Astylus atromaculatus (Coleoptera: Melyridae): abundance and role in pollen dispersal in Bt and non-Bt cotton in South Africa

Experimental oral administration of pollen beetle (Astylus atromaculatus) to cattle results in an acute lethal gastrointestinal disease

In the summer of 2023, ingestion of Astylus atromaculatus (pollen beetle) was linked to spontaneous fatal disease in grazing cattle and sheep in Argentina and Uruguay. While the disease was experimentally reproduced in sheep and guinea pigs in the 1970's, no experimental reproductions have been attempted in cattle, and controversy exists as to whether this insect is indeed noxious to cattle and at which dose. Here, we demonstrate that A. atromaculatus causes acute fatal disease in Hereford calves at single oral dosages of 2.5, 4.5, 10.0, and 15.0 g of insect/kg body weight. Death or severe disease necessitating euthanasia occurred at 38 to 48 hours postinoculation regardless of the dose, suggesting that the single fatal dosage is likely <2.5 g/kg body weight (this dose representing approximately 850 mL of intact beetles in a 100 kg calf). Clinically, the disease was characterized by acute anorexia, prolonged recumbency, reluctance to move, listlessness/apathy, depression, ruminal hypomotility and tympany, hypothermia, bruxism with frothing at the mouth, and mucoid diarrhea progressing to death. Hematologic and biochemical alterations included hemoconcentration, stress/acute inflammatory leukogram, negative energy balance, and ketosis. The pathological hallmark of this experimental disease is acute necrotizing omaso-reticulo-rumenitis, fibrinohemorrhagic enteritis, and exfoliative colitis with intralesional chitinous insect fragments. While A. atromaculatus might contain a gastrointestinal toxin or pathogen, extensive toxicological testing failed to identify a causative toxin. Other pathomechanisms such as direct physical damage caused by insect fragments on the alimentary tract seem plausible, although further studies are needed to elucidate the pathogenesis of A. atromaculatus-associated disease.

Assessment of Gene Flow Between Gossypium hirsutum and G. herbaceum: Evidence of Unreduced Gametes in the Diploid Progenitor

In the framework of a gene flow assessment, we investigated the natural hybridization rate between Gossypium hirsutum (AADD genome) and G. herbaceum (AA genome). The latter species, a diploid progenitor of G. hirsutum, is spontaneously present in South Africa. Reciprocal crosses were performed without emasculation between G. herbaceum and G. hirsutum Neither examination of the morphological characteristics nor flow cytometry analysis of the 335 plants resulting from the G. hirsutum × G. herbaceum cross showed any hybrid features. Of the 148 plants produced from the G. herbaceum × G. hirsutum cross, three showed a hybrid phenotype, and their hybrid status was confirmed by SSR markers. Analysis of DNA content by flow cytometry and morphological traits clearly showed that two of these plants were triploid (AAD). The third plant had a flow cytometry DNA content slightly higher than G. hirsutum In addition, its morphological characteristics (plant architecture, presence and size of petal spots, leaf shape) led us to conclude that this plant was AAAD thus resulting from fertilization with an unreduced AA gamete of the female G. herbaceum parent. Fluorescent In Situ Hybridization (FISH) and meiotic behavior confirmed this hypothesis. To the best of our knowledge, this is the first description of such gametes in G. herbaceum, and it opens new avenues in breeding programs. Furthermore, this plant material could provide a useful tool for studying the expression of genes duplicated in the A and D cotton genome.