Pre-flowering Phase Research Articles

Morfofisiologia de gravioleira sob estresse salino e aplicação de H2O2 na fase de pré-floração

ABSTRACT In the semi-arid region of the Brazilian Northeast, water sources generally have high levels of salts, standing out as one of the abiotic stresses that restrict the growth and development of plants. In this context, the objective of the present study was to evaluate the effects of foliar applications of hydrogen peroxide on the morphophysiology of soursop under salt stress in the pre-flowering phase. The experiment was carried out in a greenhouse, using a randomized block design and a 4 × 4 factorial arrangement, with four values of electrical conductivity of the irrigation water - ECw (0.8, 1.6, 2.4, and 3.2 dS m-1) and four concentrations of hydrogen peroxide - H2O2 (0, 10, 20, and 30 μM), with three replicates. An increase in water electrical conductivity from 0.8 dS m-1 reduced stomatal conductance, CO2 assimilation rate, instantaneous carboxylation efficiency, and leaf water saturation deficit. It inhibited the growth of soursop plants at 370 days after transplanting. Hydrogen peroxide at concentrations of up to 10 μM increased leaf transpiration and water use efficiency of soursop plants irrigated with 1.8 dS m-1 water in the pre-flowering phase.

Diagnóstico nutricional de mangueiras na pós-colheita em antecipação ao pré-florescimento evita estresse nutricional

ABSTRACT The São Francisco Valley region of Brazil is a leading exporter of mango fruits. Previous nutritional diagnosis can identify stresses, provide adjustments for nutritional limitations, and promote more efficient fertilization and nutrient management. This study aimed to compare the nutritional diagnosis of mango trees in the post-harvest and pre-flowering phases and to correlate them with productivity. Norms and indices of the Integrated System of Diagnosis and Recommendation (DRIS), as well as the Nutritional Balance Index and the Potential of Response to Fertilization were generated for each phenological phase of the mango trees. Optimal concentrations and ranges of nutrients were established, classified as deficient, balanced, or excessive, and subsequently compared to each other and to values recommended in the literature. The indices were correlated with the productivity of the orchards in each phenological phase of the mango trees. When comparing the DRIS norms of post-harvest and pre-flowering phenological phases, 55% of the averages differed. The sufficiency ranges of the post-harvest and pre-flowering phases were generally different from those referenced in the literature. Nutritional diagnoses for P, K, Ca, Mg, S, Zn, and Cl altered between phenological phases. The nutritional diagnosis performed in the post-harvest phase showed that nutritional imbalance affected productivity.

Physiological Response of Common Bean (Phaseolus vulgaris L.) to Varying Temperature and Irrigation Regimes

Background: Elevated temperature and water stress are the key limiting factors affecting the kidney bean yield. Climate change is projected to enhance these risks for successful crop production. However quantified information, which is limited, on temperatures stress at various growth phases in combination with water regimes, becomes important for optimizing management decisions for higher productivity of kidney bean. The current study is aimed to fill this gap. Methods: A field experiment was conducted during January-April 2020, to investigate the effect of irrigation and temperature regimes on growth parameters and yield of kidney bean. Temperature treatments imposed were elevated temperature for entire crop period i) ~4.6°C ii) ~3.1°C iii) ~2.8°C above mean ambient (19.6°C), iv) ambient temperature Tmax and Tmin regime of 25.9/13.4°C (mean 19.6°C), v) elevated temperature during pre-flowering phase (~3.7°C above mean ambient during that period, 19.6°C), vi) flowering phase (~5.3°C above mean ambient during that period, 23.1°C) and pod-filling phase (~5.2°C above mean ambient during that period, 28.9°C). These were combined with i) two irrigations (applied at sowing and seedling phase) and ii) three irrigations (additional irrigation at pod-filling phase). Result: Elevated temperature regimes led to shortening of the crop duration. LAI, NDVI, net photosynthesis and seed yield were higher in plants exposed to continuous elevated temperature. Heat shock during pre-flowering and flowering led to reduction in yield. Despite exposure to elevated temperature, supplemental irrigation led to higher yield. Seed yield loss was greater when temperature stress coincided with water stress. The negative effects of high temperature were significantly curtailed by provision of supplemental irrigation.

