Construction, characteristics and high throughput molecular screening methodologies in some special breeding populations: a horticultural perspective

Advanced marker technologies are widely used for evaluation of genetic diversity in cultivated crops, wild ancestors, landraces or any special plant genotypes. Developing agricultural cultivars requires the following steps: (i) determining desired characteristics to be improved, (ii) screening genetic resources to help find a superior cultivar, (iii) intercrossing selected individuals, (iv) generating genetically hybrid populations and screening them for agro-morphological or molecular traits, (v) evaluating the superior cultivar candidates, (vi) testing field performance at different locations, and (vii) certifying. In the cultivar development process valuable genes can be identified by creating special biparental or multiparental populations and analysing their association using suitable markers in given populations. These special populations and advanced marker technologies give us a deeper knowledge about the inherited agronomic characteristics. Unaffected by the changing environmental conditions, these provide a higher understanding of genome dynamics in plants. The last decade witnessed new applications for advanced molecular techniques in the area of breeding,with low costs per sample. These, especially, include next-generation sequencing technologies like reduced representation genome sequencing (genotyping by sequencing, restriction site-associated DNA). These enabled researchers to develop new markers, such as simple sequence repeat and single- nucleotide polymorphism, for expanding the qualitative and quantitative information onpopulation dynamics. Thus, the knowledge acquired from novel technologies is a valuable asset for the breeding process and to better understand the population dynamics, their properties, and analysis methods

Pyramiding of 3-resistant-gene to improve rice blast resistance of a restorer line, Fuhui 673 / 生物工程学报

To improve the blast resistance of elite rice restorer line Fuhui 673, 3 blast resistance genes Pi-1, Pi-9 and Pi-kh were introduced into Fuhui 673 from a good-quality restorer line Jinhui 1059 through 3 successive backcrosses followed by one selfing using the technique of marker-assisted selection. Ten near-isogenic lines (NILs) of Fuhui 673 carrying the 3 introduced resistance genes were created. Genotype analysis using 68 SSR markers evenly distributed in the genome indicated that 92.96%-98.59% of the NILs' genetic background had been recovered to Fuhui 673. Both indoor and field resistance tests indicated that the NILs and their hybrids with sterile line Yixiang A were all resistant to rice blast, with resistance levels significantly higher than those of controls Fuhui 673 and hybrid Yiyou 673 (Yixiang A  Fuhui 673). In addition, among the 10 hybrids between the NILs and Yixiang A, 2 showed significantly higher yield than and 4 displayed similar yield to that of control Yiyou 673, suggesting that most of the NILs retained the elite characteristics of Fuhui 673. Two new hybrid rice cultivars Liangyou 7283 and Jintaiyou 683 from NIL Line 9 showed high yield, good resistance to blast and moderate growth period in regional trial, suggesting that the NIL Line 9 has a good prospect for application.

Evaluación y selección de líneas de arveja con gen afila bajo dos densidades de población / Evaluation and selection of pea lines with afila gene in two planting densities

RESUMEN Nariño es el principal productor de arveja en Colombia, posición lograda por el uso de sistemas de tutorado y variedades mejoradas; sin embargo, estos genotipos presentan crecimiento agresivo y son de difícil manejo agronómico, lo cual, encarece los costos de producción. Como alternativa, el Grupo de Cultivos Andinos (GRINCAND), desarrolló un proceso de introducción del gen recesivo afila (af), en variedades comerciales (Andina, San Isidro y Sindamanoy), logrando reemplazar las hojas laterales por zarcillos, mejorando el agarre de las plantas. Las líneas de arveja afila resultantes fueron evaluadas en tres fases experimentales. En la primera fase, de 208 familias F3, se seleccionaron y generaron 105 líneas F4; luego, las 105 líneas se evaluaron agronómicamente y mediante la aplicación de un índice de selección, se escogieron por orden de mérito, basado en componentes de rendimiento y de reacción a enfermedades, 21 líneas promisorias. Estas líneas, se evaluaron bajo dos densidades de población (D1:83.333 y D2:166.666 plantas·ha-1), utilizando un diseño experimental de parcelas divididas. La parcela principal correspondió a las densidades de población y, la subparcela, los genotipos de arveja. En D2, la línea SXDRC118, tuvo mayor rendimiento que los testigos, con una ganancia entre 75 y 211%; además, esta línea superó al 66% de las líneas evaluadas. SX3568RC17 mostró un promedio mayor sobre San Isidro y Sindamanoy, en 86 y 188% y SX3575RC18, SX3575RC1X1 y SX3575RC19 sobre Sindamanoy, en 138 a 157%. Esto indica que la siembra de algunas líneas afila, a mayor densidad, pueden superar el rendimiento de las variedades comerciales.

