Soil Seedling Emergence Research Articles

Improving seedling recruitment and dryland restoration using a targeted fungicide seed coating

The success of seeding projects in dryland systems is sporadic, with failure primarily driven by low seedling emergence and survival. This sporadic nature is influenced by a litany of biotic and abiotic factors that act in synergy to reduce recruitment success. These factors include erratic seasonal weather patterns, competition, predation, plant material selection, and restoration strategies. While some events are unpredictable and uncontrollable, others may be mitigated through thoughtful deliberation. Pathogenesis from soil‐ and seed‐borne fungi is one form of predation that can decrease restoration success. Fungicide seed coatings are technologies used in the agriculture industry to mitigate fungal pathogens, yet these technologies are novel to wildland seeding. We evaluated the ability of a fungicide seed coating to improve bluebunch wheatgrass (Pseudoroegneria spicata) recruitment across a broad range of sites and determined how soil and climate affected seed treatments across six sites over 650 linear kilometers of sagebrush‐steppe habitat in the Great Basin, United States. Treatment effects varied by site; however, on average, the fungicide treatment increased germination by 16%, emergence by 42%, and juvenile plant establishment by 60%. Fungicide seed treatments had a greater effect on seedling emergence in soils with lower pH, reduced wet‐thermal accumulation during the winter, lower bulk density, and higher organic matter content. Most notably, the fungicide seed treatment resulted in higher plant establishment when emerged seedlings were exposed to longer periods of available soil moisture. Fungicide seed treatments can improve the establishment of native bunchgrasses, when soil and climate regimes are considered.

Tetrazolium Test for Evaluating Viability of Stored Rice (Oryza Sativa) Seeds

Germination testing of rice seeds takes 14 days, while the tetrazolium test can characterise seed viability in hours. The goal of this study was to evaluate the viability of stored rice seeds cv. Chiang Phatthalung by a practical and efficient tetrazolium method. Seeds were stored at room temperature (28°C) and in cold storage (10°C) for 0, 3, 6, 9 and 12 months and then their viability and physiological quality was tested. Seeds of all treatments were soaked in water for 18 hours, cut longitudinally and immersed in 1% tetrazolium solution for two hours at 30°C according to the ISTA method, or in tetrazolium solution at different concentrations (0.0625, 0.125, 0.25 and 0.5%) and staining temperatures (30, 35, 40 and 45°C). The modified tetrazolium test with 0.125% tetrazolium concentration and staining at 40°C of stored rice seeds correlated positively with standard germination (r = 0.98, P < 0.01), soil seedling emergence (r = 0.98, P < 0.01), shoot length (r = 0.78, P < 0.01), root length (r = 0.81, P < 0.01) and seedling dry weight (r = 0.75, P < 0.01). Thus, this staining condition can be used to efficiently estimate the viability of freshly harvested and stored rice seeds.

Improvement of the seedling emergence method in soil seed bank studies using chemical treatments

The seedling emergence method (SEM) is the most frequently used method for studying the soil seed bank. The main problem with this method is that it cannot provide a complete assessment of the seed flora present in the soil because its results are influenced by seed dormancy. In order to break seed dormancy of the soil seed bank, SEM can be combined with some chemical treatments. The objectives of this study were to determine the best chemical treatment which is able to overcome seed dormancy, and to study the effects of different chemical treatments on soil seedling emergence of different plant functional groups. Therefore, twenty soil samples were collected in the early spring in subalpine rangelands in northern Iran. Each soil sample was divided into four equal subsamples, and each subsample was treated by one of the dormancy-breaking treatments including gibberellic acid (GA3), hydrogen peroxide (H2O2), potassium nitrate (KNO3) and distilled water as control. The emergent species from the soil samples were categorized into functional groups, i.e., annual forbs, perennial forbs and perennial grasses. The results showed that the highest total seedling emergence was observed in the soil samples treated with GA3 (5465 seedlings/m2), whereas the lowest seedling emergence was found in the soil samples by KNO3 application (586 seedlings/m2). The perennial forbs were the only functional group that responded to all chemical treatments. We concluded that the use of GA3 for breaking seed dormancy can be useful for providing a more reliable estimation of the soil seed bank characteristics.

