diversity
among isolates. Both the pathogenic and molecular variability showed wide diversity among
population of B. graminis f. sp. avenae in Himachal Pradesh. The inheritance of resistance was
studied by makig crosses of 3 resistant lines i.e. OL-1847, OG-77 and OL-1689 with highly
susceptible cv. HJ-8. In all three crosses, F1 population was found resistant to powdery mildew and
F2 generation segregated into three resistant and one susceptible plant ratio, which confirmed that the
resistance to oat powdery mildew was controlled by single dominant gene.