Introduction

Drought can reduce grain production by up to 50 % (^{Asati et al., 2022}; ^{Upadhyaya et al., 2012}) and severely reduce biomass production of pastures and forages used as animal feed. This process involves molecular mechanisms with morphological manifestations that include but are not limited to a reduction in water status (water potential or relative water content), turgor pressure (^{Purbajanti et al., 2020}), and reduction of leaf expansion as the initial response of plants to drought stress (^{Perera et al., 2019}). These effects generally reduce biomass production, which is the main objective of grass and forage cultivation.

In recent years, drought periods have increased worldwide, coupled with observed decreases in precipitation volumes (^{Cruz et al., 2025}). Rainy periods have shifted or become shorter (^{Allan, 2012}), negatively affecting biomass accumulation capacity and grain production. Researchers from the agricultural and livestock sectors around the world focus their efforts on food production under climate change and a combined abiotic stresses (^{Liu et al., 2022}), particularly in arid and/or seasonally dry regions, a condition characteristic of the tropics. Some plant species tolerate a wide range of available soil moisture. This is the case for Sorghum bicolor L. Moench and Pennisetum glaucum L. (^{Cruz et al., 2025}), the latter being a relative of Napier Grass (Cenchrus purpureus (Schumach) Morrone syn., formerly Pennisetum purpureum) (^{Chemisquy et al., 2010}; ^{Mogotsi et al., 2020}), native to sub-Saharan Africa. Due to its ecological plasticity, it has been distributed in regions with partially humid climates, such as Australia, Asia, South America, Mesoamerica, and tropical Caribbean islands (^{Muktar et al., 2023}; ^{Singh et al., 2013}). Initially, its high biomass production made it a popular feed source for dairy cattle and its use subsequently expanded to other animal species. Its productive and nutritional history continues to this day.

This species has been widely used as animal feed in Cuba since 1980, although there are no records of its introduction (^{Herrera et al., 1995}). The seasonality of rainfall in Cuba leads to food scarcity due to water scarcity, negatively impacting cattle production systems. In response to these challenges, a C. purpureus improvement program was created based on physical and chemical mutagens under in vitro conditions to obtain clones tolerant to drought and combined stress situations (drought and salinity) (^{Herrera et al., 2003}). These clones maintained genetic stability, allowing them to be identified as varieties (^{Herrera, 2009}). Although they have been extensively studied in the western region of Cuba, the eastern region, especially within the Cauto Valley (which occupies 4.5 thousand km²), has not been evaluated. The Cauto Valley region is known for its livestock activity (approximately 90 %) (^{Ponce Palma et al., 2020}), and its hydrological (^{Sánchez-Sánchez et al., 2013}), and geological features (^{Gonzalez, 1916}).

These characteristics differ from those described for the western part of the country (^{Álvarez, 2017}). In the Cauto Valley, studies on the establishment and forage evaluation of the new varieties obtained by tissue culture have not yet been carried out. For this reason, the objective of the present study was to evaluate the establishment of ten new varieties of C. purpureus tolerant to drought under conditions of intense seasonal drought in the Cauto Valley, Cuba.

Materials and methods

The research was conducted on the Estación Experimental de Pastos y Forrajes of the Instituto de Investigaciones Agropecuarias “Jorge Dimitrov” in Granma, Cuba, from November 2019 to May 2020. This site constitutes a representative ecosystem of the Cauto Valley. The air temperature ranged from 24.2 °C during the dry season (November-April) to 27.7 °C during the rainy season (May-October), reaching maximum values of 28.6 °C and 32.8 °C, respectively. Annual rainfall fluctuated between 630 and 1500 mm, with periods of intense drought during the dry season, representing 7.0 to 11.9 % of the total.

Statistical analysis

Statistical analysis was performed using Statistica (version 10.0). Data normality was assessed using the Kolmogorov-Smirnov test, and homogeneity of variance using Bartlett’s test. Each variable was analyzed using one-way analysis of variance (ANOVA). Means were compared using the Newman-Keuls test. The mathematical model used for the experimental design is shown in equation 1.

