Improving seed germination indices and yield in cumin through organic biopriming with microbial consortia and soaking agents: laboratory and field investigations

Cumin (Cuminum cyminum L.) is an annual plant with diminutive seed size and low germination and vigour, often leading to weak establishment in the field. Effects of treating cumin seeds with different bioagents, including Pseudomonas fluorescens, Bacillus subtilis, Paenebacillus polymyxa, Bacillus megaterium, Bacillus paramycoides and Pseudomonas aeruginosa and soaking agents (chitosan, carrageenan, aloe vera gel compost and soil extract) on germination, root/shoot length and germination indices of cumin were investigated in the laboratory and field. In the field experiment, treatments with different combinations of bioagents and soaking agents enhanced seed germination and improved plant physiological traits (chlorophyll, root/shoot length), yield and yield attributes compared with the non-bioprimed control. Treatment with chitosan in combination with Bacillus paramycoides and Pseudomonas aeruginosa showed the greatest positive effects, though for most parameters the effects of this treatment were statistically similar to the other biopriming combinations. The biopriming treatments also increased nutrient content, soil enzyme activities (dehydrogenase, urease, acid and alkaline phosphatase), soil nutrient status and bacterial populations. In the laboratory, the combination of the first and second main components explained 83.4% of the overall variance the germination indices. In the field experiment, the first principal component alone accounted for 81.8% and 96.7% of the total variation observed in yield parameters and seed nutrient content, and post-harvest soil properties, respectively. These findings indicated that biopriming cumin seeds with microbial consortia and soaking agents enhanced seed germination, plant growth, soil health and yield of cumin, and may serve as a sustainable approach for improving cumin cultivation.