Photosynthetic Area Research Articles

Evaluating Iris Yellow Spot Disease Incidence and Severity in Onion Germplasm of Varying Leaf Characteristics

Iris yellow spot (IYS) disease, caused by Iris yellow spot virus (IYSV), results in irregular and diamond-shaped, chlorotic, and necrotic lesions on the leaves and seedstalks of onions (Allium cepa L.). These lesions reduce leaf photosynthetic area and ultimately reduce onion bulb size and yield from larger bulb classes. IYSV is vectored by onion thrips (Thrips tabaci L.) that are difficult to control under certain environmental conditions. Currently, no onion cultivar is resistant to the disease symptoms, virus, and/or thrips. Twenty-one cultivars and 17 germplasm lines were evaluated in the field for IYS disease severity and thrips densities at multiple times during the season as well as leaf color, waxiness, and axil openness of these entries. Plants were grown under conditions that favored thrips populations (high temperatures, low moisture, and no insecticidal spray applications), IYSV presence and distribution, and IYS development. Plants of New Mexico State University (NMSU) 07-10-1 had fewer thrips than several entries later in the season in both 2009 and 2010. Several entries exhibited a lower number of thrips per plant early or later in the season; however, these results were not consistent across years and were not associated with a particular foliage characteristic. Lighter leaf color and/or a lesser amount of epicuticular wax did not always result in the fewest number of thrips per plant as has been reported in the literature. Plants of NMSU 09-58 tended to exhibit fewer and less severe IYS symptoms early in the season as compared with plants of other entries.

Response of photosynthesis and chlorophyll a fluorescence in leaf scald‐infected rice under influence of rhizobacteria and silicon fertilizer

Leaf scald caused by Monographella albescens reduces the photosynthetic area, causing yield losses in rice. This study investigated the efficacy of the rhizobacteria Burkholderia pyrrocinia (BRM‐32113) and Pseudomonas fluorescens (BRM‐32111), combined with silicon (Si) fertilization, to reduce lesion size and the area under the disease progress curve (AUDPC), as well as to minimize the negative effects on gas exchange, chlorophyll a fluorescence, chlorophyll content and the activity of oxidative stress enzymes. The experiment used a completely randomized design with four replications and seven treatments. Compared with plants only fertilized with Si, plants fertilized with Si and treated with BRM‐32113 showed reductions of 22% in scald lesion expansion and 37% in AUDPC, a 27% increase in the rate of CO2 assimilation (A), a 33% decrease in the internal CO2 concentration (Ci), and a 40% increase in ascorbate peroxidase activity. It was therefore concluded that the combination of BRM‐32113 with Si fertilization reduces the severity of leaf scald, protecting the photosynthetic apparatus, thus representing a sustainable method of reducing the loss of income caused by leaf scald in rice.

Morpho-anatomical studies on the leaf reduction in Casuarina: the ecology of xeromorphy

The foliage characters found in Casuarina seedlings may represent the ancestral, scleromorphic ones found in the Casuarinaceae. In the adults studied, these are replaced by derived xeromorphic features. The ontogenetic changes in the foliage of two Casuarina species were investigated. While the cotyledons are flattened linear structures, all other leaf-types are strongly reduced. Except for the two primary leaves, all subsequent leaves are strongly fused to each other and also to the shoot axis, except for the leaf tips; the shoot axis is completely surrounded by photosynthetic leaf tissue and the branchlet is not made up of cladodes but of extended leaf sheaths which are a novel strategy for achieving reduced photosynthetic area. In seedlings there are four leaves per node, forming four shallow vertical furrows where light-exposed and non-encrypted stomata are developed. These features are also developed in the adult foliage within the strictly scleromorphic genus Gymnostoma, clearly the most mesic of the present day genera of Casuarinaceae and very likely to include the ancestral types. Thus, we assume that the Casuarina-seedling leaves reflect the ancestral scleromorphic condition. In the adult foliage, the number of leaves per node is strongly increased, which leads to the formation of several nearly closed vertical furrows on the shoot, where stomata are shaded and strongly encrypted. Thus, the adult foliage shows several xeromorphic features that are absent in the juvenile foliage. Our morpho-anatomical data mapped on ecological and palaeobotanical data show that within Casuarinaceae the foliage shifted from scleromorphic to xeromorphic. Thus, the adult xeromorphic foliage in Casuarina is the derived, advanced state.