Where: Y_ij = response variable, µ = constant common to all observations, T_i = effect of the i-the treatment (varieties) (i = 1,…,11), β_j = effect of the j-the block (j = 1,…,4), eij = random error ~ N (0, σ2e).

To explore the relationship between early establishment vigor and final agronomic performance, a Pearson correlation analysis was performed. The correlation coefficients (r) were calculated between the sprouting percentage at 29 days after planting (as an indicator of early vigor) and the main agronomic variables recorded at the establishment cut (154 days after planting), including plant height, dry matter yield, leaf-to-stem ratio, and leaf area per plant. Correlation significance was set at p < 0.05.

Results

During the first 12 days after sowing, varieties CT-608, CT-607, CT-609, CT-115, and CT-603 showed, in that order, the highest sprouting percentages (p ≤ 0.05), a pattern that was maintained throughout day 19, when the CT-600 variety was added to the highest performing group. By day 29, varieties CT-603 and CT-608 reached the highest sprouting levels, exceeding 60 %, followed by CT-600 and CT-609 with values above 50 %, and CT-607, with 44 % (p ≤ 0.05). In contrast, the remaining varieties, including the control (CT-115), showed slower sprouting, with percentages between 20 % and 40 % over the same period (Figure 1).

Figure 1 Variation in the sprouting percentage of the varieties. Estación Experimental de Pastos y Forrajes del Instituto de Investigaciones Agropecuarias “Jorge Dimitrov”. Cuba. 2020. 

The response of the evaluated varieties at the establishment cut is present in Table 2. No significant differences were observed among varieties in plant height, average daily growth, leaf area, and dry matter (DM) yield (p ≥ 0.05), indicating a uniform agronomic response after 154 days of growth under intense seasonal drought conditions and without irrigation.

Biomass indicators showed significant differences in structure and distribution. The CT-604 variety outperformed the control (CT-115) in both leaf-to-stem ratio (2.1 vs. 1.5) and leaf percentage (67.4 % vs. 57.8 %) (p ≤ 0.05). The other varieties showed no significant differences (p ≥ 0.05), except for CT-602, which presented a leaf-to-stem ratio statistically similar to that of the control (p ≥ 0.05). No prior information exists on the performance of these varieties during the establishment phase under intense seasonal drought. These results therefore represent the first documented report in a dryland livestock production system.

To further investigate the relationship between early establishment vigor and final agronomic performance, a Pearson correlation analysis was performed between sprouting percentage at 29 days (Figure 1) and the variables evaluated at the establishment cut at 154 days (Table 2). The results (Table 3) showed a positive but weak and non-significant (p > 0.05) correlation with final plant height (r = 0.32) and dry matter yield (r = 0.28). The correlation with leaf-to-stem ratio was practically null (r = −0.05). These findings suggest that, under the intense seasonal drought conditions of this study, early sprouting vigor is not a reliable predictor of final yield or biomass structural quality in C. purpureus.

Discussion

Sprouting studies conducted in western Cuba with these new varieties show similarities to the parent cultivar, CT-115, characterized by a gradual, prolonged germination pattern extending beyond 28 days (^{Herrera et al., 1995}). In this study, the observation that between 30 and 65 % of the planted buds sprouted after 29 days suggests an adequate establishment capacity under seasonal drought conditions, considering that soil moisture did not exceed 13.2 %, a value lower than the wilting coefficient desired for this type of soil (^{Hernández-Jiménez et al., 2019}). The plant height values recorded were relatively short, which may be attributable to abiotic stress, particularly water deficit. Water deficit affects plant growth due to cellular dehydration and disrupted metabolism (^{Zhang et al., 2018}), aspects that are subject to high variability, as manifested in controlled experimental conditions, when developed under production conditions, or in open fields (^{Mustamu et al., 2023}), as was the case in the present study.

