Conceptos basicos para el mejoramiento del frijol por hibridacion

The basic concepts of the genetic improvement of beans through hybridization are described. In general, the breeding process involves the following phases: (1) development of exptl. lines, (2) evaluation of exptl. lines and identification of new cv., and (3) commercialization of new cv. The main aspects that should be considered in the development of exptl. lines as well as the most common breeding methods used in beans (modified pedigree, mass- pedigree, and backcrossing) are described. The evaluation of exptl. lines and the identification of new cv. are carried out in 3 or more steps: adaptation nurseries, preliminary yield trials, and regional yield trials. For the commercialization of new cv. the newly identified materials are registered, multiplied, and distributed. (CIAT)Se describen los conceptos basicos de mejoramiento genetico del frijol por hibridacion. En general, el proceso de mejoramiento involucra las siguientes fases: 1) el desarrollo de lineas exptl., 2) la evaluacion de las lineas exptl. y la identificacion de los nuevos cv. y 3) la comercializacion de nuevos cv. Se describen los aspectos importantes que deben considerarse en el desarrollo de las lineas exptl. y los metodos de mejoramiento mas comunes utilizados en el frijol (pedigri modificado, masal-pedigri y retrocruzamiento). La evaluacion de las lineas exptl. y la identificacion de nuevos cv. se realizan en 3 o mas etapas: viveros de adaptacion, ensayos preliminares de rendimiento y pruebas regionales de rendimiento. Para la comercializacion de nuevos cv., los materiales recien identificados se registran, se multiplican y se distribuyen. (CIAT

Comparison of mass, F\u3csub\u3e2\u3c/sub\u3e-derived family, and single-seed-descent selection methods in an interracial population of common bean

Knowledge of comparative effectiveness of different selection method is necessary for identification of superior genotypes, efficient management of populations, and use of available resources. Mass, F2-derived-family, and single-seed-descent (SSD) selection methods were compared in an interracial population (ICA pijao x Pinto UI 114) of common bean (Phaseolus vulgaris L.). The F2-derived-family -method involved elimination of low-yielding F2-derived families in replicated yield trials in F4, F5 and F6. Thirty-two random lines derived from each method and the two parents were evaluated in a replicates-in-set design in two contrasting environments in Colombia in 1992. Mean seed yield of lines derived from the SSD method was significantly lower than yields obtained from the other two methods. Mean yield of lines derived from the pedigree method was the highest, indicating that even a low intensity of selection for yield among F2-derived families was effective. The F2-derived-family method also retained a comparatively higher proportion of lines with lighter-colored medium-sized seeds and indeterminate prostrate type III growth habit. Lines with darker and smaller seeds predominated in the mass and SSD methods. These two groups also had more erect type II lines than did the F2-derived family method. On average, the SSD gave early maturing and the mass method late maturing lines. No line from any method outyielded ICA Pijao, the high-yielding parent. Two lines from the F2-derived-family method, four Iines from the mass method, and no lines from the SSD method significantly outyielded Pinto UI 114

Uso de marcadores y selección de gametos para el mejoramiento simultáneo de caracteres múltiples de frijol (Phaseolus vulgaris L.) para Mesoamérica y el Caribe.

El objetivo fue describir requerimientos básicos y métodos alternativos de selección para el mejoramiento simultáneo en frijol común, en el tiempo más corto posible y considerando el máximo número de caracteres agronómicos. Esta estrategia incluye: (1) obtener claridad sobre la importancia y problemática del cultivo de frijol para la zona, (2) fijar objetivos y prioridades del mejoramiento genético, (3) identificar y usar únicamente padres que con absoluta confianza pueden considerarse donantes de genes necesarios, (4) utilizar cruzamientos múltiples con un número adecuado de polinizaciones para producir suficiente semilla de cada cruza, (5) realizar evaluación y selección para marcadores actualmente disponibles (e.g., para gorgojo, mosaico común, mosaico dorado, antracnosis, picudo, bacteriosis común y roya, entre otros) desde la etapa de hibridación, (6) métodos alternativos de selección; como selección de gametos y descendiente de semilla única (SG-DSU), selección de gametos y pedigrí usando marcadores (SG-PUM), selección de gametos y evaluación y selección agronómica de familias en generaciones tempranas (SG-EAF), o una combinación e integración de los métodos SG-PUM y SG-EAF; y (7) conseguir una estrecha y genuina colaboración e integración de actividades de mejoramiento entre diferentes investigadores a nivel de instituciones, países y la región entera, en localidades claves, para efectuar evaluaciones confiables de viveros de frijol a efectos de realizar selección simultánea para el máximo número de caracteres agronómicos

