Genotype-by-environment interaction analysis of rice (Oryza spp.) yield in a floodplain ecosystem in West Africa

West Africa has large areas of river floodplains, most of which are not currently used for farmland. Rice (Oryza spp.) is a promising crop for farming in floodplains because of its high adaptability to a wide range of water environments. On the other hand, there is great variation in soil fertility and water availability even in a small area within a floodplain. Hence, we evaluated 27 rice genotypes in four fields in three years in a floodplain of the Northern Region of Ghana to investigate genotype × environment (G × E) interactions for rice yield and to identify stable, high-yielding genotypes. The genotypes consisted of O. sativa, O. glaberrima and New Rice for Africa (NERICA), and many were selected for their reported submergence resistance because of the anticipated submergence damage in the floodplain. There were large variations in yield, which ranged from 0.14 to 5.35 t ha⁻¹ depending on the location within a floodplain, genotype and year, and there were significant genotype, environment and G × E interaction effects on yield, accounting for 24.8%, 20.2%, and 28.2%, respectively, of the total variation. The results suggested that selection of suitable location with high soil fertility and low risk of submergence is necessary to achieve high yield in a floodplain. In addition, early sowing would be effective high-yielding crop management, which reduced the risk of submergence-induced damage just after sowing and secured sufficient growth duration to achieve high yield. Genotype IR42 showed the highest average yield among environments, but its yield stability was low. On the other hand, several genotypes including Amankwatia, a local aromatic cultivar adapted to irrigated and lowland environments, and IRBL9-W[RL], a blast-tolerant variety containing the Sub1 gene for submergence tolerance, showed high, stable yield. To put these results to practical use in other floodplain areas in West Africa, physiological mechanisms causing G × E interaction for rice yield should be further studied.     

Effects of controlled irrigation and drainage on growth,grain yield and water use in paddy rice

Rice is subjected to excessive waterlogging and flash-flooding on large areas in south China. A study on water use, growth and yield effects of controlled irrigation and drainage (CID) of paddy rice at four stages was conducted in specially designed experimental tanks. The treatments were (1) CID during Stage I of tillering stage (CID-Stage I), (2) CID during Stage II of booting stage (CID-Stage II), (3) CID during Stage III of heading to flowering stage (CID-Stage III), (4) CID during Stage IV of milky stage (CID-Stage IV), (5) alternate wetting and drying irrigation during the whole stage (CK). Compared with CK, CID reduced drainage volume with 15.8–31.3% in 2008, and 13.5–28.3% in 2009, and increased the efficiency of available rainfall and irrigation by 1.98–3.46% in both years. Irrigation water application during the whole growing season across the 2 years, on average, was only 81.8%, 91.1%, 93.9%, and 94.5%, respectively, of that applied to CK. A strong reduction in root length, root weight, root-shoot ratio and harvest index were observed, however, shoot weight and total dry mass is increased from the treatments of CID-Stage II, CID-Stage III and CID-Stage IV. The highest radiation use efficiency values were for CID-Stage IV. The responses of CID from vegetative plants at Stage I and Stage II were greater than in generative plants at the latter two stages. CID-Stage II had only a small effect on subsequent development and grain yield. This decrease in grain yield to less than 7.88% and 5.72% of CK was due to reduced number of spikelets per panicle in one trial, and reduced panicle number per unit area in another. The CID-Stage I treatment showed the lowest grain yield among the treatments and reduced it by 23.3% in 2008 and by 17.3% in 2009, due to the decreases in the percentage of filled grains and total number of panicles. The effect of stress was associated with low dry matter production during the flooding stress period as well as during the stress withdrawal period following the stress. With regards to irrigation water use efficiency, it was increased under the first two treatments, and by from a minimum of 101% to a maximum of 110%.     

