Field Nursery Research Articles

Introgression of Thrips Resistance from Pima Cotton (Gossypium barbadense L.) into Upland Cotton (Gossypium hirsutum L.)

Thrips are major early season insect pests that cause significant economic damage in Upland cotton in the U.S. Development and deployment of resistant cultivars is the most effective and ecologically sustainable means of reducing thrips damage in cotton. Interspecific hybridization and backcrossing were performed to introgress thrips resistance from Pima cotton (Gossypium barbadense L.) accession Coastland 320 into Upland cotton (Gossypium hirsutum L.) cultivars Acala Maxxa (AM) and Fiber Max 966 (FM966). Backcross populations were screened for thrips resistance in thrips screening summer field nurseries in North Carolina. Thirty-two BC2F2 plants with thrips resistance were identified and backcrossed further to develop BC3F2 plants. Eleven AM derived BC2F2 resistant plants and 21 FM966 derived BC2F2 resistant plants were genotyped using CottonSNP63K array to identify the Pima chromatin in the introgression lines (ILs). In the ILs, introgressed Pima chromatin was detected on chromosomes A01, A08, A09, A10, A11, D10, D11, D12, and D13. Of these, four ILs, two each in AM and FM966 background, showed overlapped introgressed Pima chromatin on chromosomes A10 and D11. Further, four introgression lines, two each in AM and FM966 background, shared a common Pima introgression on chromosome D13. Characterization of thrips species in the screening nursery showed that predominant thrips species were tobacco thrips (Frankliniella fusca (Hinds)) followed by western flower thrips (Frankliniella occidentalis (Pergande)). The identified ILs with thrips resistance should be a useful source of genetic variability for developing Upland cotton cultivars with pest resistance.

Chrono-spatial reproductive phenology of Swertia bimaculata Hook.f. & Thomson ex C.B.Clarke reveals suitability as climate-changing bio-indicator along the Sikkim Himalayan altitude

Genus Swertia under the family Gentianaceae is morphologically and taxonomically distinct with about 14 species from Sikkim Himalayan region. A Chrono-spatial floral phenology study was conducted on Swertia bimaculata from 1580 to 2400 m altitude in West Sikkim Himalayan region. The floral phenology was studied in a field nursery at 1200 m altitude and spatial floral phenology was studied over a 1580–2400 m altitudinal range in the West Sikkim Himalayan region. Detailed study on flowering pattern and seed formation in S. bimaculata revealed late flowering at 1200 m compared to 2400 m. Plants at the lower altitude showed prolonged and variable flowering from September to November and seed formation from November to December. During September to mid-October, pentamerous and bisexual flowers were observed, followed by 9–16 % tetramerous until November; and up to 24 % trimerous and 10 % bimerous until the end of flowering season in December. By the end of December, 43 % of flowers become stamen-less (monoclinous). Less than 2 % seed formation was observed in stamen-less flowers. The temporal phenological behavior reveals a successful reproductive adaptive strategy, depicting pentamerous flowers during favorable conditions, reducing to tetramerous, followed by tri- & bimerous with female (monoclinous) flowers until the end of flowering with stressful conditions, suggesting its suitability as a stress indicator to the changing climatic conditions. Along the altitudinal range floral anomalies from the usually observed pentamerous (and very rare hexamerous) flowers in favorable conditions change to tetramerous and/or trimerous, as the environmental conditions become more stressful, suggesting that the changes in this species could be used as an indicator of stress in changing climatic conditions.

Exploring Fusarium head blight resistance in a winter triticale germplasm collection

AbstractFusarium head blight (FHB; caused by Fusarium graminearum) is a destructive disease of wheat (Triticum spp.), barley (Hordeum vulgare), rye (Secale cereale L.), and triticale (×Triticosecale Wittmack) not only reducing their yield but also contaminating the grain with mycotoxins such as deoxynivalenol (DON). Developing varieties with genetic resistance is integral to successfully manage FHB. Triticale acreage worldwide is steadily increasing. However, the genetic diversity of triticale for FHB resistance is not well characterized. In the present study, a sequential screening of a set of winter triticale accessions from a global collection was done for their type‐2 FHB resistance and DON accumulation. In the first‐year screening, 298 triticale accessions were tested for FHB in an artificially inoculated, misted‐field nursery with high inoculum density. Most of the triticale accessions were susceptible to FHB, and only 8% of the accessions showed resistance in the field nursery screening. Next, the 24 resistant accessions identified in the nursery screening were tested for 2 years in greenhouse and 17 accessions showed significantly lower FHB severity in Year 2 and/or Year 3. These 17 resistant accessions were further tested for their FHB severity and DON accumulation in Year 4 in greenhouse and for DON accumulation in Year 5 in the field FHB nursery. Eight accessions showed significantly lower FHB severity and nine accessions showed DON accumulation of less than 1 mg/kg in Year 4 greenhouse testing. Eleven accessions had significantly lower DON concentration than the susceptible check in the Year 5 field screening. The resistant accessions common across all years identified in the study can be used for enhancing FHB resistance and reducing DON accumulation in triticale breeding programs.

