Anthesis Date Research Articles

Effects of the Vrn-D1b allele associated with facultative growth habit on agronomic traits in common wheat

The Vrn-D1b allele associated with facultative growth habit was recently found in the wheat cultivars mostly distributed in the Yellow and Huai River Valley Winter Wheat Zone (YHWZ) in China. The objective of the present study was to understand the effects of Vrn-D1b on agronomic traits. A population of F3:8 derived lines, having the same allelic variation at all known vernalization loci except Vrn-D1 and photoperiod loci, was developed, from which 50 lines with homozygous Vrn-D1b genotype and 50 lines with homozygous vrn-D1 genotype were evaluated in two environments. The results showed that the Vrn-D1b-carrying lines had significantly higher grain yield (0.3 t ha−1, P ≤ 0.01), more kernels per spike (1.2, P ≤ 0.01), greater thousand kernel weight (0.8 g, P ≤ 0.05), higher seedling height (2.5 cm, P ≤ 0.01) and plant height (2.0 cm, P ≤ 0.01), fewer sterile spikelet number per spike (−0.3, P ≤ 0.01), earlier in both heading (1.0 days, P ≤ 0.01) and anthesis (1.0 days, P ≤ 0.01), compared to the vrn-D1-carrying lines. Grain yield was positively correlated with seedling height (r = 0.47, P ≤ 0.01), plant height (r = 0.37, P ≤ 0.01) and kernel number per spike (r = 0.51, P ≤ 0.01), but negatively correlated with the heading date (r = −0.50, P ≤ 0.01) and anthesis date (r = −0.55, P ≤ 0.01). Path analysis and clustering analysis based on the principal component analysis showed that the yield advantage of Vrn-D1b lines over vrn-D1 lines was attributed primarily to the increased kernel number per spike. The findings indicate that the Vrn-D1b allele had a direct or indirect effect on grain yield.

Combined impact of climate change, cultivar shift, and sowing date on spring wheat phenology in Northern China

Distinct climate changes since the end of the 1980s have led to clear responses in crop phenology in many parts of the world. This study investigated the trends in the dates of spring wheat phenology in relation to mean temperature for different growth stages. It also analyzed the impacts of climate change, cultivar shift, and sowing date adjustments on phenological events/phases of spring wheat in northern China (NC). The results showed that significant changes have occurred in spring wheat phenology in NC due to climate warming in the past 30 years. Specifically, the dates of anthesis and maturity of spring wheat advanced on average by 1.8 and 1.7 day (10 yr)−1. Moreover, while the vegetative growth period (VGP) shortened at most stations, the reproductive growth period (RGP) prolonged slightly at half of the investigated stations. As a result, the whole growth period (WGP) of spring wheat shortened at most stations. The findings from the Agricultural Production Systems Simulator (APSIM)-Wheat model simulated results for six representative stations further suggested that temperature rise generally shortened the spring wheat growth period in NC. Although the warming trend shortened the lengths of VGP, RGP, and WGP, the shift of new cultivars with high accumulated temperature requirements, to some extent, mitigated and adapted to the ongoing climate change. Furthermore, shifts in sowing date exerted significant impacts on the phenology of spring wheat. Generally, an advanced sowing date was able to lower the rise in mean temperature during the different growth stages (i.e., VGP, RGP, and WGP) of spring wheat. As a result, the lengths of the growth stages should be prolonged. Both measures (cultivar shift and sowing date adjustments) could be vital adaptation strategies of spring wheat to a warming climate, with potentially beneficial effects in terms of productivity.

Germplasm Architecture Revealed through Chromosomal Effects for Quantitative Traits in Maize.