“云大— 120 ”浸种对水稻秧苗素质及产量影响的研究

试验结果表明：用“云大— 120 ”浸稻种对种子的发芽势、发芽率、秧苗素质、有效穗和稻谷产量具有一定的促进作用，发芽势比对照提高 12.68% — 23.94% ；发芽率提高 3.75% — 18.75% ；有效穗提高 0.5% — 7.43% ；产量增加 1.03% — 8.49% 。其使用方法简单易行，在生产上具有重要的推广价值。     

Quantifying rice yield gaps and their causes in Eastern and Southern Africa

The demand for rice in Eastern and Southern Africa is rapidly increasing because of changes in consumer preferences and urbanization. However, local rice production lags behind consumption, mainly due to low yield levels. In order to set priorities for research and development aimed at improving rice productivity, there is a need to characterize the rice production environments, to quantify rice yield gaps—that is, the difference between average on-farm yield and the best farmers’ yield—and to identify causes of yield gaps. Such information will help identifying and targeting technologies to alleviate the main constraints, and consequently to reduce existing yield gaps. Yield gap surveys were conducted on 357 rice farms at eight sites (19–50 farmers per site) across five rice-producing countries in Eastern and Southern Africa—that is Ethiopia, Madagascar, Rwanda, Tanzania and Uganda—for one or two years (2012–13) to collect both quantitative and qualitative data at field and farm level. Average farm yields measured at the eight sites ranged from 1.8 to 4.3 t/ha and the average yield gap ranged from 0.8 to 3.4 t/ha. Across rice-growing environments, major causes for yield variability were straw management, weeding frequency, growth duration of the variety, weed cover, fertilizer (mineral and organic) application frequency, levelling and iron toxicity. Land levelling increased the yield by 0.74 t/ha, bird control increased the yield by 1.44 t/ha, and sub-optimal management of weeds reduced the yield by 3.6 to 4.4 t/ha. There is great potential to reduce the current rice yield gap in ESA, by focusing on improvements of those crop management practices that address the main site-specific causes for sub-optimal yields.     

New techniques for breeding maize (Zea mays) varieties with fall armyworm resistance and market-preferred traits for sub-Saharan Africa

Deploying maize varieties with fall armyworm (Spodoptera frugiperda [J.E. Smith]; FAW) resistance, desirable product profiles (PPs) and climate resilience is fundamental for food and economic security in sub-Saharan Africa (SSA). This study reviewed and identified challenges and opportunities for effective and accelerated breeding of demand-led maize hybrids with FAW resistance and adaptation to the diverse agro-ecologies of SSA. Lessons were drawn on improving breeding efficiency through adequate genetic variation delivered via prebreeding programmes, speed breeding and a reduced breeding stage plan. Appropriate PPs aligned with demand-led breeding approaches were highlighted as foundations for variety design and commercialization. Challenges to accelerated FAW resistance breeding in maize included inadequate funds and modern tools; poor adaptation of some exotic donor parental lines; lack of information on FAW resistance among local varieties; lack of integration of molecular markers associated with FAW resistance and agronomic traits into selection plans; and limited infrastructure for FAW rearing and germplasm screening. Integration of modern breeding tools and scientific innovations were recommended for accelerated development and release of FAW resistant and market-preferred maize varieties.     

Explaining rice yields and yield gaps in Central Luzon,Philippines: An application of stochastic frontier analysis and crop modelling

Explaining yield gaps is crucial to understand the main technical constraints faced by farmers to increase land productivity. The objective of this study is to decompose the yield gap into efficiency, resource and technology yield gaps for irrigated lowland rice-based farming systems in Central Luzon, Philippines, and to explain those yield gaps using data related to crop management, biophysical constraints and available technologies.Stochastic frontier analysis was used to quantify and explain the efficiency and resource yield gaps and a crop growth model (ORYZA v3) was used to compute the technology yield gap. We combined these two methodologies into a theoretical framework to explain rice yield gaps in farmers’ fields included in the Central Luzon Loop Survey, an unbalanced panel dataset of about 100 households, collected every four to five years during the period 1966–2012.The mean yield gap estimated for the period 1979–2012 was 3.2 ton ha⁻¹ in the wet season (WS) and 4.8 ton ha⁻¹ in the dry season (DS). An average efficiency yield gap of 1.3 ton ha⁻¹ was estimated and partly explained by untimely application of mineral fertilizers and biotic control factors. The mean resource yield gap was small in both seasons but somewhat larger in the DS (1.3 ton ha⁻¹) than in the WS (1.0 ton ha⁻¹). This can be partly explained by the greater N, P and K use in the highest yielding fields than in lowest yielding fields which was observed in the DS but not in the WS. The technology yield gap was on average less than 1.0 ton ha⁻¹ during the WS prior to 2003 and ca. 1.6 ton ha⁻¹ from 2003 to 2012 while in the DS it has been consistently large with a mean of 2.2 ton ha⁻¹. Varietal shift and sub-optimal application of inputs (e.g. quantity of irrigation water and N) are the most plausible explanations for this yield gap during the WS and DS, respectively.We conclude that the technology yield gap explains nearly half of the difference between potential and actual yields while the efficiency and resource yield gaps explain each a quarter of that difference in the DS. As for the WS, particular attention should be given to the efficiency yield gap which, although decreasing with time, still accounted for nearly 40% of the overall yield gap.     

