Seedlings In Field Research Articles

Integrated management of major tomato diseases

Five integrated pest management (IPM) packages for management of major tomato diseases were evaluated during kharif seasons of 2015-18 using tomato cv.NS501. The most effective integrated schedule comprised of (a) seed priming with Seed pro (combination product of Bacillus subtilis and Trichoderma harzianum) @4g/ kg of seed followed by soil application of Seed pro @10g/kg of soil while filling of pro trays and soil drenching of Seed pro @5% after seed germination (b) Covering nursery with 50- mesh nylon net, (c) border planting with two rows of maize at least 15 days before transplanting of seedlings in the main field, (d) seedling dip with 0.1% (carbendazim 12%+mancozeb 63% WP) at the time of transplanting. (e) Main field sequential spraying with acephate 75% WP @1.5g/l on 10 days after transplanting (DAT), fipronil 5% SC @1.5ml/l on 20 DAT, copper hydroxide 77% WP (2.0g/l) on 25 DAT, imidacloprid 70% WG @2g/15l on 40 DAT, and fenamidone 10% + mancozeb 50% WDG (0.25%) three times from 45 DAT at 10 days interval. Analysis of pooled data indicated that the treatment involving IPM schedule was found statistically significant and superior with consistent reduction of late blight by 31.40%, early blight by 41.17% and tomato leaf curl by 67.47% over control with highest yield (377.77 q/ha) and incremental cost benefit ratio (10.3). Pesticide residue analysis revealed no detection of residues in harvested fruits.

FIELD EMERGENCE AND SEEDLING VIGOUR OF BREAD WHEAT AS INFLUENCED BY METHOD AND LONGEVITY OF STORAGE

A laboratory experiment was carried out in the Seed Technology Laboratory, Department of Field Crop Sciences, College of Agricultural Engineering Sciences, University of Baghdad during the period 2010-2019. That was to evaluate bread wheat seeds stored in spikes in their field emergence and seedling vigour. Seeds, of stored spikes were compared with naked seeds, treated with cruise and untreated. All three treatments of seeds were grown in the laboratory and traits of days to last day of emergence, days to emerge, % of emergence, and other trails were recorded. Seeds of stored with thein spikes gave better values in days to last day of emergence, days of emergence, percent of emergence, length of plumule, seedling vigour and speed of emergence. The percent of emergence was decreased with increased years of storage, but those stored in their spikes were less affected. It was concluded that storing bread wheat with spikes had better results in field emergence as compared to seeds threshed and stored.

High density planting studies in acid lime (Citrus aurantifolia Swingle)

High density planting system is exploited to increase yield and thereby net return by accommodating higher number of plants in a given area. It is beneficial especially in fruit crops like acid lime where the plant canopy gradually increases over the years and until then land remains unutilized due to conventional wide spacing plantation. In the present study the seedlings of acid lime cv. Pramalini plantation was evaluated under ultra-high density planting (UHD - 1600 trees ha−1 at 2.5 × 2.5 m) and high density planting (HDP - 800 trees ha−1 at 5 × 2.5 m) systems over conventional or control (CON - 400 trees ha−1 at 5 × 5 m) planting spacing. The climate of the study area was tropical, dry, sub-humid having yearly average maximum and minimum temperature 34.2 °C to 20.5 and precipitation of 1128 mm. Field soil having montmorillonitic mineralogy was 40 cm deep. Data on plant growth, soil properties, insect pest (leaf miner), disease (bacterial canker), physico-chemical parameters of fruits and fruit yield were recorded three years after planting of seedlings in the experimental field. It was found that under both UHD and HDP, EC gradually decreased over the period of five years. The highest organic carbon (1.13–1.42 %) and major nutrients were observed under UHD and leaf N and K contents in HDP. Dense and vigorous plant canopy with maximum (1.49) leaf area index was found in HDP and lowest was under UHD (1.18). Although insect – pest and disease incidence was higher in close spacing plantation than CON, physico-chemical fruit parameters were not affected by spacing. The fruit yield on per plant basis was always significantly lowest under UHD. However, on area basis, under UHD plantation fruit yield (8.24–35.36 t ha−1) was more than two folds as compared to control (3.08–11.64 t ha−1) for different years. Although during last year of experiment the yield under ultra-high density planting (35.36 t ha−1) was significantly higher than high density planting (25.09 t ha−1), the B:C ratio was nearly similar in both the cases. Therefore, it may concluded that the high density planting system may be preferred during early years of production.

