Main Stem Leaf Research Articles

Changes in carbohydrate distribution of cotton and increase in boll weight reduced yield loss under high temperature.

Cotton yield is sometimes unresponsive to high temperature (HT) that induce significant reductions in fruit retention. To investigate the underlying mechanisms, a greenhouse experiment was conducted with two temperature regimes (control, control treatment, 28 °C; HT, 34 °C) for 7 days. Results showed HT did not significantly influence cotton yield, but remarkably reduce boll number and increase boll weight. 13C distribution ratio of the leaf subtending to cotton boll (LSCB) decreased while that of cotton boll increased under HT. Transcriptomic and proteomic analyses of LSCB revealed up-regulated genes involved in cytokinin and jasmonic acid synthesis, as well as SWEET15 (GH_D01G0218), which positively regulated photosynthesis and transport photosynthate, ultimately leading to increased boll weight. After 7 days recovering from HT, 13C distribution ratio of LSCB increased while that of cotton boll decreased. However, the boll weight still increased, which was related to the increased amylase and sucrose phosphate synthase activities and up-regulated sucrose transport genes in main-stem leaf and capsule wall. Thus, both the accelerated sucrose synthesis and transport in LSCB under HT and the increased sucrose supply ability in main-stem leaf and capsule wall after recovering from HT contributed to an increased boll weight, which finally maintained cotton yield.

Method for early diagnosis of verticillium wilt in cotton based on chlorophyll fluorescence and hyperspectral technology

Early and accurate detection of verticillium wilt (VW), the most common and devastating disease of cotton, is essential to prevent the spread of VW. However, it remains challenging to achieve accurate detection of VW in cotton before symptoms appear after infection with Verticillium dahliae (asymptomatic phase). This study evaluated the feasibility of detection of VW in the asymptomatic phase based on cotton main stem leaf chlorophyll fluorescence parameters (CFPs) and spectral features extracted based on continuous wavelet transform (CWT) in two different environments. The aim was to achieve accurate detection of cotton VW in the asymptomatic period by convenient methods. Hyperspectral data of cottons inoculated with V. dahliae were collected at different times, and the CFPs of main stem leaves were measured simultaneously. After preprocessing the hyperspectral data with CWT, common wavelet features for all spectral acquisition days and sensitive CFPs were extracted based on the results of ANOVA. Then, the variance inflation factor combined with least absolute shrinkage and selection operator (LASSO-VIF) was used to select the optimal wavelet features. Finally, the support vector machine, logistic regression, and k-nearest neighbors (KNN) were used to construct the models for detecting VW in asymptomatic leaves based on CFPs and optimal wavelet features, and the accuracy of the models were compared.The results showed that the CFPs were significantly affected 24 h after V. dahliae infection. V. dahliae infection reduced the maximum quantum yield (Pm') of photosystem II (PSII) and increased non-photochemical quenching (NPQt) in cotton leaves. Compared with the raw spectrum, the spectral features in the near-infrared region (800–1350 nm) extracted based on CWT could accurately reflect the subtle changes of leaves in the asymptomatic phase. Besides, compared with CFPs, the 4–5 wavelet features selected based on the LASSO-VIF were more helpful to accurately identify asymptomatic cotton leaves infected with V. dahliae, with an accuracy greater than 80 % and a Kappa coefficient higher than 0.6. Among them, the average accuracy of the logistic regression model based on wavelet features was as high as 90.62 %. The results of this study confirm the changes in CFPs in cotton leaves in the VW-asymptomatic period and the feasibility of accurate identification by using wavelet features. This study will provide a reliable reference for accurate large-scale identification of V. dahliae infection in cotton in the asymptomatic phase.

