Archna Suman

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.

Soil-Root Interface Changes in Sugarcane Plant and Ratoon Crops under Subtropical Conditions: Implications for Dry-Matter Accumulation

Poor sugarcane ratoon yields in the subtropics are responsible for decrease in overall productivity and poor sugar recovery. The present work is an attempt to assess reasons for decline in crop productivity despite providing adequate inputs. The simultaneously initiated plant and ratoon crops were compared for dry-matter accumulation and its distribution pattern in relation to changes in soil-root interface environment. In spite of well-established root system and advanced sprouting and tillering during the formative phase, dry-matter accumulation and nutrient uptake were low in a ratoon crop and were more apparent 120–210 days after planting. This decrease in nutrient uptake was due to declines in soil cation-exchange capacity, nitrate reductase (NR) activity in vivo by 19.4 and 25.9 percent, and increase in percentage leakage by 11.26 percent. These alterations at the soil-root interface in ratoons functioned as barriers for nutrient uptake and affected overall physiological growth and dry-matter accumulation adversely.

Inhibition of post harvest modulated product formation for stabilizing sucrose contents in sugarcane during stay in field

The post-harvest stay of sugarcane in the field for 8 days led to formation of abnormal levels of reducing sugars, phenols and dextran due to post harvest modulated enhanced titrable acidities and acid invertase activities in green and burnt whole cane and their billets. These impurities are known to seriously affect the stability of sucrose, diminish the process efficiency and the raw material quality. A chemical formulation sodium dodecyl sulphate+ benzalkonium chloride [SDS+ BKC (500 + 250 ppm)] is capable of inhibiting the formation of these substances till the 8th day of stay of green or burnt whole cane or billets in the field. Its application inhibited the post harvest induced changes viz., titrable acidity and acid invertase activity in green and burnt whole cane and billets. Rise in titrable acidity was checked by 53.7 and 63.1 % in green whole and billets and by 46.7 and 56.4 % in burned whole cane and billet on the 8th days of stay in the field. The chemical formulation led to significant reduction in acid invertase activity in green whole cane and billets (by 52.7 and 50.0%, respectively) while a decline by 58.7 and 51.6 % in burnt whole cane and billets, respectively was observed. These changes led to reduction in formation of reducing sugars (by 65.7 and 63.6 % in green whole cane and billets while by 69.2 and 69 % in burnt whole cane and billets), dextran (by 77.5 and 84.52 % in green whole cane and billets while by 77.29 and 75.78 % in burnt whole cane and billets.). The chemical formulation was effective enough to limit the formation of total phenols completely till the 8th day. The inhibition of formation of the mentioned products helped in stabilizing the sucrose contents and minimized the sucrose losses significantly (by 33.2 and 36.9 % in green whole cane and billets and by 36.9 and 44.5 % in burnt whole cane and billets, respectively). The formulation can be effectively used in minimizing the post sucrose losses in the field.