The Philippines
May 30, 2007
By Sosimo Ma. Pablico, PhD,
Agriculture Magazine February 2007 via
SEAMEO SEARCA
The first biotech rice variety in the Philippines is now being
produced in a large scale as the
National Seed Industry
Council (NSIC) released it recently for commercial
production.
Tagged as NSIC Rc142 or Tubigan 7, the new rice variety is the
country’s first product of a mid-level biotech technique called
marker-aided selection.
Resistant to the dreaded bacterial leaf blight (BLB) disease,
Tubigan 7 is one of the offspring produced in almost 10 years of
rigorous breeding work initiated in 1995 by Dr. Leocadio S.
Sebastian, PhilRice executive director, through a research grant
from the Rockefeller Foundation. It is the first variety
produced by the project, but it is hoped that more will be
released in the near future.
Subsequent breeding works were handled by Dr. Rodante E. Tabien,
MC Abalos, MP Fernando, Emily C. Arocena, Yolanda A. Dimaano, GM
Osoteo, Rolly C. San Gabriel, DA Tabanao, Thelma F. Padolina,
Herminia Rapusas and Genero P. Rillon.
The BLB resistance of the new variety was derived from IRBB5-21,
a line provided by the Asian Rice Biotechnology Network (ARBN)
of the International Rice Research
Institute (IRRI).
MARKER-AIDED SELECTION
Jaime A. Manalo IV of the PhilRice plant breeding and
biotechnology division reported that xa21, the BLB resistance
gene from IRBB5-21 which is known to be effective against nine
BLB races, was introduced into IR 64 using DNA markers. IR 64 is
considered a good parent for yield and grain quality.
Manalo said DNA markers, also called the breeders’ kilometer
posts, help plant breeders locate genes of interest, usually
those that are associated with desired traits like BLB
resistance.
Through the use of DNA markers, plant breeders can readily
identify off-springs (products of breeding work) that are
resistant to the much dreaded disease without waiting for the
plants to grow until a particular stage.
Dr. Antonio A. Alfonso, PhilRice plant breeding and
biotechnology division head, said the use of DNA markers makes
the selection of BLB-resistant plants easier, faster and more
effective than the conventional breeding method. He explained
that in the conventional breeding method, BLB-resistant plants
are selected at around 45 days after transplanting. This method
requires plants that are actually inoculated with the
microorganism that causes bacterial leaf blight and then
observed for disease occurrence after two to three weeks.
In marker-aided selection, on the other hand, plant breeders do
not undergo through the tedious process of growing the plants,
inoculating them with the disease microorganism; and observing
them for disease occurrence, which takes eight to nine weeks.
With DNA markers, plants with the BLB resistance gene are
evaluated and selected in the screenhouse and in the field. As a
result, “breeding efficiency is tremendously increased due to
reduced cost owing from reduced number of test entries and time
needed for selection,” Alfonso said.
“The use of DNA as markers for selection has streamlined and
facilitated the whole process even without inoculation,” Tabien
and his co-workers said earlier in a paper presented during the
13th national rice research and development conference in year
2000.
Actually, marker-aided selection started in the 1996 wet season
and continued until the 1998 wet season. Field testing started
in the 1999 dry season.
FIELD TRIALS
Together with other promising lines, Tubigan 7 was evaluated at
PhilRice Maligaya, PhilRice San Mateo and PhilRice RTR in Agusan
del Norte before it was forwarded to the National Cooperative
Test (NCT) in 2002 dry season. It carried then the code name
AR32-19-3-3.
In the NCT Phase 1, the yield of Tubigan 7 under direct wet
seeded culture was 24 percent higher than PSB Rc30 during the
dry season and 32 percent higher during the wet season. Under
transplanted condition, its yield was higher by 12.7 percent.
Although Tubigan 7 is more adaptable in direct wet seeded
culture, it could also be used in transplanted culture,
preferably during the wet season. The breeders, however, suggest
that it should be frequently monitored for blast incidence.
This new variety matures early at 105 days with a height of 85
centimeters. It has intermediate resistance to major diseases of
rice like bacterial leaf blight and sheath blight. It also has a
wide spectrum of resistance to the insect green leafhopper,
yellow stem borer and brown plant hopper. Green leafhoppers
transmit the tungro virus disease, while brown plant hoppers
could wipe out a whole crop under heavy infestation.
Tubigan 7 has good milling and eating qualities, as it is sticky
and moist when cooked because of its low amylose content. |
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