Effects of sand burial on the survival and growth of two shrubs dominant in different habitats of northern China.

Plants that grow in dune ecosystems always suffer from sand burial. Shrubs play implications on the healthy functioning of dune ecosystems due to control blowing sand. However, the survival and growth responses of shrubs to sand burial remain poorly understood. The survival rate and seedling height of two shrubs (Artemisia halodendron and Lespedeza davurica) along with the soil properties under different burial depths were examined in order to reveal the causing ecophysiological attributes of sand burial on shrubs in the desertified region. It was found that A. halodendron can survive a burial depth of 6cm greater than its seedling height, which is a dominant shrub in mobile dunes with intense burial, whereas a burial depth equivalent to three fourths of its seedling height is detrimental to L. davurica, which is dominant in fixed dunes with less burial. The reasons for the shrub death under sand burial were associated with the physical barrier to vertical growth and the reduction in photosynthetic area. In conclusion, A. halodendron can facilitate the stabilization of mobile dunes because of their high tolerance to the frequent and intensive sand burial, while L. davurica can be beneficial for the recovery process because of their higher survival rates under shallow burial following restoration of mobile dunes.

Trichoderma reduces scald and protects the photosynthetic apparatus in rice plants

ABSTRACTScald reduces the photosynthetic area, causing yield losses in rice. Changes in gas exchange parameters caused by the pathogen begin before the onset of symptoms. Chemical methods are most commonly applied to control this disease; further research into biological control methods is required. Since Trichoderma asperellum induces plant pathogen defences, increases growth, and improves photosynthetic capability, this study investigated the efficacy of T. asperellum (Ufra T06, UfraT09, Ufra T12, and Ufra T52 (Ta)) in reducing the scald lesion size and the area under the disease progress curve and in minimising the negative effects of scald on gas exchange, chlorophyll a fluorescence, chlorophyll content, and oxidative stress enzyme activity. The experiment was a completely randomised design with five replications and two treatments. Scald was reduced by 62% in plants treated with T. asperellum compared with that in control. There was a 62% increase in the net CO2 assimilation rate (A) and a drop of 78% in the transpiration rate (E) in plants treated with T. asperellum. The maximum fluorescence (Fm) was 128% higher, and ascorbate peroxidase activity was also higher in plants treated with T. asperellum than in the control. This shows that the use of T. asperellum may be effective in improving the sustainability of the integrated management of rice diseases.

First Evidence of Thaumastocoris peregrinus (Heteroptera: Thaumastocoridae) Feeding From Mesophyll of Eucalyptus Leaves.

The bronze bug, Thaumastocoris peregrinus Carpintero & Dellapé, 2006 (Heteroptera: Thaumastocoridae) originally restricted to Australia, is an important emerging pest of Eucalyptus plantations in the Southern Hemisphere. It feeds on mature leaves, causing the loss of photosynthetic surface area and defoliation and, according to some studies, even tree death. In this work, feeding activities of T. peregrinus on Eucalyptus camaldulensis Dehn leaves and its primary food resources were identified. In cross sections of leaves, solid salivary deposits on epidermal cells and in the vicinity of stomata cells were detected. In subepidermal cells of the palisade parenchyma near the stylet penetration point, disorganization and removal of chloroplasts were also observed. The presence of chlorophyll in guts of adults and nymphs was analyzed using spectrophotometry and confocal laser scanning to obtain in situ fluorescent spectra. Both spectra showed chlorophyll absorbance peaks. In addition, the presence of chlorophyll in guts of T. peregrinus using fluorescence microscopy was identified. These results provide the first evidence that T. peregrinus feeds from the palisade parenchyma (chlorenchyma) of Eucalyptus leaves.

