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The presence of 1-aminocyclopropane-1-carboxylate deaminase (ACCD) activity among the phyllosphere methylobacteria of rice was detected and its role in regulating plant ethylene level was assessed. Eighteen methylobacterial isolates from four different cultivars of rice were isolated and screened for ACCD. The 16S rRNA homology of ACCD positive methylobacterial isolate closely related to the species Methylobacterium radiotolerans. The accD gene sequence homology of the isolate was 98% similar to Rhizobium leguminosarum. Foliar spray of ACCD positive methylobacterial isolates enhanced the root and shoot length of rice and tomato seedlings under gnotobiotic condition and lower the ethylene level (60-80%) in the plant species.

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Abstract. The Agricultural intensification, an inevitable process to feed the ever-increasing population, affects the soil quality due to management-induced changes. To measure the soil quality in terms of the soil functioning, several attempts were made to develop the soil quality index (SQI) based on a set of soil attributes. However, there is no universal consensus protocol available for SQI and the role of soil biological indicators in SQI is meagre. Therefore, the objective of the present work is to develop a unitless soil biological quality index (SBQI) scaled between 0 and 10, which would be a major component of SQI in future. The long-term organic manure amended (OM), integrated nutrient management enforced (INM), synthetic fertilizer applied (IC) and unfertilized control (Control) soils from three different predominant soil types with three different cropping patterns of the location (Tamil Nadu state, India) were chosen for this. The soil organic carbon, microbial biomass carbon, labile carbon, protein index, dehydrogenase activity and substrate-induced respiration were used to estimate the SBQI. Five different SBQI methods viz., simple additive (SBQI-1 and SBQI-2), scoring function (SBQI-3), principal component analysis-based statistical modeling (SBQI-4) and quadrant-plot based method (SBQI-5) were developed to estimate the biological quality as unitless scale. All the five methods have same resolution to discriminate the soils and INM ≈ OM > IC > Control is the relative trend being followed in all the soil types based on the SBQIs. All the five methods were further validated for their efficiency in 25 farmers' soils of the location and proved that these methods can be effectively used to scale the biological health of the soil. Among the five SBQIs, we recommend SBQI-5, which relates the variables to each other to scale the biological health of the soil.