Impact of planting techniques and cutting sizes on cassava (Manihot esculenta Crantz) sprouting and subsequent vegetative growth in various nursery environments

Cassava (Manihot esculenta Crantz) is a perennial woody shrub, mainly propagated via stem cuttings. Propagation methods and growth environment have been reported to affect sprouting and vegetative growth significantly. This study aimed to examine the effect of planting methods and cutting sizes on cassava's sprouting and subsequent vegetative growth. The experiment was conducted at the Agricultural Research Institute-Tumbi Centre Tanzania. The cassava varieties used were TARICASS2, TARICASS3, TARICASS4, TARICASS5, Kiroba, Kizimbani, Mkumba, and Mwasunga. They differed significantly on the days they first sprouted. Days to 50% first sprouting was observed three days after transplanting in the low tunnel from Mkumba, Kizimbani, Mwasunga, and TARICAS5, compared to six days in the open field nursery. The early sprouting from the low tunnel may be attributed to its high relative humidity (86.5%) and soil temperature (37.4 OC). Cuttings with four nodes had the highest number of sprouts compared to cuttings with two nodes for horizontal planting. Therefore, horizontal planting should be adopted in low tunnels to ensure a massive multiplication of planting materials.

Seasonal Occurrence of Fall Armyworm (Spodoptera frugiperda J.E. Smith) in Maize: The Role of Sowing Dates

Fall armyworm is a destructive insect pest in maize farming and has expanded widely throughout various agroecological zones, which threatens food security. An experiment was carried out at the Winter Nursery (ICAR-IIMR, Hyderabad) field to study the occurrence of fall armyworm on maize single cross hybrid DHM 117 across different sowing dates during kharif and rabi seasons of 2021-22. Weekly observations were made on a whole-plot basis to record the number of plants damaged, the number of larvae, and egg masses per plant. Among the six sowing dates, the crop sown on 2nd August 2021, had a relatively lower mean percent of infestation range (4.02% - 80.37%), a minimum larval count per plant range (0.01 - 0.24), and the least number of egg masses per plant range (0.00 - 0.11). The findings will be helpful in the construction of forecasting models, facilitating the formulation of eco-friendly management tactics to manage fall armyworms in maize.

Developing causal loop diagrams for the perusal of soil health in agricultural practices – A case study of rice nursery cultivation practices in India

CONTEXTSoil is a key component of the agriculture–livestock–forestry nexus. However, it has been reported that 40% of the agricultural soil is being degraded globally; in India, 70% of the agricultural soil is undergoing degradation despite various efforts to improve soil health. Hence, the current study takes a paradigmatic shift by applying the approach of systems thinking for understanding soil health. OBJECTIVEThis study aims to present an alternative methodology to study the impact of agriculture practices on soil health with a systems approach. METHODSA practice of soil parching for rice nursery cultivation, called raab, representing the agriculture–livestock–forestry nexus, was taken as a case study. The study included field visits to rice farms in Maharashtra, India, soil sample collection at three stages of raab practice, and soil samples from non-raab fields. Thirty-one soil samples were tested for four properties: pH, electrical conductivity, available potassium, and permanganate oxidizable carbon (POXC) in raab and non-raab nursery fields. Further, a causal loop diagram of the soil ecosystem was developed based on farmer interactions, soil testing results, and literature to identify the key system archetype in this case study. RESULTS AND CONCLUSIONStatistical analysis of the results showed a significant difference in soil properties at different stages of cultivation and in comparison to the control group. The mean pH of raab fields had increased due to the raab practice from 5.76 to 7.01, and the mean electrical conductivity increased from 0.218 dS/m to 0.745 dS/m. The mean available potassium increased from 229.9 kg/ha to 1239 kg/ha in the raab fields, while direct nursery fields had a mean of 487 kg/ha at the time of sowing. The mean POXC increased from 0.02 to 0.04 mol of MnO4− reduced. The causal loop diagram developed had 17 loops, 15 of which were favorable-reinforcing loops, and two were unfavorable-balancing loops. The system archetype of “Limits to growth” was identified in this study, based on which recommendations are suggested for maintaining soil health. SIGNIFICANCEThe systemic approach aids in decision-making regarding sustainable agriculture practices considering soil ecological processes with judicious use of resources available from the forest and livestock. The direct impact of soil health on five UN Sustainable Development Goals (SDGs) and the indirect impact on seven other SDGs underscores the global significance of the novel approach discussed in this study.

