Analysis of genetic recombination in maize populations using molecular markers

An understanding of the inheritance of recombination frequency between linked genes would enhance its use as a tool in plant breeding. The objectives of this study were to: (i) Characterize recombination frequencies in two adjacent segments on chromosome 1 marked by Pgml, Adhl, and Phil isozyme loci, and in one segment on chromosome 6 marked by Idh2 and Mdh2, in three maize populations: CBMEX3 and CBCAR5, derived from corn belt x Mexican and Caribbean germplasm, respectively, and NSO, an unselected corn belt synthetic; (ii) Compare variation in recombination frequencies between populations and between families within populations for each region; (iii) Compare the effect of two environments on recombination rates for the Pgm1-Adh1 and Adh1-Phi1 regions in CBMEX3 and NSO. Recombination values (r) were computed from segregating F\sb2 progenies derived from crosses between plants of contrasting genotypes for linked loci in the respective populations. Wide ranges in recombination were observed among families in each population for all regions. For the Pgm1-Adh1 region, F\sb2 families of each population fell into two broad categories of r frequencies; $\u3e$0.30-0.49 and 0.02-0.20. No intermediate values (0.21-0.29) were found. For the Adh1-Phi1 and the Idh2-Mdh2 regions, the distribution curves of r frequencies were almost normal. Crossing-over frequencies were apparently controlled by a single gene in the Pgm1-Phi1 region, but by multi genes in the Adh1-Phi1 and Idh2-Mdh2 regions. No correlation was found between r-values of the two adjacent regions in chromosome 1, indicating that the single gene affecting recombination in the Pgm1-Adh1 region may be specific for that region. For the Pgm1-Adh1 region, no difference in mean r value was found among populations while for the Adh1-Phi1, region both CBMEX3 and NSO were significantly different from CBCAR5. For the Idh2-Mdh2 region, CBMEX3 was significantly different from NSO. The other differences between population pairs were not significant. F\sb2 families within each population were significantly different for each chromosome region. No significant differences in response to two environments (field, Florida and greenhouse, Nebraska) were detected in CBMEX3 and NSO for the two regions in chromosome 1

Flowering Without Vernalization in Winter Canola (Brassica napus): use of Virus-Induced Gene Silencing (VIGS) to accelerate genetic gain

Ciclos de reproducción cortos y la oportunidad de incrementar la ganancia genética, junto con el estudio de las bases moleculares de la vernalización, son áreas esenciales de investigación dentro de la biología de plantas. Varios métodos se han empleado para lograr el silenciamiento génico en plantas, pero ninguno reportado a la fecha para canola (Brassica napus), y en particular para inducir la floración sin vernalización en líneas de invierno a través del uso de secuencias sentido de DNA en vectores diseñados para el silenciamiento génico inducido por virus (VIGS). La presente investigación provee los métodos para transitoriamente regular a la baja, por medio de VIGS, genes de la vernalización en plantas anuales de invierno, específicamente la familia de genes de Flowering Locus C (FLC) en canola de invierno (BnFLC1 a BnFLC5). La regulación a la baja de estos genes permite a las plantas anuales de invierno florecer sin vernalización y, consecuentemente, provee los medios para acelerar la ganancia genética. El sistema de silenciamiento propuesto puede ser utilizado para regular a la baja familias de genes, para determinar la función génica, y para inducir la floración sin la vernalización en líneas de invierno tanto del género Brassica como de muchos cultivos importantes de invierno