The Effects of Climate Change on the Planting Boundary and Potential Yield for Different Rice Cropping Systems in Southern China

Based on climate data from 254 meteorological stations, this study estimated the effects of climate change on rice planting boundaries and potential yields in the southern China during 1951-2010. The results indicated a signiifcant northward shift and westward expansion of northern boundaries for rice planting in the southern China. Compared with the period of 1951-1980, the average temperature during rice growing season in the period of 1981-2010 increased by 0.4＆#176;C, and the northern planting boundaries for single rice cropping system （SRCS）, early triple cropping rice system （ETCRS）, medium triple cropping rice system （MTCRS）, and late triple cropping rice system （LTCRS） moved northward by 10, 30, 52 and 66 km, respectively. In addition, compared with the period of 1951-1980, the suitable planting area for SRCS was reduced by 11%during the period of 1981-2010. However, the suitable planting areas for other rice cropping systems increased, with the increasing amplitude of 3, 8, and 10%for ETCRS, MTCRS and LTCRS, respectively. In general, the light and temperature potential productivity of rice decreased by 2.5%. Without considering the change of rice cultivars, the northern planting boundaries for different rice cropping systems showed a northward shift tendency. Climate change resulted in decrease of per unit area yield for SRCS and the annual average yields of ETCRS and LTCRS. Nevertheless, the overall rice production in the entire research area showed a decreasing trend even with the increasing trend of annual average yield for MTCRS.

A novel Effective Panicle Number per Plant 4 haplotype enhances grain yield by coordinating panicle number and grain number in rice

Increasing effective panicle number per plant(EPN)is one approach to increase yield potential in rice.However,molecular mechanisms underlying EPN remain unclear.In this study,we integrated mapbased cloning and genome-wide association analysis to identify the EPN4 gene,which is allelic to NARROW LEAF1(NAL1).Overexpression lines containing the Teqing allele(TQ)of EPN4 had significantly increased EPN.NIL-EPN4^(TQ) in japonica(geng)cultivar Lemont(LT)exhibited significantly improved EPN but decreased grain number and flag leaf size relative to LT.Haplotype analysis indicated that accessions with EPN4-1 had medium EPN,medium grain number,and medium grain weight,but had the highest grain yield among seven haplotypes,indicating that EPN4-1 is an elite haplotype of EPN4 for positive coordination of the three components of grain yield.Furthermore,accessions carrying the combination of EPN4-1 and haplotype GNP1-6 of GNP1 for grain number per panicle showed higher grain yield than those with other allele combinations.Therefore,pyramiding of EPN4-1 and GNP1-6 could be a preferred approach to obtain high yield potential in breeding.

Cultivar selection can increase yield potential and resource use efficiency of spring maize to adapt to climate change in Northeast China

Northeast China (NEC) is one of the major maize production areas in China.Agro-climatic resources have obviously changed,which will seriously affect crop growth and development in this region.It is important to investigate the contribution of climate change adaptation measures to the yield and resource use efficiency to improve our understanding of how we can effectively ensure high yield and high efficiency in the future.In this study,we divided the study area into five accumulated temperature zones (ATZs) based on growing degree days (GDD).Based on the meteorological data,maize data (from agrometeorological stations) and the validated APSIM-Maize Model,we first investigated the spatial distributions and temporal trends of maize potential yield of actual planted cultivars,and revealed the radiation use efficiency (RUE) and heat resource use efficiency (HUE) from 1981 to 2017.Then according to the potential growing seasons and actual growing seasons,we identified the utilization percentages of radiation (P_R) resource and heat resource (P_H) for each ATZ under potential production from 1981 to 2017.Finally,we quantified the contributions of cultivar changings to yield,P_R and P_H of maize.The results showed that during the past 37 years,the estimated mean potential yield of actual planted cultivars was 13 649 kg ha^(–1),ranged from 11 205 to 15 257 kg ha^(–1),and increased by 140 kg ha^(–1) per decade.For potential production,the mean values of RUE and HUE for the actual planted maize cultivars were 1.22 g MJ^(–1) and 8.58 kg (℃ d)^(–1) ha^(–1).RUE showed an increasing tendency,while HUE showed a decreasing tendency.The lengths of the potential growing season and actual growing season were 158 and 123 d,and increased by 2 and 1 d per decade.P_R and P_H under potential production were 82 and 86%,respectively and showed a decreasing tendency during the past 37 years.This indicates that actual planted cultivars failed to make full use of climate resources.However,results from the adaptation assessments indicate that,adoption of cultivars with growing season increased by 2–11 d among ATZs caused increase in yield,P_R and P_H of 0.6–1.7%,1.1–7.6% and 1.5–8.9%,respectively.Therefore,introduction of cultivars with longer growing season can effectively increase the radiation and heat utilization percentages and potential yield.