Germplasm architecture refers to how favorable alleles for a given trait are distributed across the genome in a germplasm collection. Our objective was to assess germplasm architecture for quantitative traits among US maize ( L.) inbreds. A total of 271 inbreds were genotyped at 28,626 single nucleotide polymorphism (SNP) loci and phenotyped for anthesis date, plant height, starch and protein concentration, and resistance to northern corn leaf blight (NCLB, caused by ). Chromosomal effects were calculated as the sum of the trait effects of SNP alleles carried on a specific chromosome by an inbred. The chromosomal effects were further decomposed into the mean effects of chromosomes, mean effects of inbreds, and chromosome × inbred effects. On average, none of the 10 maize chromosomes was particularly rich or poor in favorable quantitative trait locus (QTL) alleles. However, extreme values of chromosome × inbred effects often involved chromosomes 5 and 8 for anthesis date, chromosomes 1 and 5 for plant height, and chromosome 9 for protein concentration. Inbreds with one or two chromosomes deficient in favorable alleles were candidates for improvement via chromosome-substitution lines. Specific chromosomes for which each of five genetic backgrounds (B73, Mo17, Oh43, A321, and PH207) were rich or poor for unknown favorable alleles were also identified. Chromosomal effects varied widely even when prior association mapping in the same germplasm collection had failed to identify any QTL. Genomewide marker effects, particularly when partitioned into chromosomal effects, provide a simple way to dissect germplasm architecture for quantitative traits.

Awns reduce grain number to increase grain size and harvestable yield in irrigated and rainfed spring wheat.

Genotypic variation in ear morphology is linked to differences in photosynthetic potential to influence grain yield in winter cereals. Awns contribute to photosynthesis, particularly under water-limited conditions when canopy assimilation is restricted. We assessed performance of up to 45 backcross-derived, awned-awnletted NILs representing four diverse genetic backgrounds in 25 irrigated or rainfed, and droughted environments in Australia and Mexico. Mean environment grain yields were wide-ranging (1.38-7.93 t ha(-1)) with vegetative and maturity biomass, plant height, anthesis date, spike number, and harvest index all similar (P >0.05) for awned and awnletted NILs. Overall, grain yields of awned-awnletted sister-NILs were equivalent, irrespective of yield potential and genetic background. Awnletted wheats produced significantly more grains per unit area (+4%) and per spike (+5%) reflecting more fertile spikelets and grains in tertiary florets. Increases in grain number were compensated for by significant reductions in grain size (-5%) and increased frequency (+0.8%) of small, shrivelled grains ('screenings') to reduce seed-lot quality of awnletted NILs. Post-anthesis canopies of awnletted NILs were marginally warmer over all environments (+0.27 °C) but were not different and were sometimes cooler than awned NILs at cooler air temperatures. Awns develop early and represented up to 40% of total spikelet biomass prior to ear emergence. We hypothesize that the allocation of assimilate to large and rapidly developing awns decreases spikelet number and floret fertility to reduce grain number, particularly in distal florets. Individual grain size is increased to reduce screenings and to increase test weight and milling quality, particularly in droughted environments. Despite the average reduction in grain size, awnless lines could be identified that combined higher grain yield with larger grain size, increased grain protein concentration, and reduced screenings.

Analysis of options for increasing wheat (Triticum aestivum L.) yield in south-eastern Australia: The role of irrigation, cultivar choice and time of sowing

Yield of a dryland crop such as wheat is affected by environmental, management and genotypic factors. Field experiments and computer simulations were conducted to understand the effect of supplemental irrigation, type of cultivar and time of sowing (using simulation) on grain yield and quality of two wheat varieties EGA Gregory and Livingston. There was significant effect of variety and watering regime on grain yield, harvest index, kernel weight and number and protein content. The maximum grain yield of 6.10tha−1 was obtained from the irrigated mid-late flowering variety EGA Gregory in the year the crop was sown early. The effect of irrigation on the late flowering variety EGA Gregory was higher than that on the early flowering variety Livingston. The grain water use efficiency of EGA Gregory was higher than that of Livingston in the year it was sown early. APSIM simulations of yield using historical weather data of the past 114 years show that as the sowing date is delayed, the decrease in yield of EGA Gregory becomes higher than that of Livingston and by mid-June sowing, the grain yield of Livingston becomes higher than that of EGA Gregory. As the sowing is delayed, the differences between the anthesis dates, and also grain yields of the two varieties get smaller. The simulation results show that the grain yield of late-sown EGA Gregory and Livingston increases with the amount of in-crop rainfall. However, when sown early, the yield of Livingston decreases with the amount of in-crop rainfall. Farmers need to have different cultivars on hand and sow according to seasonal condition. An early-sown mid-lateflowering cultivar is less risky.

