Use of molecular marker diversity to increase forage yield in timothy (Phleum pratense L.)

Molecular marker technologies may provide a tool to overcome the forage yield plateau in timothy (Phleum pratense L.). Therefore, a study was designed to investigate the relationship between marker‐based genetic distance (GD) estimates and yield. Genetic distances were estimated using Dice coefficients framed by 28 simple sequence repeat markers. In Experiment 1, parents with high general combining ability (GCA) from two contrasting first‐generation synthetic strains (exhibiting high and low yields) were compared. Average GDs of each strain were 0.74 (high) and 0.68 (low). These differences indicated that GD may be partially the basis for contrasting yields. In Experiment 2, GDs among 40 parents of a polycross were used for calculating general genetic distance (GGD), which is indicative of their allelic complementation. Analyses revealed a significant (P < 0.01) moderate correlation (r) between GGD and GCA for yield (r = 0.45) and a significant (P < 0.01) residual mean square for the regression of yield on GGD, suggesting that considerable non‐additive effects were associated with GCA. The results are indicative of the potential use of GD estimation for yield improvement in timothy.     

Effect of recombination in the maize breeding population with exotic germplasm on the yield stability

A little knowledge exists about the probability that recombination in the parental maize populations will enhance the chances to select more stable genotypes. The synthetic parent maize population ((1601/5 × ZPL913)F₂ = R₀) with 25% of exotic germplasm was used to assess: (i) genotype × environment interaction and estimate stability of genotypes using nonparametric statistics; (ii) the effect of three (R₃) and five (R₅) gene recombination cycles on yield stability of genotypes; (iii) relationship among different nonparametric stability measures. The increase of mean grain yield was significant (P < 0.01) in the R₃ and R₅ in comparison to the R₀, while it was not significant between R₃ and R₅. Analysis of variance showed significant (P < 0.01) effects of environments, families per set, environment × set interaction, family × environment interaction per set on grain yield. The non-significant noncrossover and significant crossover (P < 0.01) G × (E) interactions were found according to Bredenkamp procedures and van der Laan-de Kroon test, respectively. The significant (P < 0.01) differences in stability were observed between R₀-set 3 and R₅-set 3 determined by S_i⁽³⁾ S_{i}^{(3)} , R₃-set 1 and R₅-set 1 determined by S_i⁽³⁾ S_{i}^{(3)} (P < 0.05), and R₀-set 3 and R₅-set 3 determined by S_i⁽⁶⁾ S_{i}^{(6)} (P < 0.05). The significant parameters were those which take into account yield and stability so the differences could be due to differences in yield rather than stability. Findings can help breeders to assume the most optimum number of supplementary gene recombination to achieve satisfactory yield mean and yield stability of maize genotypes originating from breeding populations.     

Long-term P and K fertilisation strategies and balances affect soil availability indices,crop yield depression risk and N use

The last century has seen a large increase of fertiliser use, along with a subsequent rise of crop productivity. However, in many places its intensive use has become a burden to the environment, and legislation has been introduced to restrict nutrient applications. In combination with changing production scenarios as a result of climate change, this means an improved understanding is needed of how low nutrient availability and climatic stress factors affect yields and yield stability.We examined the long-term effects mineral and organic fertilisation on a nutrient-depleted field, and observed large annual variations: depending on the year, average spring barley yields under unfertilised management (U) were between 17–75% lower than the reference N_½P_½K_½ (60–10–60 kg ha⁻¹). Yields increased up to 174% under N₁P₁K₁ (120–20–120 kg ha⁻¹), while animal manure applications at an N availability level corresponding to N₁ were between 79 and 137%. No temporal yield trends could be observed, but long-term changes of Olsen-P and exchangeable K were related to the nutrient balances (inputs-offtake) (r² = 0.60 and 0.59, respectively, P < 0.001).Multiple linear regression analysis was used to examine the effects of the treatments in combination with annual weather variations. The results could be split into two outcomes, 1) a general relation between yields and temperatures for the periods of early spring (P < 0.01, multiple R² = 0.31) and summer (P < 0.001, multiple R² = 0.45), and 2) an interaction between temperature and nutrient applications during crop establishment, leading to a diverse response of relative yields (P < 0.001, multiple R² = 0.64), i.e. relative yield losses under the unfertilised treatment (U) were greater in years with lower spring temperatures, and, conversely, the increased nutrient availability in the fully mineral and organically fertilised treatments could partially alleviate the negative effects.After 13 years of repeated fertilisation, inputs were suspended for a single year and only N was applied to evaluate the residual effects. Yields were significantly affected by the different fertilisation histories (P < 0.001). Likewise, apparent nitrogen recovery tended to improve with previous inputs, but the observations were highly variable.Overall, the analyses agree with the notion that brief periods of stress at a critical stage may significantly affect yields, and confirmed that management of sufficient nutrient availability is critical for maintaining high and stable yields.     

