The last century was the scene of an extraordinary social and economic development of mankind. This development had the fossil energy as one of its pillars. The discovery of petrol led the society to shape a development model highly dependent on this source of energy, which has finite resources and also promotes a big increase on the greenhouse gases, with unforeseeable consequences for the human beings as well as the entire life. It is imperative that we change the pillars of energy from fossil to renewables that will be more sustainable and less aggressive to the environment. One of the sources of this new energy platform, probably the best, is biomass. Fibrous plants bring several advantages and fit well within the requirements deemed important to be elected as producers of biomass. Among these characteristics we have the high processing capacity of solar energy into biomass, fast growth, long-term canopy, possibility of large-scale production. Despite of that this plants are adapted to suboptimal environments that allows its production not compete with food production because it requires less energy input, bringing marginal lands into production with its all social-benefit consequences. Among the fibrous plants, SUGAR CANE or, better, ENERGY CANE has one of the biggest potential for biomass productions. Results from several breeding programs has showing the high biomass potential of energy cane over other biomass crops like sorghum, elephant grass and eucalyptus.

Traditional sugarcane cultivars (Saccharum officinarum) proved highly susceptible to diseases, and this led breeders to progress to interspecific crosses resulting in disease resistance. A backcrossing program to S. officinarum was then required to boost sucrose content. Clonal selection across generations and incorporation of other germplasm into cultivated backgrounds established the (narrow) genetic base of modern cultivars (Saccharum spp.), which have a man-made genome. The genome complexity has inspired several molecular studies that have elucidated aspects of sugarcane genome constitution, architecture, and cytogenetics. However, there is a critical shortage of information on chromosome behavior throughout meiosis in modern cultivars. In this study, we examined the microsporogenesis of a contemporary variety, providing a detailed analysis of the meiotic process and chromosome association at diakinesis, using FISH with centromeric probes. Chromosomal abnormalities were documented by examining high quality preparations of pollen mother cells (700 in total). Approximately 70% of the cells showed abnormalities, such as metaphase chromosomes not lined up at the plate, lagging chromosomes and chromosomal bridges, and tetrad cells with micronuclei. Some dyads with asynchronous behavior were also observed. Due to the hybrid composition of the sugarcane genome, we suggest that bivalent incomplete pairing may occur in the first prophase leading to univalency. The presence of rod bivalents showing the lagging tendency is consistent with a reduction in chiasma frequency. Finally, the presence of chromatin bridges indicates the indirect occurrence of chromosomal inversions, although chromosome fragments were not clearly recognized. Possible reasons for such meiotic abnormalities and the large prevalence of bivalent formation are discussed.

Target region amplification polymorphism (TRAP) markers were used to estimate the genetic similarity (GS) among 53 sugarcane varieties and five species of the Saccharum complex. Seven fixed primers designed from candidate genes involved in sucrose metabolism and three from those involved in drought response metabolism were used in combination with three arbitrary primers. The clustering of the genotypes for sucrose metabolism and drought response were similar, but the GS based on Jaccard's coefficient changed. The GS based on polymorphism in sucrose genes estimated in a set of 46 Brazilian varieties, all of which belong to the three Brazilian breeding programs, ranged from 0.52 to 0.9, and that based on drought data ranged from 0.44 to 0.95. The results suggest that genetic variability in the evaluated genes was lower in the sucrose metabolism genes than in the drought response metabolism ones.

In spite of the great homogeneity found in the morphological characteristics of Oxisols, there is great chemical diversity in subsurface layers of these soils. Studies indicate that crop yield presents significant correlation with the chemical attributes of the subsurface, which, are more stable than attributes found in the plough layer, subject to greater alterations as a consequence of agricultural exploration. This work evaluated the effects of subsurface chemical attributes of Oxisols of the South Central region of Brazil, on the yield of sugarcane clones and of variety RB72454, during the first, second and third cropping cycles. Productivity data were obtained between 1993 and 1998. Soils were characterized in terms of their mechanical analysis and chemical traits at 0.8 to 1.0 m; correlation studies between these attributes and mean daily productivity as well as multiple regression analysis were also carried out; variables were selected based on their R 2 values by means of the stepwise procedure. The subsurface chemical traits of the Oxisols influenced sugarcane productivity, especially the 3 rd harvest; the clone productivity model for the 3 rd harvest as a function of base saturation and phosphorus content presented R 2 = 0.31, i.e., 31% of the variation in sugarcane yield (t ha -1 day