Can genomics assist the phenological adaptation of canola to new and changing environments?

Timing of life history events (phenology) is a key driver for the adaptation of grain crops to their environments. Anthesis (flowering) date is the critical phenological stage that has been most extensively studied. Maximum crop yield is achieved by maximising the duration of the pre-anthesis biomass accumulation phase and hence yield potential, while minimising the risk of water stress and temperature stress (heat and cold) during flowering and grain-filling stages. In this article, we review our understanding of phenology of the valuable oilseed crop canola (oilseed rape, Brassica napus L.) from the perspectives of biophysical modelling and genetics. In conjunction, we review the genomic resources for canola and how they could be used to develop models that can accurately predict flowering date in any given set of environmental conditions. Finally, we discuss how molecular marker tools can help canola breeders to continue to improve canola productivity in the light of climate changes and to broaden its adaptation into new agricultural areas.

Early anthesis and delayed but fast leaf senescence contribute to individual grain dry matter and water accumulation in wheat

The physiological process of how anthesis time and leaf senescence patterns affect individual grain weight of wheat has only been partially elucidated. In this study, a recombinant inbred line mapping population of bread wheat (Triticum aestivum L. ‘Forno’) and its relative spelt (Triticum spelta L. ‘Oberkulmer’), contrasting for phasic development and leaf senescence kinetics, was used to understand the physiological and genetic relationships among anthesis time, leaf senescence, grain filling processes, and individual grain weight. Phenotypic measurements were taken in the field over two growing seasons. The results showed that earlier anthesis and delayed leaf senescence were associated with larger grains. Furthermore, early anthesis and delayed but fast leaf senescence promoted grain filling rate (but shortened its duration), grain water absorption rate and maximum grain water content, while individual grain dry matter and water accumulation displayed strong relationships with individual grain weight. A total of 118 significant quantitative trait loci (QTL) were identified in this mapping population, including six QTL for anthesis dates, 24 for flag leaf senescence, 69 for grain filling traits, and 19 for individual grain weight. Frequent QTL coincidences between these traits were observed on chromosomes 2A, 3B, 4A, 4DL, 5A, 5B, 5DL and 7B. Analysis of allelic effects confirmed the above physiological relationships. Therefore, anthesis time and leaf senescence affect individual grain weight at least partly through their effects on individual grain dry matter and water accumulation, resulting from pleiotropy or tight gene linkages. Slightly early anthesis, and delayed but fast leaf senescence, can be used to maximize individual grain weight and yield potential in wheat.

Evaluating maize growth models “CERES-Maize” and “IXIM-Maize” under elevated temperature conditions

It would be preferable to use a reliable crop growth model for studies on climate change impact assessment. The objectives of this study was to evaluate simulation performance for two maize models, including CERES-Maize and IXIM models, included in the DSSAT model (version 4.6) in terms of phenology and yield. Two early maturing cultivars, Chalok#1 and Junda# 6, were grown under controlled environment in plastic houses at Suwon, Korea. Each cultivar, which was sown at four different date in 2013 and 2014, was subjected to four sets of temperature conditions including ambient (AT), AT+1.5°C, AT+3°C, and AT+5°C. In simulations of phenology under given conditions, the anthesis date and grain filling ratio were underestimated, especially when temperature was unusually high, e.g., in 2013. The maize models also had poor accuracy in grain yield, which resulted from the fact that these models had relatively large errors in simulation of kernel number and kernel weight under elevated temperature conditions. In addition, both models were not able to simulate the drastic decrease of kernel number due to heat stress around flowering periods. These results indicated that two maize models would need improvements in simulation of crop response to supra-optimal temperature before they would be used to assess the impact of the climate change on maize yield. This studies merits further study to improve algorithms in phenology simulation at supraoptimal temperature.

