Amando Ordás

Genetic diversity in a germplasm collection of Brassica rapa subsp rapa L. from northwestern Spain

In Galicia (northwestern Spain), Brassica rapa subsp. rapa L. includes turnips, turnip greens, and turnip tops. The objectives of this study are (i) to determine the genetic diversity and morphological resemblances among the B. rapa landraces of northwestern Spain in order to have information relative to the resources preserved, and (ii) to evaluate their agronomic characteristics, considering the three potential products that can be harvested. A collection of 120 landraces was evaluated for 34 morphological and agronomical traits by an augmented design at two locations. Two landraces were the most promising for turnips production (MBG-BRS0183 and MBG-BRS0256), two showed the best characteristics for turnip greens (MBG-BRS0082 and MBG-BRS0184), and three were the most appropriate landraces for turnip tops production (MBG-BRS0143, MBG-BRS0173 and MBG-BRS0401). Landraces were classified into five clusters (A–E) using the Ward–MLM (Modified Location Model) strategy: (A) included plants with the worst agronomic potential, (B) included most of the turnip populations with rosette growth habit, (C) included turnip populations without rosette growth habit, having more vigorous plants than cluster B, (D) gathered the most vigorous local varieties, with the highest early vigor, fresh matter content per leaf, and number of secondary stems per plant, and (E) landraces characterized by their earliness, large flowering periods, high numbers of secondary stems, and large seed weights. As conclusion, landraces evaluated in this work displayed enough variability to differentiate among appropriate populations for each one of the distinct crops. Their classification, using the Ward–MLM strategy, grouped accessions with similar characteristics into homogeneous categories.

Resistance of Kale Populations to Lepidopterous Pests in Northwestern Spain

Abstract Kale (Brassica oleracea L. acephala) is common in northwestern Spain where it is severely damaged by different insect pests. Damage could be reduced by using resistant varieties. The objectives of this work were to evaluate the resistance of kale populations to leaf damage by lepidopterous pests, to determine which traits are the best indicators of resistance, and finally to study the relationship between the glossy phenotype and resistance. Fifteen kale populations, sowed early and late, were evaluated at two locations in northwestern Spain. Significant differences among genotypes were found for all damage traits. Damage was not related to planting dates. Highest levels of damage were observed from July to November. Some populations with different performance under natural infestation in 1999 were again evaluated in 2000 under artificial infestation with Mamestra brassicae (L.) eggs. Two accessions, MBG-BRS0142 and MBG-BRS0170, showed resistance to attack by lepidopterous pests. Correlation coefficients among damage traits show that general appearance rating may be an useful indicator of resistance. Phenotype of kale with glossy leaves seems to be related to resistance although further research is needed.

Morphological characterization of kale populations from northwestern Spain

Crops belonging to the genus Brassicaare widely grown in Galicia (northwesternSpain). Kales (Brassica oleracea L.convar. acephala (DC.) Alef.) are oneof the most important Brassica cropsin this region where landraces aretraditionally grown by farmers on smallplots for either human or animal food.Fifteen kale populations from northwesternSpain were evaluated in two locations andtwo planting dates (early and late). Theobjectives were i) to study theirmorphological diversity, ii) to determinetheir relationships, and iii) to evaluatetheir morphological and agronomiccharacteristics that could be incorporatedto breeding programs in the future.Significant differences were found amongpopulations for all traits while genotype ×environment interaction was not significantfor most of them. Cluster and principalcomponent analysis were performed todetermine relationships among landraces andto obtain information on the usefulness ofthe characters for the definition ofgroups. The phenogram showed five groups,two groups including most of thepopulations and three small independentgroups. Groups of landraces were associatedwith the geographical origin and withmorphological differences amongpopulations, mainly with the length oftheir vegetative phase: north and earlypopulations (cluster A) and south and latepopulations (cluster B). Morphologicaldiversity was higher in coastal populationsthan in inland populations. As conclusion,the populations evaluated in this workdisplay a wide diversity of traits whichenable us to select and combine someinteresting landraces for important traitsin order to obtain improved varieties.

