Rahim Foroughbakhch

Leaf biomass determination on woody shrub species in semiarid zones

Leaf biomass over 20 native species from thornscrub canopies was evaluated by five non-destructive allometric methods and compared in order to determine the most accurate estimating procedure. Indirect relationships between leaf biomass and some ecological characteristics of the plants may be found by using regression models. Ecological and morphological characteristics of these species were determined using a structural analysis. No single standard method estimated leaf biomass for all species on site due to the diversity of geometric shapes in these species. However, Adelaide, double sampling and the dimensional methods were the most precise, practical and simplest methods for measuring the forage leaf biomass of many shrub species. The linear models gave a better estimate of tree biomass than the logarithmic functions. The regression equations showed a close relationship between foliar biomass and growth parameters.

Genetic Variation in Bactericera cockerelli (Hemiptera: Triozidae) From Mexico

ABSTRACT Bactericera cockerelli (Sulc) is a significant pest of several solanacious crops in Mexico and the United States since 1970. In 2001 significant outbreaks of outstanding importance were observed for the first time in areas where infestations of this insect were historically rare. Molecular studies revealed that this was because of the development of a new biotype of B. cockerelli that had become adapted to south-western United States, further demonstrating that this genetic differentiation was reflected in the survival, development cycle, fertility, and growth rate of both the native biotype as well as the one recently reported. To determine genetic variation in populations of B. cockerelli from Mexico, inter simple sequence repeat were used. Results showed that populations of B. cockerelli from central and northeastern Mexico (Guanajuato, Morelos, Estado de Mexico, and Nuevo Leon states) are genetically similar, meanwhile B. cockerelli from northwest, southwest, and southeast of the country (Sinaloa, Michoacan, and Oaxaca states) are genetically distinct from each other and from the rest of the populations included in the study.