A single dominant gene controlling resistance to soil zinc deficiency in common bean

Cultivated soils often are either deficient or possess toxic concentrations of one or more mineral elements that adversely affect emergence, growth, maturity, production potential, and/or nutritional quality of common bean (Phaseolus vulgaris L.). Our objective was to study the inheritance of resistance to soil Zn deficiency. The resistant `Matterhorn' was crossed with the susceptible 'T-39'. The F1 was backcrossed to Matterhorn (BC1) and T-39 (BC2), and advanced to the F2. The two parents, F1, F2, BC1 , and BC2 were evaluated in a Zn deficient field trial at Kimberly, Idaho in 2001. Plants were classified as tall-healthy or stunted with chlorotic leaves. Leaves were sampled from the two types of plants at flowering and analyzed for Zn concentration. The tall plants had an average leaf Zn concentration of 22.5 mg kg- 1 . In contrast, stunted plants had a Zn concentration of 15.0 mg kg- 1. All F1 plants were tall resembling Matterhorn, except that unlike Matterhorn (white flowers and seeds) they had purple flowers and black shiny seeds. Thus, the resistance to Zn deficiency was dominant. A segregation of 45 resistant (R) to 20 susceptible (S) plants was observed in the F2, giving a good fit to 3 R:1 S (x2 = 1.1538, P = 0.28). All plants in BC1 were resistant. In BC2, 142 It and 139 S plants were observed, giving a ratio of 1 R to 1 S (x2 = 0.032, P = 0.86). This supports a single dominant gene controlling soil Zn deficiency resistance. The symbol Znd is proposed for the dominant allele controlling resistance to soil Zn deficiency, and znd for its susceptible counterpart

Performance of small-seeded common bean from the second selection cycle and multiple-cross intra- and interracial populations

Twenty experimental lines of small-seeded common^bean (Phaseolus vulgaris L.) of Middle American origin from the second cycle of selection (SCS) in multiple cross intra- and interracial populations were evaluated with two control cultivars from the first cycle of selection (FCS) derived from single-cross intraracial populations and three standard controls at three locations for 3 yr (1988-1990) in Colombia. A 5 x 5 lattice design with four replications was used. Each plot consisted of four rows, 5 m long in the first year and 7 m long in the next 2 years. To develop experimental lines in both selection cycles, visual mass selection for seed yield and/or resistance tb diseases in individual plants and plant-to-progeny rows was practiced in early generations. The F2 and F3 were managed by the single-pod bulk method followed by the single plant harvests (F4 or F5), progeny tests (F5 or F6), and seed increases (F6 or F7). The F4- or F5-derived lines were tested for seed yield in F7 or F8. Thirteen lines from the SCS outyielded both control cultivars from the FCS and one standard control. However, only two lines, A 785 and A774, from the SCS outyielded the best standard control, cultivar Carioca, by an average of 7.77o. Both lines were derived from interracial populations involving high-yielding parents possessing positive general combining ability for seed yield. Most improved lines from the SCS possessed higher yield per day and higher disease resistance. No apparent changes were recorded in days to maturity and 100-seed weight for high-yielding lines. Late-maturing lines usually had lower yield and yield per day

SELECTION FOR YIELD AT TWO FERTILIZER LEVELS IN SMALL-SEEDED COMMON BEAN

Selection for seed yield (visual in the F2, visual and pl:t yield from the F3 to F5, and yield tests in F6) was carried out in two crosses of common bean (Phaseolus vulgaris L.) in high and low soil fertility environments at ClAT-Quilichao, Colombia. Parents were small-seeded and tolerant to low soil phosphorus, possessed indeterminate bush growth habit, and belonged to lowland tropical gene pools of Middle America. The mean yield of selected lines from low (LFS) and high (HFS) soil fertility environments was significantly higher than the mean of the parents in both crosses when tested in high fertility (HF) but not in low fertility (LF). The highest yielding LFS and HFS lines from A 286 x (G 5059 x A 80) and the LFS line from A 286 x ICA Pijao outyielded the best check cultivar, Carioca, in HF. No line yielded significantly more than A 286, the best parent used in both crosses. The mean effect of fertilizer levels on selection for seed yield was nonsignificant. Lines selected under two environments showed similar but average response and high stability of performance under variable environments. Low soil fertility accelerated maturity and reduced 100-seed weight and seed yield\u2