Yield enhancement by short‐term imposition of severe water deficit in the vegetative growth stage of grain sorghum

Water deficit is generally thought to negatively impact crop yields, including grain sorghum (Sorghum bicolor L.), but a small body of literature reports changes in crop physiology and growth in plants with short‐term imposition of water deficit during vegetative development that could lead to increased yield. In a replicated and repeated pot experiment in which water deficit was imposed for 10‐day periods in grain sorghum plants that were otherwise well‐watered, we tested the hypothesis that relatively severe, short‐term water deficit imposed during early vegetative development could enhance grain sorghum yield. The results showed that severe water deficit (~30% of control ET) imposed during two vegetative periods enhanced grain yield compared to continuously well‐watered plants by 21% (p = .0356). Grain yield was correlated with average grain weight, grain number per head and shoot‐to‐root ratio. Yield enhancement was associated with a substantial shift in resource partitioning, as water deficit reduced root mass (p = .0032), stem/leaf mass (p < .0001) and total biomass (p = .0005), resulting in a 60% increase in harvest index. Imposition of water stress during vegetative growth in sorghum can increase grain yield.     

Effect of two-week heat stress during grain filling on stem reserves,senescence, and grain yield of European winter wheat cultivars

To examine the extent to which heat stress during grain filling impacts on the development and yield of winter wheat (Triticum aestivum L.), a 3-year field experiment was conducted on a loess soil with high water holding capacity in the North German Plain. Thirty-two mostly European winter wheat cultivars were exposed to heat stress in a mobile foil tunnel with maximum air temperatures of 45.7, 45.4, and 47.2°C in 2015, 2016, and 2017, respectively. The 14-day post-anthesis heat stress treatment caused an average 57.3% grain yield reduction compared to a close-by non-stressed control. The proportion of green crop area after the heat stress phase varied from 7% to 98% in 2016 and from 37% to 94% in 2017. The green crop area percentage did not significantly correlate with grain yield, indicating that the delayed senescence of stay-green phenotypes offers no yield advantage under terminal heat stress. The water soluble carbohydrate (WSC) concentration of the stems at crop maturity varied between 6 and 92 g/kg dry matter, showing that the genotypes differed in their efficiency at using the stem carbohydrate reserves for grain filling under heat stress. The stem WSC concentration correlated positively with the beginning of anthesis (r = 0.704; p < .001) but negatively with the grain yield (r = −0.431; p < .05). For heat tolerance breeding, the stem reserve strategy, i. e. the rapid and full exhaustion of the temporary carbohydrate storage therefore seems more promising than the stay-green strategy.     

Selection of wheat genotypes for biomass allocation to improve drought tolerance and carbon sequestration into soils

