Synopsis
Ammonium nitrogen gave much better rice yields than nitrate nitrogen. Calcium cyanamide and urea were also more effective than nitrate nitrogen. Nitrate nitrogen applied just before heading proved more beneficial to rice than that applied at the early stage of plant growth. Generally, ammonium sulphate increased rice yields more than the other nitrogen fertilizers tested.
Key chili and maize growing areas of Pakistan were selected for a focused baseline study of the levels of Aspergillus spp. Investigations were undertaken using a combination of molecular and culture-based techniques. Samples investigated included soil samples, one-year-old corn cobs, and fresh chili from selected locations. Aspergillus strains obtained from corn cobs were screened using coconut milk agar, resulting in one strain that was positive for aflatoxin production. Whole genome sequencing (WGS) with low coverage techniques were employed to screen the isolates for differences in the ribosomal RNA gene cluster and mitochondrial genome, with the aflatoxigenic strain proving to have a distinctive profile. Finally, strains were subjected to matrix-assisted laser-desorption and ionization time-of-flight mass spectrometry (MALDI-ToF-MS) in order to obtain a proteomic ‘fingerprint’ which was used to distinguish the aflatoxigenic strain from the other isolates. The next generation sequencing (NGS) study was broadened to incorporate metabarcoding with ITS rRNA for determining the microbial biodiversity of the soil samples and presumptive screening for the presence of aflatoxigenic strains. Using information gleaned from the WGS results, a putative aflatoxigenic operational taxonomic unit (OTU) was observed in four of the 15 soil samples screened by metabarcoding. This method may have beneficial applications in early detection and surveillance programs in agricultural soils and commodities.
Mycotoxins contamination of cropsposes significant economic losses to both crop producers and traders who give market discounts for the contaminated products.Aflatoxin, being one of the most abundant mycotoxins in everyday food commodities such as rice and maize is of utmost importance due to its hepatotoxic, mutagenic and carcinogenic causing characteristics along with the extensive economic losses caused by aflatoxin contamination.Aflatoxins refer to a group of four mycotoxins (B1, B2, G1 and G2) produced primarily by two interrelated fungi, Aspergillus flavus and Aspergillus parasiticus. Rice and maize are prone to aflatoxin contamination during the growing, harvesting, storage, transporting and processing stages. Therefore, there is a need to determine the present status of aflatoxin levels in supply chains of rice and maize in Pakistan for making a comparison with the permissible levels set by the food regulatory authorities in a pursuit to ensure safe food supply. Among aflatoxin management methods,biological control appears to be the most promising and sustainable approach(because the non-toxic strains of aflatoxin-causing fungi occupy the same ecological niche as the toxic strains) for control of aflatoxins in both pre-and post-harvest stages of the respective supply chains.Baseline studies need to be conducted on aflatoxins in target agro-climatic regions to improve the supply chain of cereal grains in Pakistan.
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