Identification of the Effect of Sulfur Spray on Okra (AbelmoschusesculentusL. var. MI 5)Seedlings

The study investigated that the effect of sulfur solutions as foliar spray with different concentrations on some selected growth parameters of ladies fingers plants. Pot experiment was conducted with six treatments (2g/L, 4g/L, 6g/L, 8g/L and 10g/L sulfur solutions) and three replicates. For each pot,two plants were maintained throughout the experiment. After seedling emerging, sulfur solutions were sprayed in every week using OSATU sprayer (5 L), until all the leaves got wet. After 30 days physiological features (Number of leaves, leaf length andleaf width) were recorded. Pest and disease incident also recorded at the mean time. Completely Randomized Design (CRD) with five replicates was used. Statistical analysis was performed with Duncan’s multiple range test using SAS software (version 9.1.3). Result showed that the highest significant values in number of leaves (26), leaf length (21cm) and leaf width (24cm) were observed that in 10g/L solution of sulfur applied as foliar spray. With the increasing concentration of sulfur solutions the values for the selected physiological features also increased. Pest and disease incidence was significantly higher in control experiment while all the other treated plants don’t showed any physiological damage or symptom. The results revealed that the application of sulfur as a foliar spray can be effectively use in increase the net photosynthetic area and to reduce the pest and disease incidence.

Relationship between plant canopy characteristics and photosynthetic productivity in diverse cultivars of cotton (Gossypium hirsutum L.)

Genotype and plant type affect photosynthetic production by changing the canopy structure in crops. To analyze the mechanism of action of heterosis and plant type on canopy structure in cotton (Gossypium hirsutum L.), we had selected two cotton hybrids (Shiza 2, Xinluzao 43) and two conventional varieties (Xinluzao 13, Xinluzao 33) with different plant types in this experiment. We studied canopy characteristics and their correlation with photosynthesis in populations of different genotypes and plant types during yield formation in Xinjiang, China. Canopy characteristics including leaf area index (LAI), mean foliage tilt angle (MTA), canopy openness (DIFN), and chlorophyll relative content (SPAD). The results showed that LAI and SPAD peak values were higher and their peak values arrived later, and the adjustment capacity of MTA during the flowering and boll-forming stages was stronger in Xinluzao 43, with the normal-leaf, pagoda plant type, than these values in other varieties. DIFN of Xinluzao 43 remained between 0.09 and 0.12 during the flowering and boll-forming stages, but was lower than that in the other varieties during the boll-opening stage. Thus, these characteristics of Xinluzao 43 were helpful for optimizing the light environment and maximizing light interception, thereby increasing photosynthetic capability. The photosynthetic rate and photosynthetic area were thus affected by cotton genotype as changes in the adjustment range of MTA, increases in peak values of LAI and SPAD, and extension of the functional stage of leaves. Available photosynthetic area and canopy light environment were affected by cotton plant type as changes in MTA and DIFN. Heterosis expression and plant type development were coordinated during different growth stages, the key to optimizing the canopy structure and further increasing yield.

FLUXAPYROXAD IN THE ASIAN SOYBEAN RUST CONTROL IN THE CERRADO BIOME

ABSTRACT The etiologic agent of the Asian soybean rust is the Phakopsora pachyrhizi, which causes a reduction in the photosynthetic leaf area and, consequently, in the crop yield. Chemical control is one of the main measures for its management. The objective of this work was to evaluate the efficacy and selectivity of the fluxapyroxad fungicide on controlling the Asian soybean rust, under the edaphoclimatic conditions of the Cerrado biome. The experiment was conducted in an area under no-tillage system, in the Agricultural Research Center, Rio Verde, Goias, Brazil, during the 2012/2013 crop season, using the cultivar NA7337. A randomized block experimental design was used, with twelve treatments and four replications. The treatments consisted of applications of fluxapyroxad (FX), pyraclostrobin (PT), epoxiconazole (EX) and metconazole (MZ). The average severity of the disease in the plants reached 37% in the Control. All treatments with fungicides differed from the Control. Treatments 9, 10, 11 and 12 provided the greatest rates of soybean rust control. The treatments 10, 11 and 12 had the highest thousand grain weights, and the yields of the treatments 2, 3 and 11, despite higher than the Control, were lower than the treatments 4, 5, 6, 7, 8, 9, 10 and 12, which had statistically equal yields. The increasing in yield, compared to the Control, ranged from 10.05% (pyraclostrobin, epoxiconazole + pyraclostrobin + mineral oil) to 30.55% (pyraclostrobin, pyraclostrobin + fluxapyroxad + mineral oil and pyraclostrobin + metconazole + mineral oil). The highest rates of soybean rust control were presented by fungicides containing fluxapyroxad.

