Assessment of hybrid purity in sorghum by using molecular markers
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Date
2015-05-30
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Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani
Abstract
Sorghum [Sorghum bicolor (L.) Monech], (2n=2x=20) is one of the main
staple food for the world’s poorest and most food insecure people across the semi-arid
tropic. It has been considered as a 4F crop for its usage as food, feed, fodder and fuel
crop. A correct identification of a hybrid plant may often be difficult when it
resembles more to one parent than the other or when new morphological
combinations of characters arise from recombination of distinct genotypes or when
only few morphological traits are available for the analysis. Full potential of any
hybrid can be realized only by using good quality seeds and hence determination of
genetic purity is an essential requirement for its commercial success. Molecular-based
seed purity assay provide a better alternative and it is currently receiving more
attention. In a view of ‘Protection of Plant Varieties and Farmers Right, 2001’ it has
become more important to characterize the cultivars or hybrids. The molecular
markers could be implicated in identification of specific hybrids. PCR based
molecular markers are likely to be promising for identification, registration and
protection of commercial sample.
In present investigation, four sorghum hybrids viz., CSH-14, CSH-16, CSH-25
and SPH-1641 were screened with RAPD and SSR markers for hybrid confirmation
and purity testing. Five RAPD primers (OPA-4, OPA-13, OPA-18, OPA-19 and
OPK-19) and eight SSR markers (Sb6-84, Sb6-57, Sb6-42, Sb4-72, Sb6-34, Sb5-236,
Sb4-121and Sb6-36) enabled to assess the purity of hybrid with their parents.
Among RAPD, The primer OPA-4 could produce maximum of 100 %
polymorphism while primer OPA-18 showed 71.43 % polymorphism and found to be
least polymorphic. OPA-13 and OPA-19 were found to be most informative for
identification of true hybrid.
The PIC values of eight polymorphic, SSR markers ranged from 0.44 to 0.77
with an average of 0.58. The microsatellite Sb6-84 was observed to be most
informative with the PIC value of 0.77 which significantly determined genetic
relatedness among hybrids and parental lines. Sb4-121 could confirm three hybrids
(CSH-14, CSH-16 and CSH-25) by producing male parent specific allele. It also
confirmed SPH-1641 by producing female specific allele. Sb4-72 produced
homozygous alleles in all of the four hybrids and their respective parents. Sb6-84 was
found to be useful in identifying CSH-16 and SPH-1641 as a true hybrid of their
respective male parent. Sb6-84 has also produced hybrid specific alleles (~240bp
respectively), which could enable development of marker for cultivar identification.
Based on the RAPD marker analysis, the genetic similarity values ranged from
0.35 to 0.94 whereas genetic distance values ranged from 0.06 to 0.65. Whereas, the
genetic similarity was retrieved from microsatellite (SSR) data using Dice coefficient
ranged from 0.11 to 0.89 with an average of 0.37.
The cluster analysis was also performed based on polymorphic RAPD, SSR
and combined markers. The genetic similarity values were retrieved using Dice
coefficient ranged from 0.31 to 0.87 with an average of 0.53. The clustering of the
hybrids with their male parents revealed similaritys among them being the true
hybrids.
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