Bacillus spp. as plant growth-promoting bacteria in cotton under greenhouse conditions

Abstract

The use of plant growth-promoting bacteria (PGPB) is a promising alternative method to improve plant efficiency in the utilization of chemical fertilizers, enabling a reduction of fertilizer application on crops. This study aimed to evaluate the potential of ten Bacillus strains (eight B. subtilis, one B. velezensis and one B. amyloliquefaciens) to promote growth in cotton plants under greenhouse conditions. The experiment was performed in a completely randomized design with 11 treatments and five replicates under greenhouse conditions. The parameters related to plant growth from treatments that received the bacterial isolates were compared to the control. The parameters analyzed were shoot dry matter, root dry matter, total dry matter, plant height, nitrogen content and phosphorus content in soil and in plants. The highest root dry matter was 1.24 g for the isolate 263. The total dry matter was 4.0 g for the isolate 248 and 3.54 g for the isolate 290. The highest chlorophyll content was 28 µg/cm2 for the isolate 290. The higher N content in shoot dry matter was 28 g of N for the isolate 290, 26 g for the isolate 248 and 25 g for the isolate 320. The improved P efficiency use was 32% for the isolate 248, 28% for the isolate 188 and 27% for the isolate 274. These results strongly confirm that B. subtilis isolates 248, 290 and 263 may represent a good alternative as plant growth-promoting endophytes to cotton crops, as they positively affected several parameters evaluated, such as root and shoot dry matter and phosphorus content in the soil. In addition, the parameters evaluated can strongly and positively affect plant yield. However, some isolates of B. subtilis did not promote plant growth and most likely failed as bioinoculants. This result shows the importance of properly identifying the isolate for bioinoculation to achieve success in promoting plant growth.