Search

The combined effects of soil waterlogging and compaction are important concerns in crop production. Two field experiments were performed over two seasons to examine the effects of soil waterlogging and high bulk density (BD) on the performance of winter wheat in terms of its agronomic and physiological traits. Trial 1 applied soil waterlogging at different stages (started at tillering, jointing, booting and anthesis). Trial 2 was conducted with soil waterlogging and compaction that created BD of the topsoil (1.6 g cm −3 ). Results from trial 1 showed that the tillering stage was the most waterlogging-sensitive period. A 12% lower grain yield caused by waterlogging was primarily reflected in reductions in spike numbers. Waterlogging at jointing and booting stages reduced grain weight through decreased dry matter translocation. Results from the field trial 2 showed that soil compaction decreased grain yield by 4.8%, and waterlogging aggravated this reduction by 20.7% and 22.4% when fields were waterlogged for 2 weeks (WL 2w ) and 4 weeks (WL 4w ), respectively. A reduction in spike number from fewer tillers at stem elongation stage was the main reason for grain yield loss. Soil compaction combined with waterlogging duration did not affect root weight, but soil compaction reduced above ground biomass and root weight after the jointing stage. Furthermore, waterlogging accelerated leaf senescence, especially under compacted conditions, which significantly decreased photosynthetic capacity, resulting in a lower maximal PSII photochemical efficiency (F v /F m ), apparent electron transport rate (ETR), effective quantum yield of photosystem II (ΦPSII) and photochemical quenching (qP). Root weight was positively related to the total above ground biomass; whereas the final grain yield was not linearly related to the shoot weight. SPAD value correlated positively with yield and PSII parameters (F v /F m , F v /F 0 ). The study concluded that the tillering stage was most susceptible to waterlogging, and soil compaction combined with waterlogging at tillering stage had a larger harmful effect on root and shoot growth during or after waterlogging. SPAD readings may be a good surrogate for photosynthetic activity under waterlogging and compaction conditions. [ABSTRACT FROM AUTHOR]

Knowledge about the key traits related to genetic gains in grain yield (GY) is necessary for understanding the main yield‐limiting factors and guiding future wheat (Triticum aestivum L.) breeding. The objective of this research was to investigate the genetic progress in GY and the associated physiological traits in popular wheat cultivars released from 1969 to 2012 in southwestern China. Field experiments included eight representative cultivars that were evaluated at three experimental sites for three growing seasons. Grain yield increased at a linear rate of 0.69% or 52.52 kg ha−1 yr−1, which was mainly attributed to the increases in dry matter (DM) accumulation at maturity, harvest index (HI), and thousand‐kernel weight (TKW). The soil and plant analyzer development (SPAD) values of flag and penultimate leaves at anthesis increased with the year of release and were significantly related to GY. Significant genetic gains were made in both nonstructural carbohydrate (NSC) translocation and NSC translocation efficiency from anthesis to maturity, and there was a trend over time towards a high net photosynthetic rate (Pn) of flag leaf and canopy apparent photosynthesis (CAP) at anthesis and at 30 d post‐anthesis (DPA). In addition, the linear increases in N uptake efficiency and N utilization efficiency were both significant and positive related to GY. Therefore, these key physiological traits can be used as selection criteria for further improving yield potential. Our results also reveal the potential for using synthetic hexaploid wheat in high‐yielding wheat breeding. [ABSTRACT FROM AUTHOR]