Physiological basis for the differences of productive capacity among tillers in winter wheat

摘要

The quality or structure of a wheat population is signiifcantly affected by the compositions of tilers. Little has been known about the physiological basis for the differences of productive capacity among tilers. Two winter wheat cultivars, Shannong 15 (SN15) and Shannong 8355 (SN8355), were used to investigate the differences of productive capacity among tilers and analyze the physiological mechanisms that determine the superior tiler group. Low-position tilers (early initiated tilers) had a higher yield per spike than high-position tilers (late initiated tilers) in both cultivars, which was due to their more grain number per spike, more fertile spikelet per spike, less sterile spikelet per spike and higher grain weight. According to cluster analysis, tilers of SN15 were classiifed into 2 groups: superior tiler group including main stem (0), the ifrst primary tiler (I) and the second primary tiler (II); and inferior tiler group including the third primary tiler (III) and the ifrst secondary tiler (I-p). Tilers of SN8355 were classiifed into 3 groups: superior tiler group (0 and I), intermediate tiler group (II and III) and inferior tiler group (I-p). In comparison with other tiler groups, the superior tiler group had higher photosynthetic rate of lfag leaves, higher antioxidant enzyme (SOD, POD and CAT) activities and lower levels of lipid peroxidation in leaves, higher grain ifling rate in both superior and inferior grains during grain ifling, higher single-stem biological yield and larger single-stem economic coefifcient. Correlation analysis showed that yield per spike was positively and signiifcantly correlated with the lfag leaf photosynthetic rate, grain ifling rate, the antioxidant enzyme activities and soluble protein content (except for SN15 at 5 days post-anthesis (DPA)) of lfag leaf, the single-stem biological yield, and the single-stem economic coefif-cient. Remarkable negative correlation was also found between yield per spike and MDA content of lfag leaf. These results suggested that superior tiler group had stronger leaf photosynthetic capacity, more predominance in terms of grain ifling, slower senescence rate, higher biological yield and larger economic coefifcient, and therefore, showed greater productive capacity than other tiler groups.