A Comparative Analysis of the Hybrid Maize (Zea mays L.) Seed Quality in China from 2013 to 2018

In this study, a comparative analysis of seed quality indicators of 1196 hybrid maize seed samples from the main maize-producing areas in China from 2013 to 2018 was carried out. The results showed that the maize seed quality in China had changed obviously in the past six years, and was mainly as follows: The percentage of samples with coated seed in 2015–2018 was higher than 62.8% in 2013 and all exceeded 97%; the sample rate of packaging according to seed number was from 24.5% in 2013 to 58.6% in 2018, and the percentage of samples which met the prescribed quality standards was from 89.2% in 2013 to 98.4% in 2018. Principal component analysis indicated that standard germination energy (SGE), standard germination percentage (SGP), cold test germination percentage (CTGP), accelerated aging test germination percentage (AATGP), and mean field seedling emergence (FSE) were the primary predictors of seed germination and seedling emergence. Meanwhile, combining other statistical methods, regression models of SGE, SGP, CTGP, and AATGP were established to predict the field seedling emergence. Furthermore, seed bulk density and total starch content were correlated with seed vigor, which needs to be further studied. This study offered a theoretical basis and data support to better understand the changes of maize quality in China over the past six years, and provided an important reference to further improve the maize seed quality in the future.

Selectivity of herbicides in the post-emergence sugarcane seedlings in primary selection fields

The hypothesis here proposed is that, in primary fields of mass selection (F1) of sugarcane, herbicides exert a selective action when applied in the early post-emergence of seedlings (POST-i) and supplemented after their establishment phase (POST-l) even in sandy soils. To verify such hypothesis, the selectivity of herbicides was studied on seedlings of three sugarcane families, after their application both at early and late post-emergence in primary selection fields (F1). The field had a randomized blocks design, with five replications, and the subdivided plots scheme was used. Twelve herbicide treatments were allocated in the plots (27 m-2), whereas the sub-plots (9 m-2) contained three families of seedlings. Each sub-plot consisted of a transplanted row (0.5 x 1.50 m) with 12 individuals of the same family. Six treatments were employed, namely, T1: tebuthiuron (1200 g ha-1) post-i + ametryn (3000 g ha-1) post-l; T2: diuron (1404 g ha-1) + hexazinone (396 g ha-1) post-i + ametryn (3000 g ha-1) post-l; T3: sulfentrazone (800 g ha-1) post-i + ametryn (3000 g ha-1) post-l; T4: diuron (1404 g ha-1) + hexazinone (396 g ha-1) post-i + metribuzin (1920 g ha-1) post-l; T5: sulfentrazone (800 g ha-1) post-i + metribuzin (1920 g ha-1) post-l, and T6: weeded plot. The sugarcane families were: F400 (♀IAC086155 x ♂unknown), F43 (♀IACBIO264 × ♂IAC911099), and F14 (♀IACSP991305 × ♂GlagaH). We concluded that the herbicides tebuthiuron (1200 g ha-1), diuron (104 g ha-1) + hexazinone (396 g ha-1), or sulfentrazone (800 g ha-1), when applied in the early post-emergence and supplemented with ametryn (3000 g ha-1) or metribuzin (1920 g ha-1) in late post-emergence (60 days from planting) of the sugarcane families studied, were selective to the seedlings. That is, no toxicity symptoms with a potential to impede the final selection of seedlings occurred.

Age-Dependent Resistance to Rhizoctonia solani in Sugar Beet.

