Ricardo Riegel

Expansins expression is associated with grain size dynamics in wheat (Triticum aestivum L.)

Grain weight is one of the most important components of cereal yield and quality. A clearer understanding of the physiological and molecular determinants of this complex trait would provide an insight into the potential benefits for plant breeding. In the present study, the dynamics of dry matter accumulation, water uptake, and grain size in parallel with the expression of expansins during grain growth in wheat were analysed. The stabilized water content of grains showed a strong association with final grain weight (r2=0.88, P <0.01). Grain length was found to be the trait that best correlated with final grain weight (r2=0.98, P <0.01) and volume (r2=0.94, P <0.01). The main events that defined final grain weight occurred during the first third of grain-filling when maternal tissues (the pericarp of grains) undergo considerable expansion. Eight expansin coding sequences were isolated from pericarp RNA and the temporal profiles of accumulation of these transcripts were monitored. Sequences showing high homology with TaExpA6 were notably abundant during early grain expansion and declined as maturity was reached. RNA in situ hybridization studies revealed that the transcript for TaExpA6 was principally found in the pericarp during early growth in grain development and, subsequently, in both the endosperm and pericarp. The signal in these images is likely to be the sum of the transcript levels of all three sequences with high similarity to the TaExpA6 gene. The early part of the expression profile of this putative expansin gene correlates well with the critical periods of early grain expansion, suggesting it as a possible factor in the final determination of grain size.

Relaciones filogenéticas de Rhodolirium montanum Phil. y especies afines, basadas en secuencias nucleotídicas de la región ITS y análisis cariotípico

La taxonomia de los generos chilenos de Amaryllidaceae es confusa, persistiendo problemas taxonomicos tanto a nivel de generos como de especies. Actualmente existe controversia acerca de la correcta clasificacion de especies hasta ahora asignadas a Rhodophiala C.Presl. A traves del estudio de aspectos morfologicos, recientemente se ha sugerido la rehabilitacion del genero Rhodolirium Phil., donde Rhodolirium montanum Phil. es considerada como especie tipo. Esta especie ha sido denominada Rhodophiala rhodolirion (Baker) Traub en las clasificaciones tradicionales. Dado que los datos morfologicos han provisto informacion limitada y ambigua en la clasificacion de las Amarilidaceas chilenas, este trabajo evalua la pertinencia de formalizar la rehabilitacion del genero Rhodolirium y en particular de la especie Rhodolirium montanum, a traves de un analisis de morfologia cromosomica y de secuencias nucleotidicas de la region ITS de seis especies nativas de Amaryllidaceae. Los datos moleculares indican que las especies Rhodophiala bagnoldii, R. montana, R. splendens, R. phycelloides y R. ananuca forman un grupo monofiletico mas emparentado con Hippeastrum Herb. que con Rhodolirium, genero que se presenta como grupo hermano de Phycella en el analisis filogenetico. La separacion de Rhodolirium con respecto de Rhodophiala esta respaldada por diferencias en numero y morfologia cromosomica, presentando el primero un numero cromosomico de 2n = 16 y un indice de asimetria intracromosomica (Isc) de 0,46; mientras que el segundo posee 2n = 18 e Isc de 0,59-0,62. De esta manera, los resultados de los estudios cromosomicos y moleculares, junto a diferencias en exomorfologia, tales como forma del estigma, perigonio y paraperigonio, apoyan la validez del genero Rhodolirium Phil. y por ende de la especie Rhodolirium montanum Phil.

De novo sequencing and development of EST-SSR for Gevuina avellana (Proteaceae), a nut tree from South America

UNLABELLED • PREMISE OF THE STUDY The aim of this study was to develop molecular tools to investigate the genetic structure and diversity of natural populations of Gevuina avellana (Molina, Proteaceae), the Chilean hazelnut. Simple sequence repeats (SSRs) derived from expressed sequence tags (EST-SSRs) were developed, optimized, and characterized. • METHODS AND RESULTS The microsatellite-containing sequences were selected from a cDNA library developed from the nut. The eight marker loci showed two to seven alleles in 60 unrelated trees, from two different natural populations. The observed heterozygosity (H(o)) was 0.44, ranging from 0.07 to 0.92 for different loci. When the multilocus genotype of the eight EST-SSRs was considered, all trees could be differentiated. • CONCLUSIONS The newly identified EST-SSRs in G. avellana and the multi-pooling strategy involving eight markers will facilitate future studies of clone identification, genetic structure, and diversity.

PECOSA-BAER: A NEW CULTIVAR OF WHITE LUPIN WITH DETERMINED BUSHY GROWTH HABIT, SWEET GRAIN AND HIGH PROTEIN CONTENT

The expansion of white lupin (Lupinus albus L.) cultivation in Chile is subject to the availability of cultivars presenting high yield potential, tolerance to the main fungal diseases and homogeneous ripening. In response to these requirements, a new cultivar has been developed and registered as ‘Liapec-1’, commercially registered as ‘Pecosa-Baer’. This new cultivar has determined bushy growth habit. Its flowering period is concentrated in approximately 40 days, less than the 77 days of cv. Rumbo-Baer. This trait allows it to reach harvest without heterogeneity problems. The seed is speckled, flat and medium-sized (370 g/1000 grains aprox.). The kernels are sweet and have a high protein content of around 41% (dry matter basis). In field assays, ‘Pecosa-Baer’ presents a good tolerance to diseases caused by Colletotrichum lupini and Pleiochaeta setosa. The new cultivar has outstanding stability and yield levels, even under low fertilization conditions. An average yield of 5.43 t ha -1 was obtained over four seasons in two locations. In order to maximize its yield, ‘Pecosa-Baer’ must be sown between April and June at a rate of 140-160 kg ha -1 . Given the high protein content and low alkaloid levels of the seeds, they can be included in the diet of all types of animals.

