Endozoochorous seed dispersal of glyphosate-resistant Lolium multiflorum by cattle

Abstract

Lolium multiflorum, one of the most important temperate forage grasses in the world, is used in integrated crop-livestock systems and as a cover crop. However, it is also one of the main weeds in winter crops. The continuous use of glyphosate to manage this species has led to the selection of resistant biotypes (LOLMU-R), making it important to prevent the dispersal of these seeds. This study aimed to assess the recovery and germination of LOLMU-R that have passed through the digestive system of cattle. The experiments were carried out in metabolism cages, using a completely randomized design with six replications. The animals were given 12 112 seeds each, which were recovered from their faeces over a period of 6 days. Germination of the recovered seeds was assessed in a germination chamber and compared against a control (no animal passage). After germination, a glyphosate dose-response curve was constructed. The results obtained showed a total recovery of 1109 seeds (9.1%), with maximum recovery 2 days after ingestion, decreasing to almost zero on day 6. Germination declined linearly as a function of recovery time; however, 4 days after ingestion, germination potential was 18%. The dose-response curve proved the resistance of the recovered seeds. Cattle is a dispersal agent for LOLMU-R seeds, with animals requiring 7 days of quarantine before moving from one infested area to another.

Germination, overcoming seed dormancy and endozoochory dispersal by cattle of native species from natural grassland

“…The seed recovery rate, however, varies according to the species evaluated and presents sigmoidal behaviour, with maximum recovery up to 3 days after ingestion, decreasing significantly after this (Schaedler et al, 2021; Viero et al, 2018). It explains why no differences were found during the first 3 days after ingestion.…”

“…Chemical effect can occur due to enzymes and gastric juice produced and released into the lumen of the gastrointestinal tract, as well as changes in pH that can vary from 2 to 3 in the abomasum and around 6 in the rumen (Van Soest, 1994). These processes can reduce the germination of recovered seeds (Schaedler et al, 2021; Viero et al, 2018). However, it can increase Fabaceae species germination, due to mechanical and chemical scarification that overcome seed dormancy (Milotić & Hoffmann, 2016).…”

“…On the fourth day, the seeds (5000 of P. notatum and 2500 of D. incanum to each animal) were supplied by orogastric dosage, which was performed with a tube to ensure that all seeds supplied went directly down the oesophagus to the rumen. The faeces were collected at 1, 2 and 3 days after ingestion, during which maximum recovery occurs (Schaedler et al, 2021; Viero et al, 2018).…”

Germinação, superação da dormência de sementes e dispersão endozoocórica por bovinos de espécies nativas de pastagens naturais

“…A taxa de recuperação das sementes, no entanto, varia de acordo com a espécie avaliada e apresenta comportamento sigmoidal, com recuperação máxima até três dias após a ingestão, diminuindo significativamente depois (Schaedler et al, 2021; Viero et al, 2018). Isso explica por que não foram encontradas diferenças durante os primeiros três dias após a ingestão.…”

“…O efeito químico pode ocorrer devido a enzimas e suco gástrico produzido e liberado no lúmen do trato gastrointestinal, bem como alterações no pH, que pode variar de 2–3 no abomaso e cerca de 6 no rúmen (Van Soest, 1994). Esses processos podem reduzir a germinação de sementes recuperadas (Schaedler et al, 2021; Viero et al, 2018). No entanto, podem aumentar a germinação de espécies de Fabaceae, devido à escarificação mecânica e química que quebra a dormência das sementes (Milotić & Hoffmann, 2016).…”