PhD

The present investigation entitled “Diversity analysis in landraces of rice
(Oryza sativa L.) in Wayanad through morphological and molecular
polymorphism study” was conducted at the Department of Plant Breeding and
Genetics, College of Horticulture, Vellanikkara, Thrissur and Regional
Agricultural Research Station, Ambalavayal, Wayanad during the period 2015-
2018. The study aimed to collect and characterize the rice landraces of Wayanad
at morphological level and also to characterize the popular aromatic genotypes of
the area at molecular level.
DUS characterization revealed that, all the landraces under the study
exhibited presence of leaf collar, absence of anthocyanin colouration of leaf
collar, presence of leaf ligule, split shape of leaf ligule, absence of anthocyanin
colouration for plant parts like lemma (keel), area below apex of lemma, stem
nodes and presence of secondary branching in panicle. Variability was
exhibited for majority of characters namely coleoptile colour, basal leaf sheath
colour, intensity of green colour of leaf, anthocyanin colouration of plant parts
like leaf, leaf sheath, auricles, ligules, lemma apex, area below apex of lemma,
distribution of anthocyanin colouration in leaf, pubescence of leaf blade
surface, leaf auricles, culm attitude, density of pubescence of lemma, colour of
stigma, attitude of flag leaf blade, curvature of main axis of panicle, lemma and
palea colour, presence and colour of awns, distribution of awns in panicle,
secondary branching in panicle, attitude of branches in panicle, panicle
exsertion, leaf senescence, sterile lemma colour, shape, colour and aroma of decorticated grain, gelatinization temperature and lodging nature.Thavalakannan, Mullan puncha and Sugandhamathi exhibited distinct morphological characters.
Among the 60 landraces, Kanni kayama, Ambalavayal-1, Kothandan,
Onamottan, Thondi-2, Chenthadi, Kannali and Thondi-1 exhibited significantly
high grain yield per plant, which was on par with that of Uma and Aathira
(high yielding check varieties), indicating the possibility of commercial
cultivation of these cultivars.
High PCV value than GCV for all the characters under study, indicated the
influences of environmental factors on the characters. High heritability and high
genetic gain was exhibited by the characters like length of leaf blade, width of leaf
blade, stem thickness, stem length, number of tillers per plant, number of panicles
per plant, length of panicle main axis, number of spikelets per panicle, number of
grains per panicle, seed setting (per cent), 1000 grain weight, grain length, grain
L/B ratio, decorticated grain L/B ratio and grain yield per plant, indicating that
these characters could be used in crop improvement programmes.
Character association studies including correlation and path-analysis
revealed that, five characters viz., width of leaf blade, stem length, number of
panicles per plant, weight of 1000 grains and decorticated grain width showed
both positive correlation and positive direct effect on grain yield per plant.
Cluster analysis based on qualitative characters categorized 60
landraces into 11 clusters at 74 percent similarity level. Based on D2 statistics
analysis, the landraces were grouped into seven clusters with variable number
of landraces in each cluster, indicating wide genetic diversity in the Wayanad
landraces. All the inter-cluster distances were higher than the intra-cluster
distance, indicating the wider genetic diversity among landraces of different
clusters.
Molecular characterization of aromatic rice genotypes of Wayanad by
SSR (RM) profiling revealed high level of genetic polymorphism among the
genotypes studied. Out of 86 SSR markers used for molecular characterization,
44 markers were polymorphic and remaining 42 were monomorphic.
Maximum number of amplicons was exhibited by RM247 with five amplicons,
followed by RM85, RM251, RM248 and RM493 with four amplicons each.
The highest PIC value was exhibited by RM247 (0.90), followed by RM85,
RM251 and RM493 with 0.88 PIC value each.
Out of 86 SSR (RM) markers, 21 markers distinguished Basmati from
traditional aromatic landraces of Wayanad viz., Gandhakasala and Jeerakasala.
Seven SSR markers distinguished Gandhakasala from Jeerakasala, whereas 23
markers distinguished Basmati from Jeerakasala. Twenty-two markers
distinguished Basmati from Gandhakasala and 23 markers distinguished
aromatic group from non-aromatic group.
Cluster analysis for molecular characterization revealed maximum
similarity coefficient (1.00) within all the Jeerakasala morphotypes and all the
Gandhakasala morphotypes. Cluster analysis effectively differentiated Basmati,
Jeerakasala, Gandhakasala, Uma and Aathira from each other. Among the five
clusters formed, cluster III was the largest one comprising all the 12
Gandhakasala morphotypes, followed by cluster IV with all Jeerakasala
morphotypes. Cluster I, Cluster II and Cluster V exhibited one genotype each
namely Aathira, Uma and Basmati, indicating their genetic distinctness.