Xiaoliang Qin

Uptake and distribution of stable strontium in 26 cultivars of three crop species: oats, wheat, and barley for their potential use in phytoremediation.

The main objective of this study was to investigate the accumulation and distribution of strontium (Sr) in 26 cultivars of wheat (Triticum aestivum L.), husk oat (Avena sativa L) and naked oat (Avena nuda), and barley (Hordeum vulgare L.) for their potential use in phytoremediation.Sr levels had no effect on the accumulation of shoot biomass at tillering or at maturity. Mean shoot Sr concentration of naked oat and barley at tillering was significantly (P < 0.05) higher than that of wheat; Neimengkeyimai-1, a naked oat cultivar, had the highest Sr concentrations. At maturity, of four naked oat cultivars, Neimengkeyimai-1 had the highest Sr content at all measured Sr levels. Leaves had the highest Sr concentrations, followed by roots and straw, and then grain with the lowest. Mean enrichment coefficients from soil to shoots ranged from 0.521 to 1.343; the percentage of stable Sr removed from the soil to the shoots at harvest time was more than 1.4% after 120 days. Neimengkeyimai-1 could be used as a model for further research to find more effective cultivars; and naked oat plants could be selected for phytoremediation to clean up contaminated soil.

The Effect of Grain Position on Genetic Improvement of Grain Number and Thousand Grain Weight in Winter Wheat in North China

Genetic improvements have significantly contributed to wheat production. Five wheat cultivars—widely grown in north China in the 1950s, 1990s, or 2010s—were grown in field experiments conducted in the 2014–2015 and 2015–2016 growing seasons. This study evaluated the genetic progress in wheat grain yield and its related traits in north China and explored how breeding and selection have influenced grain numbers and weights within spikelets in the past 60 years. The results showed that the significant increases in grain yield in the past 60 years were mainly due to increases in grain number per spike and grain weight, while spike number per m2 has not changed significantly. Improvements in thousand grain weight (TGW) from the 1950s to 2010s have occurred at four grain positions (G1 to G4). The relative contribution of G4 to TGW increased over time, but was much less than the contributions of G1, G2, and G3. Indeed, the average grain weight at G4 was much less than that of 1000 grains. The increase in grain number per spike since the 1950s was mainly due to an increase in grain number at G1, G2 and G3, with the relative contribution of grain position to grain number being G1 > G2 > G3 > G4. Dwarfing genes increased grain number per spike and grain number at G3 and G4, but not TGW. In future, yields could be boosted by enhancing grain weight at G4 and grain number at G3 and G4, while maintaining those at G1 and G2.

Changes in yield and agronomic traits of soybean cultivars released in China in the last 60 years

Abstract. Breeding and cultivar improvement are important for increasing crop yields. In this study, 1472 soybean cultivars released in the last 60 years and 683 landrace cultivars from three regions of China (North spring soybean region, Yellow-Huai-Hai summer soybean region, and South soybean region) were collated to examine changes in agronomic characters and plant density that might be associated with yield improvement. The yield and 100-seed weight of the soybean cultivars increased significantly over time in all three regions. Planting density decreased significantly in the Yellow-Huai-Hai summer and South soybean regions but did not significantly change in the North spring soybean region. The increased soybean yields were mainly due to increased 100-seed weight and seed number per plant. Seed protein content has not significantly changed in 60 years, but oil content has increased in all three regions. The North spring soybean region had the highest oil content, whereas the South soybean region had the highest protein content. Future increases in soybean yield in China may occur by improving seed number per plant without reducing 100-seed weight. The North spring region should focus on breeding soybean with high oil content, and the Yellow-Huai-Hai summer and South regions should focus on high protein and low oil contents.

Changes in rice grain quality of indica and japonica type varieties released in China from 2000 to 2014

China is the first country to use heterosis successfully for commercial rice production. This study compared the main quality characteristics (head rice rate, chalky rice rate, chalkiness degree, gel consistency, amylose content, and length-to-width ratio) of 635 rice varieties (not including upland and glutinous rice) released from 2000 to 2014 to establish the quality status and offer suggestions for future rice breeding for grain quality in China. In the past 15 years, grain quality in japonica rice and indica hybrid rice has improved. In japonica rice, inbred varieties have increased head rice rates and decreased chalkiness degree over time, while hybrid rice varieties have decreased chalky rice rates and chalkiness degree. In indica hybrid rice, the chalkiness degree and amylose contents have decreased and gel consistency has increased. Improvements in grain quality in indica inbred rice have been limited, with some increases in head rice rate and decreases in chalky rice rate and amylose content. From 2010 to 2014, the percentage of indica varieties meeting the Grade III national standard of rice quality for different quality traits was low, especially for chalky rice rate and chalkiness degree. Japonica varieties have more superior grain quality than indica rice in terms of higher head rice rates and gel consistency, lower chalky rice rates and chalkiness degree, and lower amylose contents, which may explain why the Chinese prefer japonica rice. The japonica rice varieties, both hybrid and inbred, had similar grain qualities, but this varied in indica rice with the hybrid varieties having higher grain quality than inbred varieties due to significantly better head rice rates and lower chalkiness degree. For better quality rice in future, the chalky rice rate and chalkiness degree should be improved in japonica rice along with most of the quality traits in indica rice.

The scaling relationship of below-and above-ground biomass of different grain crops during the seedling stage

Allometric partitioning theory showed that root biomass (MB) scales in a nearly isometric manner with respect to shoot biomass (MA) for natural plants. Artificial selection has fundamentally transformed plants; for example, the biomass allocation pattern has changed in grain crops. This study investigated 32 genotypes from 20 grain crop species to test the effects of domestication and seed size on the scaling relationship of MB vs. MA for grain crops. The scaling exponent of MB vs. MA during 30 days of growth was 0.937 across the 32 grain crop genotypes, 0.999 for the dicotyledons and 1.034 for the monocotyledons. Based on the 95% CIs of the MB vs. MA scaling exponent (αRMA) of the data sets for the 32 genotypes, eight values exceeded 1.0, nine values were less than 1.0 and the remaining 15 values were statistically indistinguishable from 1.0. Seed size was positively correlated with the scaling exponents of MB vs. MA for the 32 genotypes (P<0.05), which means large-seeded species generally had more potential for allocating biomass to roots during the seedling stage. These findings suggest that a uniform isometric relationship exists in grain crop species and that artificial selection in crop species has not changed this relationship. In addition, larger seeds are an evolutionarily-stable strategy based on high grain yield per area.