WOFOST-GTC: A new model for the simulation of winter rapeseed production and oil quality

Rapeseed is one of the most important sources of vegetable oils, and its cultivation in Europe is expanding due to the economic incentives to grow energy crops. Given the unique characteristics of this crop, simulation studies targeting yield predictions and scenario analysis should be performed using specific models rather than using generic crop simulators adapted to rapeseed via calibration. This study presents a new model – WOFOST-GTC – which implements a dynamic representation of the rapeseed canopy architecture and includes modelling approaches to simulate oil content and composition. We reduced the number of model parameters to 35, compared to the 97 parameters of the original WOFOST model, from which it derives. WOFOST-GTC was developed using data collected in dedicated field experiments carried out in northern Italy in 2012–2013. The model ability to reproduce the underlying processes was evaluated using data collected in Europe between 1993 and 2013. In particular, dynamics involved with production and oil quality were evaluated on 7 and 18 datasets, respectively. The aboveground biomass and photosynthetic area index at different depths in the canopy were accurately simulated (R2=0.86 and 0.78, respectively). Despite the lower complexity, WOFOST-GTC proved to be as accurate as the original WOFOST model. The simulation of the seed oil content (R2=0.76) and of the oleic (R2=0.95), linoleic (R2=0.88) and α-linolenic acid (R2=0.95) fractions was accurate. Hence, we propose WOFOST-GTC as a suitable simulation model to analyse the rapeseed production and oil quality under different weather and management scenarios.

An empirical test of 'universal' biomass scaling relationships in kelps: evidence of convergence with seed plants.

Biomass allocation patterns have received substantial consideration, leading to the recognition of several 'universal' interspecific trends. Despite efforts to understand biomass partitioning among embryophytes, few studies have examined macroalgae that evolved independently, yet function ecologically in much the same ways as plants. Kelps allocate photosynthate among three organs (the blade(s), stipe(s) and holdfast) that are superficially convergent with organs of land plants, providing a unique opportunity to test the limits of 'universal' trends. In this study, we used an allometric approach to quantify interspecific biomass partitioning patterns in kelps and assess whether embryophyte-based predictions of biomass scaling can be applied to marine macrophytes that lack root-to-leaf hydraulic transport. Photosynthetic area and dry mass were found to scale to approximately the ¾ power and kelp biomass allocation patterns were shown to match closely to empirical measures of allometric scaling among woody plants. Larger kelp species were found to have increased relative stipe and holdfast mass than smaller species, highlighting important consequences of size for marine macroalgae. Our study provides insights into the evolution of size in the largest marine macrophytes and corroborates previous work suggesting that the morphology of divergent lineages of photoautotrophs may reflect similar selective pressures.

Identification of new sources of resistance to fungal leaf and head blight diseases of wheat

Tan spot (TS), Stagonospora nodorum blotch (SNB), spot blotch (SB), and Septoria tritici blotch (STB) caused by Pyrenophora tritici-repentis, Parastagonospora nodorum, Cochliobolus sativus and Zymoseptoria tritici, respectively, are the four important fungal leaf spotting diseases of wheat with global importance. These diseases reduce the photosynthetic area of leaves resulting in poor grain filling and lower yields; particularly when the penultimate and flag leaves are severely infected. Fusarium head blight (FHB) is another important fungal disease that infects wheat heads causing significant yield and quality deterioration including mycotoxins contamination. Host plant resistance is one of the main strategies in the management of these diseases. To identify new resistant sources to TS, SNB, STB, SB and FHB, 110 wheat cultivars and advanced breeding lines from different geographic origins were evaluated in growth chambers and field nurseries at the International Maize and Wheat Improvement Center (CIMMYT), Mexico. These materials have been previously evaluated for their field FHB resistance (combination of type I and II resistance) and performed well, but in the current study they were tested in greenhouse with point inoculation to confirm exclusively their type II resistance. The frequency of resistant lines was similar for TS, SNB and STB with 45, 40 and 33 genotypes, respectively. However, only 11 lines showed resistance to SB while 51 genotypes showed FHB type II resistance. Two genotypes of Chinese origin, NANJING 8611 and NANJING 4840, exhibited broad-spectrum resistance to all of the studied diseases and were not significantly different (P ≤ 0.01) from the resistant check of the respective diseases. The multiple disease resistant accessions identified in this study could be utilized in breeding programs aimed at improving wheat resistance to either individual or multiple leaf and head blight diseases.

