VARIETAL CHARACTERIZATION BASED ON MORPHOLOGICAL, BIOCHEMICAL AND SSR MARKER IN COWPEA [Vigna unguiculata (L.)WALP.]
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Date
40865
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University of Agricultural Sciences GKVK, Bangalore
Abstract
out DUS test and also seed genetic purity testing which would facilitate breeding
efforts. The objective of this experiment was therefore, to characterize the elite cultivars
of cowpea [Vigna unguiculata (L.) Walp] based on morphological, biochemical and SSR
marker. A field study was conducted during kharif, 2009. Significant differences were
observed among 32 selected cowpea cultivars for the morphological traits studied. Based
on the eye pattern, cowpea cultivars were grouped into four cluster viz., Narrow eye
(IIHR 133, IT 38-956-2, GC-3, BOMBAY AVADAE, CP-18); Holstein (IIHR 137, PKB
6, ARKA SUMAN, SARIKA, TC-20); Watson (APC 642, APC 711, PKB 3, PKB 4, IC-
201, BHAGYALAXMI) and Self coloured. Further based on seed coat colour, the self
coloured ones were classified into four groups. Cultivars IIHR 135, IIHR 140, IIHR 144,
PKB 2, KM-5, TVX 944, C-152 and LOCAL were grouped under light brown; while
cultivars APC 1215, AV 5, TVX-944-2 and KBC-2 were grouped under dark brown; and
cultivars BHAGYA, VIJAYANTHI and V-240 were categorized as reddish brown.
Nevertheless, cv.APC 149-19 was the only cultivar classified under black. The hilum
colour was white in all the cultivars. Similarly based on seed shape, the cultivars were
categorized into four groups, CP-18 is the only cultivar grouped under Globose and
cultivars IIHR 137, BHAGYA, VIJAYANTHI and BHAGYALAXMI were Ovoid in
shape, while rest of the cultivars were Rhomboid in shape. Based on plant pigmentation,
the cultivars were grouped in to five categories viz., as none, slight, intermediate,
moderate, solid and extensive. Cultivars like IC-201 and TC-20 did not show any
pigmentation, while the cultivars APC 149-19, BHAGYA and VIJAYANTHI showed
extensive pigmentation and the rest of cultivars exhibited intermediate to moderate type
of pigmentation. Based on leaf shape, cultivars were grouped in to deltoid, rhomboid, sub
hastate and hastate and most of cultivars had deltoid and rhomboid leaf shape, while
cultivars APC 149-19, IIHR 135, BHAGYALAXMI, V-240, CP-18 showed subhastate
type of leaf and cultivars BHAGYA, VIJAYANTHI, ARKA SUMAN, GC-3 showed
hastate type of leaf shape. Based on flower colour, cultivars APC 642, APC 711, IIHR
137, PKB 3, PKB 6, BOMBAY AVADAE exhibited cream petal colour. However,
cultivars IC-201, SARIKA, IT 38-956-2, IT 38-956-2, TC-20 showed yellow petals and
the rest of cultivars were purple in flower colour. Pod characters like immature pod
pigmentation showed significant variations. Based on this trait, cultivars like APC 1215,
IIHR 133, IIHR 135, KBC-2, BOMBAY AVADAE, TC-20 and LOCAL did not show
any pigmentation, while cultivars APC149-19, BHAGYA, VIJAYANTHI were
uniformly pigmented and rest of cultivars showed splashes of pigments, pigmented
valves and green sutures. Similarly based on the mature pod colour, most of the cultivars
fall under pale tan to dark tan in colour, while cultivars APC 149-19, BHAGYA and
VIJAYANTHI exhibited black/purple pod colour.
Cowpea cultivars did not respond to standard phenol test but they could be
differentiated on peroxidase, NaOH, KOH and modified phenol colour reaction tests and
hence, these rapid chemical tests could also be utilized for characterization and
identification of cowpea cultivars to some extent.
Based on the zymograms of total soluble seed proteins (SDS PAGE), Region E
(20.0 to 29.0 KD) and F (14.3 to 29.0 KD) were found more useful to distinguish most of
the cultivars studied since the banding pattern was distinct in these regions for all the
tested cultivars. Although the Esterase and MDH isozymes produced polymorphic bands
in all the genotypes, but their intensities could be used for the identification of cowpea
cultivars but the ADH isozyme, did not show any variations and need further fine tuning
of protocol.
Genetic relatedness and for fingerprinting of 32 cultivars were carried out by
using microsatellite (SSR) markers. A set of 20 SSR markers were used to amplify DNA.
Out of 20 primers used, two primer pairs (VM 14 and VM 74) produced monomorphic
band, while the other 15 primers amplified two fragments and three primers failed to
amplify. A set of 17 SSR primers amplified 32 alleles in all the cowpea cultivars but
most of the primers amplified minimum of 2 alleles. Based on the stared alleles, genetic
similarity co-efficient was estimated for each pair of 32 cowpea cultivars which ranged
from 0.20 to 0.87. Cultivars IT 38-956-2 and APC 1215 were highly distinct among the
tested ones that could be successfully utilized in crop improvement programme. SSR
primers VM 68, VM 70 and VM 71 could be utilized for identification as well as
fingerprinting of cowpeas since they produced higher polymorphism.