where to find info on PI numbers??

[patty_b]

Attended the Toledo Botanical Seed Swap yesterday. Wasn't at all what i was expecting but certainly was not disappointed. Many seeds supplied by Bakers Creek, Marianna, SSE, Olds, and even some from Amishland slightly outdated but great to have the chance to try some really outstanding varieties.

All the tomatoes from Marianna was easy to find the information but this one has me stumped.

Taxon: Lycopersicon esculentum
Accession Lot: PI 131879 70AI
ID: Palo Blanco
Origin: Argentina
USDA, ARS Plant Genetic Resources Unit Cornell University,

I have the 1994 SSE yearbook and found some PI numbers but nothing to match this one. What does the PI stand for?
I am assuming the name for the tomato is Palo Blanco??

Thanks, Patty