Controle biológico de Mycosphaerella fragariae na cultura do morangueiro

The Mycosphaerella spot is one of the main foliar diseases of strawberry, degrating great leaf regions and reducing the photosynthetic area. Its control is mainly by the use of chemical fungicides, but, due the increasing demand for food free of pesticide, alternative control methods have been researched, such as biological control. This work aimed to evaluate the effect on strawberry plants, treated with the biological control agents Bacillus cereus, Saccharomyces boulardii and Saccharomyces cerevisiae, in the severity of Mycosphaerella fragariae, productivity and in the activity of β-1.3 glucanases, peroxidases and chitinases enzymes. It was verified that S. cerevisiae and B. cereus treatments were similar to fungicide for disease control. However, even reducing the severity of the disease, there was no increase in productivity, and the different control agents do not cause changes in the evaluated defense mechanisms.

Evaluating Grain Yield in Spring Wheat with Canopy Spectral Reflectance

ABSTRACTWorldwide, improving grain yield is the most important target for wheat (Triticum aestivum L.) breeders. Fast, cost‐effective, and nondestructive phenotyping methods for important traits are needed to increase the efficiency of cultivar development. The present study tested canopy spectral reflectance (CSR) as a potential high‐throughput method for assessing wheat grain yield in a diverse set of 540 spring‐habit accessions from the USDA–ARS National Small Grains Collection. Plots were grown under irrigated (IR) and terminal drought (DR) treatments over two growing seasons, and CSR was measured at several growth stages in each year. The CSR indices related to canopy water and N status, biomass, and photosynthetic area were evaluated for their relation to grain yield. The CSR indices were significantly correlated with yield at every growth stage, with anthesis and grain filling being the most useful for predicting grain yield in IR and DR environments. Single CSR indices selected up to 57% of the highest 25% yielding lines in DR conditions and the grain yield of accessions selected using CSR was 20% greater than randomly selected genotypes. Canopy spectral reflectance also identified up to 86% of the highest 10% yielding accessions. Canopy spectral reflectance may be valuable as a high‐throughput means of selecting for yield in large trials of genetically diverse wheat genotypes.

Low contribution of photosynthesis and water-use efficiency to improvement of grain yield in Chinese wheat

The contribution of photosynthesis to yield improvement is important to know in order to determine future breeding strategies. The objectives of this study were to determine the contribution of photosynthesis and water-use efficiency (WUE) to grain yield improvement of facultative wheat (Triticum aestivum L.) cultivars on the Loess Plateau of China released between 1937 and 2004. The grain yield has increased nearly sevenfold during this period. Surprisingly, these increases were not correlated with the rate of photosynthesis per unit of leaf area when the cultivars were planted and managed in the same environment. The increases were also not correlated with transpiration rate, stomatal conductance, or WUE, except at the jointing stage. The total increase in photosynthesis may be due to enlargement of photosynthetic area and photosynthesis duration. The grain yield was positively correlated with the number of grains per unit of area (r = 0.855, P<0.05), harvest index (HI) (r = 0.885, P<0.01), and thousand-grain mass (r = 0.879, P<0.01). The increase in grain yield was limited by the grain number and the grain size (sink-limited) and the yield improvement was attributed to a rise in HI over the last 70 years in a highland agricultural system in China.

Carbon storage potential of avenue trees: a comparison of Barringtonia racemosa, Cyclobalanopsis glauca, and Alnus formosana

Trees in cities play a valuable public health role for they are able to use photosynthesis to absorb atmospheric carbon dioxide (CO2), which is then stored as tree biomass. The present study compared the potential for carbon storage in the aboveground tree biomass of 3-year-old specimens of Barringtonia racemosa, Cyclobalanopsis glauca, and Alnus formosana grown in Chiayi City, Taiwan. Assessment of the carbon storage of avenue trees was based on measurement of the photosynthetic rate and leaf area, as well as the biomass of timbers, from October 2008 to 2009. Based on photosynthetic rates and leaf area, the estimated carbon stocks of B. racemosa, C. glauca, and A. formosana are 756, 615, and 2738 kg Cha−1 a−1, respectively. In addition, carbon storage can be estimated based on timber volume, and these results are 1170, 720, and 1995 kg Cha−1 a−1 for B. racemosa, C. glauca, and A. formosana, respectively. Based on these findings, A. formosana has the highest carbon fixation potential of these three trees. Although the photosynthetic rate measurements can provide detailed data on the diurnal changes in carbon stocks, this requires more time and labor. In contrast, timber volume measurements provide a rapid and convenient way to estimate carbon stocks.