Selection-Based heritability of Resistance to Pythium Ultimum in Safflower

Abstract Damping-off disease caused by Pythium ultimum can kill both germinating seeds and young seedlings and cause considerable damage in saflower cultivation. An estimation of heritability lets saflower breeders determine the most effective method for improving seedling emergence in soils infected with P. ultimum, the causal agent of seed rot and damping-off. Two cycles of selection were performed to estimate the realized heritability of resistance to the pathogen in five safflower populations. Undamaged seedlings were selected as resistant individuals and were kept to produce seed. The results showed that selection for two consecutive generations increased the emergence of seedlings in Pythium-infected soil from 46 to 53 %. The heritability estimates varied between 1.72 and 77.66 % over the genotypes and environments, in inverse proportion to the severity of the disease. Estimates of heritabilities showed that genes conferring resistance to P. ultimum in safflower are highly heritable and would respond to selection breeding, particularly in some of the studied genotypes, like Isfahan and Zarghan259. However, different breeding methods must be explored for other genotypes.

Accelerated Aging in Tomato Seeds

The tomato plant (Lycopersicum esculentum L.) is a perennial, shrubby-like vegetable with high reproductive ability, which behaves like a typical annual crop. The aim of this work was to select suitable tests to assess the quality of different lots of tomato seeds. Six batches of tomato seeds were assessed for parameter values: moisture content, germination, first count, accelerated aging (standard: 40 mL of water; saline solution: 11 g NaCl/100mL of water and saturated saline solution: 40 g NaCl/100mL water) and seedling emergence in soil. Accelerated aging through the use of saturated salt solution for 48 h or 72 h at 41°C resulted in an alternative and efficient way to evaluate the physiological quality of tomato seeds. The standard accelerated aging test was less efficient and exhibited higher moisture variation.

First Report of Fusarium commune Causing Damping-off, Seed Rot, and Seedling Root Rot on Soybean (Glycine max) in the United States

During 2007 to 2009, symptomatic and asymptomatic soybean plants were collected from fields in 18 Iowa counties. Fusarium isolates were recovered from surface-sterilized root tissue on peptone PCNB agar (2). Single-spore isolates were transferred to synthetic low nutrient agar (SNA) overlain with pieces (1 × 2 cm) of sterile filter paper, and to potato dextrose agar (PDA), and placed in the dark for 10 to 14 days for morphological identification (4). Twenty-three isolates were identified as Fusarium commune K. Skovg., O'Donnell & Nirenberg, previously in the F. oxysporum species complex (4). Colonies on PDA had white, fluffy, aerial mycelium with magenta to violet pigmentation in the medium. On SNA, macroconidia, chlamydospores, and microconidia on monophialides and polyphialides were consistent with the species description (4). Identification of all 23 isolates was confirmed by DNA sequencing of the translation elongation factor (EF1-α) gene, using ef1 and ef2 primers, and the mitochondrial small subunit (mtSSU), using primers MS1 and MS2 (4) [GenBank accessions for two representative isolates: EF1-α (JX289892 and JX289893), and mtSSU (JX289894 and, JX289895)]. Pathogenicity of two representative isolates of F. commune was tested on soybean (cv. AG2403) in a greenhouse, in water baths set at 18°C, using autoclaved soil mixed with infested sand-cornmeal inoculum (3). The experiment entailed a completely randomized design (CRD) with five replications (single plant/150 ml cone) per treatment, and was conducted three times. Dry root and shoot weights, and root rot severity (visual estimate of percent root rot on the entire root system) were evaluated after 6 weeks. Mean seedling emergence in soil infested with F. commune was 47 and 40% for the two isolates; in contrast, non-inoculated control plants had 100% emergence. There were significant differences in root (P < 0.0001) and shoot (P < 0.0001) weights, and root rot severity (P < 0.0001), between inoculated and non-inoculated plants. Seedlings that emerged were severely stunted and had dark brown lesions. F. commune was reisolated from infected roots of inoculated plants, but not from non-inoculated plants. Pathogenicity of both isolates to soybean (cv. MN1805) was also tested using a petri dish assay, in which eight seeds were placed on a plate with a 4-day-old culture growing on 2% water agar (1). Plates were rated 7 days later for seed germination, seed rot, and lesion development, using an ordinal scale (1). The experiment entailed a CRD with three replicate plates/treatment, and was conducted three times. Germination of inoculated seeds ranged from 37.5 to 75.0%, and germinated seedlings had dark brown lesions on the taproots. There was a significant difference between isolates in the petri dish assay (P = 0.0030); one isolate was less aggressive, but both isolates resulted in significantly more disease than on the non-inoculated control plants, which had 100% germination and no symptoms (P < 0.0001). F. oxysporum is a known soybean pathogen (1), but isolates of F. commune may have been misidentified as F. oxysporum in previous studies. To our knowledge, this is the first report of F. commune as a pathogen on soybean in the U.S.A.

