Effects of Preharvest Desiccation with Glyphosate on Grain Sorghum Seed¹

Abstract

The preharvest application of chemical desiccants to reduce moisture content of grain sorghum (Sorghum bicolor (L.) Moench) may make it possible to eliminate costly mechanical drying of harvested grain. The objective of these experiments was to evaluate the effect of glyphosate on the viability of seed from field‐treated plants. Seed from grain sorghum plants desiccated with 1.12, 2.24 and 4.48 kg/ha glyphosate [(N‐phosphonomethyl) glycine] produced a high percentage of abnormal seedlings with varying amounts of interveinal areas completely devoid of chlorophyll. Mildly affected seedlings recovered from the symptoms and produced normal plants with normally appearing, viable seed. Severely varlegated plants died. Seed damage was greatest when treatments were applied 25 days after flowering when the grain had a moisture content of 30 to 40%. Damage decreased as time of treatment after flowering (30, 35, and 40 days) increased. The number of abnormal seedlings observed in standard germination tests corresponded to the number of variegated seedlings observed in growth evaluation studies. Similar effects were noted for genotypes ‘Top Hand’, BT− 399, and RT− 2536. The last two genotypes are similar to the female and male parents of Top Hand. Rate and time of treatment had no effect on yield of Top Hand.

Glyphosate’s Suppression of Cytochrome P450 Enzymes and Amino Acid Biosynthesis by the Gut Microbiome: Pathways to Modern Diseases

“…Superoxide's reaction with NO to produce the highly toxic peroxynitrite (ONOO−), a potent bacteriocidal agent, is likely a critical factor. The subsequent oxidation of BH 4 disrupts its ability to act as a cofactor [188], and causes "eNOS uncoupling," leading to superoxide synthesis in a highly disruptive feedback loop.…”

“…Studies have shown sharp increases in glyphosate contamination in streams in the Midwestern United States following the mid 1990s, pointing to its increasing role as the herbicide of choice in agriculture [2]. A now common practice of crop desiccation through herbicide administration shortly before the harvest assures an increased glyphosate presence in food sources as well [3][4][5]. The industry asserts that glyphosate is nearly nontoxic to mammals [6,7], and therefore it is not a problem if glyphosate is ingested in food sources.…”

Preharvest glyphosate in alfalfa for seed production: Effect on alfalfa seed yield and quality

“…However, glyphosate reduced seed germination and vigour when applied during the seed development of such diverse crops as sorghum [Sorghum bicolor (L.) Moench], perennial ryegrass (Lolium perenne L.), and soybeans (Glycine max Merr.) (Baur et al 1977;Hampton and Hebblethwaithe 1982;Ratnayake and Shaw 1992). Due to the importance of seed quality to marketing, more data on the effects of preharvest glyphosate on alfalfa seed quality on the Canadian prairies are needed.…”

Desiccation and Germination of Grain Sorghum As Affected by Glufosinate

“…In other studies, however, glyphosate at 2.2 or 4.5 kg ha-1 reduced germination of RS 626 grain sorghum and increased the number of abnormal seedlings produced (Bovey et al, 1975). Baur et al (1977) found that glyphosate produced a high percentage of abnormal seedlings with interveinal areas devoid of chlorophyll in several grain sorghum genotypes. Unlike glufosinate, with its limited transport in xylem or phloem (Ahrens, 1994), glyphosate is highly mobile and easily translocated in plants.…”

“…Evaluation of germination and seedling growth by Baur et al (1977) indicated that glyphosate at rates of 1.1, 2.2, or 4.5 kg ha-1 produced a high percentage of abnormal seedlings by adversely affecting chlorophyll content. Consequently, glyphosate may have seed production limitations related to grain sorghum desiccation.…”