The biomass allocation pattern of plants to shoots and roots is a key in the cycle of elements such as carbon, water and nutrients with, for instance, the greatest allocations to roots fostering the transfer of atmospheric carbon to soils through photosynthesis. Several studies have investigated the root to shoot ratio (R:S) biomass of existing crops but variation within a crop species constitutes an important information gap for selecting genotypes aiming for increasing soil carbon stocks for climate change mitigation and food security. The objectives of this study were to evaluate agronomic performance and quantify biomass production and allocation between roots and shoots, in response to different soil water levels to select promising genotypes for breeding. Field and greenhouse experiments were carried out using 100 genotypes including wheat and Triticale under drought‐stressed and non‐stressed conditions. The experiments were set‐up using a 10 × 10 alpha lattice design with two replications under water stress and non‐stress conditions. The following phenotypic traits were collected: number of days to heading (DTH), number of productive tillers per plant (NPT), plant height (PH), days to maturity (DTM), spike length (SL), kernels per spike (KPS), thousand kernel weight (TKW), root biomass (RB), shoot biomass (SB), root to shoot ratio (R:S) and grain yield (GY). There was significant (p < 0.05) variation for grain yield and biomass production because of genotypic variation. The highest grain yield of 247.3 g/m² was recorded in the genotype LM52 and the least was in genotype Sossognon with 30 g/m². Shoot biomass ranged from 830 g/m² (genotype Arenza) to 437 g/m² (LM57), whilst root biomass ranged between 603 g/m² for Triticale and 140 g/m² for LM15 across testing sites and water regimes. Triticale also recorded the highest R:S of 1.2, whilst the least was 0.30 for wheat genotype LM18. Overall, drought stress reduced total biomass production by 35% and R:S by 14%. Genotypic variation existed for all measured traits useful for improving drought tolerance, whilst the calculated R:S values can improve accuracy in estimating C sequestration potential of wheat. Wheat genotypes LM26, LM47, BW140, LM70, LM48, BW152, LM75, BW162, LM71 and BW141 were selected for further development based on their high total biomass production, grain yield potential and genetic diversity under drought stress.     

Thermal imaging for assessment of maize water stress and yield prediction under drought conditions

Maize production in Thailand is increasingly suffering from drought periods along the cropping season. This creates the need for rapid and accurate methods to detect crop water stress to prevent yield loss. The study was, therefore, conducted to improve the efficacy of thermal imaging for assessing maize water stress and yield prediction. The experiment was carried out under controlled and field conditions in Phitsanulok, Thailand. Five treatments were applied, including (T1) fully irrigated treatment with 100% of crop water requirement (CWR) as control; (T2) early stress with 50% of CWR from 20 days after sowing (DAS) until anthesis and subsequent rewatering; (T3) sustained deficit at 50% of CWR from 20 DAS until harvest; (T4) late stress with 100% of CWR until anthesis and 50% of CWR after anthesis until harvest; (T5) late stress with 100% of CWR until anthesis and no irrigation after anthesis. Canopy temperature (FLIR), crop growth and soil moisture were measured at 5-day-intervals. Under controlled conditions, early water stress significantly reduced maize growth and yield. Water deficit after anthesis had no significant effect. A new combination of wet/dry sponge type reference surfaces was used for the determination of the Crop Water Stress Index (CWSI). There was a strong relationship between CWSI and stomatal conductance (R² = 0.90), with a CWSI of 0.35 being correlated to a 64%-yield loss. Assessing CWSI at 55 DAS, that is, at tasseling, under greenhouse conditions corresponded best to the final maize yield. This linear regression model validated well in both maize lowland (R² = 0.94) and maize upland fields (R² = 0.97) under the prevailing variety, soil and climate conditions. The results demonstrate that, using improved standardized references and data acquisition protocols, thermal imaging CWSI monitoring according to critical phenological stages enables yield prediction under drought stress.     

The Influence of Row Spacing and Seeding Rate on Seed Yield and Yield Components of Forage Turnip (Brassica rapa L.)

The effects of four row spacings (17.5, 35.0, 52.5 and 70.0 cm) and five seeding rates (50, 100, 200, 400 and 800 viable seeds m^?2) on seed yield and some yield components of forage turnip (Brassica rapa L.) were evaluated under rainfed conditions in Bursa, Turkey in the 1998–1999 and 1999–2000 growing seasons. Plant height, stem diameter, pods/terminal raceme, total pods/plant, seeds/pod and primary branches/plant were measured individually. The number of plants per unit area was counted and the lodging rate of the plots was scored. The seed yield and 1000‐seed weight were also determined. Row spacing and seeding rate significantly affected most yield components measured. The number of plants per unit area increased with increasing seeding rate and decreasing row spacing. Plant height was not greatly influenced by row spacing and seeding rate, but higher seeding rates reduced the number of primary branches and the stem diameter. The number of pods/main stem was affected by row spacing and but not by the seeding rate. Also, the number of seeds per pod was not affected by either the row spacing or the seeding rate. In contrast, the number of pods per plant clearly increased with increasing row spacing, but decreased with increasing seeding rate. The plots seeded at narrow row spacings and at high seeding rates were more sensitive to lodging. Seeding rate had no significant effect on seed yield in both years. Seed yield was similar at all seeding rates, averaging 1151 kg ha^?1. However, row spacing was associated with seed yield. The highest seed yield (1409 kg ha^?1) was obtained for the 35.0‐cm row spacing and 200 seeds m^?2 seeding rate combination without serious lodging problems.     