Seedling emergence response to early sowings in unprimed and osmoprimed seeds of fiber sorghums for energy biomass under semi-arid climate

Fiber sorghum is a promising industrial crop for lignocellulosic biomass to be used for energy purposes. Limits to the adoption of early sowings (March-April) for this species are found in its thermal requirements for seed germination (&gt;10°C). Seed osmopriming has been found to decrease the impact of low temperatures on seed germination of sorghum in laboratory. In this study, unprimed (UP) and primed (P) seed germination behavior in both laboratory at cold temperatures and open field conditions under early sowing in a typically Mediterranean environment, was examined in four cold-tolerant cultivars of fiber sorghum (Padana 4, PR 811F, Jumbo and PSE 24213). Seed germination in UP at 8°C was on average 82.4%, confirming the high cold-tolerance of all cultivars selected for the experiment. Germination was progressively delayed by the lowering of temperature from 25°C to 8°C. Seed osmopriming was effective in promoting germination speed at all temperatures in laboratory. It also resulted in an appreciable lowering of thermal time requirements for final germination. With the earliest planting date (March 10), minimum soil temperatures during the first ten days never dropped below 10.2°C, allowing a final seedling emergence of 79.2% in UP. However, low soil temperatures slowed down the rate of seed germination. At the 2nd sowing (end of March), daily maximum temperatures of soil exceeded 20°C but those minimum dropped below 10°C, slightly depressing seed germination in UP (76.3%). With the latest sowings (mid-April and early May), minimum soil temperatures always over exceeded minimum threshold for seed germination, allowing a regular seed germination in UP. Priming increased final emergence percentage in the two earliest sowings (those of March), whilst it enhanced the germination speed in all planting dates. Seed osmopriming also reduced thermal time requirements until the first seedling emerged from soil and promoted the seedling growth in all cultivars and sowing dates. These results suggest that it is possible to adopt early sowings (March) in cold-tolerant cultivars of sorghum under semi-arid climate, and that osmopriming allows the seed to partially overcome the limit imposed by cold soil to germination, contributing to a successful crop establishment when early plantings are adopted. Although the germination response to constant low temperatures in laboratory tests does not always provide a good index for predicting seedling emergence in soil under fluctuating uncontrolled temperatures, it may contribute to define desirable attributes for the identification of cultivars adapt to early sowings in the Mediterranean areas.

