Contribution of peduncle traits to grain yield under terminal drought and compensatory effect of stem reserve mobilization
When environmental stress develops during reproductive phases of growth, wheat plants have to rely increasingly on remobilisation of previously stored assimilates to maintain grain filling. The present study was undertaken to determine the effect of several peduncle (the uppermost stem internode) morpho-anatomical and biochemical traits on grain weight, and to assess the contribution of the peduncle water-soluble carbohydrate (WSC) reserves shortly after anthesis to its variation. In 2-year field trials, 61 wheat genotypes were used (27 F4:5 families, 17 parents used for the crosses and the 17 current best standards) comparing intact control plants (CP) with plants that were defoliated (DP) by cutting off all leaf blades 10 days after anthesis to simulate terminal stress. Estimated contributions of peduncle assimilate reserves to grain weight/spike were from 0.06 to 0.31% and from 0.11 to 0.45% in CP and DP plants, respectively. High peduncle reserve mobilization efficiency, a longer exposed part of the peduncle and larger peduncle storage capacity (through higher parenchyma and/or lower lignified area) were of specific benefit for maintaining grain weight in defoliated plants. There was a large difference in compensation of grain yield loss by dry matter remobilization within studied genotypes (in average 1.2-36.1%). Although compensation of yield loss might be improved through breeding process (our F4:5 families had slightly higher mean compensation effect than their parents under moderate stress), it does not mitigate the effect of post-anthesis drought in great extent (up to 38.4%).