Genetic variation in Bactericera cockerelli from Mexico

Bactericera cockerelli (Sulc) has been considered the primary pest in Mexico and the United States, in Solanaceae crops, since 1970. However, subsequently since 2001 significant outbreaks of outstanding importance were observed in areas where infestations of this insect were historically rare. Molecular studies revealed that this was the due to the development of a new biotype of B. cockerelli that had become adapted to these areas, 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 whether the populations of B. cockerelli from different geographic regions of Mexico are different biotypes, mitochondrial genes cytochrome oxidase I (COI), cytochrome B (cytB), as well as inter simple sequence repeat (ISSR) markers were used in this study to molecularly characterize the different populations of this insect. According to COI comparisons we found 0.8% variation in the 501 bp-long COI fragments. While 1.2% of variation was found in the 1028 bp- long CytB fragments. However, such results were not sufficient to infer the genetic relationships among the study populations with these markers.Based on ISSR markers, the populations of B. cockerelli in central and northeastern Mexico (Guanajuato, Morelos Edo. of Mexico and Texas) show greater genetic similarity, while B. cockerelli found in the northwest, southwest and southeast of the country (Sinaloa, Michoacan and Oaxaca) are genetically distinct from each other and from the rest of the populations included in the study. The ISSR data, therefore, indicate the development of new psyllid biotypes of B. cockerelli, other than those already reported in Mexico.