Interactive effect of irrigation and temperature regimes on growth and development of kidney bean (Phaseolus vulgaris L.)

Approximately 60 percent of kidney bean (Phaseolus vulgaris L.) produced in developing countries is cultivated under conditions of drought stress and low fertility/ low input. Coincidence of water and heat stress, which is projected to occur more in changing climates, cause severe yield loss. To quantify the response of kidney bean to water and temperature stress, an experiment was carried under Randomized Block Design in field and temperature gradient tunnel conditions. Temperature treatments included high temperature for entire crop growth period (~4.6℃, ~3.1℃, ~2.8℃ above mean ambient, 19.6℃), ambient temperature, elevated temperature during pre-flowering phase (~3.7℃ above mean ambient during that period, 19.6℃), flowering phase (~5.3℃ above mean ambient during that period, 23.1℃) and pod-filling phase (~5.2℃ above mean ambient during that period, 28.9℃). These were combined with i) two irrigations (applied at sowing and seedling phase) and ii) three irrigations (additional irrigation at pod-filling phase). Results indicated that plants under seasonal mean temperatures of 36.7/11.7℃, 33.9/11.6℃ and 33.1/11.7℃ had shortened crop duration with 73-78 DAS. Findings this study indicated that kidney bean exhibits phenological plasticity response to temperature and water regimes. Seasonal mean temperature of 24.2℃ lead to better performance of the crop while temperature shocks during pre-flowering and flowering significantly reduced seed yield. Additionally, exposure of kidney bean plants to water stress (available soil moisture content <10%) significantly reduced seed yield. Coincidence of temperature stress and water stress had more detrimental effects on seed yield. Given the climate scenarios indicating increased variability in temperature and rainfall, findings from this study indicate that climatic risks mayaffect kidney bean seed yield in future. Strategies such as providing supplemental irrigation can alleviate the negative effects of temperature stress and improve kidney bean yield.

Agronomic performance of soybean genotypes supplemented with micronutrients via leaf

Foliar fertilization, mainly with micronutrients, is one of the tools most recommended by researchers and professionals to growers in order to correct nutritional imbalances in crops. This work aimed to evidence the agronomic performance of soybean genotypes supplemented via leaf with micronutrients and to identify the relationships between characters. The experimental design used was in randomized blocks in a 3x5 factorial scheme corresponding to three soybean genotypes ANTA82, CD2737 and N7902 and five concentrations of leaf supplement, Triplus Anuais® with its guarantees of phosphorus 2%, boron 3.4%, molybdenum 1 % and nickel 0.35%. The leaf supplement was applied in a single dose during pre-flowering (0, 300, 600, 900 and 1200 ml ha-1). The variables were analyzed after the plants were harvested at the physiological maturation stage and the data were submitted to the assumptions of the statistical models. Analysis of variance was carried out with subsequent splitting with grouping of Scott-Knott means and polynomial regression models, in addition to simple correlation and path analysis, with grain yield as the main variable and the other variables as explanatory. The different performances of soybean genotypes were verified when submitted to foliar supplementation of micronutrients with adjustment of the most efficient dose for yield, through the regression curves. That supplementation via leaf with micronutrients in the pre-flowering phase was efficient for all soybean genotypes analyzed. However, it is worth mentioning the high yields obtained by the NS 7209 IPRO genotype at a dose of 514.23 ml ha-1. The selection of productive soybean genotypes can be performed indirectly by the number of legumes, grains per plant and the weight of a thousand grains.

