Asha Gaur

Molecular assessment of diversity among endophytic diazotrophs isolated from subtropical Indian sugarcane

Twenty-two endophytic bacterial isolates from the roots of sugarcane were compared morphologically, biochemically and genetically. Gram staining, colony pigment, texture and other cultural characteristics were taken for morphological characterization. Oxidation-fermentation tests for D-glucose and D-sucrose, production of acid and hydrogen from different carbon source, oxidase activity, antibiotic and drug resistance patterns were chosen as the biochemical and physiological criteria. Twelve random decamer primers were used to analyze and compare these isolates through RAPD among themselves as well as with known standard diazotrophic strains. The isolates were compared through dendrograms constructed on the basis of similarity patterns obtained from biochemical and RAPD analysis. The estimated diversity through RAPD analysis was more evident than the diversity on the basis of morphological and biochemical characters. Within Acetobacter group, the isolates showed substantial genetic diversity for future exploitation as PGPRs and diazotrophic associative endophytes.

Allelopathic influence of Vigna mungo (black gram) seeds on germination and radical growth of some crop plants

Intercropping of Vigna mungo (black gram) isprevalent for varied crop regimes in subtropical northern plains of India. Insugarcane, the negative impacts of a black gram intercrop on crop yields,rhizosphere soil properties and benefit: cost ratio have been reported. Thepossible allelopathic potential of black gram seeds on the germination,seedlingemergence and root elongation of other commercial crops is reported here. Theeffects of imbibed seeds of black gram, their aqueous leachate and seedextractson the germination and root elongation of seeds of four test crops viz. wheat,maize, gram and lentil, both under aseptic and soil conditions, wereinvestigated. Inhibitory effects were evident in all the bioassays of seeds ofthese crops. The black gram seeds directly and leachates were highly inhibitorybut the aqueous seed extract was less so. The observations indicate a releaseofinhibitory substances from black gram seeds leading to the observed inhibitoryeffects.

Post-harvest loss in sugarcane quality due to endophytic microorganisms.

Microorganisms colonizing internal parts of sugarcane thrive on stored sucrose and play an important role in post-harvest losses in sugarcane quality. Endophytic microbial load varied with different varieties and within cane parts also, which increased many folds upon staling. Early maturing varieties had more bacterial load as compared to mid-late maturing varieties. Total carbohydrates were utilized for bacterial proliferation and reducing sugars were produced. Data on reducing sugars and pH also indicated the selective enrichment of microorganisms in mid-late group of varieties.

Bio-organic Amendment of Udic Ustochrept Soil for Minimizing Yield Decline in Sugarcane Ratoon Crops under Subtropical Conditions

The effects of subsequent sugarcane ratooning on soil quality and the crop yields under four treatments [an absolute control (T0), application of recommended dose of nitrogen (N)–phosphorus (P)–potassium (K) (T1), application of sulfitation press mud (SPM), a sugar factory by-product (T2), and SPM along with Gluconacetobacter diazotrophicus (Gd, T3)] were evaluated for 7 years. In the control (T0) and NPK-fertilized (T1) plots, an increase in soil compaction (5.4%), decrease in infiltration rate (6.04%), lower microbial activities, and increased soil phenolic contents (72.4%) rendered the nutrients unavailable, leading to significant declines in the crop yields at the rate of 5.47 Mg ha−1 y−1 and 4.67 Mg ha−1 y−1, respectively. The crop yield declined from 53 kg ha−1 in plant crop to 18 kg ha−1 in the sixth ratoon crop under the absolute control. The rates of yield decline, however, were minimized in SPM (T2) and SPM + Gd (T3) plots to 3.54 and 3.51 Mg ha−1 y−1.

Deep Tillage, Soil Moisture Regime, and Optimizing N Nutrition for Sustaining Soil Health and Sugarcane Yield in Subtropical India

ABSTRACT A field experiment was conducted at ICAR-Indian Institute of Sugarcane Research, Lucknow, with three tillage practices (T1: Control- two times ploughing with harrow and cultivator, each followed by planking before sugarcane planting; T2: Deep tillage with disc plough (depth 25–30 cm) before planting followed by harrowing, cultivator, and planking; and T3: Subsoiling at 45–50 cm and deep tillage with disc plough/moldboard plough (depth 25–30 cm) followed by harrowing, cultivator, and planking before planting, two soil moisture regimes (M1: 0.5 irrigation water (IW)/cumulative pan evaporation (CPE) ratio and M2: 0.75 IW/CPE ratio) at 7.5 cm depth of IW, and four N levels (N1- 0, N2- 75, N3- 150, and N4-225 kg N ha−1) in sugarcane plant crop. Deep tillage and subsoiling increased porosity and reduced bulk density in surface/subsurface soil. Further, these physical changes also improved soil biological and chemical properties responsible for higher crop growth and yield. Deep tillage and subsoiling reduced the compaction by 6.12% in 0–15 cm depth in sugarcane plant crop at maximum tillering stage. The highest N uptake (158.5 kg ha−1) was analyzed with deep tillage and subsoiling compared to all other tillage practices. Maintaining suboptimal moisture regime with deep tillage and subsoiling showed the highest IW use efficiency (157.16 kg cane kg−1 N applied). Mean soil microbial biomass carbon (SMBC) in ratoon crop was higher compared to plant crop. During initial tillering stage, ratoon crop showed higher SMBC with application of deep tillage and subsoiling (1209 mg CO2-C g−1 soil day−1) at 0–15 cm depth and 1082.9 mg CO2-C g−1 soil day−1 at 15–30 cm depth. Thus, it could be concluded that besides improving sugarcane yield, soil health could be sustained by adopting subsoiling (45–50 cm depth) and deep tillage (20–25 cm depth), with soil moisture regime of 0.75 IW/CPE and application of 150 kg N ha−1 in sugarcane (plant crop).