Optimizing water management practice to increase potato yield and water use efficiency in North China

Potato is one of the staple food crops in North China.However,potato production in this region is threatened by the low amount and high spatial-temporal variation of precipitation.Increasing yield and water use efficiency(WUE)of potato by various water management practices under water resource limitation is of great importance for ensuring food security in China.However,the contributions of different water management practices to yield and WUE of potato have been rarely investigated across North China’s potato planting region.Based on meta-analysis of field experiments from the literature and model simulation,this study quantified the potential yields of potatoes without water and fertilizer limitation,and yield under irrigated and rainfed conditions,and the corresponding WUEs across four potato planting regions including the Da Hinggan Mountains(DH),the Foothills of Yanshan hilly(YH),the North foot of the Yinshan Mountains(YM),and the Loess Plateau(LP)in North China.Simulated average potential potato tuber dry weight yield by the APSIM-Potato Model was 12.4 t ha^(–1)for the YH region,11.4 t ha^(–1)for the YM region,11.2 t ha^(–1)for the DH region,and 10.7 t ha^(–1)for the LP region,respectively.Observed rainfed potato tuber dry weight yield accounted for 61,30,28 and 24%of the potential yield in the DH,YH,YM,and LP regions.The maximum WUE of 2.2 kg m^(–3)in the YH region,2.1 kg m^(–3)in the DH region,1.9 kg m^(–3)in the YM region and 1.9 kg m^(–3)in the LP region was achieved under the potential yield level.Ridge-furrow planting could boost yield by 8–49%and WUE by 2–36%while ridge-furrow planting with film mulching could boost yield by 35–89%and WUE by 7–57%across North China.Our study demonstrates that there is a large potential to increase yield and WUE simultaneously by combining ridge-furrow planting with film mulching and supplemental irrigation in different potato planting regions with limited water resources.

Yield potential and nitrogen use efficiency of China's super rice

In 1996, a mega project that aimed to develop rice varieties with super-high yield potential （super rice） was launched by the Ministry of Agriculture （MOA） in China using a combination of the ideotype approach and intersubspecific heterosis. Significant progress has been made in the last two decades, with a large number of super rice varieties being approved by the MOA and the national average grain yield being increased from 6.21 t ha^-1 in 1996 to 6.89 t ha^-1 in 2015. The increase in yield potential of super rice was mainly due to the larger sink size which resulted from larger panicles. Moreover, higher photosynthetic capacity and improved root physiological traits before heading contributed to the increase in sink size. However, the poor grain filling of the later-flowering inferior spikelets and the quickly decreased root activity of super rice during grain filling period restrict the achievement of high yield potential of super rice. Furthermore, it is widely accepted that the high yield potential of super rice requires a large amount of N fertilizer input, which has resulted in an increase in N consumption and a decrease in nitrogen use efficiency （NUE）, although it remains unclear whether super rice per se is responsible for the latter. In the present paper, we review the history and success of China＇s Super Rice Breeding Pro- gram, summarize the advances in agronomic and physiological mechanisms underlying the high yield potential of super rice, and examine NUE differences between super rice and ordinary rice varieties. We also provide a brief introduction to the Green Super Rice Project, which aims to diversify breeding targets beyond yield improvement alone to address global concerns around resource use and environmental change. It is hoped that this review will facilitate further improvement of rice production into the future.

Yield potential and stability in super hybrid rice and its production strategies

China＇s Super Hybrid Rice Breeding Program has made significant progress over the past two decades. In this paper, we reviewed our studies on the yield potential and stability in super hybrid rice and discussed the strategies for super hybrid rice production. The results of our studies show that rice yield potential has been increased by 12% in super hybrid cultivars as compared with ordinary hybrid and inbred cultivars. The higher grain yields in super hybrid rice cultivars are attributed to larger panicle size coupled with higher biomass production or higher harvest index. However, grain yields in super hybrid rice cultivars vary widely among locations depending on soil and climatic factors. Therefore, it is important to tailor target yield to local conditions in super hybrid rice production. The target yield for super hybrid rice production can be determined by the average yield method or the regression model method. Improving soil quality is critical to achieving the target yield in super hybrid rice production. Favorable crop rotations such as rice-oilseed rape and novel soil management practices, such as biochar addition, are effective approaches to improve soil quality. It is needed to develop simplified cultivation tech- nologies for super hybrid rice to meet the changes in socioeconomic environments during the period of transition. There are such technologies as no-tillage direct seeding and mechanized transplanting at high hill density with single seedling per hill.