Mapping of a gene (Vir) for a non-glaucous, viridescent phenotype in bread wheat derived from Triticum dicoccoides, and its association with yield variation

The introgression of desirable genes or alleles from the wild relatives of hexaploid wheat can be a valuable source of genetic variation for wheat breeders to enhance modern varieties. The UK Group 1 bread making variety Shamrock is an example where the introgression of genetic material from wild emmer (Triticum dicoccoides) has been used to develop a modern cultivar. A striking character of Shamrock is its unique viridescent colour compared to other UK wheats, a trait that coincides with a non-glaucous phenotype. A doubled haploid population segregating for the trait (Shamrock × Shango) was examined to map the location of Vir, and analyse any associated pleiotropic effects. The viridescence gene located to the distal end of the short arm of chromosome 2B. QTL analysis of productivity traits shows an association between Vir and a significant delay in senescence, resulting in an extension of the grain filling period. A stable yield QTL, accounting for up to a quarter of the variation in one case, was also identified at or near Vir, indicating significant yield benefits either by linkage or pleiotropy.     

水稻强化栽培下协优9308的产量及穗粒结构研究

超级杂交稻协优9308应用水稻强化栽培,移栽密度为15.3株/m2到6.9株/m2。产量以密度15.3株/m2最高,比对照增产10%,主要表现在增粒增产。移栽密度显著影响产量和每穗实粒数(R12=0.9917**,R32 = 0.9339**)。水稻强化栽培各处理密度之间比较,产量随移栽密度的下降而下降,主要是由于单株分蘖和有效穗的增加,导致平均穗型变小。单株最高苗数和有效穗数与移栽密度成显著的相关（R82 = 0.9594**,R92 = 0.9506**）。因此,在推广水稻强化栽培时应重视适宜移栽密度的选择及综合技术配套。     

Variability of winter rye grain yield in a glacial plain catchment — modelling and observation

Crop growth of winter rye (Secale cereale) was simulated on sandy soils in northwest Germany at the meso-scale (6 km² catchment, 5 year rotation). Based on site-specific soil data, simulated grain yields (Y_MOD) were compared to observed yields (Y_OBS), and the results were discussed with respect to the N balance. The mean annual yields simulated for rain-fed (3.8–7.3 t/ha) and irrigated conditions (5.2–8 t/ha) varied more strongly than those observed in the region (4.6–6.0 t/ha). Excluding years with strongly deviating simulation results, the ratio Y_OBS/Y_MOD decreased from 0.82 to 0.73 under irrigation. Spatially, the effect of plant available water (PAW) on simulated yields varied considerably over the years, explaining 5–75% of the yield variability. In reality, yields depended on water availability (PAW+irrigation) in a year with spring drought, suggesting a time-specific water stress function. In the simulation scenario, there was ample N supply, and variable N mineralization explained 10% of the yield variability. Simulated mean N uptake and export were greater than the observed (160 vs. 140 and 112 vs. 100 kg N/ha, respectively), which may explain the overestimated growth rates. The mean harvest index varied less (0.36–0.55) than the fraction of N returned with the residues (0.17–0. 50), and irrigation decreased the variation of both. With respect to scaling methods, soil data could be aggregated, and simulations based on distributed inputs could be substituted by the weighted mean of simulations based on mean inputs. Down-scaling from the EU map created the difficulty of selecting appropriate soil units. The simple factor Y_OBS/Y_MOD was unreliable for scaling simulated yields to assess regional yields because of its temporal variation in response to climatic variables. The results suggest that changes in model structure and parameters are required to describe water stress, sink limitations, and N diffusion or influx rates better.     

