Selected Indices to Identify Water-Stress-Tolerant Tropical Forage Grasses

Abstract

Periods of soil water stress have been recurrent in the Cerrado region and have become a growing concern for Brazilian tropical pasture areas. Thus, the search for forage grasses more tolerant to water stress has intensified recently in order to promote more sustainable livestock. In a greenhouse experiment, the degree of water stress tolerance of nine tropical forage grass cultivars was studied under different soil water regimes. The investigation followed a 9 × 3 factorial design in four randomized blocks. Nine cultivars from five species of perennial forage grasses were tested: Urochloa brizantha (‘BRS Piatã’, ‘Marandu’, and ‘Xaraés’), Panicum maximum (‘Aruana’, ‘Mombaça’, and ‘Tanzânia’), Pennisetum glaucum (‘ADR 300’), Urochloa ruziziensis (‘Comum’), and Paspalum atratum (‘Pojuca’). These cultivars were grown in pots under three soil water regimes (high soil water regime—HSW (non-stressful condition), middle soil water regime—MSW (moderate water stress), and low soil water regime—LSW (severe water stress)). Plants were exposed to soil water stress for 25 days during the tillering and stalk elongation phases. Twelve tolerance indices, including tolerance index (TOL), mean production (MP), yield stability index (YSI), drought resistance index (DI), stress tolerance index (STI), geometric mean production (GMP), yield index (YI), modified stress tolerance (k1STI and k2STI), stress susceptibility percentage index (SSPI), abiotic tolerance index (ATI), and harmonic mean (HM), were calculated based on shoot biomass production under non-stressful (YP) and stressful (YS) conditions. Soil water stress decreased leaf area, plant height, tillering capacity, root volume, and shoot and root dry matter production in most cultivars, with varying degrees of reduction among tropical forage grasses. Based on shoot biomass production under controlled greenhouse conditions, the most water-stress-tolerant cultivars were P. maximum cv. Mombaça and cv. Tanzânia under the MSW regime and P. maximum cv. Aruana and cv. Mombaça under the LSW regime. P. maximum cv. Mombaça has greater adaptability and stability of shoot biomass production when grown under greenhouse conditions and subjected to soil water stress. Therefore, this forage grass should be tested under field conditions to confirm its forage production potential for cultivation in tropical regions with the occurrence of water stress. The MP, DI, STI, GMP, YI, k2STI, and HM tolerance indices were the most suitable for identifying forage grass cultivars with greater water stress tolerance and a high potential for shoot biomass production under LSW regime.

Selection of forage grasses for cultivation under water-limited conditions using Manhattan distance and TOPSIS

“…All of the species were given fertilization treatment using a urea-based solution containing 80 mg kg −1 , exactly 30 days after the plants first emerged. Information on the soil chemical properties and agronomic characteristics of the investigated tropical forage grass varieties was described by Zuffo et al [ 7 ].…”

“…Drought stress categories were proposed in [ 18 ], whereby moderate and severe water stresses were achieved by maintaining soil moisture at 20%-30% and 50%-60% PC, respectively, in pots. There are also other authors who used these PC values for moderate and severe drought [ 7 ].…”

“…Tropical forage grasses are crucial in livestock production, mainly due to their role in soil and ecosystem conservation in the subtropics and tropics [ 6 , 8 ]. Water stress can reduce the growth and consequently the biomass and nutritional value of tropical forage grasses [ 5 , 7 , 10 ], as well as increase their susceptibility to pests and diseases [ 11 , 12 ]. Drought stress triggers changes in the physiological and biochemical responses of plants, including photosynthesis, water relations, antioxidant defense, and osmotic adjustment [ 10 , 13 , 14 ].…”

“…Multivariate analysis methods are employed in many areas, including agriculture, where they can help to choose the most robust species of tropical forage grasses under stress conditions, for example. Among the available methods, there are several proposals that aim to evaluate the adaptation and tolerance of plant species exposed to stressful environments [ 7 , 16 ]. The use of a new approach employing the distance (or similarity) of a vector space through the Manhattan distance and the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method allowed the selection of soybean cultivars subjected to saline stress [ 16 ].…”

Periodical Progress in Ecophysiology and Ecology of Grassland

“…The study advances our understanding of the mechanisms underpinning biodiversity-ecosystem functional relationships and has significant implications for semiarid grassland management. Zuffo et al, (2022) [8] compared the tolerance of nine cultivars belonging to five species of perennial tropical forage grasses in Brazil growing in pots with controlled soil water conditions. After comparing and evaluating of twelve tolerance indices, the mean production (MP), drought resistance index (DI), stress tolerance index (STI), geometric mean production (GMP), yield index (YI), modified stress tolerance (k 2 STI) and harmonic mean (HM) were selected as the most suitable parameters for identifying forage grass cultivars with greater water stress tolerance and a high potential for shoot biomass production under severe water stress condition.…”