The high genetic yield of Xinjiang cotton is associated with improvements in boll-leaf system photosynthesis

ContextDespite significant advancements in cotton breeding, there is ongoing debate regarding the mechanism of the yield increase in early-maturing cotton (Gossypium hirsutum L.) through photosynthesis of single leaves in Xinjiang, China. ObjectiveThis study aims to investigate the role of the boll-leaf system (BLS) involving the main-stem leaf, the sympodial leaf, and the boll, in cotton yield formation. Our hypothesis was that genetic breeding enhances cotton yield by improving BLS photosynthesis. MethodsTo examine the relationship between BLS photosynthesis and yield, we conducted a comprehensive literature review spanning 70 years to assess yield changes in the Xinjiang cotton-growing region. We also conducted a series of field experiments in 2020 and 2021 using main cultivars to further investigate the connection between BLS photosynthesis and yield. ResultsLiterature data analysis revealed a consistent increase in boll density, boll weight, and yield of the main cotton cultivars in Xinjiang since the 1950s, particularly after the 1990s. The succession of cultivars showed greater improvements in boll density than boll weight. Our experiments supported these findings by demonstrating that the gradual genetic enhancement in cotton cultivars also led to increased photosynthetic area (PA) and photosynthetic rate (Pn) of the boll-leaf system (BLS). When the BLS was isolated by stem girding, we observed a significant rise in PA, Pn, and boll weight during the genetic improvement. Notably, the boll weight of the cultivars from the 2010s showed the least impact from girdling. These results highlight the prominent enhancement of BLS photosynthesis and subsequent boll growth throughout the succession of Xinjiang cotton cultivars. Further analysis revealed that genetic breeding improved the PA and Pn of both the main-stem leaf and sympodial leaf within the BLS. Specifically, the Pn of the main-stem leaf exhibited a stronger association with boll density than boll weight. Conversely, the Pn of the sympodial leaf showed a significant association with boll weight but not with boll density. ConclusionsThe gradual genetic improvement of cotton cultivars significantly enhanced BLS photosynthesis, resulting to improvements in both boll density and boll weight. The improvement in photosynthesis of the main-stem leaf contributed to enhanced boll density, while the improvement in photosynthesis of the sympodial leaf promoted greater boll weight.

Do phloem feeders affect gas exchange? A case study of Aphis gossypii (Glover) on cotton

AbstractCotton aphid (Aphis gossypii Glover) is a worldwide pest of cotton (Gossypium hirsutum L.). High aphid densities visibly damage cotton leaves, reducing leaf photosynthesis and yield. In contrast, lower aphid densities usually do not visibly damage leaves but their effect on photosynthesis is unknown, complicating the decisions on the need for their control. The effect of cotton aphid at lower densities on gas exchange of cotton leaves was investigated under field conditions in the Namoi Valley, Australia. Photosynthesis, leaf area, stomatal opening, and aphid density were assessed on the third mainstem leaf below the terminal of aphid infested and uninfested control plants. Photosynthesis was reduced by a maximum of 27% at a density of 27.6 aphids cm−2 of leaf tissue. Negative linear relationships were found between aphid density and relative photosynthesis, relative conductance and relative transpiration. The temperature of leaves infested with >5 aphids cm−2 was higher than control leaves. Stomatal conductance was reduced faster than photosynthesis, and 87% of stomata on aphid infested leaves were closed, compared to only 34% on control leaves. Closure of stomata was implicated as a cause of reduced photosynthesis in aphid infested cotton leaves. Stomatal closure may be a direct response to cell damage from aphid feeding, as a plant defense or as a response to aphid induced stress. The results suggest that low levels of aphids (e.g., <7 aphids cm−2) on leaves in the upper canopy of cotton crops may be tolerated with low risk to photosynthesis.

Early Plant Development in Intermediate Wheatgrass

Early seedling developmental morphology influences plant growth and development and ultimately crop biomass and grain yields. We used six half-sibling plants of intermediate wheatgrass (IWG) (Thinopyrum intermedium, (Host), Barkworth and Dewey) to develop an obligate outcrossing species, to develop six maternal lines. Thousand seed weights (TSW) were consistently different amongst plants, averaging from 6.28 to 9.62 g over the three harvest years. Seedlings from the largest seed of each line were studied for early plant development under controlled conditions (22 °C/18 °C, 16/8 h day/night) with destructive harvests at 21, 28, 35 and 42 days after imbibition (DAI) through six grow-outs. Haun stage, and tiller umber and origin, were noted daily, and dry weight plant−1 (DWP) measured at the dates noted above. Leaf-blade length and width were measured in four grow-outs and leaf area estimated. Seedling development data showed some differences between lines and was similar in all lines studied. Data was combined to garner an understanding of early IWG development. Tillering began as the third leaf completed emergence. Coleoptile tillers and rhizomes were infrequent. DWP was best estimated using the main stem leaf area. A large-, a medium- and a small-seeded line were statistically identical for many characteristics including DWP indicating that TSW did not influence seedling vigor. The main stem leaf area may be used non-destructively to improve plant populations for early DWP selection.