Залежність між темпами розвитку і життєвістю особин у популяціях раритетних видів рослин високогір’я Українських Карпат

The article presents an overview of long-term research and numerous publications on the relationship between developmental rate and individual vitality in populations of rare and endemic plant species in the high-mountain zone of the Ukrainian Carpathians: a case study on Ranunculus thora, Primula halleri, Leontopodium alpinum, Gentiana acaulis, Doronicum clusii, Saussurea alpina, Oreochloa disticha, Pulsatilla alba, Rhododendron myrtifolium, Senecio сarpathicus, Festuca carpatica, Heracleum carpaticum, Phyteuma vagneri etc. Stationary in-situ research was conducted at the study sites founded 5–30 years ago. The greatest impact on the individual and population vitality is caused by the position changes in coenosis of the species of different life forms and strategies. Increasing of the shrub positions accelerates the decreasing of vitality of low shrubs and grasses especially, and vice versa, increasing of the coenotic position of high-growing shrubs and grasses cau­ses the vitality decrease of short-growing heliophytes, including most of the rare species. The individual vitality and population viability determines some influence on the dynamics of their seasonal development. The individual development is faster at higher vitality level. It results in the relatively earlier beginning of phenophases. In the coenoses where the value of population as ecosystem engineer is higher, the accelerated dynamics of pre-flowering phases and longer flowering period is observed. The individual vitality and relative age of vegetatively active species increase significantly under the developmental conditions without vegetative reproduction. The vitality of vegetative diaspores significantly change due to the effect of autonomous development of shoots and ramets in comparison to the original vitality of maternal individuals. The effect of inertia of individual and population vitality consists in the gradual change of their vitality under the changeable conditions of their existence. Only drastic adverse exogenous effects can cause a sudden decrease of their vitality. Processes of the transition of low vitality individuals to the high rank are the slowest ones.

Effects of Growth Phase and Ultraviolet-B Pretreatment in Perilla Leaves on the Two-Spotted Spider Mite.

Perilla, Perilla frutescens (L.) Britton var. crispa (Thunb.) H. Deane, is traditionally cultivated as an edible/medicinal crop in East Asia. Its essential oil contains many bioactive compounds that are expected to have high pharmacological functionality, as well as antimicrobial and insecticidal activity. Spider mites are a major pest group for perilla cultivation. The two-spotted spider mite, Tetranychus urticae Koch, possesses divergent detoxification enzymes and has developed resistance against most acaricides. The essential oil content of perilla halves from the pre-flowering phase to the flowering phase, and ultraviolet (UV)-B radiation generally increases defense compounds. To clarify the effects of this change in essential oil content and the effects of UV-B pretreatment, we investigated the developmental success and egg production of T. urticae on leaves from the preflowering and flowering phases cultivated with and without nighttime UV-B irradiation. Both the parameters significantly increased on leaves from the flowering phase in comparison with that from the preflowering phase, suggesting that constitutively produced essential oil provided protection against mite pests in a growth phase-specific manner. The defense system also extended the developmental period of mites on red perilla leaves, but not on green perilla leaves, in preflowering phase. Although egg production was lower on red perilla leaves pretreated with UV-B, no negative effects were caused on the developmental success and duration on red and green perilla and the egg production on green perilla by UV-B pretreatment. Our findings reveal a significant impact of investment allocation of perilla plants and a small contribution of UV-B irradiation to the plant defense system.

Natural post-flowering photoperiod and photoperiod sensitivity: Roles in yield-determining processes in soybean

Promising yield-determining responses to artificial photoperiod manipulation during post-flowering phases have been identified in soybean [Glycine max (L.) Merrill]. These responses enhance resource capture as a result of changes in phase duration, and resource use efficiency as a result of changes in node production and pod development, alleviating intra-node pod interference. This work aims to evaluate the relevance of these responses under natural conditions and discriminate direct from indirect photoperiodic effects, that is, effects caused by changes in the capture of resources. Two field experiments were conducted with a combination of sowing dates, with similar pre- and different post-flowering photoperiod, indeterminate genotypes including near isogenic lines and commercial varieties with different photoperiod sensitivity, and shadings with different incident radiation during post-flowering. Longer post-flowering photoperiod and higher plant photoperiod sensitivity delayed crop development, particularly in lines with alleles E2, E3 or Clark background. This delay resulted in extra radiation capture and node production, which were positively related to yield. Direct photoperiodic effects on nodes per m2 were evidenced in response to changes in post-flowering photoperiod and plant photoperiod sensitivity. The distribution of available resources such as radiation in more nodes per m2 increased use efficiency. Longer post-flowering photoperiod and higher plant photoperiod sensitivity enhanced pod establishment on usually dominated positions such as lateral racemes, affecting pods per m2. Finding these relevant yield-determining effects under natural conditions suggests that processes related to post-flowering photoperiodic responses are a plausible way to enhance resource capture and use efficiency and yield in soybean production systems. In cropping systems in which the whole growing season is used to maximize yield, these post-flowering photoperiodic responses could be adopted at the expense of the pre-flowering phase duration.