However, the parental cultivar (CT-115) is a short statured cultivar and well-suited for grazing (^{Gudiño-Escandón et al., 2025}; ^{Retureta González et al., 2019}). In the present study, no differences (p ≥ 0.05) were observed in the height of CT-115 relative to the new varieties, suggesting that, due to their genetic origin, they may inherit this trait. Thus, the reduced plant stature cannot be attributed solely to the effects of intense seasonal drought.

The higher percentage of leaves in some of the new varieties, compared to the control, indicates a favorable structural response and has positive implications for the production of quality biomass in water-constrained regions. The number of leaves is primarily reduced as a physiological compensation mechanism when the plant is under water stress, since both the morphology of this organ and its quantity constitute an important pathway for water exchange with the environment, mediating gas exchange, water balance, and photo-synthesis (^{Azcón-Bieto & Talón, 2020}). Therefore, under seasonal drought conditions, the plants’ ability to respond by producing more leaves than stems suggests potential value in animal feed.

This behavior is consistent with ^{Mengistu et al. (2022}), who highlighted the role of leaves as indicators of tolerance to water stress in forage crops. A higher proportion of functional leaf tissue can favor digestibility and nutritional forage value, representing an advantage in livestock systems located in arid areas or with irregular rainfall.

In addition to the favorable leaf production observed in the new varieties, dry matter yield was also encouraging. In studies involving the parental cultivar (Cenchrus purpureus (Schumach) Morrone cv. Cuba CT-115) productivity and yield responses are strongly influenced by the soil and climate characteristics of the experimental or production sites.

Under conditions of the Mexican subhumid tropics, evaluated several cultivars of C. purpureus, including CT-169, also obtained through genetic improvement programs, and reported yields ranging from 1.4-1.8 t ha^-1 DM (^{Villanueva-Avalos et al., 2022}), while in the Veracruz region, in a warm subhumid climate, yields of up to 18 t ha^-1 DM were reported (^{Reyes-Castro et al., 2018}). In Honduras, under a rainfall regime of 1419 mm year^-1 yields of 2.25 t ha^-1 DM at 90 days (^{Medrano-Escobar et al., 2024}). Although CT-604 did not differ structurally from the remaining varieties (p ≥ 0.05), the present results suggest that CT-604 could express relevant differences in biomass quality, as demonstrated in previous studies (^{Ray et al., 2018}). This finding justifies its subsequent evaluation under nutritional analysis and digestibility frameworks, to validate its potential for use as animal feed in rainfed areas.

The absence of a significant correlation between early sprouting and final dry matter yield (r = 0.28, p > 0.05) is a key finding of this study. This result indicates that, while rapid emergence is desirable for soil cover and weed competition, it does not predict the productive potential of the variety under prolonged water stress. Recent studies in wheat support this observation; ^{Lan et al. (2022}) found no significant correlation between early root and shoot vigor and demonstrated that traits responsible for early drought tolerance (such as root biomass) differ from those conferring tolerance to late-season drought stress (such as grain weight and leaf area).

It is possible that varieties with slower sprouting, such as CT-604, possess physio-logical mechanisms (e.g., a deeper root system or greater water-use efficiency) that allow them to match or surpass the performance of fast-sprouting varieties as stress intensifies at later growth stages. Additionally, ^{Vukasovic et al. (2022}) identified that early vigor in wheat is governed by specific genetic loci (such as QTLs on chromosomes 2D, 1B, and 5A) that are not necessarily associated with final yield, reinforcing the idea that these are genetically independent traits. This result underscores the importance of comprehensive evaluations covering the entire establishment phase, rather than relying solely on initial indicators alone.

Conclusions

The new Cenchrus purpureus varieties evaluated demonstrated adequate establishment on Fluvisol soils during the dry season, and early sprouting was not correlated to final dry matter yield. The results confirmed that, of the ten varieties studied, CT-604 showed the greatest potential during the establishment phase, based on a higher leaf percentage and a better leaf-to-stem ratio. This suggests its suitability for forage systems in arid zones and areas with intense drought in the Cauto Valley.

Interests conflict

The authors declare that there are no conflicts of interest.