Modeling leaf color dynamics of winter wheat in relation to growth stages and nitrogen rates

The objective of this work was to develop a model for simulating the leaf color dynamics of winter wheat in relation to crop growth stages and leaf positions under different nitrogen (N) rates. RGB (red, green and blue) data of each main stem leaf were collected throughout two crop growing seasons for two winter wheat cultivars under different N rates. A color model for simulating the leaf color dynamics of winter wheat was developed using the collected RGB values. The results indicated that leaf color changes went through three distinct stages, including early development stage (ES), early maturity stage (MS) and early senescence stage (SS), with respective color characteristics of light green, dark green and yellow for the three stages. In the ES stage, the R and G colors gradually decreased from their initial values to steady values, but the B value generally remained unchanged. RGB values remained steady in the MS, but all three gradually increased to steady values in the SS. Different linear functions were used to simulate the dynamics of RGB values in time and space. A cultivar parameter of leaf color matrix (MRGB) and a nitrogen impact factor (FN) were added to the color model to quantify their respective effects. The model was validated with an independent experimental dataset. RMSEs (root mean square errors) between the observed and simulated RGB values ranged between 7.0 and 10.0, and relative RMSEs (RRMSEs) ranged between 7 and 9%. In addition, the model was used to render wheat leaves in three-dimensional space (3D). The 3D visualizations of leaves were in good agreement with the observed leaf color dynamics in winter wheat. The developed color model could provide a solid foundation for simulating dynamic crop growth and development in space and time.

Boll-leaf system gas exchange and its application in the analysis of cotton photosynthetic function.

Estimating the boll development and boll yield from single-leaf photosynthesis is difficult as the source-sink relationship of cotton (Gossypium hirsutum L.) is complicated. As the boll-leaf system (BLS), which includes the main-stem leaf, sympodial leaf, and non-leaf organs, is the basic unit of the cotton source-sink relationship and yield formation, the concept of "BLS photosynthesis" is introduced in this study. We speculate that the characteristics of BLS gas exchange can more accurately reflect the photosynthetic function of the system, thus revealing the law of photosynthesis in the process of boll development. The results showed that the photosynthetic rate of single leaves measured by a BLS chamber was consistent with that measured by a standard single-leaf chamber. BLSs exhibited typical light response curves, and the shape of the curves was similar to those of single leaves. The light compensation point and respiration rate of BLSs were higher than those of single leaves, while the apparent quantum efficiency of BLSs was lower. Compared with single leaves, the duration of the photosynthetic function of BLSs was longer. Increasing plant density decreased the gas exchange rate per unit BLS more significantly under field conditions. There was a better linear correlation between the net CO2 assimilation rate, respiration rate of BLSs and boll biomass. Therefore, we think that the gas exchange of BLSs can better reveal the changes in photosynthetic function of BLSs and boll development. This provides a new basis for analyzing the mechanism and regulation of cotton yield formation.

Single boll weight depends on photosynthetic function of boll-leaf system in field-grown cotton plants under water stress.

Cotton has many leaves and even more bolls, which results in a complicated source-sink relationship. Under water stress, the single boll weight (SBW) of cotton remains relatively stable, while both the leaf area and leaf photosynthetic rate decrease greatly. It is therefore difficult to understand how the formation of SBW is regulated under water stress solely by considering single-leaf photosynthesis. Considering the cotton boll-leaf system (BLS: including the main-stem leaf, sympodial leaves, and non-leaf organs) as the basic unit of the cotton canopy, we speculated that the formation of SBW may depend on photosynthesis in the corresponding BLS under water stress. To verify this hypothesis, five water treatments were set up in the field. The results showed that with increasing water stress, the relative water content (RWC) of the main-stem and sympodial leaves decreased gradually, and the decrease in the sympodial leaves was more obvious. The SBW and the number of BLSs decreased slightly with increasing water stress, while the number of bolls per plant decreased significantly. The area of the BLS decreased gradually with increasing water stress, and the area of sympodial leaves decreased more than that of the main-stem leaves. Gas exchange showed that the photosynthetic rate of the BLS (Pn(BLS)) decreased gradually with increasing water stress. In addition, the single-leaf photosynthesis and carboxylation efficiency (CE) decreased progressively and rapidly with the increase of water stress. Compared with the main-stem leaf, the photosynthetic function of the sympodial leaf decreased more. Further analysis showed that compared with leaf photosynthetic rate, there was a better correlation between Pn(BLS) and SBW. Thus, the formation of SBW mainly depends on Pn(BLS) under water stress, and the increase of BLS to boll is also helpful to maintain SBW to some extent. In BLS, the photosynthesis of the main-stem leaf plays a very important role in maintaining the stability of SBW, while the photosynthetic performance in sympodial leaves may be regulated plastically to influence SBW.

