China spans a wide range of geographic locations from latitude
3510 N to 53330 N and from longitude 73330 E to 135050 E. From
north to south, it covers temperate and subtropical zones. A total of
2494 peanut samples were collected from farmers' fields in four
provinces, which are four main peanut producing areas under
different agro-environmental conditions. The samples included
408 peanut samples from Liaoning Province in the northeast under
a temperate monsoon climate, 1190 peanut samples from Henan
Province in the north under a transitional monsoon climate, 455
peanut samples from Sichuan Province in the Yangzi River Basin
under a subtropical temperate monsoon climate, and 441 peanut
samples from Guangdong Province in the south under a
subtropical-tropical monsoon climate (Fig. 1). The sowing areas in
these four provinces were the largest for each main producing area
and were among the top 8 sowing areas of China in 2010e2013. The
samples of at least 3.0 kg were collected yearly from 9 counties of 5
cities in Liaoning, 26 counties of 16 cities in Henan, 33 counties of
13 cities in Sichuan, and 29 counties of 15 cities in Guangdong. In
each county, each of 10e20 samples was independently harvested
from different villages. All samples were delivered to the laboratory
in sealed bags and stored under ventilated and dry conditions.
Then, impurities and dusts of each sample were removed, the
remaining was unshelled, and the seeds were cut into 0.5 cm thick
slices, ground, and thoroughly mixed in a sample grinder until they
could pass through a 0.9 mm sieve. The ground samples were put in
glass containers and stored at 4 C, and then analyzed by HPLC. All
of this work was completed within 4 weeks.