Assessing the impact of agro-climatic factors on pod filling of grass pea

Field experiments were conducted for two successive years with grass pea (cv. ‘Prateek’) sown on nine dates at weekly interval at Instructional Farm (22°58´ N, 88°31´ E), Bidhan Chandra Krishi Viswavidyalaya, West Bengal, India to investigate the impact of agroclimatic factors on pod filling of grass pea. Results showed that pod filling percentage (PFP) increased with delay in sowing dates, attaining the highest value (96.7 %) in crop sown on 30th November, beyond which it decreased gradually with further delay in sowing. Maximum and minimum temperatures, morning and afternoon soil temperatures, recorded at 5, 15 and 30 cm soil depths, morning and afternoon vapour pressure deficits at pre-flowering phase exhibited negative association and contrarily, when prevailing during reproductive and pod development phases, these parameters demonstrated positive correlation with PFP. Temperature range during reproductive phase increased with delay in sowing dates and it exhibited significant positive correlation with PFP. As demonstrated by stepwise regression analysis, Accumulated photothermal unit (APTU) prevailing at maturity phase alone accounted for 67.4 % of the total variation in PFP and together with temperature range it explained 91.3 % variation. APTU, temperature range, afternoon vapour pressure deficit and afternoon soil temperature seem to be the critical agroclimatic variables influencing the pod filling percentage significantly.

Nighttime warming increases winter-sown wheat yield across major Chinese cropping regions

Understanding the actual impacts of climatic warming on winter-sown wheat production will benefit cultivar breeding efforts and agronomic innovations and may help to improve food security. Therefore, we conducted a comprehensive study across the main Chinese winter wheat cropping regions, comprising field warming experiments at four locations and an analysis of 36 years of winter wheat yield data. In the field warming experiments, an increase of 1.0°C in nighttime temperature enhanced wheat yield by 10.1% on average (P<0.05). Warming-induced enhancement of 1000-grain weight explained most of these yield increases. Warming shortened the length of pre-flowering phase by 5.4 days, while it prolonged the length of post-flowering phase by 3.8 days. Grain yield increases with warming were similar across experimental sites, even though warming-induced changes in the length of growth periods decreased with increasing ambient temperature. Our analysis of the historical data set was consistent with our field warming experiments; between 1980 and 2015, the major Chinese cropping regions experienced significant warming, especially in daily minimum temperature. Across the historical data set, daily minimum temperature was positively correlated with wheat yield (142.0kgha−1°C −1). Our findings are inconsistent with previous reports of yield decreases with warming and may help to inform policy decisions and agronomic innovations of Chinese wheat production to better cope with future climate warming.

Disaggregating sorghum yield reductions under warming scenarios exposes narrow genetic diversity in US breeding programs

Historical adaptation of sorghum production to arid and semiarid conditions has provided promise regarding its sustained productivity under future warming scenarios. Using Kansas field-trial sorghum data collected from 1985 to 2014 and spanning 408 hybrid cultivars, we show that sorghum productivity under increasing warming scenarios breaks down. Through extensive regression modeling, we identify a temperature threshold of 33 °C, beyond which yields start to decline. We show that this decline is robust across both field-trial and on-farm data. Moderate and higher warming scenarios of 2 °C and 4 °C resulted in roughly 17% and 44% yield reductions, respectively. The average reduction across warming scenarios from 1 to 5 °C is 10% per degree Celsius. Breeding efforts over the last few decades have developed high-yielding cultivars with considerable variability in heat resilience, but even the most tolerant cultivars did not offer much resilience to warming temperatures. This outcome points to two concerns regarding adaption to global warming, the first being that adaptation will not be as simple as producers' switching among currently available cultivars and the second being that there is currently narrow genetic diversity for heat resilience in US breeding programs. Using observed flowering dates and disaggregating heat-stress impacts, both pre- and postflowering stages were identified to be equally important for overall yields. These findings suggest the adaptation potential for sorghum under climate change would be greatly facilitated by introducing wider genetic diversity for heat resilience into ongoing breeding programs, and that there should be additional efforts to improve resilience during the preflowering phase.