Rhizoctonia crown and root rot of sugar beet (Beta vulgaris L.), caused by Rhizoctonia solani, continues to be one of the important concerns for the beet industry in Minnesota and North Dakota. Use of resistant cultivars is an important strategy in the management of R. solani in combination with seed treatment and timely fungicide application during the growing season. The objective of this greenhouse study was to determine how sugar beet plants responded to increasing age in resistance to R. solani. Each of three seed companies provided three commercial cultivars with varying R. solani resistance levels: susceptible, moderately resistant, and resistant. Seed were planted at a weekly interval to create different plant age groups from seed to 10-week-old plants, with growing degree days (GDD) ranging from 0 to 1,519 thermal time (°Cd). Seed and plants were all simultaneously inoculated with R. solani AG2-2-infested barley grains. Twenty-eight days after inoculation, plants were pulled and washed, and roots were evaluated for disease severity. All cultivars were highly susceptible to R. solani when inoculated at seed to 3 weeks old (0 to 464°Cd). At 4 and 5 weeks of plant age (617 to 766°Cd), resistant cultivars started to show significant resistance to R. solani. Proportion of the affected roots with disease score ≥ 5 followed a sigmoid response, declining with increased GDD in moderately resistant and resistant cultivars, whereas it continued to decline linearly with increased GDD in susceptible cultivars. This study demonstrated that sugar beet cultivars, regardless of their assigned level of R. solani resistance, were highly susceptible to the pathogen before they reached the six- to eight-leaf stage at 4 to 5 weeks (617 to 766°Cd) after planting. Therefore, additional protection in the form of seed treatment or fungicide application may be required to protect sensitive sugar beet seed and seedlings in fields with a history of R. solani under favorable environmental conditions.

Treatment of soybean seeds with molybdenum and inoculant: nitrate reductase activity and agronomic performance

The aim of this study was to analyze the effects of molybdenum and inoculant application via seed treatment in soybean, and their role in the nitrate reductase enzyme activity, agronomic traits and physiological quality of the produced seeds. The experiment was conducted at the Federal University of Pelotas (UFPel), Rio Grande do Sul state, Brazil. The treatments were shaped by five doses of molybdenum (zero; 16; 32; 48; 64 g.100kg-1 of seeds) combined with the presence and absence of liquid inoculant (Bradyrhizobium japonicum), at a dose of 200 mL per 100 kg of seeds. The evaluations of nitrate reductase activity, agronomic traits and physiological seed quality were performed in the present work. The measured agronomic traits were: plant height, number of pods per plant, number of seed per plant and thousand-seed weight. Standard germination test was executed to evaluate the produced seed viability. First germination counting, accelerated aging test, cold test, plantlet shoot and root length, plantlet shoot and root dry mass, and field seedling emergence were utilized to measure the seed vigour. Molybdenum, both in presence and absence of inoculant, positively influenced the enzymatic activity, for both vegetative and reproductive stages. The addition of inoculant and molybdenum provided increase in the vigour of the produced seeds. The enzyme activity was positively correlated with the agronomic traits and vigour tests. The addition of inoculant and molybdenum in the seed treatment provides a better expression of nitrate reductase activity and vigour of the produced seeds.

Sowing depth of annual ryegrass seed on different substrates as a vigor test

Abstract: Annual ryegrass seeds having low physiological quality can lead to the formation of pastures with undesirable plant stands for soil cover and forage utilization pastures. Thus, the objective of this study was proposing a vigor test to classify annual ryegrass seeds. For that, different sowing depths (0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 cm) over three substrates (sand, coconut fiber, and carbonized rice husk) were tested to differentiate the physiological quality of four seed lots of annual ryegrass cv. BRS Ponteio having similarities in germination and moisture. The seed lots were classified according to vigor through the field seedling emergence (FSE), 1,000-seeds weight, saturated salt accelerated aging, and germination first count. The 2.5 cm of sand sowing depth and 3.0 cm of coconut fiber sowing depth provided separation of seed lots in similar groups of those reported to FSE test through the seedling emergence and speed of seedling emergence tests.