Suitable growing zone and yield potential for late-maturity type of Yongyou japonica/indica hybrid rice in the lower reaches of Yangtze River, China

Late-maturity type of Yongyou japonica/indica hybrids series （LMYS） have shown great yield potential, and are being widely planted in the lower reaches of Yangtze River, China. Knowledge about suitable growing zone and evaluation of yield advantage is of practicall importance for LMYS in this region. Fifteen LMYS, two high-yielding inbred japonica check varieties （CK-J） and two high-yielding hybrid indica check varieties （CK-I） were grown at Xinghua （119.57°E, 33.05°N） of Lixiahe region, Yangzhou （119.25°E, 32.30°N）of Yanjiang region, Changshu （120.46°E, 31.41°N）of Taihu Lake region, and Ningbo （121.31°E, 29.45°N） of Ningshao Plain in 2013 and 2014. The results showed that maturity dates of the 15 were later than the secure maturity date at Xinghua and 6, 14 and 15 LMYS were mature before the secure maturity date at Yangzhou, Changshu and Ningbo, respectively. One variety was identified as high-yielding variety among LMYS （HYYS） at Yangzhou, 8 HYYS in 201：3 and 9 HYYS in 2014 at Changshu, 9 HYYS at Ningbo. HYYS here referred to the variety among LMYS that was mature before the secure maturity date and had at least 8% higher grain yield than both CK-J and CK-I at each experimental site. Grain yield of HYYS at each experimental site was about 12.0 t ha-1 or higher, and was significantly higher than CK varieties. High yield of HYYS was mainly attributed to larger sink size due to more spikelets per panicle. Plant height of HYYS was about 140 cm, and was significantly higher than check varieties. Significant positive correlations were recorded between duration from heading to maturity stage and grain yield, and also between whole growth periods and grain yield. HYYS had obvious advantage over check varieties in biomass accumulation and leaf area duration from heading to maturity stage. Comprehensive consideration about safe matudty and yield performance of LMYS at each experimental site, Taihu Lake region （representative site Changshu） and Ningshao Plain （representative site Ningbo） were thought suitable growing zones for LMYS in the lower reaches of Yangtze River. The main factors underlying high yield ofHYYS were larger sink size, higher plant height, longer duration from heading to maturity stage and whole growth periods, and higher biomass accumulation and leaf area duration during grain filling stage.

Heat units-based potential yield assessment for cotton production in Uzbekistan

Cotton yields in Uzbekistan are significantly lower than those in similar agro-climatic regions,requiring the estimation of crop potential and baseline yield to track progress of production enhancement efforts.The current study estimated potential cotton development and baseline yield(maximum given no production constraints)using total heat units(THU)and potential cotton yield(PCY),respectively.Calculations were based on heat units(HU)for a 30-year(1984-2013)period.Long-term average THU and PCY,as well as PCY at three different exceedance probabilities(p=0.99,p=0.80,and p=0.75),were calculated for 21 selected weather stations across cotton-growing areas of Uzbekistan.After confirmation that the current planting date(April 15)is optimal,a comparison of THU with the accepted cotton production cutoff threshold(1444°C)suggested that areas with lower elevations and latitudes are more appropriate for cotton production.Yield gap analysis(relative difference between long-term average PCY and actual yields)confirmed that Uzbekistan cotton production is below potential,while the spatial distribution of yield gaps outlined where efforts should be targeted.Areas near the stations of Nukus,Kungrad,Chimbay,and Syrdarya should be further investigated as benefit/cost ratio is highest in these areas.A comparison between state-set yield targets and PCY values,taking into account climatic variability,suggested that all areas except Jaslyk,Nurata,and Samarkand have safe,appropriate targets.These results present a starting-point to aid in strategic actions for Uzbekistan cotton production improvement.

