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Sugarcane cultivar RB0442 has a high yield, late maturation and good drought tolerance. It is recommended for planting in restrictive environments, mainly with water-deficient soils, and is resistant to the major sugarcane diseases of the Northeastern region of Brazil.

The number of areas subject to drought is likely to increase in response to climate change and will affect the yields of globally important crops such as sugarcane. In this respect, the aim of the present study was to assess the drought tolerance of sugarcane varieties in different phenophases and identify the physiological and biochemical characteristics associated with the lowest yield loss under drought conditions. Six of the most widely cultivated varieties in the region were studied, namely SP79-1011, RB855113, RB92579, RB867515, RB72454 and RB855536. Plant physiological characteristics were assessed during the dry season in the tillering, intense growth and ripening stages, and yield was quantified after 12 months of cultivation. This study shows that different sugarcane varieties are more affected by drought in the intense growth phenophase, since plants showed a greater decline in water and osmotic potential at midday during this period. The varieties most affected by drought in this phenophase were RB855536 and RB855113, which exhibited greater reductions in water and osmotic potential. They also had larger osmoregulator accumulation as a response to drought, but not enough to prevent dehydration, which likely contributed to the lower yield. The RB867515 and RB92579 varieties underwent no significant change in osmotic potential at midday during drought stress in the intense growth phase, despite of low leaf water potential, and little variation in the osmoregulators contents. For these reasons, these two varieties showed greater drought acclimation potentials and were more productive as submitted to drought conditions.

The sugar-energy sector is highlighted in Brazilian agribusiness; however, poor water distribution and soil acidity have limited the yield and quality of cane fields. Gypsum improves the physical and chemical properties of the soil, attenuating the effects of water shortage and acidity in the edaphic environment. The aim of this study was to determine the effect of gypsum doses on the nutritional status, photochemical efficiency and technological quality of sugarcane. The experiment was conducted under field conditions using a randomized block design in a 3 x 5 factorial scheme with four replications. The treatments consisted of the combination of three sugarcane varieties (RB011941, RB92579, and RB991536) with five doses of gypsum (0 Mg ha-1; 2.5 Mg ha-1; 5.0 Mg ha-1; 10 Mg ha-1; and 20.0 Mg ha-1). The results showed that gypsum did not influence the evaluated variables. A varietal effect for leaf contents of P, K, Mg and S was observed. The RB92579 presented the highest levels of P (1.65 g kg-1) and K (14.55 g kg-1), while RB011941 showed the highest concentrations of Mg and S, 1.25 and 1.05 g kg-1, respectively. The mean values of the macronutrients presented the following concentration order: N > K > Ca > Mg > P > S. Genotypes were similar in terms of photochemical efficiency, which in turn, was not influenced by gypsum application. The best technological quality was verified in RB92579, which showed the highest Brix percentage (22.35%), Pol (19.75%), and the highest levels of TRS (151.3 kg t-1) of sugarcane.

The flowering of sugarcane (Saccharum spp. hybrids) is a developmental stage that is desirable for breeding programs but undesirable for commercial cultivation, since it causes losses in sugar content and cane yield. This study aimed to (1) characterise the flowering of four varieties of sugarcane with different flowering times and intensities, (2) determine the nutrient levels in their vegetative apexes and (3) to evaluate the effect of calcium on their flowering. The study was divided into two trials. In the first trial, we tested the effect of planting season on the flowering of four varieties of sugarcane that had contrasting flowering periods. Late or reluctant flowering varieties had higher concentrations of calcium in their vegetative apexes in relation to the early variety. At the same time, the early variety, with heavy flowering, had higher potassium in its vegetative apexes. In the second trial, the effect of calcium on their flowering was tested. The application of calcium on the leaves resulted in its accumulation in the vegetative apexes, causing a reduction in potassium levels in the same tissue. This changed the plant phenology, resulting in a month’s delay in flowering and a 50 % reduction in the final flowering intensity. Calcium application by foliar sprays can be used to delay and reduce sugarcane flowering.

Sugarcane is a crop of economic importance in tropical and subtropical countries, with a high diversity of genetic resources and a long history of genetic manipulation (breeding); however, a reassessment of the genetic variability available to breeders is required in order to further the development of modern varieties. Some methods based on morphological and genealogical data have been used, however, morphological characters are influenced by the environment and genealogical data can result in distorted information. On the other hand, SSR molecular markers can reliably distinguish between closely related individuals, a property particularly useful in crops that have a narrow genetic base. The aim of this study was to evaluate the genetic diversity of the main progenitors of sugarcane from the germplasm bank of RIDESA, using SSR markers. Forty-seven varieties were analyzed and the results showed a total of 124 polymorphic alleles with sizes ranging from 81 to 340 bp. Of these, 22 were classified as rare alleles and twelve others were considered common. The microsatellites used, showed elevated values for polymorphism and discriminatory power, as well as low indices of genetic identity. The average similarities observed between the main progenitors from RIDESA were low, probably as a consequence of high levels of ploidy and heterozygosity for this crop. Moreover, the cluster analysis showed a complex overall structure, as there was no tendency to form groups with varieties obtained from the same hybridization or parent.

New polymorphic SSR markers in sugarcane has potential usefulness to studies genetic diversity, genetic mapping, DNA fingerprinting and determination offspring as true hybrids, selfing or contaminant in germplasm from breeding program. SSR markers can be obtained in several ways, and the search for SSR-EST sequences an alternative with significant results. The aim of this study was to develop highly polymorphic SSR markers for germplasm studies in sugarcane. Di- tri- and tetra-nucleotide sequences were mined in the TGI bank and 53 EST-SSR markers developed. These markers were analyzed in five genotypes and showed to be highly polymorphic, with the PIC ranging between 0.48 and 0.95 with a mean of 0.86. The discriminatory power ranged from 0.35 to 0.94 with a mean of 0.82 and the genetic similarity was high in the accessions evaluated.

Water deficit is among the main environmental factors limiting agricultural productivity of sugarcane in Northeast Brazil by affecting virtually every aspect of plant growth, with consequent reduction of the agro-industrial productivity of this crop. This study aimed to use path analysis to evaluate the physiological components of sugarcane under two water conditions, with photosynthesis as the basic variable, in order to obtain subsidies that can help the genetic breeding of this crop by selection of superior clones with drought tolerance. The experiment was carried out in a greenhouse with a completely randomized experimental design, 4 × 2 factorial arrangements (four sugarcane genotypes × two soil moisture regimes: control, with 80–100% available water and stressed, with 0–20% water available) and with four replications. Each plot consisted of one pot with 12 kg of substrate containing one plant. Treatments were maintained at a humidity close to field capacity with daily replacement of the evapotranspired water with a water supply for 66 days of cultivation for treatments under stress. Evaluations were conducted on the fourth day after severe water stress at 70 days of cultivation. Data from nine physiological variables were considered, with six of these being used in the model after exclusion of those that were contributing to multicollinearity. Variables used in path analysis were enough to explain the variation found in photosynthesis under both water conditions. Stomatal conductance, transpiration and the SPAD index should be considered as a priority in breeding programs for sugarcane aiming to get more productive and tolerant genotypes to water stress, and selection indexes should be used with due consideration of these variables to promote gains in photosynthesis.

The expansion of sugarcane (Saccharum spp.) in Brazil has been boosted by the growing demand for bio-fuels all over the world and requires the occupation of new agricultural areas, including regions with unfavorable agro-climatic conditions. This observational study makes an analysis of the relationship between stomatal conductance, gas exchange and photosynthesis in sugarcane fields subject to different ambient conditions and growth phases. It was noted that the stomatal conductance had a much higher control on photosynthesis than on transpiration. Even under high stomatal con- ductance, photosynthesis maintained a high correlation to it. Sugarcane had an instantaneous water use efficiency of ap- proximately 4.4 μmol of fixed CO2 for each mmol of H20 expended in transpiration. Lower leaf water potential, besides leading to an internal reduction of CO2, also reduced the instantaneous carboxylation efficiency, indicating that the photo- synthesis apparatus was also affected. The variety RB92579, seems to have good water absorption system, because even under low leaf water potential, it maintained a good stomatal conductance, with a higher transpiration and photosynthesis than the others varieties. These results suggest that this variety has a tolerance mechanism to endure rather than avoid drought.

The aim of this study was to analyze the genetic similarity in commercial cultivars of sugarcane from the breeding program cultivars RB (Republic of Brazil), using SSR markers and coefficient of parentage. Eighteen microsatellite markers were used to estimate genetic similarity in 30 genotypes and coefficient of parentage was estimated in 28 accessions. Eighteen primer pairs produced an average of 3.2 alleles, the level of polymorphism (PIC value) ranged from 0.34 to 0.78 in SMC248CG and SCC2 primers, respectively. The parentage coefficient was high among cultivars, with a mean of 0.14, suggesting high relationship among the cultivars. The results here suggest that to analyzed accessions, there is a high genetic similarity which could reduce the genetic gain in breeding. However, crosses among genotypes of sugarcane produce a high variability in the progenies, suggesting a combination between the genomes of species that originated the current cultivars.

Objetivou-se, neste trabalho, avaliar padrões de crescimento e de produção de variedades de cana-de-açúcar (Saccharum officinarum L.) com os graus-dias e disponibilidade hídrica, durante os cultivos de cana-planta e cana-soca, na região dos Tabuleiros Costeiros Alagoano. O trabalho foi desenvolvido na área experimental de Agrometeorologia da Universidade Federal de Alagoas, Rio Largo-AL, num solo classificado como Latossolo Amarelo coeso argissólico. Utilizou-se o delineamento experimental de blocos cazualizados com cinco repetições e quatro tratamentos: variedades RB92579, RB931530, RB93509 e SP79-1011. As variáveis da cultura utilizadas foram: perfilhamento, altura da planta, índice de área foliar (IAF), acúmulo de matéria seca no colmo e produção final. Foram encontradas diferenças significativas entre as médias de perfilhamento das variedades em todas as épocas amostradas, de forma geral o maior perfilhamento foi observado na variedade RB92579. O crescimento das plantas apresentou curvas de formato sigmoidal, com três fases distintas. Na fase de estabelecimento da cultura, apesar de ter ocorrido ótima disponibilidade hídrica, o crescimento foi lento. Na fase de crescimento vegetativo as plantas não cresceram em potencial, porque houve deficiências hídricas. A fase final ocorreu entre 1500 e 2015 GD na cana-planta e 950 e 1800 GD na cana-soca. A variedade RB92579 alcançou valores de IAF superiores a 3, logo aos 600 GD nos dois ciclos, permanecendo o restante dos ciclos acima desse valor, contribuindo para uma melhor eficiência no uso da água e para o maior acúmulo de matéria seca. This work had the aim of evaluating the growth standard and yield of different sugarcane (Saccharum officinarum L.) varieties with meteorogical parameter, during the plant and ratoon crop cane in Mesas regions of Alagoas. This work was carried out in an experimental area of Agrometeorology used a randomized outline with five repetition and four treatments: varieties RB92579, RB931530, SP79-1011 e RB93509, in the Agrarian Center of University Federal of Alagoas in Northeast of Brazil, Rio Largo AL, in a United Argissolico Yellow Latossolo soil. The plant parameter utilized to measure the growth were: tillering, plant height, leaf area index (LAI), dry mater accumulation in stalk and yield sugarcane. No differences were observed among tillering media from varieties in all samplings, and in general, the variety RB92579 obtained the biggest tillering. The sugarcane growth showed sigmoidal shape curve, with three different phases. In the crop initial phase, although it occurred great water conditions the sugarcane growth was slow. In the elongation phase the sugarcane didn't grow in potential, due the occurred water deficit in this phase. The last phase occurred between 1500 e 2015 GD in plant cane and 950 e 1800 GD in ratoon crop. The variety RB92579 obtained LAI values of 3 very early (in 600 GD), this contributed to improve the water use efficient and to accumulate more dry matter. The variety RB92579 obtained the biggest tillering ant height of stalk, a result of that, it obtained the biggest yield sugarcane.

Resumo – Os objetivos deste trabalho foram estabelecer estimativas de repetibilidade de caracteristicas agroindustriais em 20 genotipos de cana-de-acucar, determinar a previsibilidade de cada carater e indicar a predicao do valor verdadeiro de cada clone. O delineamento utilizado foi blocos casualizados, com cinco repeticoes. Utilizaram-se a analise de variância com dois fatores de variacao (cortes e genotipos) e a analise dos componentes principais para estimar o coeficiente de repetibilidade , a partir de tres cortes. Foram obtidas estimativas de repetibilidade acima de 0,5 para fibra e toneladas de cana por hectare, em ambos os metodos, com confiabilidade maior que 84% pelo metodo dos componentes principais. As caracteristicas que ficaram abaixo de 0,5, com previsibilidade inferior a 74%, necessitam de um maior numero de avaliacoes. Os metodos dos componentes principais e analise de variância indicaram, em cinco cortes, uma previsibilidade maior que 80% para fibra, porcentagem de pol (sacarose) no caldo da cana, toneladas de cana por hectare e toneladas de pol no caldo da cana por hectare, embora o primeiro tenha sido mais eficiente. Considerando toneladas de cana por hectare e toneladas de pol no caldo da cana por hectare, os clones RB9371, RB9350 e RB9364 sao os melhores. Termos para indexacao: Saccharum, clones, selecao, analise de variância, componentes principais. Repeatability of agro-industrial characteristics in sugar cane