| Cytoplasmic male-sterile (CMS) lines, especially K (Aegilops kotchyi), V (Aegilops ventricosa), and T (Triticum timopheevi) types of cytoplasms, are of high value in heterosis utilization in wheat (Triticum aestivum L.). The sterile mechanisms of these CMS types have been focused in hybrid wheat research. As a key and rate-limiting starch biosynthetic enzyme, ADP-glucose pyrophosphorylase (AGPase) is considered to play an important role in the sterility of CMS lines. For gaining an insight into the physiological basis of the sterility in CMS lines of wheat, the activities of AGPase in leaves, young spikes, and grains were measured in K, V, and T types of isogenic CMS lines (Ji 5418 background) at different growth stages, and compared with those of their maintainer line. The dynamic accumulations of starch, amylose, and amylopectin were also investigated in both superior (the first and the second grains in a spikelet) and inferior (grains except for the first and the second grains in a spikelet) grains; In present work, 2 nuclear background male sterile lines including K, V, T, CHA-cytoplasm male-sterile lines, and restorer line and their hybrids, were employed to study the effect of different cytoplasmic types on the photosynthesis and physiological parameters: stomatal conductance (Gs), transpiration rate (Tr), CO2 concertration (Ci), atmospheric CO2 concentration (Ca), water use efficiency (WUE), intercellar stomatal limiting value (Ls) of hybrids at heading stage, anthesis stage, mid-filling stage and later-filling stage. The major results are as follows:(1)the male sterility is probably in relation to the insufficiency of energy in leaves and young pikes at floret primordium stage resulting from the high AGPase activity, and the low accumulation of starch in pollens at tetrad stage caused by low AGPase activity in young spikes. In young spikes, the AGPase activities of the three CMS lines were significantly higher (F = 133.81, P < 0.0001) with the differences of 9.33 ? 27.94μmol g?1 FW h?1 at floret primordium stage, and significantly lower (F = 13.97 ? 75.20, P < 0.0001) by 4.27 ? 7.44μmol g?1 FW h?1 at tetrad stage as compared with the maintainer line. From floret primordium to tetrad stage, the CMS lines had continuously higher level of AGPase activities in leaves than the maintainer line, with the differences ranged from 7.39 to 80.77μmol g?1 FW h?1 (F = 135.76 ? 5454.28, P < 0.0001).(2)the sterile cytoplasm has a negative effect on AGPase activity, resulting in decreases of ADPG level and starch accumulation in grains which may result in unfilled grains in CMS lines. Compared with the maintainer line, the three CMS lines all presented lower accumulations (P < 0.05) of starch, amylose and amylopectin in grain. The starch content and AGPase activity in superior grains were significantly higher than those in inferior grains for CMS lines. The dynamic accumulations of starch in superior and inferior grains fitted Logistic equations, and positively correlated with the starch accumulation rate (r = 0.4460 ? 0.7150, P = 0.0004 ? 0.0487). The AGPase activity in leaves had an insignificantly negative correlation with net photosynthetic rate.(3) The heterosis on photosynthesis and physiological parameters Ci, Gs and WUE of hybrid F1 was common. The photosynthesis of T-cytoplasm hybrid had the highest heterosis with 20.029%, K, V-cytoplasm were 10.630%,7.099% higher than those of Mid-parent, respectively.(4) The dynamic changes of Pn were restricted by the stomatal factors to some extent. The dynamic changes of hybrid F1 is the same as their parents at four stages. The dynamic changes of Pn were the same as Ci and Gs, and were different from Ls. (5) K, V, T-type cytoplasm had no negative effect on hybrid F1. Compared with CHA-cytoplasm, the Pn value of K-cytoplasm hybrid was lower, and decreased by 0.077μmolCO2·m?2·s?1, while these of V, T-cytoplasm hybrid were higher with increasing of 0.419μmolCO2·m?2·s?1, 0.725μmolCO2·m?2·s?1, respectively, but the difference was not significant.(6) The physiological parameter stomatal conductance of hybrid F1 could be improved with excellent genotype. The Gs value of hybrid F1 with tai911289 as female parent was higher than that whose female parent was ji5418 with increasing of 29.127 mmolm?2·s?1, with significantly difference.
|
PDF Full Text Request