Germinação e envelhecimento acelerado na análise da qualidade fisiológica de sementes de alfavaca-cravo

The study aimed to contribute to establish parameters for analyzing the physiological quality of seed-clove basil (Ocimum gratissimum L.), since the species is not among those described in the Rules for Testing Seeds. Seeds of basil, clove, gathered on the campus of UENP-CLM, Bandeirantes, PR, analyzed for water content, germination, accelerated aging water and saline tetrazolium and seedling emergence. The temperature of 30 ° C for the germination test and the sand substrate for the emergence test are conditions and procedures for evaluating the physiological quality of seeds of O. gratissimum. The aging test, regardless of the type of solution used, the test is correlated with seedling emergence in soil. The low germination and seed viability of O. gratissimum occurring due to deterioration and lack of internal tissue.

Época de semeadura, produção e qualidade fisiológica de sementes de milheto

O milheto (Pennisetum americanum (L.) Leeke) é uma gramínea anual, de clima tropical, utilizado no pastejo, na produção de massa e cobertura de solo no sistema de plantio direto. Para estudar o comportamento do milheto, semeado em diferentes épocas do ano em condições de Botucatu, sob túnel plástico, com a finalidade de produção de sementes, foram realizados dois experimentos. No experimento 1, estudou-se nove épocas de semeadura (abril a dezembro), empregando-se a cultivar BN2 e no experimento 2, três épocas (janeiro a março), empregando-se a cultivar Comum. O delineamento experimental foi o de blocos casualizados, com cinco repetições. Foram avaliados componentes da produção, rendimento, germinação e vigor de sementes (primeira contagem do teste de germinação, condutividade elétrica e emergência de plântulas em solo). A época de semeadura afetou a produção e a qualidade das sementes de milheto. A massa de mil sementes e o número de sementes por panícula contribuíram para os melhores resultados da produção. As épocas de semeadura promissoras para produção de sementes milheto em Botucatu são dezembro e janeiro.

Avaliação do vigor de sementes de melancia (Citrullus lunatus Schrad.) pelo teste de envelhecimento acelerado

O trabalho teve como objetivo determinar a eficiência do teste de envelhecimento acelerado para a avaliação do vigor de sementes de melancia (Citrullus lunatus Schrad). Para tanto, sementes de quatro lotes da cultivar Crinsom Sweet foram submetidas ao envelhecimento acelerado a 41 e 45°C por 48, 72 e 96 horas, a 100 e 76% de UR relacionando-se os resultados obtidos com os testes de germinação, primeira contagem de germinação, germinação a baixa temperatura e emergência de plântulas em solo. Os resultados indicaram que o teste de envelhecimento acelerado pelo método tradicional (100% UR) mostrou-se mais eficiente que o método alternativo (76% UR), se constituindo em alternativa promissora para a avaliação da qualidade fisiológica das sementes de melancia. O envelhecimento acelerado a 41°C e 100% UR por 48 horas foi o método mais promissor para a avaliação do vigor dessas sementes.

A seed vigour test for birdsfoot trefoil (Lotus corniculatus L.)

The low vigour of the Lotus corniculatus L. seedlings causes a poor stand establishment of crops; therefore to plant high vigour seed of this perennial forage legume is recommended. No suitable procedure is available for the identification of seed lots based on this quality component. The design of a specific and practical method to estimate birdsfoot trefoil seed vigour is described here. Two seed lots from the cultivar San Gabriel with similar germination percentage and different chronological age were used to determine their germination capacities at 5°C for a 21-day period. The maximum seed germination difference between the two seed lots was detected after 7 d and subsequently decreased; thus 7 d was considered the appropriate time to assess the seed vigour. Germination after 7 d at 5°C was highly correlated (r=0.83-0.99**) with the soil seedling emergence. The evaluation of this procedure using 10 seed lots enabled the verification of its high discriminatory capacity to classify seed lots according to their potential planting value. As a result, this test is more sensitive and rapid than the standard germination test used to determine the quality of a seed lot. The vigour test described here is named birdsfoot trefoil vigour test.