The net photosynthetic rate of the cotton boll-leaf system determines boll weight under various plant densities

The yield of cotton (Gossypium hirsutum L.) can be effectively maximized through high planting density. Estimating the yields from single-leaf photosynthesis under various plant densities is difficult as the source-sink relationship of cotton is complicated. By considering the boll-leaf system (BLS: including the main-stem leaf, sympodial leaf and non-leaf organs) as the basic unit of the cotton canopy, the present study asserts that the photosynthetic function of BLS determines single boll weight. This hypothesis was tested by establishing plant densities to explore changes in photosynthesis of the cotton BLS and the consequent effects on boll weight. The results showed that high plant density increased total boll number per unit ground area, whereas single boll weight remained relatively stable, thereby increasing cotton yield. High plant density significantly limited the biomass of the BLS and reduced the distribution ratio of assimilate to sympodial leaves, whereas the dry matter proportion of cotton bolls increased. Although the leaf area and photosynthetic rate of both the main-stem and sympodial leaves of the BLS decreased with increasing plant density, the extent of decrease in the latter was greater. CO2 assimilation within the BLS decreased slightly with increasing plant density, and significant decreases in CO2 assimilation were only evident in extremely high plant densities. A significant positive linear correlation was observed between CO2 assimilation of the BLS and single boll weight. Therefore, photosynthesis of the BLS was identified as the primary factor maintaining boll weight under various plant densities. The main-stem leaf plays a key role in maintaining photosynthesis of the BLS, whereas BLS photosynthesis can be improved by plastically regulating the photosynthetic performance in sympodial leaves.

Formation of the Photosynthetic Apparatus in Spring Wheat Variety Bazhenka under the Effect of Growth Regulators

The effect of growth regulators Albite and Emistim R and pesticide Bunker on the leaf area of spring soft wheat variety Bazhenka and the content of photosynthetic pigments were studied at the substation of the Northeast Federal Agricultural Research Center (FARC) under the conditions of the Kirov region in 2017 and 2019. Using the growth regulator Emistim R alone and in a tank mixture with the fungicide Bunker and the growth regulator Albite in combination with the fungicide for seed treatment, the maximum concentration of chlorophyll a and b in the flag leaf (9.1–9.4 and 5.1–6.6 mg/g of dry weight, respectively) and the highest yield (3.1, 3.5, and 3.0 t/ha, and 1.7 t/ha in the control) was observed. The significant effect of the flag leaf area per yield (r = 0.58), Chl a and b concentration, and the number of grains per head (r = 0.58; r = 0.57) was determined. The pigment content during the period from emergence to heading was affected by temperature (Chl a (r = –0.89), Chl b (r = –0.81), and carotenoids Car (r = –0.79)) and precipitation (Chl a (r = 0.90), Chl b (r = 0.85), and Car (r = 0.86)). The negative correlations with precipitation and positive correlations with temperature were detected for the leaf area of the main stem and subflag leaf.

