Certainly RU-ready corn would presumably be sprayed with RU, maybe several times. And RU acts as a chelating agent binding to and tying up some minerals. So as far as this mineral comparison goes, if the hybrids were RU-ready then I’d be surprised not to see a reduction in minerals.
But @cousinfloyd says, it’s not just RU-ready hybrids which have had the nutrition bred out of them. We often breed with just one or two goals in mind (disease resistance, color, early ripening, etc) and I doubt that many check for nutrients as part of their breeding programs.
This line of thought hearkens back to the old analysis of crops which the USDA used to publish every 10 years (I think). They suddenly stopped publishing it around 1970 saying that it wasn’t needed anymore. Even though for decades it was showing a steady decline in the nutrition of most of the crops it covered. But since no one is paying attention to this anymore, no one did any research as what the causes were of the steady decline, then or now. I suspect some would be due to the varieties people were growing now and some due to the health of our soils. But who knows.
As far as hybrid vs open pollinated goes, I tend to favor open pollinated, and not just for corn but for everything. Main reason is with OP you can save your own seed and select for traits which you want or do well in your area. Can’t do that with hybrids. (Well you can a bit, several folks have bred lines of hybrid corn, some even being marketed now)
Alan, I could name a few hundred varieties of corn with su of which Golden Bantam is an example. I’ve grown about 50 such over the years including Luther Hill, Whipple White, Buhl, and others that I sold to Sandhill Preservation for seed. Varieties with se+ are much more limited as it is a gene found after 1950 therefore was widely used in hybrids such as Kandy Korn which was available in the 1970’s. The original variety where se was found was Narrow Leaf Evergreen. One of the complications with se is that for many years it was thought to be on chromsome 4 along with su. Better analysis about 30 years ago finally determined it is on chromosome 2 therefore can be readily combined with other genes for enhanced sweetness. This is the source of the “synergistic” and “augmented” varieties commonly sold today. Synergistic combines sh2 + su + se in varying combinations so that each ear has a few kernels of each type. The usual mix is to stack sh2 and se on top of su such that 50% of kernels are su, 25% are sh2, and 25% are se. Augmented is homozygous for sh2 with se and su stacked on top such that 100% are sh2 with varying percentages of kernels on the same ear having se and su. The reason for stacking these genes is to enhance texture and flavor while boosting overall sweetness.
One problem with sweet corn is that there are very few really good open pollinated varieties. By this, I mean that combining large ears with excellent sweetness and good flavor in an OP line is very rare.
One item of trivia to know about sweet corn is that it is derived from flint corn. A single gene mutation turns flint corn into sugary corn like Golden Bantam. If you combine sugary with ordinary dent corn, too much starch is retained in the kernel resulting in odd textures and flavors.
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Cobalt is a transition metal located in the fourth row of the periodic table and is a neighbor of iron and nickel. It has been considered an essential element for prokaryotes, human beings, and other mammals, but its essentiality for plants remains obscure. In this article, we proposed that cobalt (Co) is a potentially essential micronutrient of plants. Co is essential for the growth of many lower plants, such as marine algal species including diatoms, chrysophytes, and dinoflagellates, as well as for higher plants in the family Fabaceae or Leguminosae. The essentiality to leguminous plants is attributed to its role in nitrogen (N) fixation by symbiotic microbes, primarily rhizobia. Co is an integral component of cobalamin or vitamin B12, which is required by several enzymes involved in N2 fixation. In addition to symbiosis, a group of N2 fixing bacteria known as diazotrophs is able to situate in plant tissue as endophytes or closely associated with roots of plants including economically important crops, such as barley, corn, rice, sugarcane, and wheat. Their action in N2 fixation provides crops with the macronutrient of N. Co is a component of several enzymes and proteins, participating in plant metabolism. Plants may exhibit Co deficiency if there is a severe limitation in Co supply. Conversely, Co is toxic to plants at higher concentrations. High levels of Co result in pale-colored leaves, discolored veins, and the loss of leaves and can also cause iron deficiency in plants. It is anticipated that with the advance of omics, Co as a constitute of enzymes and proteins and its specific role in plant metabolism will be exclusively revealed. The confirmation of Co as an essential micronutrient will enrich our understanding of plant mineral nutrition and improve our practice in crop production.
Cobalt is an essential nutrient for prokaryotes, human beings, and other mammals but has not been considered an essential micronutrient for plants. Instead, this element, along with other elements, such as aluminum (Al), selenium (Se), silicon (Si), sodium (Na), and titanium (Ti), has been considered as a beneficial element for plant growth (Pilon-Smits et al., 2009; Lyu et al., 2017). An element that can improve plant health status at low concentrations but has toxic effects at high concentrations is known as a beneficial element (Pais, 1992). For an element to be considered essential, it must be required by plants to complete its life cycle, must not be replaceable by other elements, and must directly participate in plant metabolism (Arnon and Stout, 1939). It has been well-documented that there are 92 naturally occurring elements on the earth, wherein 82 of which have been found in plants (Reimann et al., 2001). Plants are able to absorb elements from soils either actively or passively due to their sessile nature. The occurrence of an element in plants, particularly in shoots, must have a purpose. Active transport of an element from roots to shoots may indicate a certain role it plays in plants. As stated in the study by Bertrand (1912), potentially, every element has a biological function that can be assessed properly against a background of a deficiency state, and every element is toxic when present at high enough concentrations, which is known as Bertrand’s rule of metal necessity.
