Valdir Diola

Carbon isotope fractionation for cotton genotype selection

The objective of this work was to evaluate the carbon isotope fractionation as a phenomic facility for cotton selection in contrasting environments and to assess its relationship with yield components. The experiments were carried out in a randomized block design, with four replicates, in the municipalities of Santa Helena de Goias (SHGO) and Montividiu (MONT), in the state of Goias, Brazil. The analysis of carbon isotope discrimination (Δ) was performed in 15 breeding lines and three cultivars. Subsequently, the root growth kinetic and root system architecture from the selected genotypes were determined. In both locations, Δ analyses were suitable to discriminate cotton genotypes. There was a positive correlation between Δ and seed‑cotton yield in SHGO, where water deficit was more severe. In this site, the negative correlations found between Δ and fiber percentage indicate an integrative effect of gas exchange on Δ and its association with yield components. As for root robustness and growth kinetic, the GO 05 809 genotype performance contributes to sustain the highest values of Δ found in MONT, where edaphoclimatic conditions were more suitable for cotton. The use of Δ analysis as a phenomic facility can help to select cotton genotypes, in order to obtain plants with higher efficiency for gas exchange and water use.

Chapter 2 – Physiology

This chapter aims to present briefly the main physiological processes responsible for crop growth and development and to show how they are involved in metabolic processes of the main compounds responsible for sugarcane products commercially exploited. The study of plant physiology covers a much wider field than we will cover, ranging from the expression of specific genes to complex metabolic processes; these would require further studies. We will briefly detail the procedures for obtaining and assimilating carbon and the synthesis of sucrose, which is the main compound of interest in agronomics currently. Additionally, we will circumstantially present the processes of plant growth and development, with emphasis on the two physiological stages of great agricultural importance: flowering and maturation.

Molecular Biology and Biotechnology

Sugarcane is a perennial crop whose C4 metabolism makes it one of the most efficient species in carbon conversion. It is one of the most productive amongst all cultivated crops as well as the main feedstock for sugar production, accounting for nearly two-thirds of the world’s production. With molecular genomics, the sugarcane genome has become less mysterious, although its complexity has been confirmed in many respects. This chapter presents a general discussion of molecular bases and biotechnological processes, as well as their application and prospective advances in the sugar–alcohol sector. The topics are not addressed in detail, as the theme is very broad, the generation of new information highly dynamic and the amount of information exponential.

Tools for the Future Breeder

Currently, the genetic improvement of plants demands the selection process to be more efficient and to obtain better results in a short period of time. However, the productivity of most of the cultivations has almost reached a plateau. Many cultivations show high genomic complexity: polyploidies, aneuploidies, recombinations, structural chromosome alterations (translocation, inversion, deletion, and insertion), multiple alleles, interaction of QTLs and eQTLs, and high gene variation, which make it difficult to obtain cultivars more stable and less vulnerable to environmental alterations. Until now, the current study has prioritized production and quality phenotypic characters, selecting genotypes in only one field level. Given the increase in the difficulty of obtaining better varieties, genetic typing was used, which was very useful when backed up by phenotyping. There are many genotyping methodologies, each one having its own application characteristics and specificities, and the breeder must know and become acquainted with the most appropriate choice. Nowadays, genotyping techniques are no longer limited, due to automatization and subcontracting. It is believed that phenotyping will be one of the most limiting factors for genetic improvement, especially for large populations.This chapter will take a generalist approach to the contributions that new methodologies have already brought and will be able to bring to the improvement of plants in the very near future.

Chapter 6 – Genes Prospection

Currently, a number of molecular techniques are suitable for the identification of regions of interest and they offer a wide range of genetic information that facilitate a more specific and faster approach, reducing time and labor. Gene prospecting is a great challenge, because the accurate characterization of phenotypes and genotypes is critical to the success of the works to be achieved. That requires from the professional or from the team an extensive knowledge on various areas, integrating classical plant breeding, molecular markers, biochemistry, plant physiology, biotechnology, and bioinformatics.