Barrenness and Changes in Tassel Development and Flowering Habit of Hybrid Maize Associated with Low Air Temperatures

Severe barrenness of maize (Zea mays L.) occurred in 2003 in eastern Hokkaido (Konsen region), one of the coldest areas in Japan. In many fields, tassels with few or no spikelets were observed in the cultivar widely grown in this region. The anthesis date was delayed 7 days from the silking date in the cultivar in the field at Konsen Agricultural Experiment Station (KAES). In July, when the tassels were developing at the 6- to the 9-leaf stage, the air temperature and sunshine hours were much lower in 2003 than in the average year. Therefore, we hypothesized that the barrenness resulted from these specific climatic conditions in 2003. To examine this assumption, we applied low temperature treatment (10ºC for 7 days) to the plants of the cultivar widely grown in this region in 2003 at around the 6- to 9-leaf stage in a greenhouse at KAES. Tassels were formed at the 7-leaf stage, and developed but they did not reach their full-size at the 8-leaf stage. The tassel length was shorter when the plants were subjected to the low temperature treatment, especially at the 8-leaf stage. The days from silking to anthesis was increased by the treatment in 2 of the 3 test years. The present results suggest that the cultivar is sensitive to the low air temperature at the 8-leaf stage for the development of tassels and may result in barrenness.

Developmental ideotype in the context of the dual‐purpose use of triticale, barley and durum wheat

AbstractPhenology strongly affects the performance of dual‐purpose (forage plus grain) cereals by defining the rate of leaf and tiller appearance, the duration of the pre‐grazing period and anthesis date. Here, the combined effect of genotypic and environmental variation conditions on anthesis date and the pre‐grazing period in durum wheat, triticale and barley was analysed to define a developmental ideotype for their dual‐purpose use. The extensive variation for the Haun stage reached at the time of apex emergence from the soil surface was associated with variation in the final leaf number, regardless of environment, species and cultivar. The timing of the terminal spikelet stage was the best predictor of apex emergence. The durum wheats tillered poorly, whereas the barleys and the triticales performed comparably in three of the four environments. In general, the higher the final leaf number, the higher the number of leaves and tillers produced by the time of apex emergence, the higher the number of leaves which emerges subsequently. The development of a high number of leaves both before and after apex emergence is advantageous, provided that anthesis is not overly delayed such that flowering and grain fill occur within a period where stressful conditions are likely to occur. Barley developed many leaves and had a low phyllochron, so was identified as the species with the development best suited for dual‐purpose cropping. However, the near simultaneous emergence of the first two tiller apices exposes it to a risk of grazing damage.

Impacts of recent climate warming, cultivar changes, and crop management on winter wheat phenology across the Loess Plateau of China

Crop yields are influenced by growing season length, which are determined by temperature and agronomic management, such as sowing date and changes in cultivars. It is essential to quantify the interaction between climate change and crop management on crop phenology to understand the adaptation of farming systems to climate change. Historical changes in winter wheat phenology have been observed across the Loess Plateau of China during 1981–2009. The observed dates of sowing, emergence, and beginning of winter dormancy were delayed by an average of 1.2, 1.3, and 1.2daysdecade−1, respectively. Conversely, the dates of green-up (regrowth after winter dormancy), anthesis, and maturity advanced by an average of 2.0, 3.7, and 3.1daysdecade−1, respectively. Additionally, the growth duration (sowing to maturity), overwintering period, and vegetative phase (sowing to anthesis) shortened by an average of 4.3, 3.1, and 5.0daysdecade−1, respectively. The changes in phenological stages and phases were significantly negatively correlated with a temperature increase during this time. Differently to most other phase changes, the reproductive phase (anthesis to maturity) prolonged by an average of 0.7daydecade−1, but this was spatially variable. The prolonged reproductive phase was due to advanced anthesis dates and consequently caused the reproductive phase to occur during a cooler part of the season, which led to an extended reproductive phase. Applying a crop simulation model using a field-tested standard cultivar across locations and years indicated that the simulated phenological stages have accelerated with the warming trend more than the observed phenological stages. This indicated that, over the last decades, later sowing dates and the introduction of new cultivars with longer thermal time requirement have compensated for some of the increased temperature-induced changes in wheat phenology.