Local flooding history affects plant recruitment in riparian zones

AbstractAimsMany rivers across the globe are severely impacted by changed flooding regimes, resulting in drastic shifts in vegetation, but the processes driving the exchange of flood‐sensitive and flood‐tolerant species are understood less. We studied the role of long‐term and recent flooding histories for riparian plant recruitment in response to various changes in flooding regime.LocationVindel River catchment (Northern Sweden).MethodsWe experimentally changed long‐term flooding regimes by transplanting turfs between high and low elevations in 2000 and in 2014 (n = 8 per treatment). We sowed seeds of five riparian species in both transplanted turfs and non‐transplanted controls and counted seedling numbers over two growing seasons. Further, we inventoried natural seedling frequencies in 190 plots in 19 reaches in 2013 and 2014, and related natural seedling numbers to plot flooding history in the period 2012–2014.ResultsWe observed effects of long‐term flooding history in the second year of the transplantation study (2015), but not in the first year. In 2015, turfs transplanted to locations with less flooding resulted in higher plant recruitment while transplantation to sites with more frequent flooding reduced recruitment compared to the controls. Since these differences were only found in recently transplanted turfs and not in older turfs, the legacy effect of long‐term flooding history can be transient. In the field seedling survey, similar differences were found between flooding‐history categories in 2013, but not in 2014, when the moisture conditions of the most recent year determined flooding. Further, lowest seedling numbers were observed when the previous flooding occurred in winter, and higher seedling numbers when floods occurred in spring or not at all.ConclusionsBoth long‐term and recent flooding histories can affect plant recruitment, and their influence should be taken into account when designing restoration projects.

Multivariate analysis and vigor tests to determine the quality of Brachiaria decumbens seeds

This study aimed to verify the efficiency of multivariate analysis in the identification of promising vigor tests for the evaluation of the physiological quality of seed lots of Brachiaria decumbens cv. Basilisk. Seeds of B. decumbens cv. Basilisk were tested for the following parameters: water content, germination, first germination count, cold test, electrical conductivity, seedling growth, seedling dry mass, first count and emergence percentage of seedlings in laboratory substrate, and seedling emergence in the field. The data obtained in each test—all completely randomized experimental designs—were analyzed separately by means of analysis of variance, Scott-Knott’s test, and multivariate analysis. Principal component analysis is efficient to discriminate vigor and seed germination tests capable of identifying the top performance batch in the field. Germination, first germination count, emergence of seedlings in sand, first seedling emergence count in sand, shoot length, and the cold test are promising in the evaluation of the physiological quality of seed lots of B. decumbens cv. Basilisk, providing similar information to that from the emergence of field seedlings.

Evidence of seed transmission of dolichos yellow mosaic virus, a begomovirus infecting lablab-bean in India.

Yellow mosaic disease in field bean caused by begomoviruses belonging to the family Geminiviridae is a major threat to the cultivation of crop in South India. Appearance of bright yellow mosaic symptom in emerging seedlings in farmers field was suggestive of seed transmission of the begomovirus associated with the disease which was investigated in the present study. The begomovirus causing yellow mosaic disease was identified as dolichos yellow mosaic virus (DoYMV) and the presence of DoYMV in matured seeds was confirmed by DAS-ELISA with OD value up to 3.268. In PCR with DoYMV specific primer (DoYMV-CP) the virus was detected in different parts of the seeds viz., seed coat, endosperm and embryo. In embryo the virus was detectable up to 100 per cent followed by endosperm (69.23%). When the non symptomatic leaves of 30days old grow-out test plants were subjected to DAS-ELISA, the virus was detected up to 46.6%. This is the first evidence of seed transmission of DoYMV.

