SUMMARYA field experiment was conducted at Gandhi Krishi Vignana Kendra, University of Agricultural Sciences, Bangalore to study the effect of irrigation regimens on the biomass accumulation, canopy development, light interception and radiation use efficiency of sunflower. The treatments includes irrigating the plants at 0.4, 0.6, 0.8 and 1.0 cumulative pan evaporation. The results indicated that the aboveground biomass, canopy development, radiation interception and radiation use efficiency were influenced favorably by the irrigation regimens. Irrespective of the irrigation regimen, the radiation use efficiency of sunflower increased from 15 DAS to 75 DAS and then tended to decline. The decrease in RUE after anthesis is coupled with decrease in leaf nitrogen content. In general the RUE of sunflower ranged from 0.49 g MJ-1 to 1.84 g MJ-1 at different growth stages. The light transmission within the canopy increased exponentially with plant height and the canopy extension coefficient is found to be 0.8.
To better understand the potential for improving biomass accumulation and radiation use efficiency (RUE) of winter wheat under deficit irrigation regimes, in 2006–2007 and 2007–2008, an experiment was conducted at the Luancheng Experimental Station of Chinese Academy of Science to study the effects of deficit irrigation regimes on the photosynthetic active radiation (PAR), biomass accumulation, grain yield, and RUE of winter wheat. In this experiment, field experiment involving winter wheat with 1, 2 and 3 irrigation applications at sowing, jointing, or heading stages was conducted, and total irrigation water was all controlled at 120 mm. The results indicate that irrigation 2 or 3 times could help to increase the PAR capture ratio in the later growing season of winter wheat; this result was mainly due to the changes in the vertical distributions of leaf area index (LAI) and a significant increase of the LAI at 0–20 cm above the ground surface (LSD, <i>P</i> < 0.05). Compared with irrigation only once during the growing season of winter wheat, irrigation 2 times significantly (LSD, <i>P</i> < 0.05) increased aboveground dry matter at maturity; irrigation at sowing and heading or jointing and heading stages significantly (LSD, <i>P</i> < 0.05) improved the grain yield, and irrigation at jointing and heading stages provided the highest RUE (0.56 g/mol). Combining the grain yield and RUE, it can be concluded that irrigation at jointing and heading stages has higher grain yield and RUE, which will offer a sound measurement for developing deficit irrigation regimes in North China.
SummaryOne of the major challenges for plant scientists is increasing wheat (Triticum aestivum) yield potential (YP). A significant bottleneck for increasing YP is achieving increased biomass through optimization of Radiation Use Efficiency (RUE) along the crop cycle. Exotic material such as landraces and synthetic wheat has been incorporated into breeding programs in an attempt to alleviate this, however their contribution to YP is still unclear. To understand the genetic basis of biomass accumulation and RUE we applied genome-wide association study (GWAS) to a panel of 150 elite spring wheat genotypes including many landrace and synthetically derived lines. The panel was evaluated for 31traits over two years under optimal growing conditions and genotyped using the 35K Wheat Breeders array. Marker-trait-association identified 94 SNPs significantly associated with yield, agronomic and phenology related traits along with RUE and biomass at various growth stages that explained 7–17 % of phenotypic variation. Common SNP markers were identified for grain yield, final biomass and RUE on chromosomes 5A and 7A. Additionally we show that landrace and synthetic derivative lines showed higher thousand grain weight (TGW), biomass and RUE but lower grain number (GNO) and harvest index (HI). Our work demonstrates the use of exotic material as a valuable resource to increase YP. It also provides markers for use in marker assisted breeding to systematically increase biomass, RUE and TGW and avoid the TGW/GNO and BM/HI trade-off. Thus, achieving greater genetic gains in elite germplasm while also highlighting genomic regions and candidate genes for further study.
