GENETIC ENGINEERING OF FINGER MILLET (Eleusine Coracana) WITH Aldose Reductase GENE ISOLATED FROM Xerophyta Viscosa TO ENHANCE DROUGHT AND SALINITY TOLERANCE

ABSTRACT

Finger millet is chief food crop for millions of people in the world. It is ranked third in cereal

production in semi-arid regions after sorghum and pearl millet. It is generally grown all over

the world especially the developing countries with stable yield and strong adaptability to a

number of agro-ecological environments. Despite its importance, finger millet increase in

production is limited by abiotic stresses especially drought and salinity which affects the plant

in the field during seed germination and early phases of seedling development. Unique plants

such as Xerophyta viscosa, (a resurrection plant) that uses a number of physiological and

molecular responses in order to survive under extreme stress conditions, are valuable sources

of useful genes for crop improvement. Accordingly, XvAld1gene that encodes aldose

reductase has previously been isolated from X. Viscosa under dehydration stress. The

objective of this study was to establish a direct regeneration protocol of Kenyan finger millet

varieties and develop transgenic drought and salinity tolerant finger millet plants expressing

XvAld1 gene via Agrobacterium- mediated transformation. Six finger millet varieties

GBK043137, GBK043128, GBK043124, GBK043122, GBK043094 and GBK043050 were

used. As a prerequisite, a rapid and reproducible direct regeneration protocol was established

using shoot apical meristems. The study established that the highest shoot induction was

obtained in MS media supplemented with 1.75mg/l BAP while highest rooting events was

obtained in MS media supplemented with 4.0 μM. In order to produce drought and salinity

tolerant finger millet plants, XvAld1 gene controlled by stress-inducible XvPsap1 promoter

was introduced into finger millet via Agrobacterium-mediated transformation and the

transgenic events regenerated through direct organogenesis. The polymerase chain reaction

(PCR) and the reverse transcription PCR (RT-PCR) confirmed the integration and the

expression of XvAld1 gene with 1 positive event recorded in each finger millet line. In order

to evaluate the drought and salinity tolerance, the rate of germination, number of green leaves

and the total chlorophyll content of the transgenic compared to the wildtype plants was

examined under simulated drought and salinity stress using mannitol and sodium chloride

respectively. The study established that transgenic plants were more tolerant to drought and

salinity stresses than the wildtype plants. The results of this study demonstrate a rapid,

adoptable and effective system to transform and regenerate finger millet plant. Genetic

enhancement of finger millet will improve yield and ensure food security even during crop

failure due to hostile weather conditions associated with climate change.