Developmental and environmental effects on the assembly of glutenin polymers and the impact on grain quality of wheat

Wheat kernel development can be divided into three phases i.e. cell division, cell enlargement and dehydration. Accumulation of gluten proteins continues till the end of the cell enlargement phase. During the dehydration phase, post-translational polymerization of the glutenin subunits occurs to form very large glutenin polymers. Assembly of the glutenin polymers has been monitored by increase in the unextractable polymeric protein. Lines possessing HMW-GS related to dough strength (e.g. 5. +. 10) started accumulating large polymers several days earlier than lines with HMW-GS related to dough weakness (e.g. 2. +. 12) and maintained their higher amounts till maturity. This may be explained by faster polymerization resulting from a higher concentration of cysteine residues in the x-type HMW-GS.Sulphur deficiency leads to an increase in the ratio of HMW- to LMW-GS, causing a shift in the MWD to higher MWs, resulting in bucky dough properties. High temperature during grain development appears to shift the MWD to lower MWs with corresponding lowering of dough strength but the presence of strength-associated HMW-GS appears to confer greater tolerance to heat stress. Since sulphur deficiency and higher global temperatures may be expected to increase in the future, some suggestions how breeders may use strategies to counter these effects are put forward. © 2012 Elsevier Ltd

Effect of heat stress on wheat proteins during kernel development in wheat near-isogenic lines differing at Glu-D1

Two near-isogenic lines of the wheat variety Lance having Glu-D1a (HMW-GS 2 + 12) and Glu-D1d (HMW-GS 5 + 10) were subjected to several regimes of heat stress. In 2001, the temperature regimes were (i) 20/16 (day/night, °C) from planting to maturity, (ii) 20/16 except for a 3-day heat treatment of 35/20, 25 days after anthesis and (iii) 20/16 until 25 DAA, after which plants were subjected to 40/25 until maturity. In 2002, treatments (i) and (iii) were the same while treatment (ii) used a temperature of 40/25 °C for 3 days at 25 DAA. Seed was collected at 3-day intervals starting from 16 days after anthesis and analyzed for protein composition by SE-HPLC. The line with the Glu-D1d allele showed an earlier polymerization of glutenin than its allelic counterpart and a higher molecular weight of glutenin at maturity, this being deduced from measurements of the percentage of unextractable polymeric protein. It is postulated that the timing and rate of glutenin polymerization, and the timing of high temperature application may be the key factors contributing to an explanation of the effect of heat stress on functionality. © 2008 Elsevier Ltd. All rights reserved.The authors gratefully acknowledge financial support from the USDA Research Initiative Program. Mary Roth and Jie Hu are thanked for excellent technical assistance. Drs Fritz and Paulsen, Department of Agronomy, Kansas State University are acknowledged for invaluable assistance with growing of the plants

Overyielding in experimental grassland communities – irrespective of species pool or spatial scale

In a large integrated biodiversity project ('The Jena Experiment' in Germany) we established two experiments, one with a pool of 60 plant species that ranged broadly from dominant to subordinate competitors on large 20 × 20 m and small 3.5 × 3.5 m plots (= main experiment), and one with a pool of nine potentially dominant species on small 3.5 × 3.5 m plots (= dominance experiment). We found identical positive species richness–aboveground productivity relationships in the main experiment at both scales. This result suggests that scaling up, at least over the short term, is appropriate in interpreting the implications of such experiments for larger-scale patterns. The species richness–productivity relationship was more pronounced in the experiment with dominant species (46.7 and 82.6% yield increase compared to mean monoculture, respectively). Additionally, transgressive overyielding occurred more frequently in the dominance experiment (67.7% of cases) than in the main experiment (23.4% of cases). Additive partitioning and relative yield total analyses showed that both complementarity and selection effects contributed to the positive net biodiversity effect