Leaf norms and nutrition diagnosis of coffee conilon in floweting and graining in espirito santo

The cultivation technology of Coffea canephora advanced significantly, as well as the nutritional requirements of the plants. The objective of this study was to establish the sufficiency range and Leaf Norms (DRIS) of Conilon coffee crops in floweting and grain graining in Espirito Santo, as well as nutritional diagnosis assessment in the region by different methods. The crops selected for the establishment of leaf patterns showed productivity greater than or equal to 6,000 kg ha-1. The samples were collected in 20 farms in two seasons, floweting (June and July 2012) and grain graining (October and November 2012). To check the differences between the standards (mean, standard deviation and coefficient of variation of the nutrient and their respective relationships with other nutrients) the F test (ANOVA) was used. Nutritional diagnosis was performed using the sufficiency ranges and DRIS index. 245 fields sampled in the phase of grain filling and 313 in the pre-flowering phase. The standards set are appropriate for a representative nutritional diagnosis to the north of the Espirito Santo, since they are based on high-yield crops. The average concentrations of N, P, K, S, Cu and Zn were higher in the graining period of Conilon coffee, while the average concentrations of Ca, Mg, Mn and Fe were higher in floweting period. There were differences in 87 relations of nutrients among the 110, between two sampling periods. It is suggested that the sufficiency range approach and DRIS norms are specific to each sampling time, otherwise the diagnosis can be inconsistent.

Maturity groups and growing seasons as key sources of variation to consider within breeding programs for high yielding rice in the tropics

Differences in crop performance between seasons has raised concerns on whether or not contrasting rice varieties should be grown in each season in the tropics. Solving this question requires evaluation if key plant traits subtending grain yield are expressed similarly across seasons. Within each dry season (DS) and wet season (WS), one approach to address the issue was to group 32 high-yielding and contrasted cultivars with respect to crop duration, and to consider the crop cycle as two distinct phases: the first one from early vegetative to flowering (pre-flowering) and the second one from flowering to maturity (post-flowering). For each of these two phases, one key descriptive parameter was identified, the potential sink size (PSS) at flowering for the pre-flowering phase, and the grain filling rate (FR) for the post-flowering phase. Significant correlations were observed for grain yield with both PSS and FR within maturity groups in both seasons, indicating the strong effect of both phases in grain yield establishment. Finally, relevant traits in the DS were those favoring light capture along the whole crop cycle in both maturity groups. Traits for the WS differed among maturity groups. Traits for the early maturity group were also those favoring light capture, while the same traits were non desirable for the medium and late maturity groups, for which delayed leaf senescence and short plant height were identified. The difference between relevant traits highlights the need of developing distinct breeding programs respective of the growing seasons and maturity groups.

Differences in the impacts of nighttime warming on crop growth of rice-based cropping systems under field conditions

Abstract Great attentions have been taken to the effects of climatic warming on crop production, however, fewer were known about the actual impacts of nighttime warming under different cropping systems. Therefore, a three-year field experiment with a passive nighttime warming (PNW) facility and a one-year field experiment with free air temperature increase (FATI) facility were conducted in major Chinese rice cropping systems. Four-year field observations from different rice cropping systems all showed that nighttime warming less than 1.0 °C could shorten the length of crop pre-flowering phase period while prolonged the length of post-flowering phase period, resulting in insignificant reduction in the length of crop entire growth period. The temperature increase caused significant increments in grain yields by 16.2, 12.7 and 12.0% for late rice in the rice–rice cropping system, wheat in the rice-wheat cropping system and rice in the single rice cropping system, respectively. However, this warming declined grain yields significantly by 4.5 and 6.5% for early rice in the rice–rice cropping system and rice in the rice-wheat cropping system, respectively. Since warming-induced yield reduction was less than warming-induced increment in each cropping system, the annual yields was higher in the warmed plots than the non-warmed under all systems. Our findings can provide important references to cropping system adjustment for coping with global warming in China and other regions.