Optimizing Sorghum Productivity Using Balanced Fertilizers on Dryland

Sorghum is thefifth most required cereal crop globally.Sorghum bicolor has the advantage of being adaptive to both lowland and dryland,with drought-tolerant and wide adaptability.The low nutrient availability in dryland requires additional effective fertilizers to increase sorghum productivity.The research aimed to assess the appli-cation of organic,inorganic,and biofertilizers for sorghum productivity on dryland.Research in Central Java,Indonesia as dryland sorghum areas,from November 2022 to February 2023.The experiment cooperates with the farmers in a split-plot design,the main plot was two varieties and subplots of four fertilizers.The enhanced sorghum yield(21.38%–36.06%)with combined fertilizer was greater than the existing fertilization.Nutrient con-trol does not rely on inorganic fertilizers but also on applying biofertilizers.The sorghum farming economic value farming indicated that combinations of fertilizer treatments and varieties provide benefits of USD 929.81–1955.81 with a revenue-cost ratio(R/C)value>1.Sorghum is an essential food commodity that faces the threat of the global crisis and an unfavorable environment.This study indicated balanced fertilizers could provide suffi-cient nutrients to the soil and increase nutrient absorption availability for sorghum growth and productivity.Balanced fertilization increases the uptake of N,P,and K nutrients correlates with an increase in yield of 21.38%–36.06%.

Towards sustainable intensification of apple production in China—Yield gaps and nutrient use effi ciency in apple farming systems

China is in a dominant position in apple production globally with both the largest apple growing area and the largest export of fresh apple fruits. However, the annual productivity of China＇s apple is significantly lower than that of other dominant apple producing countries. In addition, apple production is based on excessive application of chemical fertilizers and the nutrient use efficiency （especially nitrogen） is therefore low and the nutrient emissions to the environment are high. Apple production in China is considerably contributes to farmers＇ incomes and is important as export product. There is an urgent need to enhance apple productivity and improve nutrient use efficiencies in intensive apple production systems in the country. These can be attained by improved understanding of production potential, yield gaps, nutrient use and best management in apple orchards. To the end, priorities in research on apple production systems and required political support are described which may lead to more sustainable and environmental-friendly intensification of apple production in China.

Crop Yield Forecasted Model Based on Time Series Techniques

Traditional studies on potential yield mainly referred to attainable yield： the maximum yield which could be reached by a crop in a given environment. The new concept of crop yield under average climate conditions was defined in this paper, which was affected by advancement of science and technology. Based on the new concept of crop yield, the time series techniques relying on past yield data was employed to set up a forecasting model. The model was tested by using average grain yields of Liaoning Province in China from 1949 to 2005. The testing combined dynamic n-choosing and micro tendency rectification, and an average forecasting error was 1.24%. In the trend line of yield change, and then a yield turning point might occur, in which case the inflexion model was used to solve the problem of yield turn point.

The CCT domain-containing gene family has large impacts on heading date, regional adaptation, and grain yield in rice

There are 41 members of the CCT（CO, CO-like, and TOC1） domain-containing gene family in rice, which are divided into three subfamilies： COL（CONSTANS-like）, CMF（CCT motif family）, and PRR（pseudoresponse regulator）. The first flowering gene to be isolated by map-based cloning, Heading date 1（Hd1）, which is the orthologue of CO in rice, belongs to COL. The central regulator of plant development, Ghd7, belongs to CMF. The major role in controlling rice distribution to high latitudes, Ghd7.1/PRR37, belongs to PRR. Both of Hd1, Ghd7 and Ghd7.1 simultaneously control grain number, plant height, and the heading date. To date, 13 CCT family genes from these three subfamilies have been shown to regulate flowering. Some of them have pleiotropic effects on grain yield, plant height, and abiotic stresses, and others function as circadian oscillators. There are two independent photoperiod flowering pathways that are mediated by GI-Hd1-Hd3 a/RFT and GI-Ehd1-Hd3 a/RFT in rice. CCT family genes are involved in both pathways. The latest study reveals that protein interaction between Hd1 and Ghd7 integrates the two pathways. CCT family genes are rich in natural variation because rice cultivars have been subjected to natural and artificial selection for different day lengths in the process of domestication and improvement. Alleles of several crucial CCT family genes such as Hd1, Ghd7, and Ghd7.1 exhibit geographic distribution patterns and are highly associated with yield potentials. In addition, CCT family genes are probably involved in the responses to abiotic stress, which should be emphasized in future work. In general, CCT family genes play important roles in regulating flowering, plant growth, and grain yield. The functional identification and elucidation of the molecular mechanisms of CCT family genes would help construct a flowering regulatory network and maximize their contribution to rice production.