Is Endophyte-Plant Co-Denitrification a Source of Nitrous Oxides Emission? —An Experimental Investigation with Soybean

The biological pattern of plants’ nitrous oxide (N2O) generation is not well understood because plant cells cannot form N2O from nitric oxide (NO) reduction. Hypothetically, we consider that plant-endophytic co-denitrification is potentially capable of making up for the functional loss of NO reduction in the plant cell and is thus the source of plant-derived N2O. In order to test the above hypothesis, field-cultured soybean seedlings and aseptic-cultured seedlings were used to establish plant holobionts with differentially established endophytes. The N2O fluxes, copies of the bacterial NO reductase encoding gene, and a diversity of endophytic denitrifying bacteria of these holobionts were observed by gas chromatography, real-time PCR, and 16s rDNA sequencing. The flux of N2O by the field seedlings was significantly higher than the fluxes of the aseptic seedlings and bulk soil. The N2O flux of the soybean seedlings was significantly correlated to the abundance of the bacterial NO reductase encoding gene. Eleven genera of denitrifying bacteria were observed in the soybean seedlings, and among them, two genera of aerobic denitrifying bacteria were specifically associated with colonizing plant samples. In this work we have also showed that plant N2O emission is affected by the abundance of total endophytic denitrifying bacteria. We conclude that plant sourced N2O is cooperatively generated by the plant-endophyte symbiotic system in which endophytic denitrifying bacteria help plants to emit N2O by taking over the NO–N2O reduction process.

ELEMENTS OF TECHNOLOGY FOR GROWING LETTUCE IN IRRIGATED CONDITIONS OF THE VOLGA DELTA

The article presents the results of research on the development of elements of the cultivation technology of original varieties of lettuce in irrigated conditions of the Volga delta aimed to provide the citizens with vitamin products of own production within early-spring and autumn periods. The prospective grades of lettuce are selected: Miret RZ (Iceberg variety), Bacio RZ (Romen variety), Anthony RZ (Lollo Rossa variety) and Sigal RZ (Frisse variety). It was defined the seeding time; periods of planting of seedlings in open field and cut-off of saleable products. The highest yield, in average 31,1-33,5 t/ha, was received by Iceberg and Romen varieties of lettuce. For all the planting times, it was registered the high marketability of the produced output – for the Romen and Iceberg varieties – 98%, for the Lollo Rossa and Frisse varieties – 96%. According to the results of the chemical analysis, it was found that all varieties with the summer planting on the average accumulated less of dry matter by 6,12% and the amount of sugar by 39,87%, and had more value of vitamin C by 47,27% and nitrates by 103 mg/kg. The highest level of profitability of 407,8% was received on the cultivation of the Romen variety with the early-spring seeding. Due to their high taste properties, quality and external appeal produced lettuce products are very unique and in demand on the market.

Lichens Contribute to Open Woodland Stability in the Boreal Forest Through Detrimental Effects on Pine Growth and Root Ectomycorrhizal Development

In the boreal forest, open lichen woodlands have been described as an alternative stable state to closed-crown feather moss forest. In this study, we addressed the role of terricolous lichens in stabilizing open woodlands by hindering tree regeneration and/or growth. Based on field and greenhouse experiments, we compared germination and growth of jack pine (Pinus banksiana) on feather mosses (primarily Pleurozium schreberi) and lichens (primarily Cladonia stellaris), using bare mineral soil as a control. Drivers were investigated by (1) manipulating nutrient supply, (2) simulating shade of a closed canopy on the ground layer with the assumption this would mitigate lichen influence on pine growth, and (3) examining pine root ectomycorrhizal colonization and diversity as indicators of pine ability to take up nutrients. Total growth of 6-month-old greenhouse and 2–3-year-old field seedlings, as well as belowground growth of 2-year-old greenhouse seedlings, was significantly greater in moss than in lichen. Seed germination was not affected by ground cover type. Although field phosphorus and base cation availability was greater in mosses than in lichens, fertilization did not entirely compensate for the negative effects of lichens on pine growth in the greenhouse. Ground layer shading had no impact on pine growth. Lichens were associated with reduced abundance and modified composition of the root ectomycorrhizal community. By suggesting that terricolous lichens constitute a less favorable growth substrate than mosses for pine, our results support the hypothesis that lichens contribute to open woodland stability in the potentially closed-crown feather moss forest.

