Effect of Phytase Transgenic Corn Supplemented in Feed Diets on the Utilization of Calcium and Phosphorus in Bama Boars

The study aimed to evaluate the nutritional composition and the efficacy of phytase transgenic corn. Ten-month old castrated Bama boars and replicated a 6×6 Latin square design were used to evaluate the effect of phytase on utilization of calcium of phosphorus. Six-dietary treatments included: Phosphorus adequate control diet (PC), PTC0 (low-phosphorus diet), PTC500 (lowphosphorus diet with 500 FTU phytase/kg in PTC), PTC1000 (low-phosphorus diet with 1000 FTU phytase/kg in PTC), PTC5000 (low-phosphorus diet with 5000 FTU phytase/kg in PTC), microbe500 (low-phosphorus diet with 500 FTU phytase/kg from Aspergillus Niger). Contents of the proximate components, minerals, vitamins and amino acid of PTC did not differ from CC. The PTC has lower concentrations of phytate phosphorus than CC, the apparent digestibility of calcium and phosphorus of the PTC0 group is lower (p<0.05). No obvious dose-dependent relationship about the apparent digestibility of calcium and phosphorus showed among PTC500, PTC1000 and PTC5000. Therefore, the nutritional compositions of PTC had substantial equivalence to that of control corn except for phytate phosphorus concentrations, the PTC addition can improve the apparent digestibility of phosphorus and calcium and reduce the excrement of inorganic phosphorus, PTC might be an economically efficient way to decrease environment pollutions.

Production cost of transgenic corn in the first and second harvest in different regions in Brazil

Corn culture is one of the important economic segments of Brazilian agribusiness. The increase in corn production is related to increased productivity and in the cultivated area. In addition, the variation in productivity in the different Brazilian states is highlighted, which can be explained by the technological level of production. Therefore, the objective was to evaluate the production costs of eighteen producing regions to determine the cost of production in the first harvest in three agricultural years and in the second harvest in four agricultural years with transgenic corn, in addition to analyzing the influence of productivity on the cost of production. An exploratory research was carried out with data provided by the Companhia Nacional de Abastecimento. Statistical data were analyzed in the agricultural years of 2018, 2019 and 2020 in eighteen Brazilian municipalities. The region of Chapadão do Sul - MS, in both harvests, obtained the lowest production costs per bag of 60 Kg and per hectare were in Balsas - MA and Santo Ângelo - RS. The highest production costs per bag and per hectare in the 1st harvest were in the cities of Unaí - MG and Boa Vista - RR and the lowest costs per hectare were in Campo Mourão - PR and Sorriso - MT. The highest production costs per bag in the 2nd harvest were in Rio Verde - GO and Ubiratã - PR and per hectare were in Unaí - MG and Campo Mourão - PR.

Mutations in a Novel Cadherin Gene Associated with Bt Resistance in Helicoverpa zea

Transgenic corn and cotton produce crystalline (Cry) proteins derived from the soil bacterium Bacillus thuringiensis (Bt) that are toxic to lepidopteran larvae. Helicoverpa zea, a key pest of corn and cotton in the U.S., has evolved widespread resistance to these proteins produced in Bt corn and cotton. While the genomic targets of Cry selection and the mutations that produce resistant phenotypes are known in other lepidopteran species, little is known about how selection by Cry proteins shape the genome of H. zea. We scanned the genomes of Cry1Ac-selected and unselected H. zea lines, and identified twelve genes on five scaffolds that differed between lines, including cadherin-86C (cad-86C), a gene from a family that is involved in Cry1A resistance in other lepidopterans. Although this gene was expressed in the H. zea larval midgut, the protein it encodes has only 17 to 22% identity with cadherin proteins from other species previously reported to be involved in Bt resistance. An analysis of midgut-expressed cDNAs showed significant between-line differences in the frequencies of putative nonsynonymous substitutions (both SNPs and indels). Our results indicate that cad-86C is a likely target of Cry1Ac selection in H. zea. It remains unclear, however, whether genomic changes at this locus directly disrupt midgut binding of Cry1Ac and cause Bt resistance, or indirectly enhance fitness of H. zea in the presence of Cry1Ac by some other mechanism. Future work should investigate phenotypic effects of these nonsynonymous substitutions and their impact on fitness of H. zea larvae that ingest Cry1Ac.