Climate effects on crop yields in the Northeast Farming Region of China during 1961–2010

SUMMARYCrop production in the Northeast Farming Region of China (NFR) is affected considerably by variation in climatic conditions. Data on crop yield and weather conditions from a number of agro-meteorological stations in NFR were used in a mixed linear model to evaluate the impacts of climatic variables on the yield of maize (Zea mays L.), rice (Oryza sativa L.), soybean (Glycine max L. Merr.) and spring wheat (Triticum aestivum L.) in different crop growth phases. The crop growing season was divided into three growth phases based on the average crop phenological dates from records covering 1981 and 2010 at each station, comprising pre-flowering (from sowing to just prior to flowering), flowering (20 days around flowering) and post-flowering (10 days after flowering to maturity). The climatic variables were mean minimum temperature, thermal time (which is used to indicate changes in the length of growth cycles), average daily solar radiation, accumulated precipitation, aridity index (which is used to assess drought stress) and heat degree-days index (HDD) (which is used to indicate heat stress) were calculated for each growth phase and year. Over the 1961–2010 period, the minimum temperature increased significantly in each crop growth phase, the thermal time increased significantly in the pre-flowering phase of each crop and in the post-flowering phases of maize, rice and soybean, and HDD increased significantly in the pre-flowering phase of soybean and wheat. Average solar radiation decreased significantly in the pre-flowering phase of all four crops and in the flowering phase of soybean and wheat. Precipitation increased during the pre-flowering phase leading to less aridity, whereas reduced precipitation in the flowering and post-flowering phases enhanced aridity. Statistical analyses indicated that higher minimum temperature was beneficial for maize, rice and soybean yields, whereas increased temperature reduced wheat yield. Higher solar radiation in the pre-flowering phase was beneficial for maize yield, in the post-flowering phase for wheat yield, whereas higher solar radiation in the flowering phase reduced rice yield. Increased aridity in the pre-flowering and flowering phases severely reduced maize yield, higher aridity in the flowering and post-flowering phases reduced rice yield, and aridity in all growth phases reduced soybean and wheat yields. Higher HDD in all growth phases reduced maize and soybean yield and HDD in the pre-flowering phase reduced rice yield. Such effects suggest that projected future climate change may have marked effects on crop yield through effects of several climatic variables, calling for adaptation measures such as breeding and changes in crop, soil and agricultural water management.

Models for forecasting the flowering of Cornicabra olive groves

This study examined the impact of weather-related variables on flowering phenology in the Cornicabra olive tree and constructed models based on linear and Poisson regression to forecast the onset and length of the pre-flowering and flowering phenophases. Spain is the world's leading olive oil producer, and the Cornicabra variety is the second largest Spanish variety in terms of surface area. However, there has been little phenological research into this variety. Phenological observations were made over a 5-year period (2009-2013) at four sampling sites in the province of Toledo (central Spain). Results showed that the onset of the pre-flowering phase is governed largely by temperature, which displayed a positive correlation with the temperature in the start of dormancy (November) and a negative correlation during the months prior to budburst (January, February and March). A similar relationship was recorded for the onset of flowering. Other weather-related variables, including solar radiation and rainfall, also influenced the succession of olive flowering phenophases. Linear models proved the most suitable for forecasting the onset and length of the pre-flowering period and the onset of flowering. The onset and length of pre-flowering can be predicted up to 1 or 2 months prior to budburst, whilst the onset of flowering can be forecast up to 3 months beforehand. By contrast, a nonlinear model using Poisson regression was best suited to predict the length of the flowering period.

Variations in Hormones and Antioxidant Status in Relation to Flowering in Early, Mid, and Late Varieties of Date Palm (Phoenix dactylifera) of United Arab Emirates.