Infrared Thermal Imaging as a Rapid Tool for Identifying Water‐Stress Tolerant Maize Genotypes of Different Phenology

The main task of this research was to evaluate canopy temperature and Crop Water Stress Index (CWSI) by assessing genotype variability of maize performance for different water regimes. To that end, three hundred tropical and subtropical maize hybrids with different phenology in terms of date of anthesis were evaluated. The influence of phenology on the change in canopy temperatures and CWSI was not equal during the three dates of measurement. At the end of vegetative growth (82 days after sowing, DAS) and at the blister stage (DAS 97), a high significant difference in temperatures and CWSI (P < 0.001) were obtained between the early‐ and late‐maturity genotypes. During anthesis (DAS 89), phenology had a significant effect (P < 0.01) only for the well‐watered genotypes, while under water‐stress conditions, no differences were found between early and late genotypes in terms of canopy temperature and CWSI. High significant differences (P < 0.001) in stomatal conductance (g_s) between early and late genotypes for different treatments were observed. A relationship (R² = 0.62) between g_s and canopy temperature was obtained. Under a water‐stress canopy, temperature was measured at anthesis, which was negatively correlated with grain yield of the early (r = ?0.55)‐ and late (r = ?0.46)‐maturity genotypes in the water‐stressed condition.     

Data fusion of spectral,thermal and canopy height parameters for improved yield prediction of drought stressed spring barley

Yield modelling based on visible and near infrared spectral information is extensively used in proximal and remote sensing for yield prediction of crops. Distance and thermal information contain independent information on canopy growth, plant structure and the physiological status. In a four-years′ study hyperspectral, distance and thermal high-throughput measurements were obtained from different sets of drought stressed spring barley cultivars. All possible binary, normalized spectral indices as well as thirteen spectral indices found by others to be related to biomass, tissue chlorophyll content, water status or chlorophyll fluorescence were calculated from hyperspectral data and tested for their correlation with grain yield. Data were analysed by multiple linear regression and partial least square regression models, that were calibrated and cross-validated for yield prediction. Overall partial least square models improved yield prediction (R² = 0.57; RMSEC = 0.63) compared to multiple linear regression models (R² = 0.46; RMSEC = 0.74) in the model calibration. In cross-validation, both methods yielded similar results (PLSR: R² = 0.41, RMSEV = 0.74; MLR: R² = 0.40, RMSEV = 0.78). The spectral indices R₇₈₀/R₅₅₀, R₇₆₀/R₇₃₀, R₇₈₀/R₇₀₀, the spectral water index R₉₀₀/R₉₇₀ and laser and ultrasonic distance parameters contributed favourably to grain yield prediction, whereas the thermal based crop water stress index and the red edge inflection point contributed little to the improvement of yield models. Using only more uniform modern cultivars decreased the model performance compared to calibrations done with a set of more diverse cultivars. The partial least square models based on data fusion improved yield prediction (R² = 0.62; RMSEC = 0.59) compared to the partial least square models based only on hyperspectral data (R² = 0.48; RMSEC = 0.69) in the model calibration. This improvement was confirmed by cross-validation (data fusion: R² = 0.39, RMSEV = 0.76; hyperspectral data only: R² = 0.32, RMSEV = 0.79). Thus, a combination of spectral multiband and distance sensing improved the performance in yield prediction compared to using only hyperspectral sensing.     

