Quality and yield of potato seed tubers as influenced by plant growth promoting rizobacteria

Using chemical fertilizers in agriculture increases production and improves the quality of the product; however, their higher usage globally has brought forth damage to ecosystems. Using biofertilizers is a better strategy to reduce the use of chemical fertilizers and ultimately increase soil fertility. This study aimed to isolate, identify, and characterize bacteria from the soil rhizosphere of medicinal plants (Rumex tuberosus L. and Verbascum sp.) for in vivo screening. Nitrogen fixation, phosphate solubilization, HCN, ammonia levels, Lipase, protease, catalase and siderophore production biochemical tests were also conducted. The two isolates that gave positive results from the biochemical tests were chosen out of 25 for further experiments. Based on 16S rRNA sequencing analysis the isolated organisms were identified as Alcaligenes faecalis Go1 (Accession No. OP001725) and Bacillus subtilis T11 (Accession No. OP218376). The compound fertilizer NPK was used as the positive control for field experiments, while selected stains were individually and in-combination were tested on potato crops as inoculum, over two successive cropping seasons. Plant height, number of tubers per plant, chlorophyll content, and tuber weight all increased for both isolated bacterial strains. The quality of the potato tubers was checked through visual observation for the presence or absence of disease symptoms. The treated tubers exhibited excellent quality, remaining free from any signs of disease, however, the control tubers showed infections with (Streptomyces scabiei, Fusarium sp., F. solani and Erwinia amylovora). The soil analyzed after harvesting both bacteria increased percentages of P, Ca2+, Mg2+, Na+, K+, SO4, total nitrogen content and total organic matter. The findings showed that the tested bacterial isolates could replace the use of chemical fertilizers in the production of potatoes. •Alcaligenes faecalis and Bacillus subtilis boosted plant growth significantly.•Treated potatoes showed higher quality and remained disease-free.•Application of these bacteria improved soil fertility by increasing essential nutrient levels.