Accessing the agronomic and photosynthesis-related traits of high-yielding winter wheat mutants induced by ultra-high pressure

To generate new wheat breeding lines, ultra-high pressure (UHP) (using castor oil as the medium) was used to induce mutant lines from the wheat variety 'Yanzhan 4110′. Three high-yielding mutant lines (Gaoya 2, Gaoya 3 and Gaoya 9) were selected from 1580 mutants induced by UHP and were evaluated for agronomic and photosynthesis-related traits in this study. Our results showed that these mutant lines retained higher grain yield than Yanzhan 4110 and exhibited higher biomass and harvest index, significantly higher plant height, spikelet numbers per spike and higher kernel numbers per spike but similar or lower thousand-kernel weight (α = 0.05). The reading of relative leaf chlorophyll content (SPAD) and photosynthetic traits of the high-yielding mutant lines varied to different degrees. The mutant lines had higher SPAD and higher stomatal conductance (Gs) than Yanzhan 4110 at two grain-filling stages. The net photosynthetic rate (Pn), apparent mesophyll conductance, Gs and transpiration rate (Tr) of Gaoya 2 were significantly higher than those of Yanzhan 4110 at the mid grain-filling stage (GF-2) (α = 0.05). The decreases in SPAD, Pn, Gs, transpiration efficiency (TE) and Tr in the high-yielding mutant lines were smaller than those in Yanzhan 4110 during the early grain-filling stage (GF-1) and GF-2. Fluorescence parameters, including F0, Fm, Fv, Fv/F0, and Fv/Fm, were higher in the three high-yielding mutant lines, while qN was significantly lower at GF-1 and GF-2 compared with those in Yanzhan 4110 (α = 0.05). Higher qP and ΦPSII values were also observed in the three high-yielding mutant lines. These results indicate that wheat mutations induced by UHP exhibited high yield, improved photosynthetic efficiency, decreased thermal dissipation and altered photoinhibition.