Potassium to nitrogen ratio favors photosynthesis in late-planted cotton at high planting density

Late sowing of short growing season cotton, planted in high density with one time fertilization is a potential economic alternative for the conventional cotton growing practice in the Yangtze River Valley, China. The appropriate proportion of nutrients is indispensable for an economic crop production. Therefore, the present study was designed to explore the best relative ratios of potassium (K) to nitrogen (N), under a new short-season and high density planting model, based on the photosynthetic performance of cotton plants in relation with the yield. A two-year (2016–17) field experiment was conducted with three K relative ratios to N [0.8 (K08: 168 kg ha−1 K2O), 1.0 (K10: 210 kg ha−1 K2O) and 1.2 (K12: 252 kg ha−1 K2O)]. The results indicated that K10 increased seed cotton and lint yield by 10–20% and 10–24%, respectively, over K08 and no difference was existed between K10 and K12. Similarly, K10 and K12 increased SPAD value by 3–10% and 11–18%, photosynthetic rate by 7–57% and 0.7–89%, and chlorophyll fluorescence parameters by 1–8% and 1–29%, respectively, as compared to K08. And the highest photosynthetic attributes were achieved for the 4th main stem leaf from the top at peak bloom (PB) stage. These results suggested that the K10 is the most suitable ratio as for cotton yield and economic concerns under the newly proposed planting model in the Yangtze River Valley, China.

Mepiquat chloride application does not favor leaf photosynthesis and carbohydrate metabolism as well as lint yield in late-planted cotton at high plant density

Late planting of short-season cotton under high plant density and single fertilization after rapeseed harvest is a promising alternative to traditional relay intercropping of full-season cotton in the Yangtze River Valley of China. However, it is not clear if mepiquat chloride (MC) application is still necessary in the new system. We hypothesized that MC application might reduce leaf photosynthesis and economic yield and thus not be necessary in the new system. To test the hypothesis, short-season cotton was sown in mid-May at 10 plants m−2 and with 225 kg N ha−1 applied at early flowering, and MC was applied three times at five main-stem leaf intervals initiated from the 6th leaf stage at five dosages (MC0, MC30, MC60, MC90, and MC120 represent 0, 30, 60, 90, and 120 g ha−1, respectively) in a 2-year experiment. The photosynthesis, chlorophyll contents, carbohydrate contents, carbohydrate metabolic enzyme dynamics, and cotton yield under different MC treatments were determined. Photosynthesis was reduced by 1–28% and lint yield decreased by 6–29% as MC dosage increased. However, chlorophyll a, b, a + b, sucrose, glucose, fructose, and starch contents in the 4th leaf from the top were increased by 3–56%, 2–45%, 3–51%, 4–48%, 3–48%, 2–63%, and 2–43%, respectively. The activities of enzymes involved in carbohydrate metabolism decreased by 2–25% for sucrose phosphate synthase, but increased by 2–40%, 2–30%, and 3–52% for sucrose synthase, soluble acid invertase, and neutral invertase, respectively. These findings suggest that increased accumulation of sucrose, hexose, and starch in the leaf with MC application diminished photosynthesis and thus could explain the yield loss. Therefore, MC application is not necessary for late-planted cotton.

Numerical host plant relationships of Bemisia tabaci MEAM1 (Hemiptera: Aleyrodidae) within and among major Australian field crops

AbstractThe within‐plant, vertical (internodal) distribution of the silverleaf whitefly (SLW), Bemisia tabaci (Gennadius) MEAM1 (biotype B) adult, large nymph (3rd and 4th instar) and egg stages was quantified in relation to four major Australian field crops, viz., cotton, mungbean, soybean and sunflower in 2003. The objective was to identify suitable sampling locations within the crop canopy. Ovipositional preference of SLW among the four crops under field conditions was also determined to gauge potential susceptibility and support crop choice and configuration decisions in multi‐crop systems. SLW abundance at main stem leaf nodes within each crop was characterised in a two‐stage analysis of the proportion of infested nodes and the number of SLW at the node if infested. The vertical distribution profiles of adults and nymphs from the experimental plots were validated for cotton using scouting data collected in the 2002–2003 growing season and for mungbean from an agronomic comparison of commercial germplasm conducted in 2003. Vertical distributions of adults and juvenile stages differed among the four crops. Based on their distribution profiles, the optimal sampling locations in cotton, mungbean, soybean and sunflower are leaf nodes 3–5, 2–3, 3–4 and 5–7 for adult SLW and 7–10, 4–5, 5–6 and 17–21 for large nymphs, respectively. A comparison of egg density per unit area of green leaf among the four host plant species indicated that soybean is the most attractive to ovipositing females, mungbean the least, and cotton and sunflower intermediate. The potential of each crop as a source for SLW on the basis of nymph abundance is discussed. Low preference combined with a low source potential makes mungbean the crop of choice in broad acre cropping areas in which SLW is endemic.

