Halimi Mohd Saud

Plant Growth-Promoting Rhizobacteria Enhance Salinity Stress Tolerance in Okra through ROS-Scavenging Enzymes

Salinity is a major environmental stress that limits crop production worldwide. In this study, we characterized plant growth-promoting rhizobacteria (PGPR) containing 1-aminocyclopropane-1-carboxylate (ACC) deaminase and examined their effect on salinity stress tolerance in okra through the induction of ROS-scavenging enzyme activity. PGPR inoculated okra plants exhibited higher germination percentage, growth parameters, and chlorophyll content than control plants. Increased antioxidant enzyme activities (SOD, APX, and CAT) and upregulation of ROS pathway genes (CAT, APX, GR, and DHAR) were observed in PGPR inoculated okra plants under salinity stress. With some exceptions, inoculation with Enterobacter sp. UPMR18 had a significant influence on all tested parameters under salt stress, as compared to other treatments. Thus, the ACC deaminase-containing PGPR isolate Enterobacter sp. UPMR18 could be an effective bioresource for enhancing salt tolerance and growth of okra plants under salinity stress.

MECHANISM OF ROOT GROWTH AND PROMOTION OF NODULATION IN VEGETABLE SOYBEAN BY AZOSPIRILLUM BRASILENSE

Stimulation of root growth and promotion of nodulation in vegetable soybean (Glycine max) by Azospirillum brasilense was studied under lightroom conditions to understand the possible mechanism of root growth as well as the enhancement of nodule initiation when co-inoculated with Bradyrhizobium. Root growth stimulation of vegetable soybean was positively influenced by the cell-free supernatant of Azospirillum brasilense Sp7 as well as Sp7 itself, and by indole acetic acid (IAA) application. The cell-free supernatant of Sp7 treated plants produced the highest number of roots and root length plant−1 followed by bacterial cells of Sp7 and IAA (log10 9M) application. Control plants were the lowest. The cell-free supernatant of Sp7 may contain growth stimulants similar to IAA, which was responsible for enhanced root growth. Nitrite and nitrate did not show positive role in increasing root growth in vegetable soybean. Co-inoculation of Azospirillum with Bradyrhizobium significantly (P<0.05) promoted nodulation in vegetable soybean. Bradyrhizobium strain UPMR48 performed superior role on promotion of nodule growth by co-inoculation to the strain TAL102. Azospirillum has the potential as a co-inoculant with Bradyrhizobium in vegetable soybean cultivation.

Use of Lignocellulolytic Microbial Consortium and pH Amendment on Composting Efficacy of Rice Straw

ABSTRACT The present study was conducted at the Composting Unit, Universiti Putra Malaysia to determine the physico-chemical changes, microbial dynamics, and enzyme activities during microbial composting of rice straw at different pH conditions. Different treatments comprising of composting substrates (A), substrates with microbial consortium (B), substrates, microbial consortium, and acetic acid (C), substrates, microbial consortium, and sodium hydroxide (D) were used to enhance the composting process of rice straw. In inoculated treatments, the temperature increased rapidly to higher than 50°C by day 5 and remained above 40°C up to day 17, while in the control the temperature increased slowly and peaked (46°C) at day 9 and remained above 40°C until day 23. The results showed that biodegradation was at its maximum in microbial-infused treatments within 14–21 days as indicated by profiles of pH, reduction of C/N ratio, lignocellulolytic (lignin peroxidase, endoglucanase, and exoglucanase) enzyme activities, and lignocellulose bioconversion. After day 21, the C/N ratio of microbial-infused treatment without any pH adjustment (B) was reduced to 17.5 from an initial value of 29.2 suggesting that there were no additive effects of pH adjustment during the microbial composting of rice straw.

Physical, chemical and biological changes during the composting of oil palm frond

An experiment was conducted to evaluate the physiochemical and biological changes occurred during the composting process of oil palm fronds (OPF) composts. Compost A, B and C were prepared by mixing OPF, chicken manure (CM) and rice bran (RB) at ratio of 40:40:20, 40:30:30 and 40:20:40, respectively. After day 21, the lowest C/N ratio and the highest amount of nitrogen (N), phosphorus (P) and potassium (K) were recorded in compost A with the values of 15.79, 2.33, 2.02 and 1.80, respectively. Compost A was also found to contain the highest number of bacteria throughout the composting process than that of other two composts suggesting that after day 21, OPF compost A was matured enough to be used as soil amendments to agricultural fields.

Improvement of yield potential of rice through combined application of biofertilizer and chemical nitrogen

A field experiment was conducted to evaluate the su itable combination of plant growth promoting rhizobacteria ( Azospirillum biofertilizer strain BM9 and BM11) along with diff erent nitrogenous fertilizer levels (0, 20, 40, 60, 80 and 100% N) on rice varie ty Binadhan 4 at Bangladesh Institute of Nuclear Agriculture farm, Mymensingh in Aman season of 2006 . Roots of rice seedlings were dipped in broth culture of bacterial strains in Luria-Bertani (LB) medium for half an hour before transplanting. Data were recorded on plant growth, yield, yield components a nd nutrient uptake. Results showed a significant increase in growth parameter like plant height, sho ot dry weight, root length and dry weights, grain a nd straw yields, effective tillers/hill and panicle le ngth, and nitrogen, phosphorus and potassium uptake over uninoculated under most nitrogen levels except 100% N. Number of grains per panicle and 1000 grain weights were increased considerably compared to uninoculated control. Strains BM9 and BM 11 along with 80% N produced similar grain and straw y ield to that with 100% nitrogen fertilizer applied alone. Results revealed greater scope of Azospirillum biofertilizer application for supplementing fertil izer nitrogen for achieving optimum yield of rice in Ban gladesh soil and environmental condition.