Vigor-S, a new system for evaluating the physiological potential of maize seeds

The refinement of vigor tests and the possibility of utilizing computer resources for the effective evaluation of the seed physiological potential have attracted considerable interest from research and seed technologists. The aim of this study was to evaluate the physiological potential of maize seeds using the newly-created Automated Analysis of Seed Vigor System (Vigor-S) compared with other recommended seed vigor tests; two maize hybrids were used, each represented by seven seed lots. Germination and vigor (cold test, saturated salt accelerated aging, and field seedling emergence) evaluations were conducted. For the evaluation of seed vigor with the use of seedling image analysis resources, two systems were compared: the Seed Vigor Imaging System (SVIS®), developed by Ohio State University, USA and the Vigor-S, resulting from collaboration between USP/ESALQ and EMBRAPA (Embrapa Instrumentation). Using these two systems, three day old seedlings were scanned and the images were analyzed. Similar results for the vigor index, uniformity of development, and seedling length were obtained. The computerized image analysis of seedlings using Vigor-S has advantages with respect to accuracy, speed, and the possibility of automatic application to a worksheet. It is a consistent alternative for the evaluation of maize seed vigor, and produces information compatible with that obtained by the accelerated aging test and SVIS®.

Effect of Arbuscular Mycorrhizal Fungi Based Biofertilizer on Coconut Seedlings Growth in Nursery

The success of a coconut plantation, in terms of its field establishment as well as its future performance, is heavily dependent on the quality of the seedlings used. Coconut nurseries adopt different agronomic practices to produce good quality seedlings. Applying mycorrhizal inoculants is becoming an increasingly common practice in plant nurseries as it facilitates healthy seedling growth resulting in healthy and vigorous seedlings in the nursery, helps to reduce mortality rates of seedlings in the field and reduce water and fertilizer consumption. In this study effects of mycorrhizae based biofertilizer were evaluated for the growth of coconut seedlings in the nursery and field. The experiment was conducted at the Makadura Research Center in Sri Lanka. The nursery experiment treatments were, the presence of AMF based biofertilizer (50g per seedling or per bag) and absence of mycorrhizae based biofertilizer. In the field experiment, five treatments with 500g of AMF biofertilizerwith 25% recommended inorganic fertilizer mixture for young coconut palms (YPM) per seedling, 500g of AMF biofertilizer with 50% YPM per seedling, 500g of AMF biofertilizer with 75% YPM per seedling, 500g of AMF biofertilizer with 100% YPM per seedling and with only YPM per seedling. Root and shoot growth of seedlings were measured at monthly intervals in the nursery experiment. Leaf production rate and stem girth of the seedling were measured at six months interval in the field experiment. The application of bio fertilizer increased the volume and dry weight of primary, secondary, tertiary and quaternary roots in seedlings in the nursery significantly. A significantly higher leaf production rate and stem girth was observed in the field seedlings treatment with 500g of AMF biofertilizer with 75% YPM. The experiment concluded that application of bio fertilizer is beneficial for coconut seedlings in the nursery for the production good quality seedlings with well-developed roots resulting in better field establishment and in the field for fast and vigorous growth.

Single seed precise sowing of maize using computer simulation.

In order to test the feasibility of computer simulation in field maize planting, the selection of the method of single seed precise sowing in maize is studied based on the quadratic function model Y = A×(D-Dm)2+Ym, which depicts the relationship between maize yield and planting density. And the advantages and disadvantages of the two planting methods under the condition of single seed sowing are also compared: Method 1 is optimum density planting, while Method 2 is the ideal seedling emergence number planting. It is found that the yield reduction rate and yield fluctuation of Method 2 are all lower than those of Method 1. The yield of Method 2 increased by at least 0.043 t/hm2, and showed more advantages over Method 1 with higher yield level. Further study made on the influence of seedling emergence rate on the yield of maize finds that the yields of the two methods are both highly positively correlated with the seedling emergence rate and the standard deviations of their yields are both highly negatively correlated with the seedling emergence rate. For the study of the break-up problem of sparse caused by the method of single seed precise sowing, the definition of seedling missing spots is put forward. The study found that the relationship between number of hundred-dot spot and field seedling emergence rate is as the parabola function y = -189.32x2 + 309.55x - 118.95 and the relationship between number of spot missing seedling and field seedling emergence rate is as the negative exponent function y = 395.69e-6.144x. The results may help to guide the maize seeds production and single seed precise sowing to some extent.