Interpopulation Differences in Salinity Tolerance of the Invasive Cordgrass Spartina densiflora: Implications for Invasion Process

The invasive cordgrass, Spartina densiflora, has demonstrated a high tolerance to salinity stress. However, no attempt has yet been made to assess the intra-specific variation in salinity tolerance among S. densiflora populations. The aim of this study was to analyze the effects of provenance and salinity (0, 80, 170, 510, and 1023 mM NaCl) on germination, seedling survival, growth, and physiological performance of S. densiflora adult plants from three populations of the Gulf of Cadiz (Odiel, Tinto, and Piedras, SW Spain). Our results indicate that a salinity increment decreased germination and seedling survival of all S. densiflora populations, but these impairments were also dependent on the original population of the seeds. Accordingly, the Odiel population showed greater germination (70 %) and seedling survival (86 %) percentages at 510 mM NaCl than Tinto and Piedras populations, with mean percentage values of 57 % germination and 55 % seedling survival. These differences were also clearly reflected in long-term measurements, such as those regarding total dry mass, relative growth rate, and tiller number, which were mainly determined by the extent of photosynthetic area rather than the variations in net photosynthetic rate. Also, the higher tolerance of the Odiel population could be partly explained by a reduced level of Na in its tissues. Consequently, all populations might have the ability to colonize brackish marshes and river banks, but their invasion would be severely limited under hypersaline conditions, except in the case of the Odiel population, which would have a greater capacity for invasion of sub-optimal habitats, such a salt pans.

Weed Interference Effects on Leaves, Internode and Harvest &lt;span style="font-size: 12.0pt; font-family: 'Times New Roman',serif"&gt; Index of Dry Bean (&lt;i&gt;Phaseolus vulgaris&lt;/i&gt; L.)

The development of appropriate weed management strategies and efficient use of herbicides relies upon understanding weed-crop interactions. A field study was carried out to assess the effect of weed interference on leaves, internode and harvest index of dry bean (Phaseolus vulgaris L.). The experiment was established under a randomized complete block design with two types of weed interference treatments: plots with weeds and plots without weeds at different time intervals (0, 10, 20, 30, 40 and 50 days after crop emergence). The sigmoid Boltzmann model was used to quantify the crop traits as influenced by weed interference. Prolonged delays in weed removal reduced gradually the number of leaves of the crop. Weed interference decreased dry weight of leaves as well, so that the lowest value of it (33.49 g plant-1) was observed in full season during weed-infested treatment. Infestation of weeds affected the length of the crop internodes. While the weed interference duration increased, the length of the internodes decreased. Harvest index was also sensitive to weed competition. As the crop was kept weed-infested from the emergence for increasing periods of time, harvest index decreased to a value of 28.01%. A significant negative correlation between total biomass of weeds and dry bean traits (number of leaves, leaves dry weight, internode length and harvest index) was observed. Therefore, weeds are able to adversely affect dry bean growth through constraining environmental resources and impairing leaves as the photosynthetic areas.

Effect of Tillage on the Growth and Yield of Cowpea Varieties in Sudan Savanna Agroecology of Northern Nigeria