Effect of Bt Corn (Bt 38) Cultivation on Community Structure of Collembola

Transgenic corn has been modified to express a gene derived from the bacterium Bacillus thuringiensis (Bt) to combat lepidopteran pests. Bt proteins and the altered chemical composition of Bt crops may affect the role the soil fauna plays in the decomposition of Bt plants. A 2-y field study and a laboratory feeding experiment using corn leaves were conducted in northeastern China to investigate the effect of Bt corn—consisting of Bt corn (Bt 38) and a near-isoline of non-Bt corn (Z 58)—on the abundance, species richness, morphological traits, community structure, and fitness of soil Collembola. A total of 4,419 collembolans, comprised of 22 species, were recovered in this study. We found that Bt corn cultivation did not significantly affect abundance, species richness, or community structure of Collembola. Some rare isotomids of the genera Desoria Nicolet, 1841 (Collembola: Isotomidae) and Folsomia Willem, 1902 (Collembola: Isotomidae) were only recorded in non-Bt corn varieties and not in Bt corn varieties. Morphological traits, including the number of ocelli, body size, body pigmentation level, furca development, antennal length, and antenna:head ratio of Collembola were not changed by transgenic corn cultivation in the 2-y field study. Our results clearly found that the Bt corn did not affect community characteristics or traits of Collembola during this 2-y field study.

Mutations in a novel cadherin gene associated with Bt resistance in Helicoverpa zea

Transgenic corn and cotton produce crystalline (Cry) proteins derived from the soil bacterium Bacillus thuringiensis (Bt) that are toxic to lepidopteran larvae. Helicoverpa zea, a key pest of corn and cotton in the U.S., has evolved widespread resistance to these proteins produced in Bt corn and cotton. While the genomic targets of Cry selection and the mutations that produce resistant phenotypes are known in other lepidopteran species, little is known about how Cry proteins shape the genome of H. zea. We scanned the genomes of Cry1Ac-selected and unselected H. zea lines, and identified eleven genes on six scaffolds that showed evidence of selection by Cry1Ac, including cadherin-86C (cad-86C), a gene from a family that is involved in Cry1A resistance in other lepidopterans. Although this gene was expressed in the H. zea larval midgut, the protein it encodes has only 17 to 22% identity with cadherin proteins from other species previously reported to be involved in Bt resistance. An analysis of midgut-expressed cDNAs showed significant between-line differences in the frequencies of putative nonsynonymous substitutions (both SNPs and indels). Our results indicate that cad-86C is a target of Cry1Ac selection in H. zea. Future work should investigate phenotypic effects of these nonsynonymous substitutions and their impact on phenotypic resistance in field populations.

Susceptibility of Different Instars of Striacosta albicosta (Lepidoptera: Noctuidae) to Vip3A, a Bacillus thuringiensis (Bacillaceae: Bacillales) Protein

Striacosta albicosta (Smith) (Lepidoptera: Noctuidae) is an important pest of corn, Zea mays L. in the Great Lakes region, which can be controlled by transgenic corn expressing Vip3A protein from Bacillus thuringiensis. To inform insect resistance management, the susceptibility, survival, and development of first, third, and fifth instar S. albicosta to Vip3A was determined using protein-overlay and corn tissue bioassays. Tissue bioassays were also used to determine the quantity of corn tissues with and without Vip3A-expression consumed by various instars. In diet bioassays, third and fifth instars were significantly less susceptible to Vip3A compared with first instars; however, no significant difference was observed in susceptibility of older instars. In tissue bioassays, survival was lowest for larvae fed Vip3A-expressing tissues, ranging from 0 to 21%, however, developmental measures of larvae fed Vip3A-expressing tissues did not differ from those fed artificial diet or tissues of other Bt events. Consumption of Vip3A × Cry1Ab tissues did not differ from that of Cry1Ab for each instar. Estimated Vip3A exposure of first instars ranged from 3 to 57 times higher than the concentration required for 99% mortality (LC99) based on the product of the reported Vip3A expression in transgenic corn tissues and the consumption observed in tissue bioassays; however, the estimated exposure of third and fifth instars to Vip3A was lower than their respective LC99. These findings suggest that first instar S. albicosta maybe exposed to a high dose of Vip3A under field conditions; however, Vip3A-expression in corn may not be high dose against older instars, increasing the risk of resistance development.

Macronutrient uptake and export in transgenic corn under two levels of fertilization

The objective of this work was to evaluate macronutrient uptake and export by transgenic corn hybrids under medium and high fertilization levels. For each fertilization level, a randomized complete block design was carried out in the summer crop season, under no-tillage and supplementary irrigation, with four cultivars and four replicates. Plants were sampled throughout the entire cycle and separated into leaves, stalk, husk, cob, and grains for the determination of dry matter mass and accumulation of macronutrients in the different growth stages. Under the high fertilization level, a greater dry matter mass and nutrient uptake were observed, but grain yield was similar to that under the medium fertilization level. The uptake of N, P, Ca, Mg, and S occurs until later in the cycle of the transgenic cultivars, which also showed lower concentrations of P, K, and S in grains, when compared to older hybrids. The differential behavior of the evaluated cultivars under different fertilization levels indicates the need of updating and improving nutritional management and fertilizer recommendations for the corn crop.