M Sc

he present investigation entitled “Identification of superior genotypes for water
stress tolerance in rice (Oryza sativa L.) for south central laterites of Kerala” was conducted
at Farming Systems Research Station, Sadanandapuram, Kottarakkara during 2019-21 with
an objective to identify and characterize the traditional as well as released rice genotypes
of Kerala for water stress tolerance using phenotypic and biochemical markers, suitable for
south central laterites of Kerala.
The study comprised of thirty genotypes collected from RARS, Pattambi,
Department of Seed Science and Technology, College of Agriculture, Vellanikkara, KAU,
Thrissur and ICAR- NBPGR, New Delhi. Study was conducted in two experiments viz.
laboratory and field study.
In the first experiment (Experiment-I), thirty genotypes were evaluated for moisture
stress tolerance at seedling stage for seven different morpho-physiological characters viz.
Germination percentage, speed of germination, root length, shoot length, seedling dry
weight, seedling vigor index 1 and seedling vigor index 2 in laboratory using PEG 6000
(Polyethylene Glycol- 6000) at five different concentrations of 0, 5, 10, 15, 20 percentage
(%). The study was conducted in factorial completely randomized design, replicated thrice
and the twenty-one tolerant genotypes were selected for field study.
In the second experiment (Experiment-II), twenty-one best performing genotypes
including the high performing standard check variety Apo in randomized block design
were selected and evaluated in the field where irrigation was withheld for 10 days at critical
growth stages. The seeds were sown on raised beds of 4 m2
size at a spacing of 20 cm х 20
cm and cultural operations were adopted as per the “Package of Practices (2016)” of Kerala
Agricultural University. Genotypes were evaluated for twenty-four characters which
included different biometric, physiological and biochemical observations. Significant
difference was observed among genotypes for all the characters studied in both field and
laboratory experiments.
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
recovery after stress release and minimum for days to 50 % flowering. Heritability was
high for all the characters except leaf rolling score and genetic gain was high for all the
selected characters.
Correlation studies revealed significant positive correlation for all the selected
characters except spikelet sterility, which exhibited significant negative correlation with
grain yield. Path analysis conducted for eleven characters showed significant correlation
with grain yield and also revealed that relative water content recorded high positive direct
effect on grain yield. High positive indirect effect on grain yield was recorded by grain
weight per panicle via spikelet sterility.
Genetic divergence analysis using Mahanalobis D2 statistic following Tocher’s
method grouped the twenty-one genotypes into five clusters. Cluster II with 10 genotypes
was the largest followed by cluster I (8 genotypes) and cluster III, IV, V were solitary. The
highest intra cluster distance was recorded among the genotypes of cluster II. Whereas
highest inter cluster distance was observed between the genotypes of the clusters I and V.
Among the selected characters, the relative contribution towards the genetic divergence
was much higher for root length.
In the present investigation, genotypes Parambuvattan, Apo, Vaisakh and
Chuvannavattan were identified as the best water stress tolerant ones under PEG induced
stress conditions based on various seedling parameters during laboratory experiment.
While, field evaluation of the genotypes Vaisakh, Karanavara, Karuthadukkan,
Kattamodan, Parambuvattan and Onamottan exhibited good and comparable grain yields
with the Universal drought tolerant check Apo under field level drought conditions.
Thus, it can be concluded that Parambuvattan, Karanavara, Karuthadukkan,
Kattamodan and Onamottan were recognised as best performing genotypes capable for
moisture stress tolerance despite the performance of universal check, Apo and high
yielding Vaisakh. The best performing genotypes identified in the study can be
recommended for upland cultivation in south central laterites of Kerala and also for
molecular analysis in future rice breeding programs by Kerala Agricultural University.