Significant progress has been made in plant mineral nutrition since the publication of Bertrand’s rule (Bertrand, 1912) and the essentiality concept (Arnon and Stout, 1939). Among the beneficial elements, cobalt (Co) could potentially be an essential plant micronutrient. Co is a core element of cobalamin (vitamin B12 and its derivatives) and a cofactor of a wider range of enzymes and a component of different proteins in prokaryotes and animals (Maret and Vallee, 1993; Kobayashi and Shimizu, 1999; Harrop and Mascharak, 2013; Odaka and Kobayashi, 2013). Co-containing enzymes and proteins in plants require further investigation and clarification. Rhizobia and other nitrogen (N)-fixation bacteria require Co and cobalamin for fixing atmosphere dinitrogen (N2) into ammonia (NH3), providing plants with the essential macronutrient of N. Co plays a vital role in interaction with iron (Fe), nickel (Ni), and zinc (Zn) in maintaining cellular homeostasis. Similar to other essential micronutrients, plants respond to Co concentrations in soil: at low concentrations, it promotes plant growth but causes phytotoxicity at higher concentrations. However, it is different from other beneficial elements, as plants do exhibit Co deficiency when grown in soils with limited supply.
The objective of this article was to concisely review the importance of Co as a plant micronutrient including its role in N fixation, the occurrence of coenzyme or proteins, and its effects on plant growth as well as Co deficiency and toxicity. We intended that this review could raise an awareness that Co is a potentially essential micronutrient of plants, and further research is needed to confirm this proposition.
Cobalt was isolated by Brandt in 1735 and recognized as a new element by Bergman in 1780 (Lindsay and Kerr, 2011). The importance of Co to living things was realized in the 1930s during the investigation of ruminant livestock nutrition in Australia (Underwood and Filmer, 1935). Co was discovered to be essential for animals as it is a component of cobalamin. Five scientists were awarded Nobel Prizes for the investigation of cobalamin (Carpenter, 2004).
Cobalt Is a Core Element of Cobalamin
Cobalamin is a large molecule (C63H88O14N14PCo) comprised of a modified tetrapyrrole ring known as corrin with Co3+ in the center (Osman et al., 2021). Co is not inter-exchangeable with other metals in the cobalamin and cannot be released from the ring unless the ring is broken (Yamada, 2013), implying the significance of Co to cobalamin. There are two biologically active forms of cobalamin, namely, methylcobalamin and adenosylcobalamin in ruminants (Gonzalez-Montana et al., 2020). In human beings, Co is a cofactor of two enzymes, namely, ethylmalonyl-CoA mutase (MCM) and methionine synthase. MCM catalyzes the reversible isomerisation of l-methylmalonyl-CoA to succinyl-CoA. A deficiency of MCM causes an inherited metabolism disorder commonly known as methylmalonic aciduria. Methionine synthase utilizes cobalamin as a cofactor to produce methionine from homocysteine (Table 1). Reduced activity of this enzyme leads to megaloblastic anemia (Tjong et al., 2020). Ruminant animals produce vitamin B12 if there is an appropriate supply of Co in their diet. It was reported that 3 to 13% of the Co was incorporated into cobalamin by bacteria in the ruminant animals (Huwait et al., 2015).
Cobalamin Biosynthesis in Bacteria and Archaea
The natural forms of vitamin B12 are 1,5-deoxyadenosylcobalamin, hydroxycobalamin, and methylcobalamin (Nohwar et al., 2020). They are synthesized by a selected subset of bacteria and archaea (Heal et al., 2017; Guo and Chen, 2018), which include Bacillus, Escherichia, Fervidobacterium, Kosmotoga, Lactobacillus, Mesotoga, Nitrosopumilus, Petrotoga, Propionibacterium, Proteobacteria, Pseudomonas, Rhodobacter, Rhizobium, Salmonella, Sinorhizobium, Thermosipho, and Thermotoga (Doxey et al., 2015; Fang et al., 2017). Cyanocobalamin is not a natural form but commercially synthesized B12. The production of vitamin B12 by these microbes involves about 30 enzymatic steps through either aerobic or anaerobic pathways. In addition to being essential for fat and carbohydrate metabolism and synthesis of DNA, vitamin B12 is a cofactor of many enzymes. There are more than 20 cobalamin-dependent enzymes in those prokaryotes including diol dehydratase, ethanolamine ammonia-lyase, glutamate, and methylmalonyl-CoA mutase, methionine synthase, and ribonucleotide reductase (Marsh, 1999) (Table 1). These enzymes catalyze a series of transmethylation and rearrangement reactions (Rodionov et al., 2003). Thus, Co is essential for those archaea and bacteria.
Cobalt Plays an Important Role in Biological Nitrogen Fixation
Biological N fixation is a process of converting N2 from the atmosphere into plant-usable form, primarily NH3. Biological N fixation (BNF) is carried out by a group of prokaryotes known as diazotrophs, which are listed in Table 2, including bacteria, mainly Rhizobium, Frankia, Azotobacter, Mycobaterium, Azospirillum, and Bacillus; Archaea, such as Methanococcales, Methanobacteriatles, and Methanomicrobiales, and cyanobacteria, like Anabaena, Nostoc, Toypothrix, and Anabaenopsis (Soumare et al., 2020). N2-fixing organisms are also classified into three categories: symbiotic, endophytic, and associated groups (Figure 1). Such classifications may not be accurate as some of them, such as those from Acetobacter and Azospirillum, could be associated, as well as endophytic bacteria."