Field study was conducted during the rainy seasons (July-November) of 2007, 2008, 2009 and 2010 at the Research Farm of the International Institute of Tropical Agriculture (IITA) Minjibir, Kano State, Nigeria; to compare responses of six cowpea varieties to tillage. The treatments consisted of tillage systems (zero tillage, flat tillage and ridge tillage) as the main plot and cowpea varieties (IT89KD-391, IT90K-277-2, IT97K-461-4, IT97K-499-35, IT98K-131-2, and IT98K-506-1) as the sub-plot. The treatments were arranged as split plot laid out in a randomized complete block design with four replications. Zero tillage was significantly superior in influencing days to maturity, canopy height, intercepted Original Research Article Ewansiha et al.; ARRB, 5(3): 275-284, 2015; Article no.ARRB.2015.030 276 photosynthetic active radiation (IPAR) and leaf area index but not total dry matter and grain yield of cowpea. A positive and significant association was recorded for days to physiological maturity and canopy height across the tillage systems with a correlation coefficient of ≤ 40% for days to maturity and ≥50% for canopy height. Though flat tillage showed a positive correlation with intercepted photosynthetic active radiation (IPAR) and leaf area (LAI), but this association was not significant. However, ridge tillage showed a positive and significant correlation with IPAR and LAI (r =0.378*** and 0.384***). All the tillage systems showed a high and significant positive correlation with cowpea dry matter and fodder yield (r= 0.54*** to 0.77***). Across varieties, grain yield was better with flat tillage than zero and ridge tillage systems, with 10% yield advantage over the two. Zero and ridge tillage were similar in their effects on grain yield. Except for IPAR, LAI and total dry matter (TDM), the interaction effect of cowpea varieties and tillage systems was significant. Our result point to the fact that extensive soil tillage (especially, conventional tillage) may not be necessary for cowpea production in this agro-ecology with a high percentage of sand and a sandy loam as soil textural class. Following our result, we may recommended varieties for the different tillage systems as follows: IT98K-131-2, IT97K-461-4, IT90K-277-2, IT98K-506-1 (grain) and IT89KD-391/IT97K-4614 (best for fodder) for zero tillage system; IT90K-277-2, IT97K-499-35, IT98K-131-2 and IT98K506-1(grain) and IT89KD-391/IT97K-499-35 (best for fodder) for flat-tillage; IT98K-131-2, IT90K277-2, IT98K-506-1 and IT97K-464-4(grain) and IT90K-277-2/ IT89KD-391 (best for fodder) for ridge tillage).

Population Quality and Photosynthetic Characteristics after Anthesis in Yangmai 20 with Yield Potential of 9000 kg ha-1 in Rice-Wheat Rotation System

The objective of this study was to fine-tune cultivation techniques for large-scale high yielding( ≥9000 kg ha–1) wheat production in rice–wheat rotation system. Wheat(Triticum aestivum L. cv. Yangmai 20) populations with yield level ≥9000 kg ha–1(P1) and 9000 kg ha-1(P2) were established through managing application amount, timing and splitting ratio of nitrogen fertilizer in the 2010–2011 and 2011–2012 growing seasons. The grain yield and grain number per spike in P1 population were 10.0% and 5.5% higher than those of P2 population with significant difference between each other. However, the differences in spike number and 1000-grain weight between P1 and P2 were not significant. The yield components of P1 population were 4.82–5.38 million spikes per hectare, 47–49 grains per spike, and 34–39 g of 1000-grain weight. Grain yield of different populations showed parabolic correlations with leaf area index(LAI) at booting and anthesis stages, leaf area decreasing rate and photosynthetic potential after anthesis, as well as significantly linear correlations with LAI at milk-ripening stage, grain weigh per square centimeter leaf and population growth rate. According to the experiments results in two years, P1 population was characterized with dynamic LAI of 6.5–7.0 at booting, 5.0–6.0 at anthesis and 4.0–4.5 at milk-ripening stage; grain/leaf ratio of 0.37–0.39 grains cm–2 leaf and 13.50–14.50 mg grain cm–2 leaf; LAI decrease rate of 0.13–0.15 d–1 after anthesis; population growth rate of 19–20 g m–2 d–1 after anthesis; photosynthetic potential of 1.03–1.18 million m2 d ha–1 after anthesis; and net assimilation of 9–11 g m–2 d–1 after anthesis. At the stages of 21 and 28 days after anthesis, the SPAD reading, net photosynthetic rate, malondialdehyde content, and activities of antioxidant enzymes(CAT, POD, and SOD) in flag leaves were significantly correlated with grain yield. Our results suggest the following key points of cultivar potential for 9000 kg ha–1 yield potential of Yangmai 20 in rice–wheat rotation system are suitable population spike number as the basis; synchronous increases of grain number per spike and 1000-grain weight; high photosynthetic area and photosynthetic rate before anthesis; slow decrease of photosynthetic area after anthesis with its maintainable high level, and an abundant accumulated assimilate meeting to the sink enrichment.