利用RZWQM-ERES模拟华北平原农田土壤水分动态及其对作物产量的影响

农业系统模型是农业生产多元目标优化管理的重要工具,但由于系统模型过程复杂,参数众多,校正和验证工作一直是模型研究的重点和难点。本文对RZWQM (Root Zone Water Quality Model)与CERES (Crop Environment Resource Synthesis)的结合模型RZWQM-CERES模拟土壤水分及作物产量进行了参数优化和验证,结果表明,RZWQM-CERES在禹城站和栾城站模拟不同灌溉处理土壤贮水量与测定值呈相似的变化趋势,均方根差(RMSE)分别为2.38~2.70 cm及3.49~3.73 cm;作物产量模拟结果与实测值对土壤水分的响应趋势一致(R² = 0.83^***,n = 22),其中在禹城站模拟小麦和玉米产量的RMSE分别为550 kg hm^-2和580 kg hm^-2,栾城站模拟小麦产量的RMSE为670 kg hm^-2。以上结果表明RZWQM-CERES可作为华北平原模拟和分析土壤水分对作物产量影响的有效工具。本文初步建立了一套适合华北平原作物生产的模型参数,为利用RZWQM-CERES建立农田水分优化调控策略奠定了基础,并探讨了模型评价过程中应注意的问题。     

Limited contribution of water availability in genotype-by-environment interaction in sugarcane yield and yield components

Water deficit is an important abiotic stress factor limiting sugarcane production. Understanding the effect of water deficit on cane yield, yield components and genotype × environment (G × E) interaction can aid in selecting genotypes that are adapted to water deficit conditions. In this study, response of cane yield and yield components of 10 sugarcane genotypes grown under 3 irrigation treatments—fully irrigated, semi-irrigated and rainfed—was examined across 3 locations and 3 crop-years within each location. Cane yield reduced by 32% and 9% in the rainfed and semi-irrigated treatments, respectively, compared to the fully irrigated treatment. Genotypic variation was highly significant for cane yield and yield components in all three irrigation regimes. Cane yield in the rainfed treatment showed significant genetic correlation with stalk diameter (r_g = 0.68), leaf number (r_g = 0.64), node number (r_g = 0.67) and stalk number (r_g = 0.68). Genotype × irrigation variance was negligible compared to genotype, genotype × location and genotype × crop-year variances. Commercial genotypes had higher yield in most environments except in low-yield potential environments, which caused a significant genotype × location × irrigation effect, suggesting opportunities for improving sugarcane productivity in these environments.     

The intercropping common bean with maize improves the rhizobial efficiency,resource use and grain yield under low phosphorus availability

In order to better understand how mixed crop cultures mitigate stressful conditions, this study aims to highlight the beneficial effect of the intercropping legume-cereal in enhancing soil phosphorus (P) availability for plant growth and productivity in a P-deficient soil of a northern Algerian agroecosystem. To address this question, common bean (Phaseolus vulgaris L. cv. El Djadida) and maize (Zea mays L. cv. Filou), were grown as sole- and inter-crops in two experimental sites; S1 (P-deficient) and S2 (P-sufficient) during two growing seasons (2011 and 2012). Growth, nodulation and grain yield were assessed and correlated with the rhizosphere soil P availability. Results showed that P availability significantly increased in the rhizosphere of both species, especially in intercropping under the P-deficient soil conditions. This increase was associated with high efficiency in use of the rhizobial symbiosis (high correlation between plant biomass and nodulation), plant growth and resource (nitrogen (N) and P) use efficiency as indicated by higher land equivalent ratio (LER > 1) and N nutrition index (for maize) in intercropping over sole cropping treatments. Moreover, the rhizosphere P availability and nodule biomass were positively correlated (r² = 0.71, p < 0.01 and r² = 0.62, p < 0.01) in the intercropped common bean grown in the P-deficient soil during 2011 and 2012. The increased P availability presumably improved biomass and grain yield in intercropping, though it mainly enhanced grain yield in intercropped maize. Our findings suggest that modification in the intercropped common bean rhizosphere-induced parameters facilitated P uptake, plant biomass and grain yield for the intercropped maize under P-deficiency conditions.     

