Effects of long-term callus culture on stability and agronomic perfomance of maize regenerants among three Kenyan hybrids and an Open Pollinated Variety

Abstract

Maize (Zea mays) is a member of the maydeae tribe of the grass family Poaceae. It is planted by over 80% of the rural smallholder farmers in East and Central Africa. Commercial maize production is concentrated in the Kenya highland and moist transitional zones, which produce 90% of the maize that is marketed in the country. However over 70% of Kenya's land falls under the arid and semiarid zones which is unsuitable for rain fed agriculture. The major abiotic factor affecting Kenya's maize production is inadequate rainfall in the ASAL areas or erratic and unfavorable distribution of rainfall in other areas. The resulting drought conditions in these areas leads to yield loses of up to 71% high, due to lack of suitable drought resistant varieties. It is therefore important to produces high yielding maize that is tolerant to drought. Biotechnology application in maize improvement is a promising option that is suitable for the production of new varieties specifically to overcome the constraints facing maize production in the different Kenyan agroecological zones. In this study three Kenyan hybrids Pwani Hybrid I(PHI) and its hybrid, Dryland Hybrid 2 (DH02), and an Open Pollinated Variety; Katumani (KAT), calli were maintained culture media for a long time (6 to 12 months) and then used for plant regeneration. The regenerated plants Ro (primary regenerants) and Rl (progeny of primary regenerants) were then evaluated for the degree of somaclonal variation in their phenotypes and how they performed agronomicaly. Dehydration test on both germination of (Rls, Ro and control) seeds and maize plants was also done to assess the effect of the culture process on the ability of the seeds and plants to withstand drought stress. In this study regeneration was observed to be genotypic dependent with rates of 177.4%, 94%, and 27% for KAT, PHI, and DH02 respectively. Regeneration was also observed to decrease with callus age with a negative correlation (R2 = 0.85). The Ros revealed many phenotypes but only the grained tassel was transmitted to the Rls. most of which bear similarities in the maize database and other published data. The mutants are important in the study of the effect of different genes on the phenotype and their effects in biochemical pathways in plant function. Data showed that all parameters tested in the Ro genotype performed significantly from the control. However no significant difference was observed in the agronomic performance of the Rl genotype compared to the control from commercial seeds. The Rls matured earlier than those of the controls, had a short ASI and when stressed they performed better than the controls.