Molecular Characterization of Different Biotypes of the Southern Chinch Bug Affecting St. Augustinegrass.

The Southern Chinch Bug (SCB), Blissus insularis Barber, is the most destructive insect pest of St. Augustinegrass [Stenotaphrum secundatum Waltz (Kuntze)] throughout the southern region of USA.  Throughout this region, ‘Floratam’ St Augustinegrass has been widely planted because of its high level of resistance to SCB (80% to >90% mortality within a 7 day feeding period).  Due to the breakdown of the resistance in ‘Floratam’ in 1985, turfgrass breeders have been searching for a replacement cultivar with resistance to SCB. ‘FX-10’ and ‘Captiva were developed and released in Florida and are resistant to Florida chinch bugs (>90% mortality within 14 days).  Our preliminary studies show that Floratam, FX-10 and Captiva are susceptible to chinch bugs collected from south Texas (< 20% of chinch bugs killed by either cultivar within a 7-day feeding period in the laboratory). These SCB from Texas appear to be a new virulent biotype.  The objective of the present study is to investigate the genetic diversity between different biotypes of SCB using Amplified Fragment Length Polymorphism (AFLP).  SCB were collected from St. Augustinegrass growing in four geographically different locations in Texas as well as four locations in Florida. Twenty samples from each of these eight populations were screened with five primer pairs, making a total of 800 reactions.  The presence and absence of AFLP markers were detected using a computer program called Genographer 2.1.4, and then confirmed manually.  Analysis of Molecular Variance (AMOVA) will be used to statistically analyze genetic diversity within and between populations.  This study will be useful to grass breeders developing improved resistance to multiple biotypes of SCB.