Effects of Row Spacing, Support Plant Species and Support Plant Mixture Ratio on Seed Yield and Yield Characteristics of Hungarian Vetch (Vicia pannonica Crantz)

The effects of row spacing (17.5 or 35.0 cm), support plant species (barley or triticale) and the proportion of crops in mixtures (no support plant or support plant 20, 40 or 60 %, respectively) on the seed yield and yield characteristics of Hungarian vetch (Vicia pannonica Crantz) were investigated. Increasing the row spacing increased the seed yield of V. pannonica from 881.0 to 1248.0 kg ha^?1. On average, in a pure stand the seed yield of V. pannonica was 1141.0 kg ha^?1. In mixtures with barley and triticale, the seed yield of V. pannonica averaged 986.0 and 1143.0 kg ha^?1, respectively. In single mixed stands the seed yield of V. pannonica varied between 551.0 kg ha^?1 (60 % support plant barley) and 1603.0 kg ha^?1 (20 % support plant triticale). The yield advantage of V. pannonica in this triticale mixture was 40 % compared to the V. pannonica pure stand. With respect to the total yield in the mixture with 20 % triticale (1902.0 kg ha^?1) the yield advantage over the V. pannonica pure stand was as high as 65.1 %. In the mixed stands the number of seeds per pod and the thousand‐seed weight of V. pannonica were higher than in V. pannonica pure stands.     

Wheat cellular thermotolerance is related to yield under heat stress

Cellular thermotolerance in terms of cellular membrane thermostability is often implied as an indication of crop heat tolerance and it is therefore considered as a possible selection criterion for heat tolerance. While there is ample genetic variability for cellular thermotolerance in wheat and other crop plants its relations to yield under heat stress is not sufficiently established. This study was performed to assess the genetic relations in wheat between cellular thermotolerance and yield under heat stress. In one study the co-segregation among cellular membrane thermostability (CMS), yield under chronic heat stress and yield under non-stress conditions was evaluated in a random inbred line (RIL) population of a cross between heat resistant (Danbata) and heat susceptible (Nacozari) cultivars. In a second study the same association was evaluated for yield under heat stress in 49 F₇ breeding lines randomly selected from a breeding program. CMS was assayed in growth chamber grown and heat-hardened seedlings. Yield was evaluated under Mediterranean summer irrigated conditions where chronic heat stress caused a reduction in mean yield of the RIL population by 47% as compared with the normal winter growing conditions (non-stress). The RILs varied significantly (p<0.05) for CMS, biomass and yield under stress and non-stress conditions. The two parent cultivars did not differ in biomass or yield under non-stress (winter) conditions but they widely differed for both traits under heat stress. Yield of RILs under heat stress was well distributed between the extreme values of the parent cultivars. There was a significant RIL by season interaction for biomass (F = 9.74; p<0.0001) and yield (F = 10.08; p<0.0001), indicating specific adaptation to heat stress of certain lines in terms of their productivity. Broad-sense heritability for yield was high and nearly the same in the winter (h ²=0.71)and the summer (h ²=0.67). Broad-sense heritability for CMS was high (h ²=0.74). CMS was positively and significantly (p<0.01) correlated across 98 RILs with biomass (r = 0.60* *) and yield (r = 0.53^**) under stress but rot with biomass or yield under non-stress conditions. The 49 breeding lines varied significantly (p<0.01) for CMS and yield under chronic heat stress in the summer season. CMS and yield were significantly correlated (r = 0.56^**) across lines. Overall the associations between CMS and yield under heat stress were reasonably strong and significant but not perfect. Other factors besides cellular thermostability may support yield under heat stress. CMS alone cannot be used as the exclusive selection criterion for heat tolerance in wheat breeding. lt may be valuable as a supplemental criterion in the final breeding stages or as a rough selection tool to reduce a large population into the most likely heat tolerant core at the early stages of the breeding program.     