Relationships Among Brassica napus (L.) Germplasm from Spain and Great Britain as Determined by RAPD Markers

The genetic diversity and the relationships among a collection of Brassica napus L. European populations were evaluated using random amplified polymorphic DNA markers. The study included 33 accessions of B. napus collected from Galicia (northwestern Spain) and 18 British cultivars, 16 accessions of B. napus and two accessions of Brassica oleracea L. used as controls. DNA from 25 individuals per population was analyzed using 18 decamer primers. One hundred thirty-eight amplification products were scored of which 105 were polymorphic. These bands ranged in size from 350 to 2500 base pairs. Similarity coefficients and cluster analysis were computed and six groups were obtained. Cluster I was the largest and included all the landraces from northwestern Spain, except two accessions that grouped separately into Clusters III and IV, respectively. A low level of genetic variability was detected among the B. napus Spanish genotypes, while considerable diversity was present among the British ones, which grouped into three groups, two main clusters and one group formed by one accession. Cluster II included all commercial varieties grown in Great Britain whereas Cluster V grouped local varieties maintained by the growers for many years. Cluster VI was a singularity formed by one entry. British accessions of B. oleracea had the greatest dissimilarity with all the other populations and grouped separately in Clusters VII and VIII. As conclusion, B. napus landraces used in northwestern Spain as leafy-green vegetable probably have an independent origin from B. napus crops grown in other European regions. Besides, separate domestication in northwestern Spain and Great Britain for a different end use might have led to two distinct gene pools.

The nabicol: A horticultural crop in northwestern Spain

Nabicol (B. napus L. var. pabularia) is a traditional crop in the Northwest of Iberian Peninsula (South of Galicia and North of Portugal) where it is grown during the winter season on small farms and gardens using traditional varieties. A collection of 36 populations of nabicol from Galicia (northwestern Spain) was evaluated during 2002 and 2003 in two locations and two growing seasons (spring/summer and autumn/spring) for 28 agronomic and morphological traits. The objectives of this study were to: (i) evaluate a collection of nabicol landraces from northwestern Spain, (ii) determine the suitability of this germplasm as a summer crop and (iii) study the genetic diversity among local populations. Significant differences were observed among populations for most traits. Genotype × environment interaction was significant for most of them. Spring/summer growing season could be recommended for growing nabicol but resistance to Lepidoptera pests attacking Brassica crops should be improved. Most populations had an agronomic value similar to the commercial variety. The most promising variety for horticultural use was MBG-BRS0063, which showed the highest yield. Morphological and agronomic data were subjected to cluster analysis and four groups were defined with a group clustering most populations. The low genetic diversity could be explained because populations were collected in close geographical areas and the selection made by farmers was always for a horticultural use. These results give information about the diversity and breeding value of the nabicol Spanish germplasm, which could be useful in breeding programs.

Inheritance of Resistance to Ear Damage Caused by Sesamia nonagrioides (Lepidoptera: Noctuidae) in Maize

Abstract Sesamia nonagrioides Lefebvre is a major insect pest of maize (Zea mays L.) in northwestern Spain. The inheritance of ear resistance in field corn to this pest has not been studied. This work aims to determine the importance of genetic (additive, dominance, and epistatic effects) and environmental effects in the inheritance of ear resistance to S. nonagrioides. Three field corn inbreds (CM109, EP31, and EP42) were used as parents and two crosses (CM109 × EP31 and CM109 × EP42) were made. These inbreds show different ear resistance levels to S. nonagrioides, with CM109 more resistant than EP31 and EP42. For each cross, parents (P1, P2), F1, F2, and backcrosses to each parent (BC1 and BC2) were evaluated. Correlations among ear damage traits showed that general appearance of the ear should be useful indicator of ear resistance. Ear resistance was dominant to susceptibility and was transmitted from inbreds to their hybrids. The additive-dominance model fit the generation mean analysis for both crosses and the degree of genetic control varied depending on the cross and trait. For both crosses, additive and dominance effects were significant for most ear damage traits. Epistatic gene effects were significant for husk and shank damage, and gene effects for number and length of tunnels were not significant. Because ear resistance involved additive and dominance effects for this set of inbreds, breeding procedures based on both types of gene action should be effective.

