Exploration and identification of potassium solubilizing rhizo-bacteria isolate colony morphology from corn plant rhizosphere that potentially as a potassium solubilizing biofertilizer

Abstract

Herdiyantoro D, Simarmata T, Setiawati MR, Nurlaeny N, Joy B, Hamdani JS, Handayani I. 2018. Exploration and
identification of potassium solubilizing rhizo-bacteria isolate colony morphology from corn plant rhizosphere that potentially as a
potassium solubilizing biofertilizer. Pros Sem Nas Masy Biodiv Indon 4: 178-183. The availability of potassium (K) in soil for plants is
very low since most (98%) of K elements are in the form of primary silicate minerals such as K-feldspar or fixed in secondary silicate
minerals such as 2:1 type clay. Potassium solubilizing rhizo-bacteria (KSRB) can facilitate increased availability of K elements for
plants. The purpose of this research was to isolate and identify morphologically the colonies of KSRB isolates from the corn plant
rhizosphere as a potential biofertilizer that could facilitate the availability of plant K elements. The research was carried out by
explorative method through sampling of soil rhizosphere of corn cultivated around Experimental Garden of Faculty of Agriculture,
Padjadjaran University, Jatinangor (J1, J2, J3, J4 and J5). Serial dilutions using physiological saline solution were carried out to 10-5 to
obtain the source of bacterial isolates and then inoculated into a petri dish containing Aleksandrov solid medium (K-feldspar as sole K
source) ranging from 10-3 to 10-5 by 0,25 mL and 0,50 mL in duplicate. Colonies of bacteria that grow on Aleksandrov solid medium
and produce clear zones were KSRB isolate colonies. The research results showed: (i) The proportion of KSRB isolate colonies obtained
from sampling point J1, J2, J3, J4 and J5 were 33% (8% clear, 25% white), 100% (92% clear, 8% white), 33% (8% clear, 25% white),
33% (8% clear, 25% white) and 8% (8% white); (ii) The main morphological features of KSRB isolate colonies were: (a) clear colored
colonies (shape: rounded, edge: slippery, elevation: convex, size: small to large, and produce clear zone) and (b) white colored colonies
(shape: rounded with spread edges, edge: like wool, elevation: arise, size: small, and produce clear zone); and (iii) Colonies of KSRBDHJ2
isolates dominated the acquisition of KSRB isolate colonies with the main morphological characteristic of clear colored colonies.