Parents were selected on the basis of canopy architecture, i.e.,
upward
or downward
inclination and post-noon leaf temperature
of the leaves, from 34 inbred lines screened in a trial during the year
2009, under heat stress. Parental and tested germplasm belonging
to diverse origin and climatic conditions was introduced from
the USDA national plant germplasm system and ordered through
the online (http://www.ars-grin.gov/npgs/searchgrin.html)
germplasm resource information network free of charge. Crosses
were attempted among inbred lines during 2009 to develop F1
seeds. In
2010, the F1 plant population was grown and selfed
to obtain F2 seeds. F1 plants were randomly chosen and heads
(reproductive capitula) were bagged before anthesis in order to
avoid foreign pollen contamination