Managing Wheat From Space: Linking MODIS NDVI and Crop Models for Predicting Australian Dryland Wheat Biomass

This study explored the relationships between moderate resolution imaging spectroradiometer (MODIS) NDVI observations with both measured and simulated fractional green cover (FGrC), leaf area index (LAI), and above ground biomass (AGB) for dryland wheat in Australia. A total of 37 paddocks in north-western Victoria, Australia, were sampled during 2003-2006 for AGB at anthesis, and for FGrC, NDVI (from an active optical sensor), and AGB during 2012. The 2012 FGrC and NDVI measurements were fitted to MODIS NDVI, resulting in positive, linear relationships when the MODIS NDVI values were \leq {\bf 0.80}. Measured AGB was also positively, linearly related to MODIS summed NDVI, resulting in an overall {{\bf R}^{\bf 2}} of 0.81 and root mean square error (RMSE) of 1397 kg/ha. Crop simulations were run for the fourteen paddocks from 2003 to 2006, and six paddocks from 2012. Four crop phenological points were selected to extract corresponding NDVI and simulated crop parameters: emergence, peak LAI, the mid-point between emergence and peak LAI, and anthesis. Linear models were fit between the MODIS NDVI and simulated values of FGrC, LAI, and AGB. Overall, the highest {{\bf R}^{\bf 2}} values corresponded to using all of the dates for FGrC ({{\bf R}^{\bf 2}} = {\bf 0.82}) and AGB ({{\bf R}^{\bf 2}} = {\bf 0.92}), and anthesis dates for LAI ({{\bf R}^{\bf 2}} = {\bf 0.74}). For FGrC and AGB, the RMSE with simulated parameters were comparable or better than the equivalent results from the in situ measurements (note that there were no LAI in situ measurements to compare with). The results support the notion for extending the value of the MODIS NDVI using crop simulation models. The combination of remotely sensed and simulation data might offer regional maps of spatial AGB and ultimately grain yield, which would have high value for research, resource management, policy, and potentially, crop management.

Determining optimum sowing date of wheat using CSM-CERES-Wheat model

Wheat production in the south of Khuzestan, Iran is constrained by heat stress for late sowing dates. For optimization of yield, sowing at the appropriate time to fit the cultivar maturity length and growing season is critical. Crop models could be used to determine optimum sowing window for a locality. The objectives of this study were to evaluate the Cropping System Model (CSM)-CERES-Wheat for its ability to simulate growth, development, grain yield of wheat in the tropical regions of Iran, and to study the impact of different sowing dates on wheat performance. The genetic coefficients of cultivar Chamran were calibrated for the CSM-CERES-Wheat model and crop model performance was evaluated with experimental data. Wheat cultivar Chamran was sown on different dates, ranging from 5 November to 9 January during 5years of field experiments that were conducted in the Khuzestan province, Iran, under full and deficit irrigation conditions. The model was run for 8 sowing dates starting on 25 October and repeated every 10days until 5 January using long-term historical weather data from the Ahvaz, Behbehan, Dezful and Izeh locations. The seasonal analysis program of DSSAT was used to determine the optimum sowing window for different locations as well. Evaluation with the experimental data showed that performance of the model was reasonable as indicated by fairly accurate simulation of crop phenology, biomass accumulation and grain yield against measured data. The normalized RMSE were 3%, 2%, 11.8%, and 3.4% for anthesis date, maturity date, grain yield and biomass, respectively. Optimum sowing window was different among locations. It was opened and closed on 5 November and 5 December for Ahvaz; 5 November and 15 December for Behbehan and Dezful;and 1 November and 15 December for Izeh, respectively. CERES-Wheat model could be used as a tool to evaluate the effect of sowing date on wheat performance in Khuzestan conditions. Further model evaluations might also be needed for other cultivars which are released for this region.

Genetic variation for the duration of pre-anthesis development in durum wheat and its interaction with vernalization treatment and photoperiod.

A recombinant inbred durum wheat population was grown under three contrasting regimes: long days following vernalization (LDV), long days without vernalization (LD), and short days following vernalization (SDV). The length of several pre-anthesis stages and the number of leaves and the phyllochron were measured. Different groups of genes were involved in determining the phenology in the three treatments, as demonstrated by a quantitative trait locus (QTL) analysis. The length of the period required to reach the terminal spikelet stage was correlated with the time to anthesis only in the case of LDV- and LD-grown plants where the timing of anthesis depended on the final leaf number. However, for SDV-grown plants, anthesis date was more dependent on the length of the period between the terminal spikelet stage and anthesis and was independent of leaf number. The involvement of the phyllochron in determining the duration of pre-anthesis development was also treatment-dependent. QTL mapping of the various flowering time associated traits uncovered some novel loci (such as those associated with the phyllochron), in addition to confirming the presence of several well-established loci.

