Molecular mapping in tropical maize (Zea mays L.) using microsatellite markers. 1. Map construction and localization of loci showing distorted segregation

Microsatellites have become the most important class of markers for mapping procedures. Primarily based on restriction fragment length polymorphism (RFLP) markers, several molecular genetic maps of maize have been developed, mainly using temperate inbred maize lines. To characterize the level of polymorphism of microsatellite loci and construct a genetic map in tropical maize, two elite inbred lines, L-08-05F and L-14-4B, were crossed to produce 400 F-2 individuals that were used as a mapping population. A survey of 859 primer pair sequences of microsatellites was used. The polymorphism screens of each microsatellite and genotype assignment were performed using high-resolution agarose gels. About 54 % of the primer sets gave clearly scorable amplification products, 13 % did not amplify and 33% could not be scored on agarose gels. A total of 213 polymorphic markers were identified and used to genotype the mapping population. Among the polymorphic markers, 40 showed loci deviating from expected Mendelian ratios and clusters of deviating markers were located in three chromosome regions. Non-Mendelian scoring was present in 19 markers. The final genetic map with 117 markers spanned 1634 cM in length with an average interval of 14 cM between adjacent markers.13929610

Two-dimensional electrophoresis of Cereus peruvianus (Cactaceae) callus tissue proteins

Two-dimensional electrophoresis of Cereus peruvianus callus tissues grown in culture media containing two different 2,4-dichlorophenoxyacetic acid (2,4-D) and kinetin combinations was used to identify minor differences in polypeptide composition of these cell clones. Altered expression during growth in the two 2,4-D and kinetin combinations was apparent for 13 polypeptides when calluses in the two media were compared. The number of proteins with differential expression (presence or absence of specific spots) was higher in callus tissues cultured in the 4.0 mg/L 2,4-D and 8.0 mg/L kinetin combination than in callus tissues cultured in the 4.0 mg/L 2,4-D and 4.0 mg/L kinetin combination. The present results show that the callus tissues maintained at 4.0 mg/L 2,4-D and 8.0 mg/L kinetin can be used as a matrix for in vitro selection programs.20362662

RAPD markers to evaluate callus tissue of Cereus peruvianus Mill. (Cactaceae) maintained in different growth regulator combinations

RAPD markers were used to detect DNA polymorphisms in callus tissues maintained at different auxin and cytokinin combinations. There is a higher level of genetic variablity in callus tissue maintained with the highest kinetin versus 2,4-D concentration. Callus tissues subcultured in a 4.0 mg/L 2,4-D and 4.0 mg/L kinetin combination showed high similarity and can be recommended as more suitable sources for industrial procedures of extraction of natural products such as secondary metabolites since extraction protocols can be easily standardized using genetically uniform materials. The higher genetic diversity in callus tissues of C. peruvianus cultured at 4.0 mg/L 2,4-D and 8.0 mg/L kinetin indicates this tissue as a matrix for in vitro selection of cell lines for higher natural products production. RAPD markers are, therefore, effective tools useful for detecting DNA polymorphism in callus tissue as well as in the DNA identification of callus tissues maintained in different auxin and cytokinin combinations.404192135135

Mapping QTLs for kernel oil content in a tropical maize population

Maize cultivars often have low kernel oil content. To increase the oil content, efficient maize breeding programs have to be developed, which require the knowledge of the inheritance of this trait. Thus, the objective of this research was to map quantitative trait locus (QTLs) and estimate their effects for kernel oil content in a tropical maize population. Two maize inbred lines, contrasting for kernel oil content, were used to develop an F-2 population. Four hundred and eight F-2 plants were self-pollinated, and their kernels (F-2:3 progenies) were used for kernel oil evaluation. A genetic map with 75 microsatellites was developed, and the QTLs were mapped using the composite interval map (CIM); also, estimates of genetic and phenotypic variances, and heritability coefficient were computed. The map presented 10 linkage groups, spanned 1,438.6 cM in length with an average interval of 19.18 cM between adjacent markers. The kernel oil content averaged 58.40 g kg(-1), and the broad-sense heritability was high (h(2)=0.98). Thirteen QTLs were mapped, which were distributed into eight chromosomes, and explained 26.64% of the genetic variation. QTLs in chromosomes 1, 5, and 6 contributed the most for kernel oil content. Nine out of 13 QTLs with favorable alleles were from the parental inbred with the highest kernel oil content. The average level of dominance was partial, but gene action of the QTLs ranged from additive to overdominance. Eight out of 13 mapped QTLs were already reported for temperate maize populations.137225125

Genetic diversity in tropical maize inbred lines: heterotic group assignment and hybrid performance determined by RFLP markers

Tropical maize inbred lines, eight derived from a Thai synthetic population (BR-105) and 10 from a Brazilian composite population (BR-106), were assayed for restriction fragment length polymorphisms with 185 clone-enzyme combinations. The aim of this study was to investigate genetic distances among tropical maize material and their relationship to heterotic group allocation and hybrid performance. Genetic distances (GDs) were on average greater for BR-105 x BR-106 lines (0.77) than for BR-106 x BR-106 (0.71) and for BR-105 x BR-105 (0.69) lines. Cluster analysis resulted in a clear separation of BR-105 and BR-106 populations and was according to pedigree information. Correlations of parental GDs with single crosses and their heterosis for grain yield were high for line crosses from the same heterotic group and low for line combinations from different heterotic groups. Our results suggest that RFLP-based GDs are efficient and reliable to assess and allocate genotypes from tropical maize populations into heterotic groups. However, RFLP-based GDs are not suitable for predicting the performance of line crosses from genetically different heterotic groups.119649149