What does LASTI2 stand for?

Lathyrus stipulaceus (Pursh) Butters & H. St. John var. incanus (J. G. Sm. & Rydb.) Butters & H. St. John - Scientific name - Accepted name: Lathyrus polymorphus ssp. incanus - Family: Fabaceae - USDA National Plant Data Center symbol - Botany - Taxonomy (USDA)