Screening of cultivable endophytic bacterial isolates for their plant growth promoting activity in rice

Large amounts of chemical fertilizers are being used to enhance the growth and development of the rice (Oryza sativa L.) crop. Chemical fertilizers are too expensive; hence, endophytic bacteria with growth promoting activity can be considered to promote the crop plant growth to minimize the usage of chemical fertilizers and to have sustainable rice cultivation. This study was undertaken to explore the potential of endophytic bacterial isolates (EBIs) which were isolated previously. The objective of this study was to evaluate 800 EBIs for auxin-like activity and its effect on early seedlings growth of rice. Surface sterilized rice seeds were treated separately with different EBIs and allowed to grow in Petriplates (containing sterile cotton) for 10 days. On the 10^th day, the root length of the rice seedlings was measured and recorded to determine the auxin-like activity of EBIs. Results showed that 9 different isolates out of 800 EBIs screened to have significant effect on rice root and shoot growth when compared to control. The increase in root length was in the range of 58.30% to 81.68%, in comparison to root length of seedlings from control category. Based on the results, it was concluded that the positive root growth promoting response of rice seedlings could be due to the production of auxin-like compounds by the EBIs. These research findings could be useful in developing endophytic bacteria based formulation to enhance the growth of rice crop.