The Effect of Late-terminal Drought Stress on Yield Components of Four Barley Cultivars

Barley (Hordeum vulgare L.) is an important winter cereal crop grown in the semiarid Mediterranean, where late‐terminal drought stress during grain filling has recently become more common. The objectives of this study were to investigate the growth performance and grain yield of four barley cultivars under late‐terminal drought stress under both glasshouse and field conditions. At grain filling, four barley cultivars (Rum, ACSAD176, Athroh and Yarmouk) were exposed to three watering treatments: (1) well‐watered [soil maintained at 75 % field capacity (FC)], (2) mild drought stress at 50 % FC, (3) severe drought stress at 25 % FC in the glasshouse experiment and (1) well‐watered (irrigated once a week), (2) mild drought (irrigated once every 2 weeks), (3) severe drought (non‐irrigated; rainfed) in the field. As drought stress severity increased, gross photosynthetic rate, water potential, plant height, grain filling duration, spike number per plant, grain number per spike, 1000‐grain weight, straw yield, grain yield and harvest index decreased. In the glasshouse experiment, the six‐row barley cultivars (Rum, ACSAD176, and Athroh) had higher grain yield than the two‐row barley cultivar (Yarmouk), but the difference was not significant among the six‐row cultivars under all treatments. In the field experiment, Rum had the highest grain yield among all cultivars under the mild drought stress treatment. The two‐row cultivar (Yarmouk) had the lowest grain yield. In general, the traditional cultivar Rum had either similar or higher grain yield than the other three cultivars under all treatments. However, the yield response to drought differed between the cultivars. Those, Rum and ACSAD176, that were capable of maintaining a higher proportion of their spikes and grains per spike during drought also maintained a higher proportion of their yield compared with those in well‐watered treatment. In conclusion, cultivar differences in grain yield were related to spike number per plant and grain number per spike, but not days to heading or grain filling duration.     

Biochar Mitigates Salinity Stress in Potato

A pot experiment was conducted in a climate‐controlled greenhouse to investigate the growth, physiology and yield of potato in response to salinity stress under biochar amendment. It was hypothesized that addition of biochar may improve plant growth and yield by mitigating the negative effect of salinity through its high sorption ability. From tuber bulking to harvesting, the plants were exposed to three saline irrigations, that is 0, 25 and 50 mm NaCl solutions, respectively, and two levels of biochar (0 % and 5 % W/W) treatments. An adsorption study was also conducted to study the Na⁺ adsorption capability of biochar. Results indicated that biochar was capable to ameliorate salinity stress by adsorbing Na⁺. Increasing salinity level resulted in significant reductions of shoot biomass, root length and volume, tuber yield, photosynthetic rate (A_n), stomatal conductance (g_s), midday leaf water potential, but increased abscisic acid (ABA) concentration in both leaf and xylem sap. At each salinity level, incorporation of biochar increased shoot biomass, root length and volume, tuber yield, A_n, g_s, midday leaf water potential, and decreased ABA concentration in the leaf and xylem sap as compared with the respective non‐biochar control. Decreased Na⁺, Na⁺/K⁺ ratio and increased K⁺ content in xylem with biochar amendment also indicated its ameliorative effects on potato plants in response to salinity stress. The results suggested that incorporation of biochar might be a promising approach for enhancing crop productivity in salt‐affected soils.     

不同行距配置方式对夏玉米冠层结构和群体抗性的影响

为探究行距配置方式对冠层微气象因子及群体抗逆性的影响,明确夏玉米适宜的行距配置方式,在方城和辉县设置大田试验,以3个不同株高类型的玉米杂交种为材料(中秆品种郑单958、高秆品种先玉335和矮秆品种512-4),设置2个种植密度(60 000株 hm^-2和75 000株 hm^-2),研究了5种行距配置方式(50 cm、60 cm、70 cm、80 cm等行距和80 cm+40 cm宽窄行)下冠层结构和群体抗逆性的变化。结果表明,不同株高类型杂交种在相同密度下,随行距扩大,株型变得松散,穗部叶片叶向值减小,并偏离种植行,向种植行垂直方向发展,冠层温湿度降低,群体抗逆性增强,但冠层光照截获率降低,产量也随之减少。对比发现,不同品种和密度下,60 cm等行距能够较好地协调冠层微气象因子与玉米产量的关系,叶片分布适宜,冠层温湿度和光能分布合理,显著提高了中下部的光能截获率,病虫害和倒伏的发生率较低,获得最高产量的频率最高,且适宜机械化田间作业,建议作为适宜黄淮海地区推广的种植方式。     