Reducing maize yield gap by matching plant density and solar radiation

Yield gap exists because the current attained actual grain yield cannot yet achieve the estimated yield potential. Chinese high yield maize belt has a wide span from east to west which results in different solar radiations between different regions and thus different grain yields. We used multi-site experimental data, surveyed farmer yield data, the highest recorded yield data in the literatures, and simulations with Hybrid-Maize Model to assess the yield gap and tried to reduce the yield gap by matching the solar radiation and plant density. The maize belt was divided into five regions from east to west according to distribution of accumulated solar radiation. The results showed that there were more than 5.8 Mg ha^(–1) yield gaps between surveyed farmer yield and the yield potential in different regions of China from east to west, which just achieved less than 65% of the yield potential. By analyzing the multi-site density experimental data, we found that the accumulated solar radiation was significantly correlated to optimum plant density which is the density with the highest yield in the multi-site density experiment(y=0.09895 x–32.49, P<0.01), according to which the optimum plant densities in different regions from east to west were calculated. It showed that the optimum plant density could be increased by 60.0, 55.2, 47.3, 84.8, and 59.6% compared to the actual density, the grain yield could be increased by 20.2, 18.3, 10.9, 18.1, and 15.3% through increasing plant density, which could reduce the yield gaps of 33.7, 23.0, 13.4, 17.3, and 10.4% in R(region)-1, R-2, R-3, R-4, and R-5, respectively. This study indicates that matching maize plant density and solar radiation is an effective approach to reduce yield gaps in different regions of China.

Breaking wheat yield barriers requires integrated efforts in developing countries

Most yield progress obtained through the so called ＂Green Revolution＂, particularly in the irrigated areas of Asia, has reached a limit, and major resistance genes are quickly overcome by the appearance of new strains of disease causing organisms.New plant stresses due to a changing environment are difficult to breed for as quickly as the changes occur.There is consequently a continual need for new research programs and breeding strategies aimed at improving yield potential, abiotic stress tolerance and resistance to new, major pests and diseases.Recent advances in plant breeding encompass novel methods of expanding genetic variability and selecting for recombinants, including the development of synthetic hexaploid, hybrid and transgenic wheats.In addition, the use of molecular approaches such as quantitative trait locus（QTL） and association mapping may increase the possibility of directly selecting positive chromosomal regions linked with natural variation for grain yield and stress resistance.The present article reviews the potential contribution of these new approaches and tools to the improvement of wheat yield in farmer＇s fields, with a special emphasis on the Asian countries, which are major wheat producers, and contain the highest concentration of resource-poor wheat farmers.

Analysis of Precipitation Resource and Weather Modification Potential in Anyang

Using ground water vapor pressure and precipitation data at four times of one day during 1985- 2014 in each county（ city） of Anyang,precipitable water at each station was calculated,and temporal-spatial distribution of atmospheric maximum precipitable water and its change trend over the years in the city were analyzed. Results showed that atmospheric maximum precipitable water in Anyang City had the characteristics of summer far more than winter,autumn slightly higher than spring,west and south more,and east and north less,and presented the increasing trend year by year. We further analyzed the characteristic of monthly rainfall enhancement potential in each county,and mean in whole year was 80%. In spring and winter,rainfall enhancement potential in the west was bigger than east,while rainfall enhancement potential in the east was bigger than west in summer and autumn. The research provides reference basis for rationally carrying out artificial rainfall work,which could effectively ease uneven temporal-spatial distribution problem of water resource in Anyang City.

Simulation of China’s potential rice yields by coupling land system evolution and climate change

Land systems and climate,which are the key elements of agricultural production and key drivers of crop yields,affect the quality of arable land.However,a quantitative model to reveal the mechanism of how potential grain yields are affected by macro-scale arable land evolution and climate change has not yet been developed.In this study,we constructed a Grey Prediction Model-Future Land Use Simulation(GM-FLUS),which combined land system evolution with climate change data,to simulate changes in China’s land system over the next 40 years.We improved the Global Agro-Ecological Zone(GAEZ)model,estimated China’s potential rice yields and their spatial distribution in the next 40 years under four scenarios(shared socioeconomic pathway SSP1-2.6,SSP2-4.5,SSP3-7.0,and SSP5-8.5)of the Sixth International Coupling Model Intercomparison Project,analysed the spatiotemporal variations in the potential rice yields and their drivers,and provided appropriate suggestions for increasing rice yields.The simulation results indicated an increase in China’s potential rice yields during 2020–2060 under the SSP1-2.6 and SSP3-7.0 scenarios and a decrease under the SSP2-4.5 and SSP5-8.5 scenarios.Moreover,China’s development strategy of“achieving carbon peaking by 2030 and carbon neutrality by 2060”was similar to the SSP1-2.6 scenario,under which rice yields were relatively stable.Furthermore,under China’s arable land protection policy,China’s paddy field area will change slightly during 2020–2060,and potential rice yields will be influenced by climate.Under the four climate change scenarios,air temperature increased and was negatively correlated with potential rice yields in main rice-producing regions.Additionally,potential rice yields were positively correlated with precipitation,which increased stably under the SSP1-2.6 and SSP3-7.0scenarios and decreased under the SSP2-4.5 and SSP5-8.5 scenarios.These results suggest that the development of heat-resistant rice varieties and the implementation of measures that will mitigate the impacts of future temperature increases on rice yields are important for the conservation of paddy fields.Additionally,improving irrigation and drainage facilities is necessary to irrigate drought-prone paddy fields and drain flooded water.