ABSTRACT Nariño is the principal pea producer in Colombia, given its position in the use of improved varieties and trellis system. However, these genotypes have difficult agronomic managements, because their aggressive growth, which increases production costs. As alternative, the group of investigation Cultivos Andinos (Gricand), developed a process of introduction afila (af) gene in the pea varieties Andina, San Isidro and Sindamanoy, replacing lateral leaves by tendrils, to get a better grip of plants. The lines afila resulted were evaluation in three experimental phases. In the first phase, 208 family F3 were selection and generated 105 lines F4. In following cycle, the lines selected were evaluated for yield components and applying a selection index, 21 lines promising for merit order were selected. Subsequently, these lines were evaluated in two planting densities (D1: 83.333 and D2: 166,666 plantas·ha-1), used a splits plot design. The main plot with the densities and the subplot the pea genotypes. In the planting density D2, the line SXDRC118 had higher yield than the controls, with a gain between 75 and 211%; furthermore, it surpassed with 66% the other lines. SX3568RC17 showed a higher average yield than San Isidro and Sindamanoy, respectively, 86 and 188% and SX3575RC18, SX3575RC1X1 and SX3575RC19 regarding Sindamanoy with 138 to 157%. This indicates that some lines with af gene have potential for higher yield than commercial varieties with normal leaves when planted at higher density.

Marker-assisted backcrossing using microsatellites and validation of SCAR Phs marker for resistance to white mold in common bean

Molecular markers may accelerate selection through the identification of plants with higher proportion of recurrent parent genome, as well as identifying those plants bearing target alleles like quantitative traits loci (QTLs) for white mold resistance. The objectives of this work were: 1) to employ microsatellite markers (SSR) in order to accelerate the recovery of recurrent parent genome 2) to validate sequence characterized amplified region (SCAR) Phs associated with a QTL that confers resistance to white mold, as previously identified in bean populations. Lines G122 and M20 were crossed, which generated 267 F1 plants from backcross (BC) BC1 and 113 plants from backcross BC2.SSR polymorphic markers were adopted. The relationship between BC plants and the recurrent parent was estimated based on the recurrent genome proportion (PR) in each BC plant, and the Sorensen-Dice genetic similarity (sg ir). To determine how much the phenotypic variation is explained by SCAR Phs, 56 F1:2BC1 progenies were evaluated on the field following a random block design with two replications through the straw test method. SSR markers are efficient in identifying individuals with a greater proportion of the recurrent genome. SCAR Phs was not efficient for the indirect selection of common beans for white mold resistance.

Allele frequency and selection efficiency in cross populations of Andean x Mesoamerican common beans (Phaseolus vulgaris L. Fabales, Fabaceae)

Strategies were investigated for improving efficiency in the use of segregating common bean (Phaseolus vulgaris) populations using crosses between the Andean cultivar BRS-Radiante and the Mesoamerican parent cultivar Carioca-MG by developing populations with 12.5%, 25%, 50%, 75% and 87.5% of the allele frequency of one of the parents. For each of the five populations we evaluated for two traits, the number of days to the beginning of flowering and grain yield (g plot-1), in the F2:3 (sown in February 2006) and F2:4 (sown in July 2006) generation progenies using 15 x 15 lattice design experiments, with 44 progenies (n = 220 plants) plus the two parents and three controls being evaluated for each generation. In terms of variability release, the populations with different parental allele frequencies presented no consistent tendency of alteration. In general, genetic variance was stated among progenies in all populations, indicating success with selection. For grain yield, the lowest mean was observed in the populations with 50% of the alleles of both parents. If, for instance, the objective is to develop earlier flowering lines, the best strategy is to perform two, or at least one, backcross with the earliest parent. The most suitable allele frequency is to be determined according to the desired grain type.

Molecular Marker Related to Fruitbody Color of Flammulina velutipes

White and brown strains of Flammulina velutipes were inter-crossed. All F1 showed light-brown fruitbody, suggesting that a gene for the brown fruitbody was incompletely dominant against the white one. And backcross experiment showed that more than two genes were involved in color determination. To isolate a molecular marker linked to fruitbody color, a set of primers was designed from a sequence of clones derived by a bulked segregant analysis. These markers showed a specific band which co-segregated with brown fruitbody forming strains.

Breeding of Flammulina velutipes Strains Adaptable to Elevated-temperature

Winter mushroom, Flammulina velutipes, needs low temperature during its cultivation. To save on farm costs, especially during summer, a strain adaptable to a higher or elevated-temperature must be developed. At the start of breeding program, parental strains which could endure high temperature were obtained. Seuenty four dikaryotic strains were collected and divided into four groups according to the nature of temperature. They also had different fruiting temperature. Finally we selected three brown strains ASI 4048, 4057 and 4072, and collected their spores. These selected strains can germinate even at a high temperature of 32degrees C, which were dramatically higher than the other strains. Based on these results, the new white strain adapted to mid-temperature by backcross mating was developed. Molecular markers were applied to select white fruit-body producing strains without cultivation. They showed a specific band which co-segregated with brown fruitbody forming strains in BC1F1 progenies. Selected white strains were tested under several elevated temperature conditions.