Allan Andersson

Individual and interactive effects of cultivar maturation time, nitrogen regime and temperature level on accumulation of wheat grain proteins.

BACKGROUND Background and reasons for differences in wheat grain protein accumulation and polymerization are not fully understood. This study investigated individual and interactive effects of genetic and environmental factors on wheat grain protein accumulation and amount and size distribution of polymeric proteins (ASPP). RESULTS Individual factors, e.g. maturation time of a cultivar, nitrogen regime and temperature level, influenced grain protein accumulation and ASPP, although interaction of these factors had a greater influence. Early maturation time and long grain maturation period (GMP) in a cultivar resulted in high amounts of sodium dodecyl sulphate (SDS)-extractable proteins (TOTE) and low percentage of SDS-unextractable polymeric proteins in total polymeric proteins (%UPP). Cultivars with late maturation time and short GMP resulted in low TOTE and high %UPP. Late versus early nitrogen application regime resulted in low %UPP versus low TOTE and high %UPP, respectively. High versus low temperature resulted in high %UPP and low %UPP, respectively. Differences in ASPP at maturity started as changes in protein accumulation from 12 days after anthesis. CONCLUSION Length of GMP, especially in relation to length until maturity, governs gluten strength (%UPP) and grain protein concentration (TOTE). Length of GMP is determined by cultivar, temperature during GMP and late nitrogen availability.

Post-anthesis nitrogen accumulation and distribution among grains in spring wheat spikes

Knowledge of nitrogen accumulation to the grains is of great importance for identifying breeding and growing strategies to improve cereal yield and quality. The aim of this study was to investigate post-anthesis N translocation in the spike and into different spikelets of two cultivars of spring wheat ( Triticum aestivum L.) grown to maturity in solution culture. Sport (short grain filling time, low yield and high grain protein concentration) and WL (normal grain filling time, high yield and low protein concentration) were the cultivars used. Plants received stepwise declining rates of N on a daily basis, until 109 days after planting (DAP). Anthesis for cv. Sport was 92 DAP and for cv. WL 78 DAP. On seven occasions (from anthesis in cv. WL until maturity), 15 N was given to selected groups of plants for 4 days. Then these plants were sampled and separated into plant parts. Spikelets and grains were separated according to spikelet position. Plant parts were weighed and analysed for N and 15 N. The N concentration in the grains was uniform for the spikelets in cv. WL but differed in cv. Sport. Final N concentration in a spikelet position was obtained at 126 DAP in cv. Sport and 112 DAP in cv. WL and was constant to the end of experiment at 154 DAP in cv. Sport and 147 DAP in cv. WL. A positive correlation between % atom excess 15 N to spikelet position numbered from the base of the spike was exhibited in the lowermost part of the spike just after anthesis. Later, during grain filling, a negative correlation between % atom excess 15 N to spikelet position was exhibited (−0·991 P =0·000). A positive correlation between % atom excess 15 N to grain weight in the top of the spike was exhibited. Accumulation of 15 N proceeded 14 days longer in the lowermost fertile spikelets than in the uppermost spikelets. It was concluded that the duration of N accumulation in the spikelets was dependent on spikelet position and uppermost spikelets had a shorter N accumulation period and contained lighter grains than lowermost spikelets.

Breeding for improved stability in bread-making quality.

: Both genotype and environment influence the bread-making quality of wheat and a better stability in quality is desired. The reasons for variation and stability of wheat quality were investigated in Swedish and Baltic cultivars using Size Exclusion-High Performance Liquid Chromatography (SE-HPLC) and Reversed Phase-High Performance Liquid Chromatography (RP-HPLC). The results showed that; • Both grain protein concentration and gluten strength vary due to environmental influences. • Differences in gluten strength were due to differences in amount and size distribution of monomeric and polymeric proteins. • Differences in protein concentration were related to accumulation of glutenins and gliadins in the grain but not to differences in amount and size distribution of polymeric proteins. • Differences in cultivar stability for gluten strength were found, and correlated to stability in amount and size distribution of polymeric protein. • The ending of the grain-filling period varied in different grain positions in the spike, with the longest grain-filling time in the lower-mid part of the spike. • Variations in amount and size distribution of polymeric proteins at grain maturity were due to a change in extractability of polymeric and large monomeric proteins during grain development, indicating influences on disulphide bond formation. The amount and size distribution of polymeric proteins is thus of high importance in breeding cultivars of good and even quality between years. Environmentally influenced changes in amount and size distribution of polymeric proteins are due to changes in extractability of the polymeric proteins, indicating influences on disulphide bond formation. Successful breeding of more stable polymeric protein formation would lead to cultivars with more stable bread-making quality.