Philippine Journal of Science
147 (1): 113-122, March 2018
ISSN 0031 – 7683
Date Received: 03 Jul 2017

Enhanced Root System Developmental Responses to Drought by Inoculation of Rhizobacteria (Streptomyces mutabilis) Contributed to the Improvement of Growth in Rice

Roel R. Suralta¹*, Ma. Ysabera T. Batungbakal², Justine Camille T. Bello²,
Lance M. Caparas², Vincent H. Lagunilla², Katreen Mae D. Lucas²,
Joeffrey U. Patungan², Angela Joyce O. Siping², Jayvee A. Cruz¹,
Maria Corazon J. Cabral¹, and Jonathan M. Niones¹

¹Philippine Rice Research Institute (PhilRice) Central Experiment Station,
Maligaya, Science City of Muñoz, Nueva Ecija 3119 Philippines
²Muñoz National High School, Science City of Muñoz, Nueva Ecija 3119 Philippines

*Corresponding author: rrsmfs@yahoo.com

ABSTRACT

Drought limits rice production under upland conditions. This study quantified the effect of rhizobacteria inoculation on root system development during germination stage under laboratory conditions and in early vegetative stage in soil subjected to drought, as well as their contribution to soil water uptake and dry matter production using NSIC Rc192 variety. The source of inoculant was Streptomyces mutabilis, a bacterium capable of producing plant growth promoting compounds such as ACC deaminase, indole-3-acetic acid, and phosphatase. In the first experiment, pre-germination inoculation of seeds by S. mutabilis significantly increased the shoot and seminal root length as well as root hair lengths, relative to the uninoculated control. In the second experiment, inoculation of S. mutabilis generally had longer total root length under drought – regardless of the timing of inoculations – relative to the uninoculated control. Consequently, improved root system development contributed to the increase in soil water uptake under drought and thus, resulted in the increase in dry matter production. Among inoculation treatments, one-time inoculation of S. mutabilis either at pre-germination or pre-drought stress at 14 days after sowing (DAS) had significantly greater shoot dry matter production than three-time inoculation at pre-germination, thinning (3 DAS), and pre-drought stress (14 DAS). This study demonstrated the effectiveness of rhizobacteria (S. mutabilis) containing growth promoting compounds for enhancing drought dehydration avoidance root traits and improving the growth of rice plants under drought conditions.