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A key step in the pre-breeding stage of plant breeding is the selection of cultivars with desirable characteristics for use as parents to develop new crop varieties. With the development of technology, numerous laboratory techniques have emerged as key tools for breeding programs to save time and resources. For these reasons, the aim of this review was to describe techniques based on cytological and cytogenetic studies that are feasible for the selection of parents during the pre-breeding stage. Among the cytological techniques addressed in this review are: pollen viability and quality, stigmatic receptivity to know how long the stigma is receptive, and pollen tube growth to study incompatibility events. Another key step in pre-breeding is to determine the chromosomal number of the parents, which is possible by different techniques of classical cytogenetics (studies during mitosis and meiosis) and molecular cytogenetics (flow cytometry, Fluorescent in situ Hybridization and Genomic in situ Hybridization) that are discussed in this review. [ABSTRACT FROM AUTHOR]

Rhizobia (Rhs) and arbuscular mycorrhizal fungi (AMF) are soil microsymbionts associated with crop roots. For Rhs most of them are legumes and for AMF there is a wider host range; however, there are crops that develop colonization by both symbionts. In any of the symbiotic relationships, crops receive benefits when colonized by these microorganisms are varied and contribute to the use of alternatives for sustainable agriculture. The mechanism by which both symbionts penetrate their plant host has been studied at the molecular level and common genes have been identified, as well as the pathways in which they are involved. Some of these genes are related to the reception of the signal mediated by Nod factors in the case of Rhs and by Myc factors in the case of AMF, others are related to the penetration mechanism and finally to the route by which the symbiont and the plant communicate. In the present review, a list of studies concerning microsymbionts, at the level of pre-colonization, colonization and shared mechanism is made. A proposal of possible common candidate genes for Rhs and AMF to apply genetic engineering is presented, in such a way that a research field called: gene optimization is explored. Because of the similarity by which these symbionts penetrate their host and the potential for genetic modification that this implies, a close molecular, metabolic and physiological relationship is described. [ABSTRACT FROM AUTHOR]

Objective: To ratify the importance of the application of molecular tools in the pasture breeding programs. Materials and Methods: Fifty-nine papers were consulted and reviewed, which approach the methods based on molecular (genetic markers, CRISPR technology and molecular cytogenetics), available in databases (Google Scholar, Dialnet, Redalyc, SciELO, REDIB, DOAJ and Latindex), in order to obtain information about their application in pasture breeding. Results: Information was compiled about the main molecular markers (microsatellites, randomly amplified polymorphic DNA, single-nucleotide polymorphism, amplified fragment length polymorphism), utilized to analyze the genetic diversity in pastures. Which ones are more effective and versatile was researched. It was noted that the phenomenon of apomixis can be utilized to maintain the hybrid vigor in pasture lines and that molecular marks contributed to identify apomictic plants at early ages. It was validated that the CRISPR (clustered regularly interspaced short palindromic repeats) technology can be applied in pasture species to improve agronomic attributes. Conclusions: Molecular markers, especially SNPs, are ideal for genetic diversity studies in pastures and for the identification of apomictic plants at early ages. The CRISPR technology of genomic edition constitutes a versatile tool applicable in pastures. [ABSTRACT FROM AUTHOR]

Bromeliads have a high commercial potential as ornamental species. The creation of new varieties is of utmost importance for the market. The objective of this research was to evaluate the morpho-agronomic variability of hybrids from intra and interspecific crosses of Guzmania lingulata, G. freya, G. wittmackii, G. conifera, G. zahnii and the Vriesea "Electric" cultivar. Ten groups of plants from crosses between accessions of Guzmania and Vriesea were studied for a commercial exploitation of bromeliads between 2017 and 2018, to which the quantitative variables were measured: plant height, plant diameter, peduncle length, number of leaves, length of leaves, width of basal leaves, length of inflorescence and diameter of inflorescence. Descriptive statistics were determined for these variables as mean, CV and SD and an ANOVA was performed with a Duncan mean separation test at 0,05%. The variables were subjected to an analysis of principal components and Pearson's correlations. Regarding results, it was obtained that crossing 1 reached the highest values for all the variables except NH and DI, while crossings 4 and 6 showed the lowest values for most of the variables (p<0,05). Highly correlated variables were found, such as peduncle length (Lped) and plant height (AP), peduncle length (Lped) and plant diameter (DP), leaf length (LH) and plant diameter (DP). and inflorescence height (AI) with plant height (AP). In general, in the principal components analysis, it was found that all the variables, except the Inflorescence Diameter (DI), contribute to the variability in the first two components. According to the analyzes carried out and the quantified variables, sufficient variability was found to develop a plant breeding program. [ABSTRACT FROM AUTHOR]