Climate change increases risk of fusarium ear blight on wheat in central China

AbstractTo estimate potential impact of climate change on wheat fusarium ear blight (FEB), simulated weather for the A1B climate change scenario was input into a model for estimating FEB in central China. In this article, a logistic weather‐based regression model for estimating incidence of wheat FEB in central China was developed, using up to 10 years (2001–2010) of disease, anthesis date and weather data available for 10 locations in Anhui and Hubei provinces. In the model, the weather variables were defined with respect to the anthesis date for each location in each year. The model suggested that incidence of FEB is related to number of days of rainfall in a 30‐day period after anthesis and that high temperatures before anthesis increase the incidence of disease. Validation was done to test whether this relationship was satisfied for another five locations in Anhui province with FEB data for 4–5 years but no nearby weather data, using simulated weather data obtained employing the regional climate modelling system PRECIS. How climate change may affect wheat anthesis date and FEB in central China was investigated for period 2020–2050 using wheat growth model Sirius and climate data simulated using PRECIS. The projection suggested that wheat anthesis dates will generally be earlier and FEB incidence will increase substantially for most locations.

The variation of the water deficit during the winter wheat growing season and its impact on crop yield in the North China Plain

The North China Plain (NCP) is one of the main agricultural areas in China. However, it is also widely known for its water shortages, especially during the winter wheat growing season. Recently, climate change has significantly affected the water environment for crop growth. Analyzing the changes in the water deficit, which is only affected by climate factor, will help to improve water management in the NCP. In this study, the Decision Support System for Agrotechnology Transfer (DSSAT) was used to investigate the variations in the water deficit during the winter wheat growing season from 1961 to 2010 in 12 selected stations in the NCP. To represent the changes in the water deficit without any artificial affection, the rainfed simulation was used. Over the past 50 years, the average temperature during the winter wheat growing season increased approximately 1.42 °C. The anthesis date moved forward approximately 7-10 days and to late April, which increased the water demand in April. Precipitation in March and May showed a positive trend, but there was a negative trend in April. The water deficit in late April and early May became more serious than before, with an increasing trend of more than 0.1 mm/year. In addition, because the heading stage, which is very important to crop yield of winter wheat, moved forward, the impact of water deficit in late April was more serious to crop yield.

Responses of wheat growth and yield to climate change in different climate zones of China, 1981–2009

The experiment observations at 120 agricultural meteorological stations spanning from 1981 to 2009 across China were used to accelerate understandings of the response of wheat growth and productivity to climate change in different climate zones, with panel regression models. We found climate during wheat growth period had changed significantly during 1981–2009, and the change had caused measurable impacts on wheat growth and yield in most of the zones. Wheat anthesis date and maturity date advanced significantly, and the lengths of growth period before anthesis and whole growth period were significantly shortened, however the length of reproductive growth period was significantly prolonged despite of the negative impacts of temperature increase. The increasing adoption of cultivars with longer reproductive growth period offset the negative impacts of climate change and increased yield. Changes in temperature, precipitation and solar radiation in the past three decades jointly increased wheat yield in northern China by 0.9–12.9%, however reduced wheat yield in southern China by 1.2–10.2%, with a large spatial difference. Our studies better represented crop system dynamics using detailed phenological records, consequently better accounted for adaptations such as shifts in sowing date and crop cultivars photo-thermal traits when quantifying climate impacts on wheat yield. Our findings suggest the response of wheat growth and yield to climate change is underway in China. The changes in crop system dynamics and cultivars traits have to be sufficiently taken into account to improve the prediction of climate impacts and to plan adaptations for future.