Field studies were conducted on durum wheat to assess the effects of three sowing dates and three cultivars with different flowering times on the stability of the biomass accumulated per unit of solar radiation intercepted that is usually considered constant in crop-simulation models. Aboveground dry matter varied widely, with minimum values ranging from 292 g m–2 at booting to 384 g m–2 at maturity and maximum values ranging from 1452 g m–2 at booting to 2565 g m–2 at maturity. The cumulative intercepted radiation at each phenological stage decreased as sowing was delayed. The leaf area index (LAI) ranged from 1.5 to 7.6 at booting and from 0.1 to 4.6 at the beginning of grain filling across treatments. Sowing dates and cultivars did not differ significantly in extinction coefficient values (0.38 ± 0.015). The estimated radiation use efficiency (eRUE) differed significantly between the two seasons (1.16 ± 0.09 g MJ–1 in 2000 and 1.61 ± 0.08 g MJ–1 in 2001) due to waterlogging in 2000 but did not differ among sowing dates and cultivars within each season. Under optimal growing conditions, eRUE of different cultivars of durum wheat were relatively stable across sowing dates, confirming their reliability for crop modelling in durum wheat as well as in bread wheat. Although eRUE was constant over the whole crop cycle regardless of the sowing date, it was lower at pre-anthesis in the latest sowing, in parallel with the variation in LAI. This study indicates that pre-anthesis eRUE may vary with sowing date under some conditions, depending on the variation in LAI in the period before anthesis.
Eight wheat (Triticum aestivum L.) cultivars including soft white spring, hard red spring, Canada Prairie Spring (CPS) and durum types were grown on rain-fed and irrigated land from 1987 to 1990 at Lethbridge, AB, to assess the relationship between yield components and radiation-use efficiency. Canopy reflectance measurements were used to estimate seasonal absorption of photosynthetically active radiation (APAR). At maturity, yield components including tillers per plant, heads per plant, kernels per head and kernel weight were determined. Whole-plant phytomass and grain yield were also determined. Harvest index was determined from the ratio of grain yield to whole-plant (excluding roots) phytomass and radiation-use efficiency (RUE) was calculated from the ratio of whole-plant phytomass to APAR. Significant grain yield differences confirmed that soft white and CPS wheats yielded more and responded more to irrigation than hard red or durum wheats. The yield components that were consistently different among cultivars were kernels per head and kernel weight which would be expected to increase if a consistent supply of assimilate was available during grain filling. Soft white and CPS wheats had higher harvest indices than the hard red or durum wheats, particularly under irrigation. Whole-plant phytomass was closely related to APAR and there were few differences among cultivars for RUE. There was no difference in RUE between rain-fed and irrigated treatments, indicating that there was probably no crop water stress on the rain-fed plots. RUE estimates for 1988 were lower than for the succeeding years, indicating an environmental or edaphic stress in that year.Key words: Remote sensing, radiation-use efficiency, yield components
RADIATION USE EFFICIENCY, ABOVE GROUND BIOMASS ACCUMULATION, CANOPY DEVELOPMENT, LEAF AREA-LIGHT INTERCEPTION PROFILES AND RADIATION INTERCEPTION OF SUNFLOWER (Helianthus annuus L.) AS INFLUENCED BY IRRIGATION REGIMEN / INFLUENCIA DEL RÉGIMEN DE IRRIGACIÓN SOBRE LA EFICACIA DEL USO DE LA RADIACIÓN, LA ACUMULACIÓN DE BIOMASA, EL DESAROROLLO DEL CANOPEO, EL ÁREA DE LA HOJA Y LOS PERFILES DE INTERCEPCIÓN DE LUZ Y DE RADIACIÓN EN GIRASOL (Helianthus annuus L.) / EFFICACITÉ DE L’UTILISATION DES RADIATIONS SOLAIRES, ACCUMULATION DE LA BIOMASSE DANS LA PARTIE AÉRIENNE, DÉVELOPPEMENT DE L’OMBRELLE, PROFILS D’INTERCEPTION DE LA LUMIÈRE PAR LA FEUILLE ET INTERCEPTION DES RADIATIONS SOLAIRES CHEZ LE TOURNESOL (Helianthus annuus L.) SOUS L’INFLUENCE D’UN RÉGIME D’IRRIGATION