Breeding Effects on Dry Matter Accumulation and Remobilization in Different Internodes of the Stem in Iranian Wheat Cultivars

Remobilization of stored dry matter in the stem of wheat is an important contributor to grain filling especially under harsh environmental conditions. Changes in traits related to carbon accumulation and remobilization resulting from breeding in Iranian wheat cultivars were studied. Eighty–one wheat cultivars released from 1930 to 2006 were examined under well watered condition at Parsabad-Moghan during 2013–2014 growing season. Improvement in main stem grain yield was 8 mg spike-1 y-1. Large variations were found for internodes weight at 16 days after anthesis (16 DAA). There were no significant associations between peduncle and penultimate weight measured at 16 DAA and year of cultivar release. But, the lower internodes and main stem weight marginally decreased with year of release. Averaged among cultivars, remobilization of stored dry matter from peduncle, penultimate, and the lower internodes were 62, 88, and 93 mg, respectively. Release of dry matter from different internodes did not change significantly from old to modern cultivars. The same trend was observed for remobilization efficiency. Changes over time in the contribution of mobilized dry matter to the main stem grain yield were not significant in the case of the upper internodes. But when the lower internodes were considered, this parameter decreased from old to modern cultivars.