The present study was carried out to assess the status of various hormones responsible for the flower induction of Nagal, Lulu, and Khalas date palm varieties in UAE. The nonenzymatic antioxidant compounds and the antioxidant enzymatic activities at preflowering, flowering, and postflowering stages of the date palm varieties were quantified. The ABA and zeatin concentrations were found to be significantly higher during the preflowering stage but gradually decreased during the flowering period and then increased after the flowering stage. Gibberellic acid (GA) concentrations were significantly higher in the early flowering varieties and higher levels of ABA may contribute to the delayed flowering in mid and late varieties. The results on hormone profiling displayed a significant variation between seasons (preflowering, flowering, and postflowering) and also between the three date palms (early, mid, and late flowering varieties). Ascorbic acid (AA) concentration was low at the preflowering stage in the early flowering Nagal (0.694 mg/g dw), which is similar with the late flowering Lulu variety (0.862 mg/g dw). However, Khalas variety showed significantly higher amount of AA content (7.494 mg/g dw) at the preflowering stage when compared to other varieties. In flowering stage, Nagal (0.814 mg/g dw) and Lulu (0.963 mg/g dw) were similar with respect to the production of AA, while the mid flowering variety showed significantly higher amount of AA (9.358 mg/g dw). The Khalas variety produced the highest tocopherol at 4.78 mg/g dw compared to Nagal and Lulu, at 1.997 and 1.908 mg/g dw, respectively, during the preflowering stage. In Nagal variety, the content of reduced glutathione (GSH) at the preflowering stage was 0.507 mg/g dw, which was not significantly different from the flowering and postflowering stages at 0.4 and 0.45 mg/g dw, respectively. The GSH was significantly higher in Khalas compared to Nagal and Lulu varieties, at 1.321 mg/g dw in the preflowering phase followed by 3.347 mg/g dw and 2.349 mg/g dw at the flowering and postflowering phases, respectively. Catalase activity increased with different stages of growth. The lowest catalase activity was observed at the preflowering stage in Khalas (0.116), with similar observations noted during flowering (0.110) and postflowering stage. This study provides an insight into the possible roles of endogenous hormones and antioxidants and in the activities of antioxidant enzymes in the regulation of flower development in date palm varieties.

Assessment of pest insects of &lt;i&gt;Capsicum annuum&lt;/i&gt; L.1753 (Solanaceae) in a cultivation cycle in Yaoundé

Pepper, Capsicum annuum is appreciated in tropical regions for its taste and its ability to increase the appetite level of food. This study aimed at investigating pest insects’ diversity of pepper right from pricking out to harvest. It also examined how aphids and whiteflies populations vary in the plant’s life cycle and specific fruit pests’ effects on the yield. During five months, individual plant organs were examined weekly. Insects encountered were captured, counted and identified. Immature stages were bred for identification purposes. Regular sampling allowed us to identify 28 species from 7 orders. During the pre-flowering phase, 5 orders were obtained: Hemiptera, Hymenoptera, Coleoptera, Lepidoptera and Orthoptera. The same orders were found at Flowering-fruiting phase, with appearance of one new order, the Thysanoptera. At this stage, exponentialgrowth of Hemiptera and Hymenoptera was also observed. During maturation, Diptera and Lepidoptera were the most abundant pests. Ceratitis capitata and Cryptophlebia leucotreta were responsible for yield losses (20.46%). Aphids and whiteflies affected plant’s fitness, either directly through sap sucking or indirectly through viral transmissions. Ants’transport, disseminate and protect Hemipterans. Since plants phenology influences pest diversity, it should be taken into account in the efforts of developing IPM strategies.Keywords: Spice, phenology, yield, IPM.

