MAPPING OF GENE(S) FOR RESISTANCE TO POWDERY MILDEW IN SESAMUM (Sesamum indicum L.)
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Date
2011
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ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY
Abstract
Powdery mildew is a serious disease of sesamum (Sesamum indicum L). It occurs
in epidemics under heavy rainfall conditions followed by low night temperatures and
high humid conditions. Powdery mildew causes yield loss of 25 to 50% depending upon
the severity. Classical breeding for incorporation of resistance using backcrossing is
difficult because consistent disease reaction in the field is hard to achieve due to
environmental factors. Identification of molecular markers linked to powdery mildew
resistant gene(s) is one approach to improve selection for resistant cultivars. The
objective of this study was to identify the mode of inheritance of disease resistance and to
use microsatellite (SSR) markers to identify markers linked to resistance gene(s) and map
gene(s) resistance to powdery mildew. In the present study Swetha til, a high yielding
popular white seeded variety but susceptible to powdery mildew and BB3-8 accession of
Sesamum mulayanum resistant to powdery mildew from RARS, Jagtial were selected as
parents for hybridization. F1 was developed by crossing the resistant parent ( BB3-8
accession of Sesamum mulayanum ) and the susceptible parent (Swetha til) during Late
summer, 2009. F1 was selfed during Kharif 2010 to generate F2. Four populations
including P1, P2 , F1, F2 were sown during Late summer, 2010 to screen powdery mildew
under field conditions. The F1 of the cross between Swetha til and BB3-8 accession of
S.mulayanum exhibited susceptible reaction to the disease suggesting resistance to be
governed by recessive gene. On screening of 104 plants of F2 population, the plants
segregated into 61 susceptible and 43 resistant plants. Chi-square analysis showed the
observed ratio to confirm the expected ratio of 9:7 ratio (susceptible : resistant) and the
resistance to disease was governed by two pairs of recessive genes contributed by
S.mulayanum. The two parents were screened for parental polymorphism using 300
sesame microsatellite markers, of which 240 showed clear amplification pattern and 24
markers exhibited polymorphism (10%) and the same were used for genotyping. DNA
from 104 F2 progenies were collected for genotyping with 24 Polymorphic SSR primers.
Molecular linkage map was constructed with SSR markers SM10 178 and SM10 176
using the MAPMAKER/EXP version 3.0 Both the markers were mapped to one and the
same linkage group at a distance of 14.2 cM. These two markers were found to be linked
to the powdery mildew resistance gene.
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Keywords
diseases, genetics, genes, planting, oilseeds, polymorphism, chromosome mapping, dna, breeds (animals), crops, Sesamum indicum L