SELECTION FOR YIELD AT TWO FERTILIZER LEVELS IN SMALL-SEEDED COMMON BEAN

Selection for seed yield (visual in the F2, visual and pl:t yield from the F3 to F5, and yield tests in F6) was carried out in two crosses of common bean (Phaseolus vulgaris L.) in high and low soil fertility environments at ClAT-Quilichao, Colombia. Parents were small-seeded and tolerant to low soil phosphorus, possessed indeterminate bush growth habit, and belonged to lowland tropical gene pools of Middle America. The mean yield of selected lines from low (LFS) and high (HFS) soil fertility environments was significantly higher than the mean of the parents in both crosses when tested in high fertility (HF) but not in low fertility (LF). The highest yielding LFS and HFS lines from A 286 x (G 5059 x A 80) and the LFS line from A 286 x ICA Pijao outyielded the best check cultivar, Carioca, in HF. No line yielded significantly more than A 286, the best parent used in both crosses. The mean effect of fertilizer levels on selection for seed yield was nonsignificant. Lines selected under two environments showed similar but average response and high stability of performance under variable environments. Low soil fertility accelerated maturity and reduced 100-seed weight and seed yield\u2

Use of interracial hybridization in breeding the race Durango common bean

Recently, interracial hybridization was used successfully in breeding common bean (Phaseolus vulgaris L.), but its use has not been adequately documented. Approximately 125 lines with medium-sized seed were selected in the first cycle, mostly from race Durango x race Mesoamerica (both from the Middle American domestication center) single- and multiple-cross populations, for disease resistance and race Durango characteristics. Fifteen of these improved lines, three race Durango control cultivars, and one control cultivar each from races Jalisco and Mesoamerica were evaluated for 3 yr (1989-1991) at three locations in Colombia. A randomized complete block design with three replications was used. Lines were developed using visual mass selection for seed yield and/or resistance to diseases in F2 and F3, followed by single plant harvests in F4 or F5 and seed increases in F6 or F7. Lines resistant to bean common mosaic virus and possessing other desirable traits were yield-tested in F7 or F8. All but two lines outyielded Alteho and Flor de Mayo, the highest yielding control cultivars from races Durango and Jalisco, respectively. Two lines also outyielded Carioca, the race Mesoamerica control cultivar. Improved lines tended to possess higher yield per day. All lines were resistant to bean common mosaic virus and most lines also carried a high level of resistance to anthracnose. Plant, seed, and maturity characteristics of most improved lines were similar to those of race Durango control cultivars. These results support the use of interracial hybridization in improving race Durango common bean

SELECTION FOR YIELD AT TWO FERTILIZER LEVELS IN SMALL-SEEDED COMMON BEAN

Selection for seed yield (visual in the F2, visual and pl:t yield from the F3 to F5, and yield tests in F6) was carried out in two crosses of common bean (Phaseolus vulgaris L.) in high and low soil fertility environments at ClAT-Quilichao, Colombia. Parents were small-seeded and tolerant to low soil phosphorus, possessed indeterminate bush growth habit, and belonged to lowland tropical gene pools of Middle America. The mean yield of selected lines from low (LFS) and high (HFS) soil fertility environments was significantly higher than the mean of the parents in both crosses when tested in high fertility (HF) but not in low fertility (LF). The highest yielding LFS and HFS lines from A 286 x (G 5059 x A 80) and the LFS line from A 286 x ICA Pijao outyielded the best check cultivar, Carioca, in HF. No line yielded significantly more than A 286, the best parent used in both crosses. The mean effect of fertilizer levels on selection for seed yield was nonsignificant. Lines selected under two environments showed similar but average response and high stability of performance under variable environments. Low soil fertility accelerated maturity and reduced 100-seed weight and seed yield\u2