Identification of virus and nematode resistance genes in the Chilota Potato Genebank of the Universidad Austral de Chile

Potato Genebank of the Universidad Austral de Chile (UACh) is an important gene bank in Chile. The accessions collected all over the country possess high genetic diversity, present interesting agronomic and cooking traits, and show resistance to biotic and abiotic stress. A particularly interesting subgroup of the gene bank includes the accessions collected in the South of Chile, the Chilota Potato Genebank. The focus of this study is the identification of virus and nematode resistant genes in potatoes (Solatium tuberosum L.), using the RYSC3 and YES3-3B molecular markers. The Potato virus Y(PVY) resistance genes Ryadg and Rysto were identified. Furthermore, the CP60 marker was used to assess the Rx resistance gene that confers resistance to Potato virus X (PVX). In addition, the HC and GRO1-4 markers were utilized to identify the GpaVvrn_QTL and Gro1-4, resistance genes of Globodera pallida and Globodera rostochiensis, respectively. Both G. pallida and G. rostochiensis are Potato Cyst Nematodes (PCN). The plant material used in this study included leaves from 271 accessions of the gene bank. These samples were collected in the field where natural pathogen pressure of potential viruses and diseases exists. ELISA assays were run for field detection of PVY and PVX. However, there have been no previous reports of nematode presence in the plant material. The results herein presented indicate presence of virus and nematode resistance genes in accessions of the Chilota Potato Genebank. In terms of virus resistance, 99 accessions out of the 271 tested possess the Ryadg resistance gene and 17 accessions of these 271 tested have the Rysto resistance gene. Also, 10 accessions showed positive amplification of the Rxl resistant gene marker. As to nematode resistance, 99 accessions have possible resistance to G. pallida and 54 accessions show potential resistance to G. rostochiensis as detected using the available molecular markers.

Distribución geográfica y caracterización fenotípica y molecular de Neonectria fuckeliana, asociado a cancros fustales de Pinus radiata en Chile

Neonectria fuckeliana es un hongo saprofito o debilmente patogeno sobre coniferas nativas del hemisferio Norte. Sin embargo, en Chile y Nueva Zelanda se presenta como patogeno sobre plantaciones de Pinus radiata, causando cancros y malformaciones fustales. El objetivo de este estudio fue determinar la distribucion geografica de esta enfermedad en Chile y caracterizar fenotipica y molecularmente aislados de N. fuckeliana provenientes de cuatro localidades (Carahue, Tolten, Pucon y Paillaco). La distribucion se determino con prospecciones en terreno, atendiendo a sintomas y signos asociados a la presencia del patogeno. La caracterizacion fenotipica evaluo el color de las colonias, tasas de crecimiento y tamano de conidias. Molecularmente se amplifico y secuencio la region parcial del gen 18S rRNA y del espaciador interno transcrito ITS. Segun los resultados, este patogeno se encuentra distribuido a lo largo (> 450 km) de la zona costera de Chile, desde la region del Biobio (5860100N - 627358E 18H) hasta la de Los Lagos (5423863N - 636153E 18G). Fenotipicamente se identificaron tres colores de colonias: rojas, amarillas y amarillo palidas, siendo predominante el color rojo (> 70 %) en todas las localidades. Los aislados recuperados desde localidades de La Araucania presentaron mayores crecimientos y tamanos de conidias que las de Los Rios. La caracterizacion molecular corroboro la identificacion de N. fuckeliana, con un 99 % de identidad con secuencias de N.fuckeliana de Europa y Nueva Zelanda depositadas en Genbank (KJ022020 y HQ840404) y sin demostrar diferencias geneticas entre los aislados chilenos obtenidos en este estudio.

Mating system and gene flow of Nothofagus alpina (Poepp. & Endl.) Oerst. in a clonal seed orchard

BackgroundUnderstanding pathways of genetic information transfer from one generation to another is particularly important when open-pollinated seeds are collected for reforestation or for enrichment of native forests. Nothofagus alpina (Poepp. & Endl.) Oerst. is native to temperate forests of southern Chile and Argentina. However, lack of knowledge of its reproductive biology has hampered its management in forest plantations and conservation of natural populations. Therefore, a clonal seed orchard of N. alpina in southern Chile was used to analyse the mating system and to estimate the number of pollen donors in this species.MethodsThe mating system was investigated using manual pollination tests on six clones, open-pollinated seeds were collected from four other clones to study gene flow and paternity analysis was done on progenies using microsatellite genetic markers. Pollen donors were inferred for 194 offspring of four adult trees using five microsatellite loci and an exclusion process.ResultsThis species is exogamous and largely self-incompatible. The effective number of pollen donors found was 5, which was less than the 19 expected theoretically. Results indicated that pollen flow in the seed orchard is deficient. This could be a result of limitations in the wind-pollination system, coupled with phenological dissynchrony among clones present.ConclusionsN. alpina is an exogamous, highly self-incompatible species. It does not reproduce through agamospermy, since there was no seed formation in the absence of pollen. Only a few trees contributed to the paternity of the progeny evaluated. This finding indicates that there exists a limited gene flow within the orchard due to reproductive isolation among genotypes.