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Sugarcane (Saccharum spp.) is an efficient and sustainable alternative for energy generation compared to non-renewable sources. Currently, during the mechanized harvest process, the straw left in the field can be used in part for the second generation ethanol and increasing the electric energy production. Thus, this study aimed to provide information on the potential for residual biomass cultivars of sugarcane cropping system. This study provides the following information: yield of straw, depending on the calculated leaf area index and the number of tillers per linear meter; primary energy production of several sugarcane genotypes; contribution of dry tops and leaves; biomass yield; and evaluation of fiber, cellulose, hemicellulose and lignin. Preliminary results obtained by researchers of the State of São Paulo, Brazil, and reCviews related studies are presented. The results suggest that the production of sugarcane straw content varies according to the cultivars; the greater mass of sugarcane straw is in the top leaves and that the potential for the crude energy production of sugarcane per area unit can be increased using fiber-rich species or species that produce more straw. The straw indexes was shown to be a good indicator and allow the estimation of straw volumes generated in a sugarcane crop. The cellulose, hemicellulose and lignin composition in sugarcane is distinct among varieties. Therefore, it is possible to develop distinct biomass materials for energy production and for the development of sugarcane mills using biochemical processes and thermal routes.

The Brazilian sugarcane industry plays an important role in the worldwide supply of sugar and ethanol. Investigation into the genetic structure of current commercial cultivars and comparisons to the main ancestor species allow sugarcane breeding programs to better manage crosses and germplasm banks as well as to promote its rational use. In the present study, the genetic structure of a group of Brazilian cultivars currently grown by commercial producers was assessed through microsatellite markers and contrasted with a group of basic germplasm mainly composed of Saccharum officinarum and S. spontaneum accessions. A total of 285 alleles was obtained by a set of 12 SSRs primer pairs that taken together were able to efficiently distinguish and capture the genetic variability of sugarcane commercial cultivars and basic germplasm accessions allowing its application in a fast and cost-effective way for routine cultivar identification and management of sugarcane germplasm banks. Allelic distribution revealed that 97.6% of the cultivar alleles were found in the basic germplasm while 42% of the basic germplasm alleles were absent in cultivars. Of the absent alleles, 3% was exclusive to S. officinarum, 33% to S. spontaneum and 19% to other species/exotic hybrids. We found strong genetic differentiation between the Brazilian commercial cultivars and the two main species (S. officinarum: = 0.211 and S. spontaneum: = 0.216, P<0.001), and significant contribution of the latter in the genetic variability of commercial cultivars. Average dissimilarity within cultivars was 1.2 and 1.4 times lower than that within S. officinarum and S. spontaneum. Genetic divergence found between cultivars and S. spontaneum accessions has practical applications for energy cane breeding programs as the choice of more divergent parents will maximize the frequency of transgressive individuals in the progeny.

ABSTRACT. Although polycrosses have been used to test the potential of cross-combination of a large number of sugarcane parents, the male parent of the half-sib progenies produced is unknown. The present study aimed to integrate the molecular marker technology to the sugarcane polycross approach by the application of microsatellite markers to identify the male parent of 41 elite clones derived from polycross families. Ten microsatellite [single sequence repeats (SSRs)] primer pairs were used to identify the most likely male parent considering markers present in the selected clone but absent in the female parent. The number of alleles generated by the 10 microsatellite primer pairs ranged from 102 (cross-pollination lantern 4) to 120 (cross-pollination lantern 2) with an average of 113.25 alleles per SSR. The average genetic similarity among the involved parents in the polycrosses was 45.9%. The results of the analysis of the SSR markers absent in the female parent and present only in the selected clone as well as the genetic Paternity identification in sugarcane polycrosses similarity values allowed the identification of the most likely male parent in 73% of the total clones evaluated and also to detect probable contaminations. The obtained results highlight the importance of using molecular marker technology in the identification and confirmation of the male parent of high-performance clones derived from polycrosses in the sugarcane breeding programs.