Leaf appearance rate and final main stem leaf number as affected by temperature and photoperiod in cereals grown in Mediterranean environment

In the present study, a two-year field trial was carried out with the aim to evaluate daylength and air temperature effects on leaf appearance and related rates in two durum wheat (Triticum durum Desf.), two bread wheat (Triticum aestivum L.) and two barley (Hordeum vulgare L.) cultivars, using six different sowing dates (SD). Significant effects of SD on final main stem leaf number (FLN), thermal leaf appearance rate (TLAR), daily leaf appearance rate (DLAR) and phyllochron (PhL) were found. Cultivars resulted inversely correlated to mean air temperature in the interval emergence - fifth leaf full expansion (E-V). Linear response of leaf number over days after sowing was shown for all SD and cultivars, with R2 higher than 0.95. FLN linearly decreased from the first to the last SD for durum wheat, while more variable behaviour was observed in bread wheat. TLAR and DLAR showed a linear increment of the rate from the first to the last SD in durum wheat, while did not for bread wheat and barley. PhL in durum wheat decreased from the first to the last SD. Barley and bread wheat showed the highest values on those SDs which did not reach flowering. The increase of TLAR was affected by photoperiod and photothermal units in durum wheat, while by temperatures only in barley and bread wheat. Present results might find practical application in the improvement of phenology simulation models for durum wheat, bread wheat and barley grown in Mediterranean area in absence of water and nutrient stress.

Modeling the leaf angle dynamics in rice plant.

The leaf angle between stem and sheath (SSA) is an important rice morphological trait. The objective of this study was to develop and validate a dynamic SSA model under different nitrogen (N) rates for selected rice cultivars. The time-course data of SSA were collected in three years, and a dynamic SSA model was developed for different main stem leaf ranks under different N rates for two selected rice cultivars. SSA increased with tiller age. The SSA of the same leaf rank increased with increase in N rate. The maximum SSA increased with leaf rank from the first to the third leaf, then decreased from the third to the final leaf. The relationship between the maximum SSA and leaf rank on main stem could be described with a linear piecewise function. The change of SSA with thermal time (TT) was described by a logistic equation. A variety parameter (the maximum SSA of the 3rd leaf on main stem) and a nitrogen factor were introduced to quantify the effect of cultivar and N rate on SSA. The model was validated against data collected from both pot and field experiments. The relative root mean square error (RRMSE) was 11.56% and 14.05%, respectively. The resulting models could be used for virtual rice plant modeling and plant-type design.

Changed Growth Characteristics with Bacillus thuringiensis Gene Introduction and Nitrogen Regulation in Bt Cotton

Core Ideas Bt cotton cultivars had higher sympodium leaf number and plant height. Bt cotton cultivars had higher growth rates of main stem leaf and lower growth rate of sympodium leaf area. Bt cotton cultivars had higher numbers of fruiting branches, fruiting nodes, bolls, and retained boll rates. N‐deficit and N‐rich treatments affected number and rates of vegetative and reproductive organs. Changes in vegetative and reproductive growth have been widely observed in Bacillus thuringiensis (Bt) transgenic cotton (Gossypium hirsutum L.). The objectives of this study were to determine the characteristics of vegetative and reproductive growth after the Bt gene was introduced into cotton and to study the effect of N on vegetative and reproductive growth to determine if N nourishment could provide a potential mechanism for changed growth characteristics in Bt cotton. Three Bt cultivars (Sikang1, Ccsi41, and Ccsi45), with their current parents (Simian3, Ccsi23, and Jimian7, respectively), were chosen to compare the characteristics of vegetative and reproductive growth and N distribution, in 2011 to 2012; the same six cultivars with two N fertilizer application rate treatments (0 and 450 kg/ha) were further designed to investigate the N regulation impact on growth in 2013. The results indicated that the Bt cotton cultivars had higher growth rates of main stem leaf area, sympodium leaf number, and plant height and a lower growth rate of sympodium leaf area than their parents. Higher numbers and development rates of fruiting nodes, fruiting branches, bolls, and retained boll rates were also observed but lower fruiting branch positions than their parents. The N‐deficit and N‐rich treatments affected both vegetative and reproductive growth of Bt cultivars. The Bt cultivars had reduced numbers and rates of vegetative and reproductive organs under N deficit compared with their parents. These results show that the introduction of the Bt gene changed growth characteristics, including reduced vegetative and reproductive organ development under N deficit.

