Leaf and Canopy Architecture for Heat Resistance in Field Pea.

Western Canada produces field pea (Pisum sativum L.) as a dryland crop, where it is exposed to heat stress when temperatures exceed 28°C.  Several days of heat cause flower and pod abortion and most cultivars are heat sensitive.  To seek traits for improved heat resistance we measured a 94-member pea collection.  Pea cultivars originated from north America, western and eastern Europe, and Australia.  We tested this collection under high temperatures in the field in Arizona in 2012, and in Saskatchewan with shorter periods of heat in 2012, 2013 and 2015.  Traits measured included canopy temperature, canopy greenness (SPAD and various vegetation indices), reproductive node number, pod number, seeds per pod, flower abortion rates, ovule retention, and yield.  A wide range of vegetation indices were calculated from spectra (300-1100 nm) collected in the field from single leaves with a handheld spectral radiometer several times in 2015.  Genotypes groupings were based on previous association mapping and discriminant analysis results.  Results will be presented for how cultivar leaf type, leaf size and shape, canopy habit, flower color, and genotypic grouping relate to canopy temperature, canopy color, vegetation indices, and the various yield-based traits.  The goal is to identify how various canopy features in pea relate to heat resistance for maintaining cooler canopies and reducing reproductive flower, pod and ovule abortion.