My research interests
I had worked mainly with two crops, rice
and rubber. It was very exciting and quite challenging to work with two totally
different crop genetic resources, which I loved very much.
I started my scientific career from my
post graduation days at the Tamil Nadu Agricultural University (TNAU), when I was working on the hybrid rice
(Oryza sativa L) with wild abortive cytoplasmic male sterility (WA-CMS). WA-CMS revolutionized the hybrid rice
production in China. We tested three male-sterile lines carrying WA-CMS namely
ZhenShan 97A, Er-jiu-Nan 1A and COMS37A crossed with IR50 to identify the
restorer system with aim of identifying a series of restorer combinations
possessing both high yield and and high fertility restoration. Pollen and
spikelet fertility segregated in 9:7 ratio indicating digenic control. A number
of selection lines were identified for further evaluation and development of
restorers for WA-CMS based cytosteriles. Using these population I could identify
strong pleiotropic association of panicle exsertion and male sterility.
Interestingly, these genes also favored the phenotypes develop sheath rot (ShR)
disease caused by Sarocladium oryzae.
For my doctoral studies, I was attached to
work with a Rockefeller Foundation funded project on nitrogen uptake in rice to
the TNAU. We were developing a molecular linkage map of rice using a recombinant
inbred line (RIL) population developed from a cross between Basmati 370 x ASD
16. ASD 16 is a high yielding indica variety and Basmati 370 is a high
grain quality, aromatic rice variety closer to japonica. I had worked on,
Field multiplication and maintenance of
RIL population using single seed descent method from F9 onwards.
Agronomic evaluation of RILs under
different nitrogen regimes.
Molecular marker profiling of RILs and
parents using simple sequence repeat (SSR) markers.
Construction of molecular linkage map.
Biochemical profiling of RILs and parents
for primary nitrogen assimilation enzymes like nitrate reductase (NR),
glutamine synthetase (GS) and glutamate synthase (GOGAT).
Designing primers specific to unspliced
coding sequences and upstream promoter specific regions for key nitrogen
assimilation enzymes, ammonium and nitrate transporter genes.
Mapping of Quantitative trait
loci (QTLs) linked to nitrogen assimilation and associated agronomic
Determination of QTL x nitrogen
Identification of nitrogen
sensitive locus for helping the development of low nitrogen stable genotypes
in future through Marker assisted selection (MAS)
The RILs were also subjected
cooked grain quality evaluation and QTLs associated with these traits
also were identified.
During this period, I used software such as MAPMAKER/EXP, QTLMAPPER, PLABQTL,
QTL Cartographer, SAS, EPISTAT, MAPCHART, QTL Network, FastPCR, Primer 3 etc.,
apart from all the procedures and equipments to run molecular and biochemical
profiling of RILs. At the end of my doctoral, I could identify a specific
chromosomal region on the long arm of chromosome 3, particularly sensitive to
nitrogen, which associated strongly with yield under different nitrogen regimes
and biomass production. This region also showed high association with GS
activity. This region is further awaiting fine mapping attempts.
While at TNAU, I also worked with MAS for
drought tolerance using near flowering lines (NFL) of the crosses between IR 64
x Norungan and IR 50 x Norungan. Norungan was a landrace known for its drought
tolerance. Panicle exsertion was found to be a secondary trait highly associated
in determining yield under the reproductive stage moisture stress. We have
worked on QTL validation and found specific genomic regions associated with
drought tolerance were favored by alleles from Norungan and strongly associated
with yield under reproductive phase moisture stress. We have also worked on
fingerprinting of rice accessions including landraces suitable for drought
tolerance and medicinal importance.
My earlier work at at the
Rubber Research Institute of India (RRII) was with Hevea brasiliensis
genetic resources, especially with the wild Hevea collections brought in
from Rubber Research Institute of Malaysia (RRIM). These collections were done
during 1981 at the centre of primary diversity in Brazil, specially from the
states of Acre, Rondonio and Mato Grosso, in an international expedition
organised by the International Rubber Research and Development Board (IRRDB),
London, UK. The collections were maintained at RRIM then on. With these
germplasm providing tremendous potential for improvement of Hevea, we
started to work on,
i. Conserving the
germplasm ex situ at our own gardens as source bush nurseries.
ii. Characterization of the germplasm lines and development of
iii. Quantitative evaluation and numerical taxonomy
iv. Determination of provenance diversity
v. Genetic potential for pre-breeding
I worked with the wild germplasm at
North-East India, where Hevea was experiencing low temperature stress. We
could identify few promising accessions based on secondary traits. Some
selections were sent to other hot spot regions of India for further evaluation.
Parallelly, we could also identify ideal selections for commercial cultivation
at North East India, from the cultivated germplasm originated from the Wickham
collections dating back to 1876. My studies were focused on cold stress and we
i. Growth pattern of
different clones under the agroclimate at North East India
ii. Yielding trend of different clones under cold and non-cold
iii. Genotype x environment interaction studies
iv. Selection combining yield and stability
v. Recombination breeding
With the tremendous exposure with a
abiotic stress situation, I continued to work with Hevea breeding lines
at another non-traditional region at Coastal Karnataka. The region was
characterized by heavy rains, hot summer, with excessive surface soil heating
due to high deposits of iron ore native to this region. This region supports the
growth of Hevea well, but require specific care in immature period to
ward of the damages due to sun scorch. But, more prevalent were various diseases
affecting Hevea, starting from the leaf diseases like, Phytophthora
leaf fall, Colletotrichum leaf spot, Corynespora leaf fall,
Oidium powdery mildew and stem diseases like pink disease caused by
Corticium salmonicolor, patch canker, bark rot and brown root disease.
Selecting high and stable yielding clones with disease tolerance was the focus
of crop improvement at Coastal Karnataka. Here I worked on,
i. Growth pattern of
clones under the agroclimate of Coastal Karnataka
ii. Clonal performance for yield and associated traits, for
iii. Identification of disease tolerance of clones
c. Other crops
At TNAU, I have worked for the induction
of cytoplasmic male sterility in pigeon pea (Cajanus cajan L.),
by attempting to transfer of alien cytoplasm from Atylosia cajanifolia,
Cajanus scarabaeoides, C. acutifolius and C. platycarpus. Embryo
rescue techniques were attempted to salvage inter-specific hybrids. Molecular profiling using isozyme and DNA markers of the
successful hybrids was done. Successful crosses were obtained in field. I was also
involved in molecular
characterization and profiling of interspecifc crosses of Sesamum and
studied the pollen pistil interaction as the pre-zygotic hybridization barriers
in many wide crosses of Sesamum. DNA marker profiling of a hybrid between
S. indicum x S. radiatum was attempted.