Advances in Photosynthetic Characteristics of Peanut

Peanut is an important oil crop and economic crop in China. In this pa- per, the status and advances of the factors affecting peanut photosynthesis, such as light intensity, temperature, carbon dioxide concentration, water deficit and fertility situation, the relationship between peanut photosynthetic rate and different cultivation system, and the relationship between peanut photosynthetic rate and varieties yield potential, were deeply reviewed, expecting to provide references for peanut variety breeding with high photosynthetic efficiency and high yield potential.

A MODEL OF POTENTIAL MAIZE YIELD IN RELATION TO ACCUMULATED TEMPERATURE AND ITS APPLICATION IN ASSESSING THE IMPACT OF CLIMATIC CHANGE

Plant breeding for different maturities plays an important role in agricultural strategies for adaptation to climatic change.In this paper using the data of ten corn hybrids with early,medium and late maturities and different leaf angles, including erectophile and planophile,observed in Beijing,Yanqing,Tai'an,Gongzhuling of Jilin and Shihezi of Xinjiang,a normal growing function was derived on the basis of the main pattern of accumulated dry matter: W=1/1+exp(8.56-13.52u) In accordance with the function authors built up a model of potential maximum biomass which depends on accumulated temperature B_(max)=100+1.11∑~T_m(kg/mu)(1ha=15mu) The model was applied to estimate the potential corn yield of hybrids with different maturities,and applications of the results in assessing the impact of climatic change are discussed.

Production potential and yield gaps of summer maize in the Beijing-Tianjin-Hebei Region

Crop potential productivity is a key index of scientifically appraising crop production and land population-supporting capacity. This study firstly simulated the potential and waterlimited yield of summer maize in the Beijing-Tianjin-Hebei （BTH） region using WOFOST model with meteorological data of 40 years, and then analyzed yield gaps between the actual and potential yield based on statistical data at county level. The potential and water-limited yield of summer maize in the BTH region is 6854–8789 kg/hm2 and 6434–8741 kg/hm2, and the weighted average for whole region is 7861 kg/hm2 and 7185 kg/hm2, respectively. The simulated yields gradually decrease from northeast to southwest with changes in climatic conditions particularly temperature and precipitation. Annual variation of potential yield is higher in the central and southern parts than the northeastern part. Compared to potential yield, the water-limited yield has higher coefficient of variation （CV）, because of precipitation effects. The actual yield of summer maize was 2537–8730 kg/hm2, regionally averaged at 5582 kg/hm2, about 70% of the potential yield, implying that the region has room to increase the yield by improving crop management and irrigation systems.

Physiological traits contributed to the recent increase in yield potential of winter wheat from Henan Province, China

This experiment aims to test the traits responsible for the increase in yield potential of winter wheat released in Henan Province, China. Seven established cultivars released in the last 20 years and three advanced lines were assayed. The results showed that grain yield was positively correlated with harvest index（HI）, kernel number per square meter, and aboveground biomass. In addition, the HI and aboveground biomass showed an increasing trend with the year of release.Therefore, we can conclude that bread wheat breeding advances during recent decades in Henan Province, China,have been achieved through an increase in HI, kernel number per square meter, and aboveground biomass. A higher d13C seems also to be involved in these advances, which suggests a progressive improvement in constitutive water use efficiency not associated with a trend towards lower stomatal conductance in the most recent genotypes. However, genetic advance Researchdoes not appear related to changes in photosynthesis rates on area basis when measured in the flag leaf or the spike,but only to a higher, whole‐spike photosynthesis. Results also indirectly support the concept that under potential yield conditions, the spike contributed more than the flag leaf to kernel formation.