Relationship between Planting Date, Growing Degree Days and the Winter Rye (Secale cereale L.) Variety “Rymin” in Minnesota

This study evaluated the influence of fall planting date on winter rye (Secale cereale L.) anthesis at three Minnesota locations for five dates from late August through October. This represents the time when fall-planted cover crops would likely be seeded in Minnesota. Earliness to anthesis is important in organic production systems where timing of rye management is affected by rye growth stage. The relationships among growing degree days (GDD), growth stage, and aboveground biomass were evaluated to predict how these factors influence anthesis date and how late in the fall rye could be planted without delaying anthesis. The study occurred in 2006 and 2007, which happened to have abnormally warm and cool growing seasons, with the earliest anthesis dates in 2007 being 25 May, 28 May, and 5 June at St. Paul, Lamberton, and Roseau, respectively, and dates in 2008 of 10 June, 11 June, and 17 June. Our results indicate that there was no fall biomass requirement but also that it was critical to accumulate at least 309 GDD in the fall so as not to delay spring anthesis. This information enables growers to choose appropriate planting dates for rye that will not delay anthesis. The optimal planting date corresponded to planting by late September (∼20) in southern and early September (∼8) in northern Minnesota.

Analysis of variability, heritability, and genetic advance in seed yield and related traits of orchardgrass (Dactylis glomerata L.) populations

Orchardgrass (Dactylis glomerata L.) genotypes from different natural sources in the Eastern Anatolian Region of Turkey were clonally evaluated to study genetic variation and the relationships between seed yield and its components using a randomized complete block design. Results showed very significant genotypic variances among genotypes for all traits, including agronomic (seed, dry matter, and biological yields), morphological (plant height; panicle length; crown diameter; numbers of fertile, sterile, and total stems; and stem intensity), physiological (percent fertile stems, harvest and fertility indexes), and phenological (heading and anthesis dates) traits, as well as genotype × year interaction variances. Genotypic components were the main contributor to phenotypic variation of all traits (except physiologic traits, stem intensity, and number of sterile stems), resulting in high broad-sense heritability (>50%). Agromorphological and physiological traits had greater phenotypic (PCV), genotypic (GCV), and environmental coefficients of variation, while these were lower for phenological traits. After the phenological traits, plant height, crown diameter, and panicle length were the least variable traits, while stem intensity and fertility index were highly variable. Heritability estimates increased as GCV values approached PCV values. Expected genetic gain greatly increased as heritability estimates and PCV both increased, rather than heritability values alone. The first 5 principle components accounted for 84.90% of total variance. All agromorphological traits (except number of sterile stems) and fertile stem percentage were primary sources of variation of the PC1 axis, while harvest and fertility indexes were for PC2. Out of the 4 clusters, genotypes in cluster 4 of higher seed yield were faster in aboveground biomass accumulation. They also had the best agromorphological traits coupled with early maturity. Seed yield greatly increased as aerial biomass increased without any change in harvest index, but there was a significant decrease in fertility index. It was concluded that selection for dry matter yield could result in a simultaneous increase in seed yield.

Genetic changes in agronomic and phenologic traits of Iranian wheat cultivars grown in different environmental conditions

Information on genetic gains in different traits of wheat is important in breeding cultivars with improved grain yield. Changes in agronomic and phenologic traits resulting from breeding in Iranian wheat cultivars were studied. Eighty one wheat cultivars released from 1930 to 2006 were examined under well watered (WW) and terminal drought stress (DS) conditions at Karaj during 2007–2008 and 2008–2009, and under WW conditions in the Moghan region during 2010–2011. Improvements in grain yield were 31 and 20 kg ha−1 y−1 in Karaj (under WW and DS conditions) and at Moghan, respectively. In response to DS, grain yield loss was less in modern than in old wheat cultivars, suggesting that, in line with grain yield improvement, breeding has increased the resistance of wheat to terminal DS. Significant genetic changes over time were found for HI, grain number per square meter and spike dry weight at anthesis in all conditions tested. No changes were observed for above–ground dry matter and 1,000 grain weight. Dates of booting and anthesis decreased significantly from old to modern cultivars, and the amount of decrease was more evident at Karaj. Karaj experiments showed that length of the grain filling period, the anthesis—maturity phase, was increased significantly by breeding. However, this trend was not found in the Moghan experiment. These findings indicate that there was an interaction between genetic gains in different traits and environmental conditions in which the genetic gains were studied.