Analysis of the ozone effect on soybean in the Mediterranean region: II. The consequences on growth, yield and water use efficiency

Soybean plants were subjected, during their growing seasons, to well-watered and water-stressed conditions, and three levels of ozone concentration (zero, low and high) in open top chambers (OTCs). At the end of the soybean growing season accumulated AOT40 values were zero, 3400 and 9000 ppb h for the filtered (control), low and high levels of ozone concentration, respectively.

In well-watered conditions, an increase in ozone concentration led to a reduction in leaf area, dry matter and reproductive organs. Whereas, an increase in ozone had no effect on plants in water-stressed conditions. At a high level of ozone concentration, there was a 47% reduction in yield and a 25% reduction in WUE in comparison with the control treatment. The reduction in yield was due to a lower number of pods per plant and 1000-grain weight. Despite changes in the grain yield, the yield quality was not altered by ozone.

During the 3-year study, AOT40 was significantly correlated with the leaf area and the final above-ground dry matter. The latter was less sensitive to ozone than leaf area. These results were reliable and would be useful in soybean yield-prediction models.

Finally, the conclusion highlights the reliability of the approach adopted, which was to make observations on various time scales (hourly, daily and entire crop cycle).     

Growth and development of bambara groundnut (Vigna subterranea) in response to soil moisture: 1. Dry matter and yield

The effect of drought on the growth and development of bambara groundnut (Vigna subterranea (L.) Verdc.) was studied in controlled-environment glasshouses in the UK. There were three landraces (S19-3, DipC and UN from Namibia, Botswana and Swaziland, respectively) and two watering regimes; a control that was irrigated weekly to 90% field capacity and a drought treatment with no irrigation from 49 days after sowing (DAS) until final harvest (147 DAS). Bambara groundnut responded to drought by reducing the rate of leaf area expansion, final canopy size and total dry matter (TDM) during vegetative growth. Drought also caused significant reductions in pod dry matter (PDM), pod number, seed weight and harvest index (HI), leading to a decrease in final pod yield that was different between landraces. Across landraces, drought reduced mean pod yield from 298 g m⁻² to 165 g m⁻², representing 45% yield loss. Despite the reduction in all landraces, the mean pod yield across the droughted treatments that had received no water for almost 100 days indicated the resilience of the species to drought. The three landraces differed in their phenology; S19-3 exhibited a reduced phenology while UN maintained the longest life cycle. The different responses of the landraces reflect their adaptation to their local climates where mean annual rainfall ranges between 365 mm (Namibia) and 1390 mm (Swaziland). We discuss the significance of these results for future breeding programmes on bambara groundnut.     

Haplotype structure in grain weight gene GW2 and its association with grain characteristics in rice

GW2, a grain weight quantitative trait locus (QTL) in rice encodes a ring type E-3 ubiquitin ligase. A single nucleotide deletion at the 346th nucleotide position in the ligase domain of GW2 was earlier reported to result in higher grain weight in rice. The present study aimed at validating the known functional polymorphism and identifying additional natural genetic variation if any, in the region that included the functional domain of GW2 in a set of indica and aromatic genotypes for which ninety three rice genotypes were phenotyped for grain length, grain width and 100 grain weight. A wide range of variation was observed for these traits. PCR amplification and sequencing of GW2 target region revealed absence of insertion/deletion (InDel) at the 346th position which suggested that the genetic variation in grain weight in Basmati and non-Basmati indica genotypes was not explained by this InDel. However, four new single nucleotide polymorphisms (SNPs) were discovered at nucleotide positions 406, 461, 466 and 501 in the fifth exon and one InDel each in second and fourth introns. Only two of these SNPs, at positions 461 and 501 led to amino acid substitutions. A total of 10 haplotypes were constructed based on these four SNPs which could be regrouped into four categories based on their amino acid substitutions. Association genetic analysis of these haplotypes with different grain traits revealed a moderate association with grain width (R² = 0.18 at P < 0.05). Thirteen haplotypes constructed using both intronic and exonic polymorphisms did not have any association with grain traits.     

