Grasslands are a significant source of forage plant diversity. Within these ecosystems, grasses serve as the foundation of livestock nutrition due to their nutritional value, which enhances secondary productivity (Schaub et al., 2020); (Blaix et al., 2023). However, extensive grazing in arid zones has low production potential (Quero-Carrillo, 2013). Arid zones are characterized by irregular and scarce precipitation, leading to water-deficient conditions. These conditions, in turn, negatively influence the water relations, physiology, and morphology of forage plants, thereby limiting forage yield and even species survival (Shaaban et al., 2023). In search of alternatives to mitigate these effects, practices are implemented where certain grasses are introduced for forage or erosion control. Nevertheless, many of these are invasive species that disperse throughout ecosystems, replacing native vegetation cover and resulting in environmental degradation, biodiversity loss, and economic vulnerability (Rai & Singh, 2020); (Yang et al., 2025).

Consequently, responsible and efficient management schemes must be developed for the utilization of all resources available in extensive grazing. This is essential to achieve a balance with ecosystem energy flows and ensure high profitability (Quero-Carrillo, 2013). Agroecological practices such as characterizing agroecosystem components, as well as collecting, selecting, and conserving native seeds, can help achieve this (Cartmill et al., 2025). However, prior evaluations are required to consider various physical and physiological aspects of the materials intended for establishment. This approach is highly beneficial for identifying and selecting high-quality seeds that can subsequently be sown with a high success rate to effectively restore and conserve grassland ecosystems (Slodowics et al., 2023). In northern Coahuila, grasslands dominate the areas where agricultural activities have taken place, but accurate information is needed on the species, their seeds, and their potential for regional management (Contreras-Cisneros et al., 2022); (Guillen-Cruz et al., 2022). We hypothesized that, under the semi-arid conditions in southern Coahuila, introduced forage grass species would exhibit seed physical and physiological qualities significantly different from those of native species, and that the removal of accessory structures would increase germination. The novelty of this study lies in the fact that, although livestock farming is a major industry in the region, no studies have been conducted to assess the physical and physiological quality of the forage species found in the grazing lands. Therefore, the objective of this study was to determine the physical and physiological quality of the diaspores and caryopses of eight forage grass species found in grazing areas across four municipalities in southern Coahuila, Mexico, within the region known as La Comarca Lagunera.

Collection of the evaluated materials was carried out at four sites in La Comarca Lagunera, located in the state of Coahuila. These sites correspond to the municipalities of: Matamoros (25°31’41” N; 103°13’49” W), San Pedro de las Colonias (25°45’28” N; 102°58’59” W), Viesca (25°20’37” N; 102°48’23” W), and Francisco I. Madero (25°46’30” N; 103°16’23” W). The selection criterion for the sites was their location within grazing areas for small ruminants (sheep and goats).

For sampling, field surveys were conducted, and 1,000-meter-long transects were established, where spikes and spikelets of the present forage grass species were 30 randomly collected. Species were identified (Table 1), and diaspores were extracted at the Herbarium and Biotic Resources Laboratory of the Department of Agroecology at UAAAN-UL. Additionally, caryopses were obtained via manual friction using a rubber mat and pad. Subsequently, the samples were stored in paper bags for two to three days at room temperature until analysis.

Several criteria were evaluated to determine physical and physiological quality, in accordance with the methodology described by (I.S.T.A., 2016) and (Ramírez-Segura et al., 2022), as described below.

The sampling location is situated at an altitude of 1,112 m above sea level (asl) and is characterized by a Bw(h´) hw(e) climate. This is defined as an arid-warm climate with an average annual precipitation of 215 mm, a mean annual temperature of 22.7 °C, and an evaporation rate of 2,600 mm ( Figure 2).

The results for purity percentage and damaged percentage are presented in Table 2. No interaction effects were found (p>0.05). The highest purity percentage (p≤0.05) was found in Eragrostis lehmanniana, while the species with the lowest filling percentage (p≤0.05) was Cynodon dactylon. Furthermore, the percentage of damaged caryopses showed differences between species: Panicum obtusum exhibited the highest percentage of damaged caryopses (p≤0.05), while C. dactylon showed the lowest.

Regarding TSW, Sorghum halepense and Pennisetum ciliare exhibited the highest weights (p≤0.05), with 3.95 g and 2.55 g for diaspores and caryopses, respectively. Similarly, the lowest weights (p≤0.05) were found in E. lehmanniana and Eragrostis spp., with 0.10 g and 0.08 g for diaspores and caryopses, respectively (Table 2).

The introduced species exhibited the highest TW (Table 3). E. lehmanniana showed the highest TW in diaspores (0.97 g), while S. halepense recorded the highest TW in caryopses (11.24 g). Regarding caryopsis size, S. halepense showed the greatest dimensions in length, width, and thickness (p≤0.05). This contrasts with Eragrostis spp., which had significantly smaller dimensions, although E. lehmanniana showed relatively higher length, width, and thickness (p≤0.05) within its genus. This is because their size corresponds to the smallest seeds (p≤0.05) among all evaluated species.