Effects of Soil Salinity on Sucrose Metabolism in Cotton Leaves.

This study investigated sucrose metabolism of the youngest fully expanded main-stem leaf (MSL) and the subtending leaf of cotton (Gossypium hirsutum L.) boll (LSCB) of salt-tolerant (CCRI-79) and salt-sensitive (Simian 3) cultivars and its relationship to boll weight under low, medium and high soil salinity stress in Dafeng, China, in 2013 and 2014. The results showed that with increased soil salinity, 1) both the chlorophyll content and net photosynthetic rate (Pn) decreased, while the internal CO2 concentration firstly declined, and then increased in the MSL and LSCB; 2) carbohydrate contents in the MSL reduced significantly, while sucrose and starch contents in the LSCB increased, as did the activities of sucrose phosphate synthase (SPS) and sucrose synthase (SuSy) in both the MSL and LSCB; 3) but invertase activity in both the MSL and LSCB did not change significantly. Our study also showed that the LSCB was more sensitive to soil salinity than was the MSL. Of the measured physiological indices, higher SPS activity, mainly controlled by sps3, may contribute to adaption of the LSCB to soil salinity stress because SPS is beneficial for efficiently sucrose synthesis, reduction of cellular osmotic potential and combined actions of Pn, and sucrose transformation rate and SPS may contribute to the reduction in boll weight under soil salinity stress.

EFFECT OF REGULATION OF SOURCE-SINK RELATIONSHIP ON GRAIN YIELD AND ITS COMPONENT OF DIFFERENT BREAD WHEAT CULTIVARS

A field trial was conducted at Abu-Ghraib Research Station-Agricultural Research Directorate-Ministry of Agriculture during the growing seasons of 2012-2013 and 2013-2014. The objective was to investigate the effect of source-sink Regulation on grain yield and its companents of five bread wheat cultivars (Triticum aestivum L.). Randomized complete block design with the arrangement of split-plots with three replicates was used. Bread wheat cultivars (Bohooth-22, IPA 99, Abu-Ghraib-3,Al-Fath and Al-Rasheed) occupied the main plots while treatments of source-sink relationship regulation occupied the sub-plots. They included eight treatments: Con. control (Con.), S1 (removal of lamina of the flag leaf of main stem), S2 (removal of laminas of the leaf beneath the flag leaf), S3 (removal of both lamina of the leaf and the leaf under flag leaf), S4 (removal of upper third spikelets),S5 (removal of median third spikelets), S6 (removal of lower third spikelets) and S7 (removal all spikelets from one side of spike) . Characteristics of plant height, flag leaf area, spike length, no of spikelet per spike, spike weight, and grain yield and its components were measured and estimated. Results of the present study indicated the followings: Cultivar (Bohooth-22) gave the highest 1000 grain weight (35.70 and 35.31 g) the highest grain yield (5.467 and 5.148 t.ha-1) in both seasons, respectively compared with Abu-Ghraib3 and Al-Rasheed cultivars which gave lowest grain yield (4.918,4.364, 4.239 and 4.352 t.ha-1) in both seasons, respectively and then less 1000 grain weight (30.15, 32.66, 32.61 and 32.77 g), in both seasons, respectively. Treatment (Con.) i.e no modification of source-sink relationship gave the highest grain yield (5.93 and 5.66 t.ha-1) in both seasons, respectively. Treatments of regulation source (S1 and S3)gave grain yield (4.909, 4.698, 4.621and 4.356 t.ha-1), respectively while (S5) treatment gave the lowest grain yield (4.203 t.ha-1) in the first season and (4.061 t.ha-1) in the second season. This indicates that sink regulation treatment was the most influencial in reducing grain yield than the source regulation treatment, especially, treatment (S5) in both seasons where the median third of spikelets had been removed due to the reduction of spike growth rate (3.18 and 2.49 g.day-1) in both seasons compared with the (Con) treatment which gave the highest values of spike growth rate (3.91 and 3.12 g.day-1) in both seasons, respectively which resulted in the reduction of dry matter translocation in the (S5) treatment (1.87 and 1.74 g.day -1) and consequently in the reduction of 1000 grain weight (30.09 and 31.199) compared with (34.99 and 37.12 g) in the (Con.) treatment in both seasons, respectively.