Bayesian network modeling of early growth stages explains yam interplant yield variability and allows for agronomic improvements in West Africa

Yams (Dioscorea spp.) are important species, especially for resource-poor farmers of West Africa, where crop yields are affected by early plant size hierarchy linked with uneven emergence. Although the causes of this phenomenon are not fully known, yams, like other vegetatively propagated crops, have heavy planting material that is liable to induce such interplant variability. In addition, planting practices may mitigate this phenomenon via the selection of the seed-tuber size or state. To gain further insight into yam interplant variability, this study identified and quantified, for the first time, the direct and indirect dependency between planting practices, early growth variables and yield components of Dioscorea rotundata and Dioscorea alata, the two main food yam species. The experimental dataset came from six field trials carried out in Benin at two locations between 2007 and 2009. Additive Bayesian network modeling was used for structure discovery—its directed acyclic graph offers an ideal background for discussing complex systems when theoretical knowledge is lacking, e.g., for yams. Here we found that the emergence date was the only direct cause of plant yield variability common to both species. For D. rotundata, we observed a direct contribution of the cataphyll number to the plant tuber weight. These combined results suggest the existence of some uncontrolled latent variables (i.e., seed-tuber physiological age and reserves). For D. alata, the model did not reveal any effect of seed-tuber size, despite a strong effect noted for D. rotundata. We suggest that the transposition of traditional native D. rotundata planting practices may have led to oversized D. alata seed-tubers, resulting in wastage of planting material. This study demonstrated that traditional West African cropping systems have a serious drawback concerning the uncontrolled wide range of physiological ages and reserves in seed-tuber lots, which affect the plant size hierarchy and ultimately the marketable yield.     

Plant growth regulator and its interactions with environment and genotype affect maize optimal plant density and yield

Increasing planting density is important to raise maize yield, however, high density often leads to an increase risk of lodging due to dense canopy and weak stem. Maize yield and optimal plant density are increased by applying plant growth regulator compound of ethephon and DA-6, however, we do not know if this compound would interact with location and genotype. In this study, a novel plant growth regulator, as the synthesis of N, N- diethyl − 2 − hexanoyl oxygen radicals − ethyl amine (2-ethyl chloride) phosphonic acid salt (DHEAP), combining the effects of ethephon and DA-6 in one chemical, was developed and tested at three locations, five plant densities (6.75, 8.25, 9.75, 11.25 and 12.75 plants m⁻²) and three cultivars in 2014–2015. This study aimed to quantify the interactions between environment, genotype and management (Appling DHEAP and plant density) on lodging-related optimal plant density and yield. DHEAP significantly increased grain yield by 10.7% due to the increases of kernel weight by 3.2% and kernel number per ear by 4.4%. On average across genotypes and environments, applying DHEAP increased optimum plant density by 6%. The optimal plant density interacted with cultivar, DHEAP and environment. Applying DHEAP reduced lodging percentage by lowering ear height. The yield-lodging relationship was affected by genotype and location. We concluded that maize yield could be enhanced by optimizing plant density, applying DHEAP and cultivar selection, but climatic and environmental differences of locations should be considered.     

Genotypic variation for tolerance to phosphorus deficiency in rice and the potential for its exploitation in rice improvement

Deficiency in phosphorus (P) can severely limit rice yields. Developing cultivars with tolerance to P deficiency may represent a more sustainable solution than sole reliance on fertilizer application. To assess genotypic variation for tolerance to P deficiency the P uptake of 30 genotypes was measured on P‐deficient soil. Variation for P uptake was high, ranging from 0.6 to 12.9 mg P/plant. Traditional varieties were superior to modern varieties. A major quantitative trait locus for P uptake had previously been identified in a population developed by crossing the modern variety ‘Nipponbare’ with the P deficiency‐tolerant landrace ‘Kasalath’. This quantitative trait locus was transferred to ‘Nipponbare’ by three backcrosses. Under P deficiency this improved line surpassed ‘Nipponbare’ in P uptake by 170% and in grain yield by 250%. These results show that the genotypic variation for tolerance to P deficiency in rice can be used successfully in rice improvement. By combining high P uptake of the donor variety ‘Kasalath’ with a high harvest‐index characteristic of modern varieties it was possible to more than triple the grain yield of ‘Nipponbare’ under P deficiency.     

