No abstract

SummaryThe genetic diversity of 95 representative Chilean common bean (Phaseolus vulgaris L.) landraces was analyzed using phaseolin seed protein and eight isozyme systems as genetic markers. Four types of phaseolin were found, "C", "T", "S" and "H", in decreasing order of frequency. Each type had a different distribution between the Northern and Southern regions of the country. Nei's genetic distance based on isozyme diversity indicated that a high percentage of the total variation found in this sample occurred between tandraces and only a small percentage of the variation was detected within populations. Cluster analysis based on Nei's genetic distance and a principal component analysis of isozyme frequencies did not detect a clear association between the geographic distribution of the landraces and their isozyme constitution. However, Nei's genetic distance analysis clustered the bean landraces into two major groups which had a specific isozyme pattern, seed color, and seed size. The genetic analysis also detected a rare polymorphism for the Mdh-2 locus, a null allele at the Diap-2 locus, and polymorphism for the Aco-2 locus. The principal component analysis of isozyme frequencies showed that only 30% of the genotypes analyzed were similar to the Andean check and 5% of the samples were similar to Middle American check. This finding suggests a high frequency of hybridization between the Middle America and Andean gene pools in cultivated common bean from Chile.

Variation for segregation ratios and recombination rates was analyzed in crosses involving 13 common bean (Phaseolus vulgaris L.) genotypes from different gene pools and races. The segregation of RFLP, isozyme, and phaseolin markers belonging mostly to linkage groups D5 and D7 was analyzed in 11 F 2 populations derived from Middle American x Andean, and Andean x Andean crosses. An average level of 10.4% segregation distortion for RFLPs was observed compared with 19.2% for isozyme markers. Preferential transmission of Middle American alleles was detected in crosses between the two gene pools. Levels of recombination were highly variable among a subset of four of the 11 F 2 populations analyzed. These data, and comparisons with data published previously, suggest that recombination in common bean is under genetic control, although environmental factors may also affect it.

1 2 3 2 Oscar PAREDES , Manuel SOUDRE , Jaime CHAVEZ , Wilson GUERRA Se evaluó el prendimiento del injerto de bolaina blanca (Guazuma crinita Mart.) por influencia de la técnica de injertación, el sistema de protección y el nivel de sombreamiento al interior de la cámara injertadora del vivero del Instituto de Investigaciones de la Amazonía peruana (IIAP), en la región Ucayali. Se empleó el diseño de bloques completos al azar, con arreglo bifactorial (2a x 3b) y seis tratamientos que derivaron de la combinación de dos técnicas de injertación (púa central y empalme) y tres sistemas de protección del injerto (bolsa de polietileno, cinta parafilm y sin protección); los bloques implicaron exponer a las plantas injertadas a tres niveles de sombra (60, 80 y 95%). Al término de 100 días, se determinó que no hubo diferencias (p<0.05) significativas entre la técnica de injertación de púa central y empalme, es decir, ambas técnicas mostraron ser igual de exitosas, en combinación con los sistemas de protección (bolsa de polietileno y cinta parafilm) y con sombreamiento de hasta 80%, produciendo un porcentaje de prendimiento promedio de 78% en injertos de bolaina blanca; en contraste, la combinación de las mismas técnicas de injertación, sin ningún sistema de protección (testigo) no presentaron prendimiento alguno (0%). Se concluye que es posible injertar bolaina blanca empleando cualquiera de las dos técnicas de injerto (púa central o empalme), un sistema de protección (bolsa de polietileno o cinta parafilm) y 60% de sombreamiento durante 30 días. La presencia de segmentos vegetativos más jóvenes en la vareta y en el patrón también influye positivamente en el éxito del injerto. PALABRAS CLAVES:Guazuma crinita, técnica de injertación, sistema de protección, sombreamiento, Amazonía Peruana.The success of grafting of bolaina blanca (Guazuma crinita Mart.) as effected as the grafting techniques, protection system and the level of shading in the grafting chamber was evaluated in the nursery of the Peruvian Amazon Research Institute in the Ucayali Region. A complete randomized block design was used in a factorial 2X3 treatments arrangement as result of two grafting techniques (central stake and jointed) and three protection systems of the grafting (polystyrene bag, paraffin film ribbon, and no protection). Three shading (60, 80 and 90%) level were the blocking factor. After 100 days, no significant differences (p<0.05) were found for the grafting techniques, both techniques showed similar results in combination with the protection systems with 80% shading, resulting in 78% of successful grafting. The combination of the same techniques without protection system resulted in 0% grafting. These results showed that it is possible to successfully graft bolaina blanca by any of the two grafting techniques using a protection system at 60% shading during 30 days. The presence of young vegetative parts in the grafting material and the stump positively influence the success of grafting.