Pectobacterium carotovorum subsp. carotovorum [Pcc (formerly Erwinia carotovora subsp. carotovora)] PC1 causes soft-rot disease in a wide variety of plant species by secreting multiple pathogenicity-related traits. In this study, regulatory mechanism of air-liquid (AL) biofilm formation was studied using a cytR homolog gene deletion mutant (ΔcytR) of Pcc PC1. Compared to the wild type (Pcc PC1), the ΔcytR mutant produced fragile and significantly (P < 0.001) lower amounts of AL biofilm on salt-optimized broth plus 2% glycerol (SOBG), yeast peptone dextrose adenine, and also on King’s B at 27°C after 72 h incubation in static condition. The wild type also produced significantly higher quantities of AL biofilm on SOBGMg^– (magnesium deprived) containing Cupper (Cu²⁺), Zinc (Zn²⁺), Manganese (Mn²⁺), Magnesium (Mg²⁺), and Calcium (Ca²⁺) compared to the ΔcytR mutant. Moreover, the wild type was produced higher amounts of biofilms compared to the mutant while responding to pH and osmotic stresses. The ΔfliC (encoding flagellin), flhD::Tn5 (encoding a master regulator) and ΔmotA (a membrane protein essential for flagellar rotation) mutants produced a lighter and more fragile AL biofilm on SOBG compared to their wild counterpart. All these mutants resulted in having weak bonds with the cellulose specific dye (Calcofluor) producing lower quantities of cellulose compared to the wild type. Gene expression analysis using mRNA collected from the AL biofilms showed that ΔcytR mutant significantly (P < 0.001) reduced the expressions of multiple genes responsible for cellulose production (bcsA, bcsE, and adrA), motility (flhD, fliA, fliC, and motA) and type III secretion system (hrpX, hrpL, hrpA, and hrpN) compared to the wild type. The CytR homolog was therefore, argued to be able to regulate the AL biofilm formation by controlling cellulose production, motility and T3SS in Pcc PC1. In addition, all the mutants exhibited poorer attachment to radish sprouts and AL biofilm cells of the wild type was resistant than stationary-phase and planktonic cells to acidity and oxidative stress compared to the same cells of the ΔcytR mutant. The results of this study therefore suggest that CytR homolog is a major determinant of Pcc PC1’s virulence, attachment and its survival mechanism.

A field experiment was conducted at the Bangladesh Agricultural University (BAU) to find out possible effects of alternate wetting and drying irrigation (AWDI) on the yield, water use and water use efficiency (WUE) of Boro rice. The experimental layout was furnitured using split-plot design (SPD) with two modern varieties (MV) of rice viz. BRRIdhan 28 and BRRIdhan 29, which received four irrigation treatments randomly and was replicated thrice. The treatments ranged from continuous submergence (T1) of the field to a number of delayed irrigations (T2, T3 and T4) denoting application of 5 cm irrigation water when water level in the perforated PVC pipe fell 10, 20 and 30 cm below ground level (G.L.), respectively. The study revealed that treatment T1 attributed by the highest total water use (122.2 cm) and the lowest WUE (58.53 kg/ha/cm) produced the highest grain yield (6.86 t/ha). Treatment T2, on the contrary, gave the second highest yield (6.58 t/ha) and consequently the second highest WUE (69.48 kg/ha/cm) indicating quite a large water saving (15 cm) compared to treatment T1. The yields in treatments T3 (6.27 t/ha) and T4 (5.86 t/ha) were significantly lower at 1% level of significance compared to that of treatment T1. No significant effect was found either for the treatment or for the varieties on the number of effective and total tillers hill-1 nor did they affect 1000 grain weight. Reduced plant height, no. of effective tillers hill-1, grain yield, straw yield, biological yield and harvest index were found with the increasing water stress. Key words: Alternate wetting and drying irrigation; Boro rice; Yield; Water use efficiency DOI: 10.3329/jbau.v6i2.4841 J. Bangladesh Agril. Univ. 6(2): 409-414, 2008

Pectin, a polysaccharide, is widely used as a gelling and thickening agent in the food industry. This study undertook optimization of pectin extraction from the peels of Baccaurea ramiflora Lour. (Burmese grape or lotkon), an abundantly grown wild fruit in Bangladesh. We applied the Box–Behnken Design of Response Surface Methodology with varied processing parameters including pH, time, and temperature. The Response Surface Methodology, employing a second‐order polynomial model, successfully optimized the extraction conditions for the maximum pectin yield. The model predicted a pectin yield of 10.73%, which closely matched the experimental yield of 10.56%. The optimal conditions for pectin extraction were determined as pH (2.4), extraction time (56 min), and temperature (76°C). Further analyses of the extracted pectin under optimized conditions confirmed its excellent potential for food applications. The pectin was characterized by its moisture content (10.42%), water activity (0.51), ash content (3.41%), equivalent weight (769.23 mg/mole), methoxyl content (7.75%), anhydrouronic acid content (66.88%), degree of esterification (65.79%), and acetyl value (0.39%). These determined parameters strongly support that the pectin extracted from the peels of Burmese grapes is of good quality.

Okra is a well-known and economically important vegetable grown in Bangladesh for consumption and seed production. The yield of okra is low compared to developed countries that can be increased using irrigation water efficiently. Traditional irrigation methods are used for okra cultivation in the developing countries, resulting in significant water loss. One of the options that appears to be promising for reducing this water loss is drip irrigation since it applies water directly to the plant’s root zone. However, farmers frequently complain about manual inspection and water wastage from the overhead tanks in small-scale microirrigation systems. An automated microirrigation system can help to solve this problem. This approach was developed at Bangabandhu Sheikh Mujibur Rahman Agricultural University to evaluate the performance of okra in terms of plant growth, seasonal water usage, and yield factors. For a better understanding of specialist crop irrigation management, the effectiveness of water utilization was also investigated. The experimental field was set up in a Randomized Complete Block Design (RCBD) from March to May 2021, with three different treatments such as T1 (Conventional irrigation), T2 (Drip irrigation) and T3 (Timer drip irrigation), for comparing the treatments with four replications. To construct an automated microirrigation system, a pump controller with sensing probes to regulate the water level in the irrigation tank and irrigation timers for watering the okra field depending on scheduling were used. According to the data, only the length of the pod varied significantly, whereas the other factors were non-significant. The yield components, such as the weight of pod per plant and yield, did not varied significantly among the treatments. The highest (12.95 kg/m3) and the lowest (10.47 kg/m3) water use efficiency were obtained in T3 (Timer drip irrigation) and T1 (Conventional irrigation) respectively. The study reveals that automated microirrigation technology can save 11% more irrigation water than conventional irrigation.