Balathandayutham Karthikeyan

Alterations in seedling vigour and antioxidant enzyme activities in Catharanthus roseus under seed priming with native diazotrophs

An experiment was conducted on Catharanthus roseus to study the effect of seed treatments with native diazotrophs on its seedling growth and antioxidant enzyme activities. The treatments had significant influence on various seedling parameters. There is no significant influence on dry matter production with the diazotrophs, Azospirillum and Azotobacter. However, the vital seedling parameters such as germination percentage and vigour index were improved. Azotobacter treatment influenced maximum of 50% germination, whereas Azospirillum and Azotobacter were on par with C. roseus with respect to their vigour index. There was significant difference in the population of total diazotrophs. Azospirillum and Azotobacter between rhizosphere and non-rhizosphere soils of C. roseus had the same trend and were observed at various locations of the study. The activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POX) and catalase (CAT) were increased to a significant extent due to the treatment with diazotrophs.

Interaction of Rhizobacteria with Arbuscular Mycorrhizal Fungi (AMF) and Their Role in Stress Abetment in Agriculture

Plants during the process of growth and development are subjected to numerous biotic and abiotic stresses. These stresses they encounter play a major role in effecting the productivity in agriculture. Interestingly, 70 % of plant species are harbored by AM fungi and this interaction plays a major role in influencing plant growth, nutrient absorption, and protection against pathogenic microbes. In addition to their interaction with plants, they are also known to interact with microorganisms in the rhizosphere. These types of interactions include interactions with phosphate-solubilizing bacteria (PSB), nitrogen-fixing bacteria, and biocontrol agents. Additional interactions are reported to happen in the fungal spores and hyphae. These interactions between AM fungi and microorganisms may play a major role in regulating plant growth, development, and resistance to different stresses they encounter. However, despite numerous studies, these interactions are only partially understood; this chapter tries to bring out the merits of tripartite interactions, i.e., interactions between AM fungi–Microorganisms–plants. In this chapter, we try to bring some important aspects on the AM fungi–Microorganisms based interactions.

Effect of AM Fungi and Plant Growth-Promoting Rhizobacteria (PGPR) Potential Bioinoculants on Growth and Yield of Coleus forskohlii

Coleus forskohlii (family Lamiaceae) grows perennially in the tropical and subtropical regions of India, Pakistan, Sri Lanka, East Africa, and Brazil. Its roots are the source of a labdane diterpene compound called forskolin having a unique property to stimulate adenylate cyclase. Forskolin is also a potent vasodilatory, antihypertensive, and inotropic agent. The crop has a great potential due to the expected increase in demand for forskolin, which is widely used in the treatment of glaucoma, cardiac problems, and also certain types of cancers. The mode of interaction between AM fungi and PGPR is a universally recognized interaction, marketing each symbiont as an individual entity capable of inducing growth. The inoculation of treatment (T4) AM fungi (G. fasciculatum) and PGPR inoculation had significantly increased the maximum plant height, number of tubers per plant, tuber length, tuber yield (wet weight and dry of tubers), and the total forskolin yield which were recorded at 180 DAP, respectively. The uninoculated control treatment (T5) recorded the minimum of growth and yield parameters in Coleus forskohlii plant.