Amalio Santacruz-Varela

A Restricted Selection Index Method Based on Eigenanalysis

Selection indices, used in animal and plant breeding to select the best individuals for the next breeding cycle, are based on phenotypic observations of traits recorded in candidate individuals. The restrictive selection index (RSI) facilitates maximizing the genetic progress of some characters, while leaving others unchanged. Recently a selection index (SI) was proposed based on the eigen analysis method (ESIM), in which the first eigenvector (from the largest eigenvalue) is used as the SI criterion, and its elements determine the proportion of the trait that contributes to the SI. However, the current ESIM, which has two main limitations, is based on the assumption that the vector of coefficients of the index is equal to the genotypic variance-covariance matrix among the traits multiplied by the vector of economic weights, and does not allow one to restrict the number of traits. In this study, we develop a more general ESIM that has two main features, namely, it makes no assumption concerning the coefficients of the index and it can be generalized to a restrictive ESIM (RESIM). We use two datasets to illustrate the theoretical results and practical use of ESIM and RESIM, and to compare them with standard unrestrictive and restrictive selection indices. The main advantages of RESIM over traditional unrestrictive and restrictive SIs are that its statistical sampling properties are known; its selection responses are equal to or greater than those estimated from the traditional restrictive SI; and it does not require economic weights and thus can be used in practical applications when all or some of the traits need to be improved simultaneously (traditional SIs cannot improve several traits simultaneously if economic weights are not available). Finally, we prove that the coefficients of the traditional RSI belong to the space generated by the eigenvectors of RESIM.

A Molecular Selection Index Method Based on Eigenanalysis

The traditional molecular selection index (MSI) employed in marker-assisted selection maximizes the selection response by combining information on molecular markers linked to quantitative trait loci (QTL) and phenotypic values of the traits of the individuals of interest. This study proposes an MSI based on an eigenanalysis method (molecular eigen selection index method, MESIM), where the first eigenvector is used as a selection index criterion, and its elements determine the proportion of the traits contribution to the selection index. This article develops the theoretical framework of MESIM. Simulation results show that the genotypic means and the expected selection response from MESIM for each trait are equal to or greater than those from the traditional MSI. When several traits are simultaneously selected, MESIM performs well for traits with relatively low heritability. The main advantages of MESIM over the traditional molecular selection index are that its statistical sampling properties are known and that it does not require economic weights and thus can be used in practical applications when all or some of the traits need to be improved simultaneously.

Evaluación de poblaciones nativas de maíz en ambientes con heladas en Valles Altos de Puebla

RESUMEN En Mexico la superficie sembrada con maiz es de ocho millones de hectareas, de las cuales 1.2% es siniestrada por heladas. En el estado de Puebla este porcentaje es 0.8% y en Valles Altos 1.7%. El objetivo de este estudio, fue evaluar el efecto de las heladas en rendimiento de grano y seleccionar poblaciones nativas con mayor rendimiento en ambientes con presencia de heladas. Para ello se evaluaron 61 poblaciones nativas y tres variedades mejoradas, mediante un diseno experimental latice simple 8∗8 con dos repeticiones. Los experimentos se establecieron en tres localidades del estado de Puebla. Las fechas de siembra fueron el 30 de marzo en Emiliano Zapata, Cuyoaco, el 7 de abril en Santa Ines Borbolla, Chalchicomula de Sesma y el 4 de mayo en Santa Cruz Coyotepec, San Juan Atenco; estas localidades se caracterizan por ser de temporal y con presencia de heladas en 2007. El analisis de varianza combinado indico que las heladas afectaron el rendimiento de grano de las poblaciones nativas y mejoradas; pero hubo variedades como la CPue-131, CPue-448 y CPue-134 que mostraron mayor rendimiento promedio y mayor estabilidad ambiental que las mejoradas. La prueba de medias para localidades en el analisis combinado, indico que Emiliano Zapata fue el ambiente menos afectado por heladas con 3 510 kg ha

Vegetative, reproductive and fruit yield characteristics of "poblano" pepper landraces.

Besides its cultural importance, poblano pepper is a source of income and food for rural families of the region of Sierra Nevada in Puebla, Mexico. However, poblano pepper yield and cultivated land have decreased in the last year, due to factors as: landraces, frosts, pests and diseases, among other issues, which could lead to loss of genetic diversity. Nonetheless, little research has been done to solve its current problematic. Thus, the aim of this study was to evaluate the vegetative, reproductive and fruit yield characteristics of the native variety of poblano pepper from the region of Sierra Nevada in the state of Puebla, and to choose local cultivars for further breeding. A group of 49 landraces were evaluated using a triple 7x7 lattice design in two localities. According with the combined analysis, the traits that had significant differences among varieties were days to flowering /70 to 96), days to fructification (78 to 109), plant height (37.9 to 56.8 cm), plant width (24.1 to 44.3 cm), branching density (5.7 to 6.8), fruit weight (4.7 to 24.8 g) and fruit number (2.2 to 7.2). The 20 % outstanding varieties had fresh fruit yield that ranged between 7.4 and 9.6 t·ha-1. The existence of morphological diversity in local poblano pepper landraces, expressed through the tested characteristics, could be integrated into plant diversity preservation and breeding programs. ADDITIONAL