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Improved nitrogen use-efficient cultivars could be the most economically beneficial and environmentally friendly approach to reduce pollution associated with excessive N fertilization. The performance and genetic gain in grain yield and nitrogen use efficiency (NUE) of a historical set of 12 bread wheat cultivars released for a heat-stressed environment were investigated at four N levels (0 (N0), 43 (N43), 86 (N86), and 129 (N129) kg/ha) for two seasons. Averaged across seasons, increasing N level from N0 to N43, N86, and N129 resulted in yield increases ranging from 4−45%, 13–69%, and 34–87% at N43, N86, and N129, respectively. These yield increases were associated with increases in biomass (r = 0.86, P < 0.01). Regressing grain yield of cultivars released during 1960 to 2006 against the year of release showed no trend at N0 and positive nonsignificant trends at N43;. however, significant positive trends were found at N86 and N129 with genetic gain rates of 12.65 and 15.76 kg ha−1 year−1, respectively. This gain was associated with progresses in harvest index (HI) at N43, N86, and N129 but not at N0. On the other hand, during the period from 1960 to 1990, the genetic gain in grain yield at N86 was 24.5 kg ha−1 year−1. Regressing NUE against the year of release showed significant linear trends at N86 and N129 (R2 = 0.511 and R2 = 0.477, respectively), but not at N43. The results indicate that breeders improved grain yield and NUE over 46 years under the heat-stressed environment of Sudan although the rate of increase in yield has been slowed down in recent years. Further improvement in NUE might require broadening the genetic diversity and simultaneous evaluation at low and high N levels. [ABSTRACT FROM AUTHOR]

Soybean [Glycine max (L.) Merr.] genetic improvement studies conducted under different stresses have provided conflicting results while maize (Zea mays L.) studies have shown that new cultivars were tolerant to a wide range of stresses. Using 25 genetic improvement studies from the literature, the objectives of this study were to compare estimates of genetic improvement under a range of yield capacities and also to determine the Finlay-Wilkinson adaptability of old to newer cultivars. The 25 genetic improvement studies were performed under a range of yield capacities due to varying density, fertility, irrigation, fungicide treatments, or year-to-year variation. Genetic improvement rates for each experiment were estimated from linear regression of cultivar yield on year of release. A cultivar's adaptability was estimated from regression of cultivar yield on site yield. In general, higher estimates of genetic gain were found in highyielding environments regardless of whether the higher yields were provided by reducing stress (controlling weeds or diseases, increasing nitrogen or water) or increasing stress using higher plant densities. Newer cultivars had higher adaptability values, indicating they are better adapted to high-yield environments. Older cultivars appear to have little utility for current use in any of the cropping systems in these studies. Plant breeders need to consider the possibility of lower genetic progress if using lower-yieldpotential testing environments such as reduced fertility or weed control. The use of high-yield sites may maximize genetic progress even if it does not reflect current producer environments. [ABSTRACT FROM AUTHOR]

Grain protein has recently received attention in several countries because of a premium associated to increased protein concentration (PC) in grains. Nitrogen (N) fertilizer management with its timing of application and rates plays a crucial role in increasing PC. The objectives of the present study were to: (1) quantify the effects of different N fertilizer rates and timing of application on grain yield and grain protein of six durum wheat cultivars, and (2) identify the best cultivar in terms of net return, yield, and protein content in typical pedo-climatic condition of southern Italy. The field experiments were conducted in Foggia during three growing seasons (2002–2003, 2003–2004, and 2004–2005). Results from this study showed that N application at sowing did not influence the cultivars performance. N applied at stem elongation increased yield and protein content provided there is adequate soil water for N uptake. In absolute terms, the best combination was the cultivar Svevo managed using 104 kg N ha−1split between tillering and stem-elongation stage. The excessive N splitting reduces yield and does not provide any improvement in terms of protein content. [ABSTRACT FROM PUBLISHER]

To understand the genetic gains of grain yield in the Southern China Winter Wheat Region (SCWWR), two yield potential trials, i.e., YPT 1 including 11 leading cultivars from the Middle and Low Yangtze Valley (Zone III) and YPT 2 including 15 leading cultivars from the Southwestern China Region (Zone IV) from 1949 to 2000, were conduced during the 2001–2003 cropping seasons. A completely randomized block design of three replicates was employed with controlled field environments. Molecular markers were used to detect the presence of dwarfing genes and the 1B/1R translocation. Results showed that average annual genetic gain was 0.31% ( P < 0.05) or 13.96 kg/ha/year and 0.74% ( P < 0.01) or 40.80 kg/ha/year in Zones III and IV, respectively. In YPT 1, changes of all other traits were not significant, but plant height was significantly reduced. In YPT 2, the genetic improvement of grain yield was primarily attributed to the increased thousand kernel weight (TKW) (0.65%, P < 0.01) and kernel weight/spike (0.87%, P < 0.01), reduced plant height and increased harvest index (HI). The dwarfing gene Rht 8 was most frequently present (46.1%), Rht-B1b was observed in three genotypes in Zone III, and Rht-D1b was present in only one genotype in Zone IV. The 1B/1R translocation was present in four genotypes. Utilization of Italian germplasm and development of landmark cultivar Fan 7 were the key factors for grain yield improvement in SCWWR. The future challenge of wheat breeding in this region is to continue improving grain yield and disease resistance, and to develop cultivars suitable for the reduced tillage of wheat/rice double cropping. Utilization of Mexican germplasm could provide opportunities for future yield improvement. [ABSTRACT FROM AUTHOR]