多参数冬小麦估产模型研究及产量影响因素分析

产量估算研究对制定粮食政策和经济计划,科学地进行粮食宏观调控有着重要意义。针对以往线性遥感估产模型中多是基于NDVI和LAI的研究,且参数间存在多重共线性等问题,该研究以河北省南部石家庄、保定、邯郸、邢台、衡水、沧州六市为研究区,选用2000—2008 年的种植区最佳时相NDVI、LAI累加值,并引入与小麦生物量积累密切相关的不同月份地表温度作为原始估产指标,针对参数累加值存在的误差,提出一个修正公式对NDVI、LAI 进行修正,再对选用参数进行主成分分析,将结果与冬小麦产量数据建立出4 个多参数综合作用的冬小麦遥感估产模型。结果表明,利用2009 年数据对模型进行验证,结果表明4 个模型的R2介于0.714~0.818 之间,估产精度均在93.0%以上,其中,综合所有遥感参数的模型拟合效果最好,R2为0.818,估产精度达95%,而且引入温差主成分的模型精度高于仅用NDVI、LAI作参数的模型,另外深入分析各参数对产量估测的影响可知4 月中旬和5 月中旬的地表昼夜温差对冬小麦的后期产量具有较大影响。     

Genetic association of yield with its component traits in a recombinant inbred line population of cotton

Lint yield of upland cotton (Gossypium hirsutum L.) is determined by its component traits, boll number, boll weight, and lint percentage. Selecting high yielding lines is based on the ability to manipulate component traits. In this study, 188 recombinant inbred lines and two parental lines were grown in 1999 and 2000 at Mississippi State University. Lint yield and its three component traits were measured and analyzed by an extended conditional mixed linear model approach. Boll number unit-area^–1 made the largest contribution to genotypic and genotype × environment (G × E) variations for lint yield. Both boll number and lint percentage, and boll number and boll weight jointly accounted for more than 70% of the genotypic and G × E variations in lint yield. Ninety-nine percent of the genetic and phenotypic variation in lint yield could be explained by the three component traits, indicating that lint yield was mainly dependent on its three component traits. Small phenotypic variation in lint yield could be accounted for by effects of genotype, G × E interactions of boll number or boll number combined with other component trait(s) (Table 5). For boll number unit-area^–1 a wider distribution of genotypic contribution effects was detected than for lint percentage and boll weight in this study. Boll number and boll weight interacted to affect lint yield, indicating that balanced selection for boll weight and boll number is needed in high-yielding line development. Comparative results with other approaches were also discussed in this study.The U.S. Governments right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged     

气候变化对北京地区小麦玉米两熟种植制度的影响

研究了北京地区小麦和玉米生产与气象条件的关系，并根据未来气候变化 的研究设计了气候情景，在此基础上讨论了未来气候化对小麦玉米一年二熟种植制度的影响。结果表明，温度升高对小麦和玉米生产有利，玉米产量的提高大于小麦；降水减少首先对小麦生产不利，当降水进一步减少时，对玉米生产也不利。     

六盘山叠叠沟小流域草本地上生物量的变化及其与环境因子的关系

根据宁夏六盘山叠叠沟小流域草地生物量的调查和实验数据,分析了该地区草地生物量的动态变化规律及其与环境因子的关系。结果表明,从坡向上看,草本总生物量的大小&#61472;为：半阳坡>半阴坡>阳坡;从坡位上看,不同坡面的草地生物量差异性有所不同,半阳坡草本生物量随着坡位升高呈现增加的趋势,半阴坡和阳坡呈现出先增后减的趋势;草本生物量与0～20cm土层的土壤容重呈负相关;与土壤含水量呈正相关关系。