In terms of physiological seed quality, Panicum obtusum exhibited the best germination rates for both caryopses and diaspores (Table 4). Conversely, the lowest germination percentages were observed in E. lehmanniana and Eragrostis spp. Regarding vigor, the species with the greatest plumule and radicle size (p≤0.05) in both caryopses and diaspores was S. halepense. Similarly, the species Eragrostis spp. exhibited the lowest vigor in both plumule and radicle for diaspores and caryopses. Finally, viability results showed that Buffelgrass (P. ciliare) had the highest values (p≤0.05) for Class I seeds, whereas Bouteloua barbata presented the lowest quantity of viable seeds.

The results show that the physical and physiological characteristics of the seeds could be influenced by environmental conditions (Scarfó et al., 2024). Regarding the purity percentage of the caryopses, the results could be attributed to the type of spikelets present and the extraction method used to obtain caryopses. In this regard, Eragrostis lehmanniana is characterized by having many caryopses per branchlet. Furthermore, regardless of low rainfall conditions, it is able to survive and invade without any adverse effects on its physiological development (Burruss et al., 2022).

For their part, (Quigley et al., 2023) point out that seed size influences physical quality and is also related to physiological quality. In this particular case, the species S. halepense and P. ciliare showed a close relationship between TSW and caryopsis size, as they yielded values higher than the rest of the species evaluated. Such data are crucial given that both species are highly invasive and have high dry-matter yields; these characteristics improve their phenotypic plasticity, enabling rapid adaptation to environmental stress (Boyles et al., 2019); (Wei et al., 2025). In areas where, for instance, stress conditions—such as high temperatures and low precipitation during seed production—reduce caryopsis size, this could largely explain the observed response in native species (Ravi et al., 2022).

Regarding the physiological quality of the seeds, results found for P. obtusum contrast with the report by (Anderson & N, 1974), who state that seed germination for this species is low, resulting in deficient field establishment. Nevertheless, these results open a window of opportunity where it is essential to evaluate the response of each species within its specific agroecosystem. Since germination depends on factors such as genotype, environmental conditions, dormancy, and harvest time, determining optimal germination conditions is necessary to significantly improve the success of field establishment (Lamichhane et al., 2018); (Machado et al., 2019). Nevertheless, our study found zero germination in the caryopsis and diaspore stages of Eragrostis species. This is likely to explain the low response in our study, as E. lehmanniana reportedly needs 6 to 48 months to break dormancy (Wright, 1973), while our seeds were harvested (October/autumn) only four months prior to testing (February/winter).

Other reports (G. et al., 2022) evaluated germination and vigor using seeds harvested during October with storage periods of two to three years. Their findings showed variations in the days to emergence, with most evaluated species germinating two days after sowing. However, E. lehmanniana again showed low germination levels, while P. ciliare exhibited the highest values, like our findings.

Seed sizes also appear to influence this attribute, as observed in S. halepense. In this regard, studies (Sonkoly et al., 2020) indicate that invasive species possess traits—such as seed quantity, size, and adaptive germination processes—that contribute to the success of their invasive behavior. This was observed in S. halepense and P. ciliare, which produce large, heavy seeds that show a marked difference compared to native species and even other introduced species with smaller seeds.

Regarding viability, P. ciliare has been reported to enter dormancy and is more tolerant of arid conditions than native species, which could be related to its caryopsis germination percentage(Ravi et al., 2022). Similarly, for this species, the dormancy period has been quantified between 16 and 20 months post-harvest (Effect of seed storage on seed germination and seedling quality of Festulolium in comparison with related forage grasses, 2020). However, dormancy was not observed in our results, as a high percentage of the seeds were viable. (Farrell & Gornish, 2019) note that P. ciliare modifies water availability by reducing its germination requirements, thus establishing a feedback response for its invasive behavior and allelopathy tolerance. These characteristics could explain its adaptability to the arid and semi-arid conditions of Mexico, as well as its resistance to grazing.

This feedback response of P. ciliare triggers a cyclical reduction in native grass populations, which are primarily affected by overgrazing and inappropriate stocking rates. These factors are further intensified by extreme temperature events in arid zones, which undermine their resilience—unlike what occurs with species such as P. ciliare(Farrell & Gornish, 2019). This behavior could help explain the low viability found for Chloris virgata and Bouteloua barbata, a pair of native species that show viability and germination indexes of between 10% and 40%; negative effects are attributed to these factors, compromising their adaptive processes and leading to a diminished presence in rangelands and a greater prevalence of invasive species (Gioria et al., 2026).

This study has some limitations that should be considered when interpreting the results: collection was conducted during a single period, and physiological evaluation was performed after a short storage period; therefore, quality and germination performance may vary across years, seasons, and storage durations.

Seed physical and physiological quality differed among the forage grass species evaluated. Invasive species had heavier and larger seeds, which likely contributes to higher germination rates by eliminating bracts and accessory structures. On the other hand, although native species did not show significant results, they persist in the semi-arid region of southern Coahuila. These findings are very important, as they will enable the development of technologies to improve the establishment of forage banks, thereby helping to limit erosion in grazing lands.

The Authors declare that there is no conflict of interest.

The authors would like to express their gratitude to the Research Department of the Universidad Autónoma Agraria Antonio Narro for funding this research (project code: 3811-425609002-2844).

The authors declare that no artificial intelligence tools were used in any of the experimental stages, from the conception of the study to the final writing of the results presented in this manuscript.