Muhammad Baqir Hussain

Combined application of compost and Bacillus sp. CIK-512 ameliorated the lead toxicity in radish by regulating the homeostasis of antioxidants and lead

Lead (Pb) contamination is ubiquitous and usually causes toxicity to plants. Nevertheless, application of compost and plant growth promoting rhizobacteria synergistically may ameliorate the Pb toxicity in radish. The present study assessed the effects of compost and Bacillus sp. CIK-512 on growth, physiology, antioxidants and uptake of Pb in contaminated soil and explored the possible mechanism for Pb phytotoxicity amelioration. Treatments comprised of un-inoculated control, compost, CIK-512, and compost + CIK-512; plants were grown in soil contaminated with Pb (500mgkg-1) and without Pb in pot culture. Lead caused reduction in shoot dry biomass, photosynthetic rate, stomatal conductance, relative water contents, whereas enhanced root dry biomass, ascorbate peroxidase, catalase, malondialdehyde and electrolyte leakage in comparison with non-contaminated control. Plants inoculated with strain CIK-512 and compost produced significantly higher dry biomass, photosynthetic rate and stomatal conductance in normal and contaminated soils. Bacterial strain CIK-512 and compost synergy improved growth and physiology of radish in contaminated soil possibly through homeostasis of antioxidant activities, reduced membrane leakage and Pb accumulation in shoot. Possibly, Pb-induced production of reactive oxygen species resulted in increased electrolyte leakage and malondialdehyde contents (r = 0.88-0.92), which led to reduction in growth (r = -0.97) and physiology (r = -0.38 to -0.80), however, such negative effects were ameliorated by the regulation of antioxidants (r = 0.78-0.87). The decreased activity of antioxidants coupled with Pb accumulation in aerial part of the radish indicates the Pb-phytotoxicity amelioration through synergistic application of compost and Bacillus sp. CIK-512.

Amelioration in Growth and Physiological Efficiency of Sunflower (Helianthus annuus L.) under Drought by Potassium Application

ABSTRACT The present study investigated the induced drought tolerance in sunflower through foliar application of potassium (K) at critical growth stages (head formation or achene filling). Five genotypes of sunflower (G-101, SF-187, Hysun-33, Hysun-38, and 64-A-93) were tested for drought tolerance at −0.55, −1.36, and −1.60 MPa osmotic potential using polyethylene glycol 6000. Hysun-33 showed the highest stress tolerance index as calculated from germination percentage, seedling height, root length, and dry matter. This genotype was further evaluated in the field under drought at head formation or achene filling stages, with or without 1% K foliar application. Treatments were arranged in a randomized complete block design with three replicates. Drought at head formation or achene filling stage significantly decreased biological yield, head diameter, plant height, 1000 achene weight, and achene yield as compared to unstressed control. Potassium application significantly improved all the aforementioned parameters and therefore could be a better strategy for ameliorating drought stress in sunflower.

Impact of Environmental and Pathogenic Variability on Breaking of Host Rust Resistance in Wheat Cultivars under Changing Climatic Conditions

The rust fungi especially emergence of new rust races has serious threat to global wheat production. This is mainly due to the widespread use of race-specific seedling resistance genes and evolution of new virulence races like Yr9, Yr27, and Sr31. Several quantitative disease resistance (QDR) or durable resistance genes i.e. Lr34/Yr18/Pm38/Sr57, Lr46/Yr29/Pm39/Sr58, Lr67/Yr46, Lr68 providing resistance to rust diseases at either high or low temperatures have been identified. But, changing climatic conditions affect the level of resistance in cultivars, as at high temperature Lr34/Yr18 genes which confer durable resistance in wheat become less effective and at low temperature it provides high resistance. While in contrast, yellow rust resistance genes; Yr36 and Yr39 confer resistance at high temperature and later growth stages. This review provides a detailed discussion on, the different aspects of climate change that how it affect host resistance and pathogenic variability and its sustainable control by developing cultivars with high level durable resistance.

Ameliorating Salt Stress in Crops Through Plant Growth-Promoting Bacteria

Abiotic stresses are emerging vicious environmental factors limiting agricultural productivity around the world, while food demand is increasing with growing population. Among these abiotic stresses, salt stress is a serious threat to put down crop production especially in arid and semiarid regions of the world. Therefore, some serious steps are required to stop or slow down the lethal effects of salinity for ensuring food security. Various strategies are adopted to tackle the deleterious impacts of salinity to crops including breeding techniques and genetic engineering, but these techniques have their level of significance and cannot satisfy the whole demand. However, some biological strategies are cost-effective, environment friendly, and easy to adopt/operate. In this scenario, the use of various microorganisms (bacteria, fungi, algae) to enhance salinity resilience in crops is encouraged due to their vital interactions with each other and crop plants. Bacteria are widely used to mitigate deleterious impacts of high salinity on crop plants because they possess various direct and indirect plant beneficial characteristics including exopolysaccharide and siderophore production, biofilm formation, phosphate solubilization, induced systemic resistance, and enhanced nutrient uptake, and they act as biocontrol agents to protect crop plants from many diseases by killing pathogens. This chapter focuses on the negative effects of high salinity on plants, bacterial survival in salt stress, and their mechanisms to mitigate salinity stress and the role of beneficial microbes to enhance crop tolerance against salinity stress.

Breeding Wheat for Salt Tolerance and Stem Rust Resistance

Fast and effective hydroponics screening technique that could identify physiological variation in salinity tolerance of wheat was applied. A set of 442, previously unexplored wheat varieties/lines representing a wide range of genetic diversity was planted as control in ½ strength Hoagland’s nutrient media, whereas two sets of the same material were exposed to salt (NaCl) application under two treatments i.e., 10 dS m−1 and 20 dS m−1 for the first 2 years (2003–04 and 2004–05). For the third year (2005–06), more intensive stress was applied with salinity levels of 12.5 dS m−1 and 25 dS m−1. Salinity tolerance was defined as differences in biomass (root-shoot ratio) production in saline versus non-saline conditions over prolonged periods, of 3–4 weeks (seedling to pre booting stage). For this purpose parameters like shoot length, root length, shoot weight and root weight alongwith their relative ratios were measured. As a result of 3 year study 11 common salt tolerant varieties/lines were identified including Pasban-90, LU 26S, V-01078 (Seher 06) and V-01180. Under saline field conditions some of these lines like Gamdow-6, BAV 92//SAP/MON and Lakata-1 produced higher grain yield, whereas, Uqab-2000 was the best yielding in saline field conditions, although it was found non tolerant in hydroponic studies. Line Ning 8319 showed good resistance for stem rust comparable to Parula and Pavon. These selected lines are being used in specific breeding programs for the development of high yielding wheat varieties having high degree of salt tolerance and stem rust resistance.