A Novel Color Analysis Technique for Differentiation of Mix Grass Cover under Shade and without Shade in Green Infrastructures

Abstract Color analysis was found to be a low-cost and noninvasive technique to distinguish plant and soil, crop and weed, living and dead plant, diseased and healthy leaves, and human and plant in field and automatic seedling transplantation systems. However, color analysis was rarely utilized to differentiate various types of shade by grass cover. The main objective of this study was to quantify and differentiate mix grass cover under shade and light in a green infrastructure. The spatial heterogeneity of mix grass species in the selected site was categorized into three different portions, i.e., (1) mix grass cover under tree shade (MUT); (2) mix grass cover under self-shade (MUS); and (3) mix grass cover without shade (MWS). Field monitoring was conducted for about six months to validate the color analysis technique. A java-based image analysis tool, ImageJ, was used for color analysis. Lab color space was adopted for the present study, which identifies the spatial heterogeneity of mix grass cover based on lightness variation of green color. L describes lightness, and a and b represent the color opponents green–red and blue–yellow. ImageJ categorizes L, a, and b using 256 segments on a scale varying between 0 and 255. The range of L values for MUT, MUS, and MWS were found to lie within 20–91, 92–162, and 162–233, respectively. Ranges of a and b values were found to be 0–134 and 154–255, respectively, for the three categories of mix grass. Proportions of MUT, MUS, and MWS were found to vary within 0.2–3.0 %, 0–53 %, and 12–49 %, respectively. Variation in MUT and MWS proportions was found to be consistent with change in rainfall depth during the dry period. However, MUT and MWS were found to change with respect to shoot growth rate during the wet period. The MUS proportion variation trend was not found to be consistent with rainfall depth or shoot growth during the wet period.

Qualidade de sementes de alface avaliada pelo teste de envelhecimento acelerado

Accelerated aging as a vigor test has been one of the most used, and its application suits many crops. The aim of this research was to analyze the applicability of the accelerated aging test in the vigor of lettuce seeds (Lactuca sativa) by its correlation with other tests for the expeditious evaluation of the physiological quality of the horticultural seeds. Six lots of lettuce seeds were used. The first count of germination, standard germination, electrical conductivity, accelerated aging, controlled deterioration, and seedling's field emergence was performed. The design was completely randomized, with four replications. The use of the accelerated aging test at 41°C per 24 h period using saturated NaCl solution is indicated for the evaluation of lettuce seed vigor.

Vigor tests in assessing the quality of signal grass seeds

The correct assessment of the physiological quality of seed lots is necessary for the quality control program of companies. For such purpose, tests that detect differences in the physiological potential of seed lots and that meet the minimum market requirements. Thus, the study was conducted towards assessing the efficiency of laboratory tests in differentiating the quality of Brachiaria brizantha cv. Xaraés seed lots. Seeds from nine lots were assessed regarding water content, germination, first germination count, electrical conductivity and seedling emergence in sand in the laboratory (normal seedlings, first count and germination rate index), and the results were compared with those from the seedling emergence test conducted in the field. The experimental design used was completely randomized, with four replicates, and the Pearson correlation coefficient between the values from the germination, vigor and field seedling emergence tests was determined. The germination and seedling emergence in sand tests and the seedling emergence rate index efficiently assess the physiological quality of Brachiaria brizantha cv. Xaraés seed lots, providing data similar to those from seedling emergence in the field.