Molecular characterization of stress tolerant plant growth promoting rhizobacteria (PGPR) for growth enhancement of rice.

The study was undertaken to characterize plant growth promoting rhizobacteria (PGPR) for growth enhancement and stress tolerant traits and their efficacy on early establishment of rice seedling. In vitro growth promoting traits revealed that out of 30 PGPR isolates, 18 fixed nitrogen, 17 solubilized tri-calcium phosphate, 29 and 17 produced IAA with or without addition of L-tryptophane. In case of stress tolerant activities, PGPR isolates tolerated pH ranging from 5 to 10, Nacl from 1 to 6% and polyethylene glycol (PEG) from 10 to 40%, respectively. They showed antagonistic activity against Pyricularia oryzae with PIRG values ranging from 7−68%. After two-stage of screening, isolates UPMR7 and UPMR17 were identified based on 16s rRNA gene sequences and matched to the genus Bacillus and Citrobacter with 97−98% similarity. UPMR 7 and UPMR 17 were further evaluated on early growth promotion of rice variety MR219. Results revealed that PGPR inoculation had significant effects on plant growth compared to non-inoculated plants. Thus, it could be suggested that the isolates UPMR7 and UPMR17 have the potential to be used as biofertilizer and bioenhancer in sustainable rice cultivation.

Changes of Physical and Chemical Characteristics during Microbial Composting of Rice Straw at Various pH Levels

ABSTRACT The physical and chemical parameters were monitored for seven weeks during Trichoderma/Aspergillus inoculated rice straw composting at various pH levels. Three treatments (A, B, and C) were inoculated with lignocellulolytic microbial consortium (Aspergillus niger, F44 and Trichoderma viride, F26) and three were un-inoculated (D, E, and F). pH of the starting materials was amended to 5.75 (A and D), 6.75 (B and E), and 7.75 (C and F) with either acetic acid or sodium hydroxide. Three typical phases of temperature were observed both in inoculated and un-inoculated treatments during composting: mesophilic phase, thermophilic phase, and followed by cooling and maturation phase. The bioconversion were maximum in Trichoderma/Aspergillus inoculated treatments within 14–21 days as indicated by the profiles of electrical conductivity, bulk density, total carbon and nitrogen, and germination index. After day 21, the germination index of Trichoderma/Aspergillus inoculated treatment (B) without any pH amendment was increased to 74.5 indicating the maturity of compost and suitability for field application.

Bio-Efficacy of Microbial Infused Rice Straw Compost on Plant Growth Promotion and Induction of Disease Resistance in Chili

ABSTRACT Microbial fortified organic amendment in chili cultivation may affect plant development and disease suppression. Microbial infused rice straw compost, commercial rice straw compost, and fungicide Benomyl for chili (Capsicum annum L.) cultivation and control of Sclerotium foot rot were studied under glass house condition. Chili seed cv. Kulai were sown in the Sclerotium rolfsii infested and non-infested soil. After two weeks, five healthy seedlings were transplanted into planting bags. Growth performance and development of disease symptoms associated with S. rolfsii foot rot infection were assessed. Applying microbial infused rice straw compost increased seed germination and plant growth, and suppressed development of foot rot compared to using commercial rice straw compost and the Benomyl. A higher disease reduction (84.6%) occurred with 15 Mg · ha−1 microbial infused rice straw compost (62.7%), followed by Benomyl (53.8%), and 15 Mg · ha−1 commercial rice straw compost (46.2%). Application of microbial infused rice straw compost at 15 Mg · ha−1 yielded optimum seed germination and seedling establishment, plant growth, and disease suppression. Microbial infused rice straw compost is a good alternative to chemical fungicide in controlling Sclerotial disease in chili.

Development of a potential lignocellulolytic resource for rapid bioconversion of rice straw

This study was conducted at the Laboratory of Food Crops and Floriculture, Institute of Tropical Agriculture, Universiti Putra Malaysia to characterize the potential lignocellulolytic bacteria for rapid bio-bioconversion of rice straw. Fifty isolates of bacteria were isolated from several in-situ and in-vitro sources. Isolates B3, B13, B21, B37 and B46 showed the highest enzymatic activities to starch, carboxymethyl cellulose (CMC) and Azure B amended media. They were further screened on rice straw powder (RSP) amended media for their adaptability on rice straw (RST). The isolate B37 obtained from thermophilic phase of in vitro composting of rice straw and showing the optimum lignocellulolytic activity and adaptation to RSP amended media was identified as Bacillus pumilis . Key words: Rice straw, lignocellulose, microbial degradation, Bacillus pumilis .

Microbial Composting of Rice Straw for Improved Stability and Bioefficacy

Rice is an important cereal crop in the world. Annually, a large amount of straw is produced as by-product from rice cultivation. Proper disposal of rice straw is a concern across the world due to its bulk volume. Composting is an alternative way for recycling of rice straw into a valuable end product for agricultural use. However, composting of rice straw is time consuming as it is composed of lignocellulosic material. Therefore, the aim of this chapter is to summarize the pioneering and recent composting studies and provide information about the uses of potential lignocellulolytic microorganisms in composting as an alternative method for sustainable management of rice straw. In addition, the role of rice straw composts in maintaining of soil health, plant growth promotion and disease suppression as bioenhancer and bioprotectant is discussed. This knowledge could help build a platform for researchers in this area to understand the recent developments in rice straw composting by means of addressing the environmental pollution concerns as well.