Abstract:

In order to study the cytoplasmic effects of male sterile wheat, male sterile lines of CHA (chemical hybridizing agent) and cytoplasmic K (Aegilops kotschyi), T (Triticum timopheevi), V (Aegilops ventricosa) types of male sterile wheat at different developmental stages were compared with their maintainer lines in the diurnal changes of photosynthetic and physiological parameters, comprising net photosynthetic rate (P_n), stomatal conductance (G_s), transpiration rate (T_r), water use efficiency (WUE), photon flux density (PFD), intercellular CO₂ concentration (C_i), atmospheric CO₂ concentration (C_a), leaf temperature (T_i), atmospheric temperature (T_a), and stomatal limiting value (L_s). And these parameters may reflect the photosynthetic efficiency of the leaves and environmental adapting capability of the plant. The experiment was conducted to analyze the diurnal changes and the physiological mechanism of photosynthetic midday-depression, the response to male sterile cytoplasms of female parent genotypes and the differences of photosynthetic and physiological parameters of 4 male sterile lines and their maintainer lines, which can reflect differences of heredity of 4 male sterile cytoplasms under the same nuclear background and also exhibit differences of the effect of nuclear-cytoplasmic interaction. The result indicated that, the curve of diurnal changes of P_n presented two peak values, with one peak at 10:00 higher than the other at 14:00. And the phenomenon of photosynthetic midday-depression of leaf happened at noon. The diurnal changes of Pn was positively correlated with G_s, C_i and negatively correlated with L_s, and the correlation coefficients were 0.8187*, 0.8136*, and －0.8496* respectively. Accompanied by the decline of G_s, C_i and the raise of L_s, P_n declined distinctly in midday, which means the limitation of Pn by stomatal factor. Compared with their maintainer lines, CHA and K, T, V-male sterile lines had lower P_n values, decreasingly 0.88, 2.76, 3.30, and 2.04 μmol CO₂ m^-2 s^-1 respectively, indicating that the CHA and K, T, V-cytoplasm has negative effects on Pn with different extent, especially T and K-types. K, T, V cytoplasmic male sterile lines had lower WUE values than their maintainer lines, decreasingly 0.94–1.54 μmol CO₂ mmol^-1 H₂O, and indicating that K, T, V-cytoplasm has significantly negative effects on WUE. Compared with the maintainer lines, CHA-sterile lines has no significant difference in WUE values, indicating chemical hybriding agent (BAU-9403) has no significantly negative effects on the water use efficiency of wheat flag leaf. The influences of damage caused by BAU-9403 were less than the negative effects of other male sterile cytoplasms. Moreover, the Pn value varied between genotypes of different female parents, Pn of Ji 5418 and its CMS lines showed significant or highly significant differences with that of Tai 911289, indicating that genotypes of female parents have different effects on different cytoplasms in Pn. This result also demonstrates the enormous potential for improving the photosynthetic capability in Ji 5418. Therefore, it is better to reduce the negative effects of male sterile cytoplasms on photosynthetic function of wheat by selecting preponderant recurrent parent to make backcross in a breeding project.

Key words: Cytoplasmic effect, Male sterile lines, Photosynthesis, Diurnal changes