Identification of genes related to germination in aged maize seed by screening natural variability

Ageing reduces vigour and viability in maize inbred lines due to non-heritable degenerative changes. Besides non-heritable genetic changes due to chromosome aberrations and damage in the DNA sequence, heritable changes during maize conservation have been reported. Genetic variability among aged seeds of inbred lines could be used for association studies with seed germination. The objective of this study was to identify genes related to germination in aged seeds. The sweet corn inbred line P39 and the field corn inbred line EP44 were used as plant material. Bulks of living and dead seeds after 20 and 22 years of storage were compared by using simple sequence repeats (SSRs) and, when the bulks differed for a marker, the individual grains were genotyped. Differences between dead and living seeds could be explained by residual variability, spontaneous mutation, or ageing. Variability was larger for chromosome 7 than for other chromosomes, and for distal than for proximal markers, suggesting some relationships between position in the genome and viability in aged seed. Polymorphic SSRs between living and dead seeds were found in six known genes, including pathogenesis-related protein 2, superoxide dismutase 4, catalase 3, opaque endosperm 2, and metallothionein1 that were related to germination, along with golden plant 2. In addition, five novel candidate genes have been identified; three of them could be involved in resistance to diseases, one in detoxification of electrophillic compounds, and another in transcription regulation. Therefore, genetic variability among aged seeds of inbreds was useful for preliminary association analysis to identify candidate genes.

Molecular evaluation of two methods for developing maize synthetic varieties

A generalized way to obtain a maize (Zea mays L.) synthetic variety is to randomly mate all possible crosses among inbred lines, but, when the number of lines is large, it would save time and effort to use other mating methods. This work is aimed to determine the utility of two alternative methods, assuming that an equal contribution of each inbred line to the synthetic is the goal (; 1993). Eight Reid inbred lines originated from the U.S. Corn Belt population ‘Reid’, and eight non-Reid unrelated inbreds were the base meterial for synthetic verieties EPS20 and EPS21, respectively . Each variety was built using both alternative methods: i) controlling the balanced contribution of each parental inbred (convergent cross method), and ii) randomly mating a seed mixture from the eight inbreds (random method). In the convergent cross method, single crosses between inbreds, and double crosses were performed in 1995, and 1996, respectively, as the first step to create EPS20c and EPS21c. Finally, in 1997, about 40 plants from each double-cross hybrid were mated only once (as male or female) in plant-to-plant crosses between double cross-hybrids, to generate about 20 ears that provided the base material for synthetics EPS20c and EPS21c. In the random method, a total of 304 seeds from the eight inbred lines, 38 seeds from each one, were bulked and sown in ten rows of 15 two-kernel hills per row in 1998 to form EPS20r and EPS21r. After thinning, 150 plants were left, and random plant-to plant crosses were made (where each plant was used only once as male or female), that resulted in 38 and 39 ears, respectively. The two crossing schemes were followed by two generations of recombination. A sample of 40 individuals from each synthetic variety was genotyped with 17 SSR (simple sequence repeat) markers loci. Primer sequences and chromosomal locations are available at the MaizeDB (www.agron.missouri.edu/ssr.html). Genetic drift due to the relatively small samples used to constitute balanced synthetic varieties, and/or natural selection could modify the original frequencies, but did not cause allele or heterozygosity losses. Therefore, the convergent cross method appeared to be appropriate for developing synthetic varieties either from related or non related inbreds. The random method should be used with caution, especially when inbred parents are genetically different, since relative adaptive advantages of some inbred lines could cause loss of genetic variability.

Quantitative Trait Loci for Cold Tolerance in the Maize IBM Population

B73 and Mo17 represent the main families of elite maize (Zea mays L.) inbred lines. B73 and Mo17 significantly differed in their proportion of germination under low‐temperature conditions, and the IBM population derived from the cross \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape