Humans are facing very serious health threats from food contamination with cadmium (Cd), and Cd uptake by wheat is amongst the main causes of Cd entrance into the food chain. The current study examined the effect of foliar application (0, 1.50, 3.00 and 4.00 mM) of various silicate chemicals (calcium silicate and potassium silicate) on wheat growth and Cd addition by wheat under Cd stress 20 mg kg−1 of soil using CdCl2. The results revealed that under control conditions, the application of Si improved all the growth, physiological, biochemical and quality attributes by reducing malondialdehyde contents and electrolyte leakage. Under Cd stress, the supplementation of Si conferred a better growth rate, gaseous exchange for metabolic activity and maintained the tissues’ turgor and membranes’ stabilities compared to those obtained under control (without Si). The enzymatic activities (superoxide dismutase, peroxidase and catalase) also show rapid action by the application of Si supplement, which were associated with elevated osmoprotectant contents and antioxidants, having role in antioxidant defense against Cd stress. These results suggested that a 4.50 mM concentration of Si supplement (potassium silicate) works effectively against Cd stress. The given results showed that Si supplement is beneficial for the enhancement of many metabolic activities that takes places in plants during the growth period that proved a feasible approach in controlling the Cd concentration within wheat plants and, ultimately, in humans.
Biofortification of micronutrients, particularly of the iron (Fe) in cereals, is a viable, attractive, and sustainable strategy to cope with malnutrition as cereals are the major staple diets, particularly in developing countries. Increased concentrations of heavy metal/(loid)s (HMs); i.e. cadmium (Cd), lead (Pb), arsenic (As) etc. in agricultural soils is an increasing and serious challenge, posing severe health problems through food chain contamination. Accumulation of HMs in plants is challenging and contrasts to the development of biofortification strategies to combat micronutrient deficiencies. Agricultural biofortification strategies aim to increase plant uptake of mineral nutrients from soil and the translocation/storage of micronutrients to edible portions of cereal grains. However, it also means that any strategy to increase the uptake of Fe in plants may result in increased uptake of other toxic HMs. Therefore, the issue of HM contamination in cereals needs further understanding. This review describes the advancements in Fe biofortification strategies and the conflicting issue of HM accumulation in the grain of cereals.
Aloe vera is a valuable medicinal crop of the world. It suffers from several diseases but among them alternaria leaf spot and dry rot is most serious fungal disease which effects the commercial production and quality losses to Aloe vera. A survey was conducted to estimate the prevalence of dry rot disease in different nurseries located in urban areas of Faisalabad. During this survey maximum disease incidence was recorded in Horti club nursery (100%) and minimum disease incidence recorded at Faiz baho nursery and Qadir baksh form (13.8%). Among in-vitro tested fungicides Score gives maximum mycelial growth inhibition (89.5%) and maximum disease control (17.7%) as compared to control and other tested chemicals. Among in-vitro tested plant extracts Neem gives maximum mycelial growth inhabitation (41.2%) and in green house gives 14.2% disease control. Out of four tested fungicides and plant extracts Score and Neem gives best results against A. alternata mycelial growth and disease control.
Chili (Capsicum annuum L.) is an important vegetable crop in Pakistan. During summer of 2019, chili leaf spot symptoms were observed on 3-month-old plants in the fields, with 30 to 40% of disease incidence, in District Faisalabad, Punjab, Pakistan. Diseased leaves were characterized by numerous tiny round spots (0.5 to 2.0 mm in diameter, average 1 mm) that were white to grey with a sunken center, surrounded with dark brown edge and chlorotic halo. The lesions gradually enlarged and coalesced into large, nearly circular, or irregularly shaped lesions that could be as long as 3 cm. Small pieces of symptomatic leaf tissues were surface sterilized in 1% sodium hypochlorite for 1 min, rinsed in sterile water, and plated on potato dextrose agar (PDA) amended with streptomycin (100 ppm). After 5 days at 25°C with a 12-hour photoperiod, same fungal colonies developed. The colonies initially appeared white and then turned olive-green. The conidiophores were brown septate and generally branched. Conidia borne singly or in short chains were multicellular, obclavate to obpyriform, and 16.2 to 38.5 µm (average 27.35 ± 2.1 µm) in length and 8 to 16.5 µm (average 12.25 ± 1.6 µm) in width, with zero to three longitudinal and two to five transverse septa (n=35). The fungus was identified as Alternaria sp. (Fr.) Keisel based on its morphological characteristics (Simmons et al. 2007). For molecular identification, genomic DNA of two representative isolates (SSUAF1 and SSUAF2) was extracted using DNAzol reagent and PCR amplification of the internal transcribed spacer (ITS)-rDNA region, Glyceraldehyde 3-phosphate dehydrogenase gene (GAPDH) gene and RNA polymerase II second largest subunit (rpb2) were performed with primers ITS1/ITS4 (White et al. 1990), gpd1 and gpd2 (Berbee et al. 1999), RPB2-5F/RPB2-7cR (Liu, et al. 1999), respectively. The obtained sequences were deposited in GenBank with acc. nos. MT249008.1 and MT249009.1 for ITS-rDNA; MT318220.1 and MT318221.1 for the GAPDH; and MT318236.1, and MT318237.1 for RPB2 gene. A BLAST search in GenBank showed 100% identity with A. alternata for both ITS region (MT279999.1), GAPDH gene (MK637438.1) and RBP2 gene (MK605900.1). To confirm pathogenicity, 2-month-old healthy potted C. annuum plants were inoculated using an atomizer in a greenhouse. A total of 12 plants at the true leaf stage in each experiment were sprayed with a conidial suspension (106 conidia/ml) of both isolates amended with 0.1% (vol/vol) of Tween 20 until runoff (1.5 to 2 ml per plant). Four plants were inoculated with each of the two isolates, whereas four control plants were sprayed with sterile distilled water amended with 0.1% Tween 20. The plants were incubated at 25 ± 2°C in a greenhouse. After 10 days of inoculation, each isolate induced leaf lesions that were similar to typical lesions observed in the field. The experiment was conducted twice with similar results. The fungus was readily reisolated from symptomatic tissues whereas the control plants remained symptomless. Re-isolated fungal cultures were morphologically and molecularly identical to A. alternata, thus fulfilling the Koch’s postulates. Previously, A. alternata has been reported in Italy and India (Devappa et al. 2016; Garibaldi et al. 2019). To our knowledge, this is the first report of A. alternata causing leaf spot of C. annuum in Pakistan. This report will help the identification of leaf spot of chili and the development of management strategies for control of this disease in Pakistan.
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