Establishing a “Microbial-Plant” as means to control rice blast disease

Njiru P.N., J.I K, Kimani J.N., R.K W. Establishing a “Microbial-Plant” as means to control rice blast disease.; 2012.


Kenya is facedwith serious food insecurity. To reverse this, there is need to increase food crop
productivity or yield per hectare. This will involve plant genetic transformation,
disease control and improvement of agronomic practices. One way of increasing rice
yield without increasing the acreage under rice (0ry2a sativa L.) cultivation is the
use of hybrid rice technology. Two genetically fixed varieties are cross-pollinated to
produce filial generation one [Fr) or hybrid seeds. Even with this rice blast (Pyricularia
grisea) continue to erode yields and its is responsible for over $5 billion in yield loss.
In ongoing project we intend to produce hybrid rice that is resistant to blast. Our main
object to create amicrobial-plant interface that enables transfer of high yield and blast
resistance genes such as RCC2 ha into rice plant using Agrobacterium tumefaciens.
Additionally hybridization, by exploiting rice plant diversity and heterosrs, will bring
about a multi-gene interplay under a single rice plant hence further boost in blast
resistance. Material to be utilized will be rice plants; Basmati3 70; Photoperiod sensitive
geneic male sterile IPGMSJ; and Thermosensitive genic male sterile (TGMS). PGMS
and TGMS are sterile when grown under long day-light length and high temperature
conditions respectively and revert to fertility in normal day-light length and low
temperature growth conditions. Te develop biological guard against P. grisea bacteria
(Actinomyctes, Bacillus and Pseudomonas) and fungal antagonists (Trichodermd spp.,
Penicillium, Myrothecium verrucaria, Chaetomium globosum and Laerisaria arvalis)
will be used while nitrogen fixing bacteria Rhizobium oryzae sp. Nov. will be included
to test ability of rice to fix nitrogen. Methods to be used will include isolating bacteria
from various soil samples that will be assayed through serial dilution. Bacteria will be
multiplied in broth medium and their single and combined effects against P grisea will
be evaluated in laboratory and field conditions, Successful combination will be tested
and packaged for commercial use.

To exploit plant genetic diversity in blast resistance, Basmati 370 will be backcrossed
with blast disease PGMS/TGMS varieties up to BC*F, and then anther culture will be
done to fixed the genes using doubled haploid approach. These will be used as male
parents to be cross with blast disease PGMS/TGMS in hybrid rice seed production
programme. Additionally, bacterium of rhizobium genus (Rhizobium oryzae sp. Nov) will be
inoculated in Basmati with a view of determining its efficacy to fix nitrogen in
Basmati3T0 rice backgrounf. Pollen from F, will be cultured to produce callus which
will be transformed by co-cultivation with Rhizobim spp with an aim to regenerating
plantlets with nitrogen fixing ability. Our expected product is high yielding hybrid
Basmati3Tg that is dir""t" resistant (or guarded to blast disease attack)' This will
increase farmers' income and food security in this Country.

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