Abstract
ABSTRACT: The intergenotypic competition of tetraploid ryegrass with natural diploid population may be a tool to reduce the frequency of resistant individuals in an area. This study aimed to identify and compare the phenological development, fitness cost, and competitive ability between diploid and tetraploid ryegrass genotypes. Genotypes were grown in pots, and the morphological variables of genotype growth were assessed every 15 days up to 120 days after emergence to evaluate the fitness cost. Phenological development and seed yield components were measured in a single time together with the fitness cost. Competitive ability was determined in a replacement-series experiment with proportions of tetraploid and diploid ryegrass, in which the number of tillers, plant height, leaf area, and shoot dry weight were assessed at 50 days after emergence. The results of fitness cost showed that the number of tillers, leaf area, root dry weight, and the number of seeds were higher for tetraploid ryegrass, which presented a higher competitive ability than the diploid genotype regardless of the tested proportions. Tetraploid ryegrass may be useful for reducing the frequency of herbicide-resistant diploid ryegrass because of its higher competitive potential.
Highlights
Lolium multiflorum is the main winter grazing crop that composes the agricultural systems in the South region of Brazil due to its bromatological qualities, low production costs, and natural potential of soil seed bank replenishment (Aguinaga et al, 2008)
This study aimed to identify and compare the phenological development, fitness cost, and competitive ability between diploid and tetraploid ryegrass genotypes
Each experimental unit consisted of plastic pots filled with a sandy loam textured Red-Yellow Argisol belonging to the mapping unit of Pelotas, RS, with pH and fertility previously corrected according to soil analysis based on the recommendations of fertilization and liming of cold season grass forages (CQFS RS/SC, 2004)
Summary
Lolium multiflorum (ryegrass) is the main winter grazing crop that composes the agricultural systems in the South region of Brazil due to its bromatological qualities, low production costs, and natural potential of soil seed bank replenishment (Aguinaga et al, 2008). In Brazil, there are ryegrass biotypes with simple and multiple resistance to 5-enolpyruvyl-3-phosphate synthase (EPSPs), acetyl-coenzyme A carboxylase (ACCase), and acetolactate synthase (ALS) (Heap, 2017) herbicides inhibitors The resistance to these sites of action hinders the adoption of chemical management due to the lack of selective post-emergence herbicides to winter cereals. It is necessary to search for management alternatives that may contribute to reducing the ryegrass seed bank and its adverse effects on crops
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