MSc

Rice blast caused by Magnoporthe oryzae is one of the most devastating diseases
that is reported repeatedly from the rice growing areas of Kerala. The most effective
strategy to combat this is development of resistant varieties.
Jyothi (Ptb39), one of the most popular high yielding rice variety of Kerala, with
very good cooking and nutritional qualities, is highly susceptible to blast disease.
Similarly, Kanchana (Ptb50), another high yielding variety suitable for both upland and
wetland cultivation, is also highly susceptible to blast. The present study entitled
‘Incorporation of blast resistance into Jyothi and Kanchana rice (Oryza sativa L.)
varieties through Marker Assisted breeding’ was attempted to transfer blast resistant
genes from ‘Parambuvattan’, the traditional rice variety of Kerala, carrying two genes for
resistance Pi-1 and Pikh genes for resistance using tightly linked microsatellite markers.
Studies were conducted during January 2020 to February 2022. The parents were
evaluated for the agro-morphological characters from 20 plants for each variety.
Observations recorded were plant height, number of tillers per plant, panicles per plant,
panicle length, days to flowering, filled grains per panicle, sterile grains per panicle, 100
seed weight and grain weight per plant.
The polymorphic SSR markers, RM224 for Pi-1 and RM206 for Pikh, were able
to differentiate between the parents with the expected amplicon sizes of 148 and 146 bp
in donor parent and the product size in susceptible parents was 170 and 160 bp,
respectively.
For recovering the recurrent parent genome in the segregating generations,
background markers were identified by screening the parents with 42 primer (distributed
all over the chromosomes). Results indicated that eleven primers were polymorphic and
produced distinct reproducible amplicon patterns for Parambuvattan and Jyothi while
fifteen were polymorphic for Parambuvattan and Kanchana.
F1 seeds were developed by crossing Parambuvattan with Jyothi and Kanchana to
transfer the blast resistance genes. A total of 52 F1 seeds were developed from the cross
Jyothi x Parambuvattan and 48 from Kanchana x Parambuvattan.
Among eighteen F1 seedlings of Jyothi x Parambuvattan only, four plants (Plant
No. 3, 9, 13 and 18) exhibited the presence of both Pi-1 and Pikh genes in heterozygous
condition whereas, among the fifteen F1 seedlings of Kanchana x Parambuvattan only,
three plants (Plant No. 1, 4 and 13) exhibited the presence of both Pi-1 and Pikh genes in
heterozygous condition.
Seeds of the parents and F1s of both the crosses were germinated and artificially
inoculated. The inoculated seedlings were observed 6 and 10 DAI. Disease scoring was
done using 0-9 scores as described in IRRI-SES scale. Per cent Disease Severity (PDS)
was calculated for parents by taking total number of seedlings and for F1 seedlings total
number of leaves were taken into consideration. The donor Parambuvattan had a PDS of
26.6 whereas Jyothi and Kanchana were highly susceptible with PDS of 68.8 and 78.8,
respectively.
PDS score of F1 seedlings of the cross Jyothi x Parambuvattan was 34.3 while
Kanchana x Parambuvattan had 32.4. PDS score of F1 seedlings was similar to the donor
Parambuvattan, indicating their partial resistance.
Four F1 seedlings of Jyothi x Parambuvattan (Plant No. 3, 9, 13 and 18)
had the PDS 24.8, 31.1, 28.8 and 29.7, respectively. Three F1 seedlings of Kanchana
x Parambuvattan (Plant No. 1, 4 and 13) had the PDS of 26.6, 31.3 and 28.9. The
results indicated that the selected plants were showing presence of both Pi-1 and Pikh
genes and partial resistance when inoculated. Hence, these selected plants can be
forwarded for further generations to develop high yielding blast resistant rice lines.