Environmental factors affecting yield variability in spring and winter rapeseed genotypes cultivated in the southeastern Argentine Pampas

Rapeseed yields in Argentina are low (averaging 1400kg/ha nationwide) with a high inter-annual variability. One of the limiting factors for improving yields is the lack of information on the adaptability of the cultivars, especially in the main rapeseed-producing area, the southeastern Pampas. The objectives of this study were to (i) quantify and analyze the yield variability of winter and spring rapeseed hybrids introduced in Argentina, (ii) identify the main environmental factors that affect the yields of the spring and winter genotypes in the southeastern Pampas, and (iii) model and validate rapeseed yields from environmental variables in the pre- and post-flowering periods. Principal component analysis (PCA) and linear regression methods were used to analyze 129 data points from 16 comparative yield trials in eight sites of southeastern Pampas. The rainfed crops were sown between April and July and from 2007 to 2009. Pre- and post-flowering phases were recorded in each experiment; temperature, frost occurrences, rainfall and radiation were measured during each phase. Yield variability (600–3700kgha−1) was slightly lower in spring than in winter genotypes (CV 0.25 versus 0.38). Sixty percent of the winter genotype variability was explained by the first axis which was associated to the pre- and post-flowering durations, while 25% of the variability was explained by the second axis associated to yield. Almost 50% of the spring genotype variability was explained by the first axis associated to pre-flowering and total durations, while 27% of the variability was explained by the second axis in which post-flowering duration was associated to yield. Winter genotypes evidenced vernalization requirements that were either partially or not fulfilled, so, the longer the photoperiod, the longer the pre-flowering phase duration. In the critical period of 30d post-flowering, yield was not associated to the photothermal quotient. In winter genotypes, yield was associated to a linear model which included rainfall during the crop cycle, radiation and pre-flowering temperatures (R2=0.50). The model was adequately validated with independent data (n=116) from official trials. For spring genotypes, only the frost occurrences during the critical period were relevant (R2=0.26) and placing the flowering time after October decreased the risk of late frost damage. Water use efficiency (WUE) values ranged from 1.6 to 6.7kgha−1 per mm of rain without a clear trend between spring and winter genotypes for this trait. In conclusion, winter genotypes did not necessarily yield more than the spring materials. In addition, rainfall during the crop cycle and frost occurrences during flowering were the main limiting factors of the winter and spring genotype yields, respectively, in the southeastern Pampas.

Water and thermal regimes for field pea in Australia and their implications for breeding

There is a large gap between the refined approaches to characterise genotypes and the common use of location and season as a coarse surrogate for environmental characterisation of breeding trials. As a framework for breeding, the aim of this paper is quantifying the spatial and temporal patterns of thermal and water stress for field pea in Australia. We compiled a dataset for yield of the cv. Kaspa measured in 185 environments, and investigated the associations between yield and seasonal patterns of actual temperature and modelled water stress. Correlations between yield and temperature indicated two distinct stages. In the first stage, during crop establishment and canopy expansion before flowering, yield was positively associated with minimum temperature. Mean minimum temperature below ~7°C suggests that crops were under suboptimal temperature for both canopy expansion and radiation-use efficiency during a significant part of this early growth period. In the second stage, during critical reproductive phases, grain yield was negatively associated with maximum temperature over 25°C. Correlations between yield and modelled water supply/demand ratio showed a consistent pattern with three phases: no correlation at early stages of the growth cycle, a progressive increase in the association that peaked as the crop approached the flowering window, and a progressive decline at later reproductive stages. Using long-term weather records (1957–2010) and modelled water stress for 104 locations, we identified three major patterns of water deficit nation wide. Environment type 1 (ET1) represents the most favourable condition, with no stress during most of the pre-flowering phase and gradual development of mild stress after flowering. Type 2 is characterised by increasing water deficit between 400 degree-days before flowering and 200 degree-days after flowering and rainfall that relieves stress late in the season. Type 3 represents the more stressful condition with increasing water deficit between 400 degree-days before flowering and maturity. Across Australia, the frequency of occurrence was 24% for ET1, 32% for ET2 and 43% for ET3, highlighting the dominance of the most stressful condition. Actual yield averaged 2.2 t/ha for ET1, 1.9 t/ha for ET2 and 1.4 t/ha for ET3, and the frequency of each pattern varied substantially among locations. Shifting from a nominal (i.e. location and season) to a quantitative (i.e. stress type) characterisation of environments could help improving breeding efficiency of field pea in Australia.