EFFECT OF REGULATION OF SOURCE-SINK RELATIONSHIP ON SPIKE GROWTH RATE AND DRY MATTER ACUMUILATION FOR DIFFERENT WHEAT CULTIVARS

A field trial was conducted at Abu-Ghraib Research Station-Agricultural Research Directorate-Ministry of Agriculture during the winter seasons of 2012-2013 and 2013-2014. The objective was to investigate the effect of source-sink Regulation on grain yield and its companents of five bread wheat cultivars (Triticum aestivum L.( Randomized complete block design with the arrangement of split-plots with three replicates was used. Bread wheat cultivars (Bohooth-22, IPA 99, Abu-Ghraib-3,Al-Fath and Al-Rasheed) occupied the main plots while treatments of source-sink relationship modification occupied the sub-plots. They included eight treatments: Control (Con.), S1 (removal of lamina of the flag leaf of main stem), S2 (removal of laminas of the leaf beneath the flag leaf), S3 (removal of both lamina of the leaf and the leaf under flag leaf), S4 (removal of upper third spikelets),S5 (removal of median third spikelets), S6 (removal of lower third spikelets) and S7 (removal all spikelets from one side of spike) . Characteristics spike growth rate (g), accumulated temperature (GDD), dry matter translocation All cultivars were significantly different in all studied characters in both seasons. Treatments of source-sink relationship regulation were significantly different in most studied characters in both seasons. Cultivar (Bohooth-22) gave higher spike growth rate (3.79 and 3.05 g), higher dry matter translocation (2.255 and 2.182 g) in both seasons, respectively, ) compared with Abu-Ghraib3 and Al-Rasheed cultivars which gave lowest as they possessed less spike growth rate (3.36 , 2.743, 3.65 and 2.687 g), less dry matter translocation (1.739, 1.829. 2.251 and 2.116 g) in both seasons, respectively. treatment (S5) in both seasons where the median third of spikelets had been removed due to the reduction of spike growth rate (3.18 and 2.490 g) in both seasons compared with the (Con) treatment which gave the highest values of spike growth rate (3.915 and 3.129 g) in both seasons, respectively which resulted in the reduction of dry matter translocation in the (S5) treatment (1.50and 1.749 g) in both seasons, respectively.

Phenotypic variation and identification of quantitative trait loci for ozone tolerance in a Fiskeby III × Mandarin (Ottawa) soybean population

Soybean quantitative trait loci for ozone response. Ground-level ozone reduces yield in crops such as soybean (Glycine max (L.) Merr.). Phenotypic variation has been observed for this trait in multiple species; however, breeding for ozone tolerance has been limited. A recombinant inbred population was developed from soybean genotypes differing in tolerance to ozone: tolerant Fiskeby III and sensitive Mandarin (Ottawa). Plants were exposed to ozone treatment for 5days in greenhouse chambers followed by visual scoring for foliar injury. Mean injury score in the mid-canopy was 16% for Fiskeby III, and 81% for Mandarin (Ottawa). Injury scores were lower in younger leaves for both parents and progeny, compared to scores in the older leaves. Segregation was consistent with multigenic inheritance. Correlation coefficients for injury between leaf positions ranged from 0.34 to 0.81, with the closer leaf positions showing the greater correlation. Narrow sense heritability within an ozone treatment chamber was 0.59, 0.40, 0.29, 0.30, 0.19, and 0.35 for the 2nd, 3rd, 4th, 5th, 6th, and combined 3rd-5th main stem leaf positions (numbered acropetally), respectively, based on genotypic means over three independent replications. Quantitative trait loci (QTL) analysis showed that loci were associated with distinct leaf developmental stages. QTL were identified on Chromosome 17 for the 2nd and 3rd leaf positions, and on Chromosome 4 for the 5th and 6th leaf positions. Additional loci were identified on Chromosomes 6, 18, 19, and 20. Interacting loci were identified on Chromosomes 5 and 15 for injury on trifoliate 4. The ozone sensitive parent contributed one favorable allele for ozone response.