Phosphorus uptake and utilization efficiency in response to potato genotype and phosphorus availability

Increased phosphorus (P) use efficiency (PUE) of potato production systems through P uptake and P utilization efficiency (PUPE and PUTE, respectively) is one of the main challenges for potato breeding and crop management programs. The aim of this study was to assess PUE, PUPE, PUTE and related traits in different potato genotypes (Solanum tuberosum L.) in response to P availability. Three field experiments were carried out in southern Chile in Andisol soils. In each experiment treatments were the factorial combination of (i) 22 genotypes of potatoes and (ii) two P fertilization rates (0 and 130 kg P ha⁻¹, −P and +P, respectively). On average, biomass, P concentrations and P uptakes were reduced (P < 0.05) 32, 13 and 41% by −P, respectively. Conversely, −P increased PUTE (1.2-fold), PUPE (7-fold) and consequently PUE (8.3-fold). All traits were consistently affected (P < 0.01) by genotype (G), and the coefficient of variation (up to 47%) for each trait reflects the genotypic variability under both +P and −P. In all experiments, PUE and its main components were affected (P < 0.01) by P × G interaction. PUE was highly correlated with tuber yield, total biomass, P uptake and PUPE (P < 0.01; r = 0.74 − 0.99) but not to PUTE. In addition, PUPE was well correlated to yield and highly correlated with total P uptake (P < 0.01; r = 0.94–0.99). By contrast, PUTE was strongly negatively correlated (P < 0.01; r = −0.85 − 0.89) with P concentration in tubers. Genotypes from native (1 and 4), national cultivar (Puren-INIA, Yagana-INIA and Patagonia-INIA) and advanced line (R 89063 and RD 36–35) groups were among the best regarding PUE under −P. The PUPE was found to be more important than PUTE in determining PUE across a broad range of genotypes. Moreover, there is important genotypic variability in these traits with the potential to be used to improve PUE in potato crops through breeding and crop management programs.     

Effects of Stem-Injected Sucrose on Photosynthesis and Productivity of Water Stressed Corn Plants

Water stress during silking or early kernel development decreases the number of kernels set by corn (Zea mays L.) plants. Previous work has suggested that lack of assimilate supply due to water stress at silking was a major factor in the resulting reproductive failure. A greenhouse experiment was conducted to test the hypothesis that sucrose supplementation of water stressed corn plants can prevent decreased kernel set. Sucrose was injected into corn stems at three concentrations [0 (distilled water), 150 and 300 g L^?1] for 30 days starting at silking. Water availability was controlled by either maintaining a water table at 50 cm from the soil surface (well watered) or by withholding water starting one week before silking (water stress) until the fifth day after silking. The photosynthesis rate of water stressed plants was 25% that of well-water plants on the first day of silking. On average, the daily injection rate for distilled water was 1 mL higher than that of the sucrose treatments over a 30 day injection period. No difference in daily uptake rate was observed between the 150 and 300 g sucrose L^?1 treatments. Over water availability treatments approximately 17 g sucrose were injected into corn plants during the 30 day injection period. Corn plants receiving sufficient water supply produced bigger ears, with more seeds and greater 100-seed weight values, leading to higher total plant dry matter accumulation than water stressed plants. Injection of 300 g sucrose L^?1 increased the weight of the injected internodes by 28%, compared with distilled water injection. The highest grain yield was for the plants injected with 150 g sucrose L^?1, but only under sufficient water supply. The plants injected with 300 g sucrose L^?1 produced the least grain regardless of moisture availability. Thus, the exogenous sucrose supplementation influenced kernel set only under conditions of sufficient soil water supply. These results indicate that plant reproductive development after silking was limited more by water availability than assimilate supply, suggesting that some overall plant response to water stress, perhaps mediated by hormonal signalling, was more important than carbohydrate supply. These results indicated that plant desiccation occurred during floral development or pollination; irreversible loss of florets on unsuccessful pollination could result, thus, grain yield would be limited more by sink size than by availability of photosynthate.