Superação da dormência de sementes de carrapicho-beiço-de-boi

Visando a obtenção de um tratamento para acelerar a germinação de sementes de Desmodium tortuosum (Sw.) DC., foram realizados dois experimentos, nos quais, segmentos unisseminados de lomentos (testemunha) foram submetidos a debulha manual; debulha manual seguida por escarificação manual empregando-se lixa n. 220; debulha mecânica (processador doméstico ); escarificação química com H2SO4 (95%) por 1,5 e 8 mim pré-aquecimento à 53°C por 4,10 e 16h em estufa com circulação forçada de ar; embebição, utilizando-se H,0 à 80°C por 1,3,5 e 10 min; H20 à 27°C por 2h e embebição com alternância térmica (H,0 à 80°C/ 5min e H20 à 13 °C / 1min) . Para a avaliação dos tratamentos foram empregados os testes de germinação, de emergência de plântulas em solo (E), de primeira contagem de germinação (PG) e de emergência (PE), índices de velocidade de germinação (I.V.G.) e de emergência (I.V.E.), e o comprimento de plântulas (CP). 0 delineamento estatístico adotado foi o inteiramente casualizado com 4 repetições de 100 (G, PG, I.V.G.) ou 20 sementes (C P) por tratamento no primeiro experimento e 4 repetições de 50 (G, PG, I.V.G.) ou 100 sementes (E, PE, I.V.E.) no segundo experimento. No primeiro experimento, os tratamentos que provocaram significativa redução da dormência (D) e, conseqüente elevação da germinação (G), em comparação à testemunha (D=82%; G=15%) foram, em ordem decrescente de eficácia: debulha e escarificação manuais (D=3%; G= 92%), debu lha mecânica (D=13%; G= 81%), embebição em H20 à 80°C por 1min (D=68%; G= 29%) e por 3 min (D=65%; G=32%). No segundo experimento, (testemunha com D=93% e G=3%) destacaram-se: debulha e escarificação manuais (D=2%; G= 93%), debulha mecânica (D = 2%; G = 87%), embebição em H20 à 80°C por 5min e alternância térmica (ambos com D=85% e G= 11%). 0s testes de vigor PC, I.V. G., I.V. E., CP, e E corroboraram esses resultados. 0s métodos de escarificação manual com lixa 220 e debulha mecânica, empregando-se processa dor, podem ser recomendados para a superação da dormência e promoção da germinação de sementes de D. tortuosum.

Damping-off disease of pine seedlings on soils treated with simulated acidic rain

Damping-off during seed germination and early seedling growth of Pinusrigida Mill., Pinusechinata Mill., Pinustaeda L., and Pinusstrobus L. were observed for 28 days on three New Jersey (U.S.A.) Pine Barrens soils (Atsion, Downer, Lakewood) treated with simulated acidic rain solutions of pH 4.2, 3.5, or 3.0 (SO42−:Cl−:NO3−, 2.2:1.4:1.0). The soils were sandy, highly acidic, and deficient in mineral nutrients. Treatment with rain solution was started 53 days before planting the pine seeds and continued during germination. Seedling emergence and seedling mortality were affected significantly by solution pH, soils, and species. Seedling emergence of all pine species on Atsion and Lakewood soils decreased with increasing solution acidity. On Downer soil seedling emergence was unaffected by solution acidity probably because the buffering action of the soil decreased the acidity of the rain solution. Seedling mortality of all species increased with increasing treatment acidity on all soils and was significantly higher on Atsion (100% at pH 3.0) than on the other soils. Although solution acidity significantly increased the concentration of Al in the soil solution, there was no evidence of Al toxicity. Two isolated fungal species, a Trichoderma and a Penicillium, significantly reduced seedling emergence and increased seedling mortality of P. rigida in sterile, acid-washed quartz sand; however, neither seedling emergence nor seedling mortality was affected significantly by solution acidity.