Fitness Cost and Competitive Ability to Different Ploidy Levels in Ryegrass Genotypes

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.

Fitness Cost of Imazamox Resistance in Wild Poinsettia (Euphorbia heterophylla L.)

“…The lower height of the wild poinsettia R plants in stages of advanced vegetative development can obstruct pollination, since in this weed, pollination is mainly done by insects [23]; thus, it is possible that R plants may produce fewer seeds per plant than S plants. Additionally, taller plants better intercept solar radiation [24], and at the same time shade smaller plants [25]. Reduction in plant height as a pleiotropic effect of herbicide resistance was also reported in glyphosate-resistant Lolium perenne L. [26] and atrazine-resistant Brachypodium hybridum Catalan, Joch.…”

“…However, it cannot state that this leaf shape is a trait associated with the fitness cost or with resistance to imazamox, since the wild poinsettia presents foliar polymorphism, regardless of the growing conditions, being the characteristic linked to its scientific name (E. heterophylla). In the absence of herbicide selection pressure, decreasing the amount of a photosynthetically active area per unit of plant mass may decrease carbon assimilation [24]. In contrast, species with a higher leaf area (up to an optimum leaf area) tend to be more successful in competition and interception for light and carbon assimilation [28].…”

Winter cover crops reduce the soil seed bank and infestations of Italian ryegrass in no‐tillage system

“…Lower Italian ryegrass development caused by competition can significantly reduce the number of tillers, reducing seed inputs into the soil. In a crop–weed competition free environment, one plant of Italian ryegrass can produce more than 40 tillers and shed up to 10,500 viable seeds (Schmitz et al., 2019), highlighting the role of cover crops as a tool to reduce the seeds inputs into the soil. Cereal rye, common vetch, feral radish, and black oat strongly reduced the Italian ryegrass soil seed bank, reducing more than 95% of weed infestations due to lower development and seed inputs into the soil (Figures 2 and 3).…”

May the crossing between diploid and tetraploid Italian ryegrass transfer glyphosate resistance to the next generation?

“…For the tetraploid Italian ryegrass, polyploidy induction increased the palatability and forage digestibility as result of the greater amount of soluble sugars and lower stem/leaf ratio (Nair 2004). Furthermore, tetraploid plants have faster initial growth rate, greater tillers number, higher forage production, and longer vegetative period compared to the diploid Italian ryegrass plants, important characteristics to growth and rapid establishment in agricultural systems (Tonetto et al 2011;Schmitz et al 2019).…”