Abstract

The effect of pH and moisture contents on microbial colonization of maize roots was studied. Roots of SWAN and TZSRY cultivars were subjected to different pH levels (3, 6.9, and 11) and moisture contents (MC) of (30, 70, and 100%) for 5 weeks. Highest bacterial population (2.36 - 3.70 x 10⁹ cfu/g root) was observed at pH 11 with SWAN cultivar and least at pH 6.9 with TZSRY cultivar (1.24 - 1.62 x 10⁹ cfu/g root). The highest fungal count (2.6 - 10.4 x10⁴ cfu/g root) was obtained throughout the period studied at pH 3 with TZSRY. Both the bacterial and fungal populations were significantly different at the pH levels, with consistently higher count for pH 11 and 3, respectively. All the MCs showed a general decrease in bacterial population at the second and fifth week; however, MC 70% with TZSRY had the highest population (2.0 - 1.02 x 10⁹ cfu/g root). MC 30% with SWAN showed a consistent high fungal population throughout at 3.6 - 13.0 x10⁴ cfu/g root. SWAN cultivar generally showed more bacterial and fungal colonization than TZSRY. Bacillus sp., Saccharomyces sp., Pseudomonas fluorescens, Bacillus subtilis, Staphylococcus epidermidis and Micrococcus roseus were the common endophytic microorganisms of both maize cultivars. This work shows that there were differences in the bacterial and fungal populations (resistance/susceptibility to environmental factors) in the roots of maize. The cultivars also differed in tolerance to pH and moisture contents implying that plants have influence on the microorganisms in its own rhizosphere.

Key words: Bacteria, fungi, endophytes, colonization, maize roots.