Competitive outcomes of quinoa genotypes with wild radish and ryegrass at increasing levels of infestation

The weed species wild radish (Raphanus raphanistrum) and ryegrass (Lolium multiflorum) exhibit high competitive ability for resources such as water, light, and nutrients when infesting quinoa crops. The present study aimed to compare the competitive ability of three quinoa genotypes (Q 1303, Q 1331, and Q 1324) in the presence of wild radish and ryegrass. The experiments were conducted under greenhouse conditions using a randomized complete block design with four replicates. Initially, the optimal plant density for quinoa genotypes and competing weeds was determined based on the point at which shoot dry matter production stabilized (20 plants per pot). Subsequently, five replacement series experiments were established to assess the competitive interactions between quinoa and the weeds, combining species in relative proportions of 100:0, 75:25, 50:50, 25:75, and 0:100, corresponding to 20:0, 15:5, 10:10, 5:15, and 0:20 plants per pot, respectively. Competitiveness was analyzed using replacement series diagrams and relative competition indices. Variables evaluated included plant height, stem diameter, number of leaves/tillers, chlorophyll index, leaf area, shoot dry matter, and nutrient content in both quinoa and competing plants. The quinoa genotypes competed for the same environmental resources as the weeds and showed similar competitive ability against each weed species. Overall, quinoa exhibited greater relative growth in the presence of ryegrass and reduced growth when infested with wild radish, which proved to be a more competitive weed species.