M Sc

The present study entitled “Genetic analysis of medium duration rice genotypes for
tolerance to iron toxicity in South Central Laterites of Kerala” was conducted at Farming
Systems Research Station, Sadanandapuram to evaluate and select rice genotypes tolerant
to iron toxicity suited to South Central Laterites of Kerala during 2019-2021. The project
was implemented as two experiments and in Experiment-I, initial evaluation of rice
genotypes for iron toxicity tolerance was done as pot culture study. In Experiment-II,
genotypes selected from experiment-1 was evaluated in paddy field where soil iron is at a
toxic level.
Thirty rice genotypes were collected from different research stations under KAU. Growing
media consist of washed sand in polybags kept in plastic basins filled with Hoagland
solution at different concentration (0,200,400,600 mgl-1
) of iron at a constant pH of 4.0.
Rice genotypes Uma, Karishma, Thekkan chitteni, Pournami, Panchami, Gouri, Bharati,
Aiswarya, Asha, Pavithra and Samyuktha were selected from 30 genotypes screened in the
laboratory based on morphological characters and iron toxicity score at highest iron
concentration (600 mgl-1
).
Eleven rice genotypes were evaluated in field in iron toxicity affected field with pH
(4.9) and iron content (544 mg kg-1
), in randomized block design. Germinated seeds were
sown in nursery and 21 days old seedlings were transplanted to main field. Seedlings were
transplanted at a spacing of 20cm X 15cm. Agronomic practices which include lime
application (600 kg ha-1
) were carried out according to “Package of Practices
Recommendation Crops 2016” of Kerala Agricultural University (KAU, 2016). A control
block without lime application containing all treatments were maintained.
The genotypes were evaluated for 33 characters including biometric and
biochemical characters associated with iron toxicity tolerance. The genotypes showed
significant differences for all the characters studied. Genetic parameter analysis was
performed for 21 characters and for all the characters PCV values were higher than GCV
values indicating the influence of environment. The phenotypic and genotypic coefficient
of variation were maximum for straw yield per plant and minimum for days to 50%
flowering. High heritability coupled with high genetic advance was observed for plant
height, total number of tillers per plant, number of productive tillers per plant, panicle
weight, sterility percentage, root length, grain yield per plant, straw yield per plant, number
of fresh roots (20 DAT), iron content on root, iron content on 3rd leaf from tip, iron content
in oldest fully opened matured leaf, iron content in grain, iron content in straw.
Days to 50% flowering, number of tillers per plant, number of productive tillers per plant,
panicle length, panicle weight, number of grains per panicle, number of filled grains per
panicle, 1000 grain weight, root length and total number of roots(20 DAT) showed positive
correlation with grain yield per plant. The path analysis provides information on
contribution of traits by partitioning the total correlation into direct and indirect effects.
Path analysis revealed highest positive direct effect of days to 50% flowering on grain yield
per plant. Highest indirect effect of number of grains per panicle through days to 50%
flowering.
Cluster analysis aids in the selection of genetically divergent parents for hybridization
programme which results in greater heterosis. Cluster analysis using Mahanalobis D2
statistic following Tocher’s method grouped the 11 genotypes into five clusters.Cluster I
with 7 genotypes was the largest and cluster II, III, IV, V were solitary. Intra cluster
distance was recorded only in cluster I (11.32). Highest intercluster distance observed
between genotypes of cluster V and cluster II.
The present study revealed that genotypes Panchami (6.4 t/ha) recorded maximum yield
and was followed by Pournami (5.7 t/ha). These varieties can be recommended for iron
toxic low land paddy fields of South Central Laterites of Kerala. Genotypes Panchami,
Pournami, Uma, Karishma, Gouri and Pavithra recorded lowest leaf bronzing score at
maturity under iron toxic field conditions. These genotypes can be used in breeding
programmes to develop iron toxicity tolerant rice varieties.