Sugarcane (Saccharum spp.) is an important crop due to sugar, ethanol and bioenergy production. Its cultivation may occur in tropical regions exposed to high salinity. The aim was to identify cultivars tolerant to salinity to allow the cultivation of sugarcane (Saccharum spp.) in saline soils. To test the hypothesis that sugarcane show natural genotypic variation to salinity tolerance, we tested ten cultivars (SP80-3280, RB855453 RB966928, RB855156, SP80-1842, SP80-1816, RB928064, RB867515, RB92579, RB855536) and two sugarcane species: IM76-228 (S. robustum) and IN84-82 (S. spontaneum) under two concentrations of sodium chloride (NaCl): control (concentration found naturally in the soil used: electrical conductivity of 0.083 dS m-1) and soil enriched with NaCl: EC of 7.2 dS m-1. Biometry and photosynthesis traits were evaluated. The plants were collected and leaf (LDM), stem (SDM), root and total dry matter were used to estimate the tolerance index (TI). A cluster analysis was done to identify phenotypic dissimilarity. Three distinct groups regarding salinity tolerance on biomass-basis were formed. The cultivars RB855156, SP80-1842, SP80-1816 and species IM76-228 showed no reduction in LDM and SDM. Nonetheless, the cultivars SP80-3280, RB928064, RB92579 and species IN84-82 were impaired by salinity. The cultivar SP80-1816 showed the highest biomass accumulation and the highest TI. Therefore, we found a great genotypic variation regarding salinity tolerance in sugarcane, which can be explored by growers to cultivate in saline soils. Also can be used by the Sugarcane Breeding Programs to improve the salinity tolerance.

Events by changes in climate alter the growth and physiology of sugarcane. In this context, the study aimed to investigate the morphological, anatomical, and physiological responses of two different sugarcane varieties under a condition of high carbon dioxide (CO₂) associated with water deficit, testing the hypothesis that sugarcane responses to drought are modulated by high (CO₂) in different plant scales. Thirty days after sprouting, the plants were grown under two (CO₂) in the atmosphere (400 and 680 μmol CO₂ mol⁻¹ of air) and under water restriction conditions. At the morphological level, we assessed total biomass, plant height, stem diameter, leaf area, and root-shoot ratio; at the physiological level, relative water content, water use efficiency, in vivo maximum rate of Rubisco, and PEPC carboxylation, photosynthesis, total organic carbon, and nitrogen, and carbon-nitrogen ratio. At the anatomical level, we assessed stomatal density at adaxial and abaxial surfaces and wall thickness bundle sheath cells. The results indicate that at all levels, the response of sugarcane plants exposed to high CO₂ concentration and drought is genotype-dependent. In general, variety RB855536 showed greater physiological responses: a better water use efficiency and alteration in the carboxylation rate of Rubisco enzyme, while variety RB867515 showed a greater morphological response determined by changes in biomass allocation and anatomical alterations of stomatal densities and functionality. The sugarcane varieties exposed to water deficit and high CO₂ concentration developed different strategies based on morphological, physiological, and/or anatomical changes that are useful for facing climate change scenarios, and the effects of drought can be mitigated by the high (CO₂) in the air.

RESUMO O objetivo deste trabalho foi avaliar as habilidades competitiva e biológica do consórcio de beterraba com caupi-hortaliça, em função de quantidades de biomassa de flor-de-seda incorporada ao solo e de arranjos espaciais. O delineamento experimental utilizado foi o de blocos completos casualizados, em esquema fatorial 4 x 3, compreendendo a combinação de quatro quantidades de flor-de-seda incorporadas ao solo (20, 35, 50 e 65 t ha-1 de matéria seca) e três arranjos espaciais, entre fileiras de plantas, das culturas componentes do consórcio (2:2, 3:3 e 4:4). Foram avaliados os índices de competição: o de perda ou de ganho real de rendimento, o de superação e o coeficiente relativo populacional e de razão competitiva. Os índices de eficiência biológica avaliados foram: uso eficiente da terra, da beterraba e do caupi-hortaliça. A cultura do caupi-hortaliça apresentou maior ganho de produção e melhor capacidade de competição do que a cultura da beterraba, e os arranjos espaciais não influenciaram o desempenho produtivo das culturas. A maior viabilidade biológica do consórcio de beterraba com caupi-hortaliça foi obtida na quantidade de 65 t ha-1 de biomassa de flor-de-seda incorporada ao solo. Não houve influência dos arranjos espaciais na habilidade competitiva e na viabilidade agroeconômica do consórcio de beterraba com caupi-hortaliça.

Intercropping of beet with cowpea-vegetable is increasing in the State of Rio Grande do Norte, Brazil. However, its management requires scientific information and technologies pertaining to space arrangement and adequate fertilization with roostertree. The present study evaluated the agronomic/biological performance of the beet and cowpea-vegetable intercropping system with different amounts of roostertree and spatial arrangements of the component cultures. We established a 4 × 3 factorial completely randomized design with four blocks. The first factor was the amount of roostertree biomass incorporated into the soil (20, 35, 50, and 65 t ha-1 in dry matter), while the second was the spatial arrangement of beet rows alternated with cowpea rows (2:2, 3:3, and 4:4). We evaluated the total, commercial, and classified productivities of beet roots, as well as the number of green pods per m2, green and dry pod productivities, the number of green grains per pod, the weight of 100 green grains, and green and dry grain productive of cowpea. The agronomic efficiency of the intercropping system was evaluated by the land equivalent ratio, productive efficiency index, and score of the canonical variable z. The results showed no significant interactions among the amounts of roostertree biomass and spatial arrangements for any evaluated trait or agronomic index. The highest agronomic efficiency of the intercropping system was obtained with 65 t ha-1 of roostertree biomass and the 2:2 spatial arrangements.