Due to high production cost and prevention of environmental pollution, it is important to reduce the amount of nitrogen (N) fertilizer used on wheat (Triticum aestivum L.). The aim of this study was to evaluate N use of 6 × 6 diallel wheat F2 progenies and parental lines at low (N0, no N fertilizer) and high (N+, 160 kg N ha- 1) N levels. Significant differences were found between N+ and N0 application in grain N content, grain N yield, N use efficiency for grain N yield (NUEgn), and N use efficiency for grain yield (NUEgy). The cultivar '84ÇZT04' showed positive and high general combining ability (GCA) effects for all traits at low N level. Also, it was the best combiner for all traits at both N levels. The cultivar 'Genç 99' was the best parent for GCA effects for grain yield and NUEgy. Hybrids 'Genç 99 × 84ÇZT04' and '84ÇZT04 × Weaver' showed positive specific combining ability (SCA) effects for all investigated traits at low and high N levels. Variety '84ÇZT04 × Apogee' had the best SCA effects for all traits at low N level. Overall, the data suggest that it is probable to select promising lines suitable for low N conditions by the crossing of high N use efficient parents. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate nitrogen partitioning in entire plants, including roots, of spring wheat in two temperature regimes during grain filling. Six cultivars, genetically different and with varying grain protein concentration, were grown in solution culture to full maturity. After anthesis, half the plants were grown in high temperature (23/17 °C, day/night) and half in low temperature (18/12 °C). Root nitrogen concentration was genetically influenced. The roots had ability to redistribute nitrogen to aboveground plant parts. At maturity the roots contained 10–20 % of the total nitrogen amount in the plants. Harvest index (HI) and harvest index for the entire plant (HItot) for cv. Heta were significantly higher at low temperature than at high. Cv. Heta had a rapid development rate from planting to maturity. Due to slow senescence at low temperature, cv. Kärn II showed lower HI and nitrogen harvest index (NHI) at low, compared with high, temperature. Cvs Kärn II and Sport showed higher nitrogen amount in the roots and shoots at low, compared with high, temperature. A negative correlation was found between NHI and NHItot vs. root weight, total shoot weight and root N amount. Because of the latter correlation, breeding for low root N concentration is suggested. [ABSTRACT FROM AUTHOR]

Andean blackberries (Rubus glaucus Benth) are fruits rich in phytocomponents with high antioxidant activity. In this work, the changes in the total polyphenol content (TPC), the total flavonoid content (TFC), and the total anthocyanin content (TAC) of four blackberry varieties at three maturity stages (E1-25%, E2-50%, and E3-100%) were measured. The antioxidant activity (AA) was evaluated using the 2,2'azinobis-(3-ethylbenzthiazolin 6-sulphonic acid (ABTS) and ferric reducing antioxidant power (FRAP) methods. TPC and TFC content decreased with the increase in the maturity stage. The blackberry Brazos cultivar presented TPC values of 51.26, 38.16, and 31.59 mg of gallic acid equivalents (GAE)/g dry weight (DW) at E1, E2, and E3, respectively. The TAC and soluble solids increased with the increase in the maturity stage of the fruits. The Andimora variety at E3 presented a high TPC content, and the Colombiana variety presented a high TFC content. The blackberry Colombiana cultivar presented TAC values of 1.40, 2.95, and 12.26 mg cy-3-glu/100g DW at E1, E2, and E3, respectively. The blackberry Colombiana cultivar presented a high AA value at 1278.63 µmol TE/g DW according to the ABTS method and 1284.55 µmol TE/g DW according to the FRAP method. The TPC and TFC showed a high correlation with the AA according to the ABTS and the FRAP methods. The Pearson correlation between the TFC and AA/ABTS has a value of r = 0.92. The TFC and AA/FRAP present a value of r = 0.94. [ABSTRACT FROM AUTHOR]

Grain number and weight within a spikelet are major yield components which determine the grain yield in wheat. The objective of this study was to explore genetic gains in grain performance within wheat spikelets at the individual grain level and its effect on grain yield and evaluate genetic progress in stem internode length and other yield-related traits. We conducted field experiments across three growing seasons in the western Yellow and Huai Valley of China; incorporating 17 bread wheat cultivars released from 1948 to 2012. Yields were significantly correlated with year of release. Yield gains equated to 3.95 g m−2 yr−1 in response to increases in total grain weight per m2 (GW) in proximal (G1 and G2) and distal (G3 and G4) grains, despite a decline in the proportional contribution of proximal grains to yield and increase in the proportional contribution of distal grains to yield with year of release. Grain number per m2 (GN), thousand-grain weight (TGW), and harvest index (HI) increased with year of release, but plant height decreased. Both grain number per spikelet of proximal and distal grain contributed to the increase in total GN. However, the contribution ratio of GN in proximal grains to total GN declined, and the proportion in distal grains increased. Average single grain weight (SGW) increased linearly at G1, G2, G3, and G4 with year of release and contributed to the increase in TGW. The G3 and G4 grain positions had much lower individual grain weights but increased at a faster rate than G1 and G2. At G1, G2, and G3 grain positions, from bottom to top spikelets, the newly released cultivars had the heaviest grains and the old cultivars had the lightest grains. New cultivars had more spikelets than old cultivars and the number of grains (proximal and distal grains) in the apical spike increased with year of release. The length of five internodes decreased significantly with year of release, more so in the upper than lower internodes, all of which contributed to the decline in plant height. In summary, increasing the number and weight of distal grains could increase grain yield, TGW, and GN. [ABSTRACT FROM AUTHOR]