Armyworm population dynamics and damage assessment in rice agroecosystems at Jampuijala, Tripura, India

Rice cultivation faces persistent challenges from various insect pests, including invasive species. The emergence of four armyworm species (rice swarming caterpillar, Spodoptera mauritia (Boisduval), common cutworm, Spodoptera litura (F.); rice ear-cutting caterpillar/paddy armyworm, Mythimna separata (Walker); and fall armyworm, Spodoptera frugiperda (J.E. Smith), along with other herbivores, poses significant threats to Asian rice ecosystems, causing considerable economic losses. This study investigates the occurrence and distribution of these armyworm species in rice agro-ecosystems across three Village Councils (VCs). Only S. mauritia larvae were observed, appearing in nursery fields approximately16-27 days after sowing and displaying sudden mass attacks primarily targeting seedlings at the 1-5 leaf stages. Damage manifestations included cutting leaf tips, creating shot holes on leaf blades, and occasionally severing seedlings at the base. The Ranjit variety in Kalaibari VC and the Gomati variety in Killa Verma VC showed the highest infestation rates (18.0%) and larval populations (1.7 larvae/m2). These findings offer valuable insights for stakeholders involved in rice cultivation across Asian rice-producing nations. Keywords: Oryza sativa, Spodoptera mauritia, Spodoptera frugiperda, Spodoptera litura, Mythimna separata.

Supervision Encounters “That Are Not So Nice”: Experiences of Teachers in Guyana

Expected positive outcomes of teacher supervision in Guyana are not always achieved. This qualitative study explores forces that may be hindering desirable outcomes of supervision provided by Nursery Field Officers (NFOs) and is intended to be an attempt to improve practice. Through thematic analysis of interviews with 30 teachers, five critical areas of undesirable encounters were discovered. These encounters were framed as fault-finding, controlling and mechanically oriented, unproductive, emotionally unsettling, and disruptive. Caution about the danger of identification of pedagogical weaknesses in the absence of accompanying solutions and recommendations is flagged, and remedial strategies are identified. The findings reframe, reinforce, and complement existing knowledge about educational supervision, serve to chronicle Guyanese teachers’ experiences with the supervision of NFOs, and might be informative to professional development programs that rely on supervision to sustain pedagogical growth. Program providers and other stakeholders might find the teachers’ experiences a reference point to consider critical issues regarding the quality of and approach to supervision.

Identification of synthetic wheat lines with broadly effective stripe rust resistance

Wheat stripe/yellow rust (WYR), caused by Puccinia striiformis f. sp. tritici (Pst), is a major constraint in global wheat production. A set of 766 hexaploid synthetic wheat lines, including primary crosses of Triticum turgidum x Aegilops tauschii and their derivatives, were screened in artificially rust inoculated field nurseries for three seasons. From this set, a core set of 94 non-lodging lines with unique pedigrees and resistance to Pst that was consistent across years was established. The core set was tested for adult plant field response under field conditions for three seasons in Australia and at least one crop season in Ethiopia, India, Kenya, Nepal and Pakistan. It was also challenged with an array of well-defined Pst pathotypes at seedling growth stages in the greenhouse, and genotyped with molecular markers linked to the adult plant resistance (APR) genes Yr18, Yr36 and Yr46. Combined analysis of field rust responses, multi-pathotype seedling phenotyping and marker genotyping resolved seven classes of Pst resistance: uncatalogued (new) APR (UAPR, 11%), uncatalogued seedling resistance (USR, 46%), known seedling resistance (KSR, 5%), KSR + USR (2%), Yr18 + UAPR (4%), Yr18 + USR (29%) and Yr18 + KSR (3%). A majority of the lines carrying UAPR and USR either singly or in combination showed high levels of field resistance across all field sites and years of testing, demonstrating that these lines represent a valuable resource for breeding wheat for resistance to Pst.

Overcoming the Nursery Industry Labor Shortage: A Survey of Strategies to Adapt to a Reduced Workforce and Automation and Mechanization Technology Adoption Levels

US nurseries are experiencing a workforce shortage that is expected to intensify. A mixed-mode survey of decision-makers representing the US nursery industry was conducted in 2021. The survey assessed practices used in 2020 to elicit a better understanding of nursery approaches to the challenges presented by persistent labor scarcity. We compare our results with survey data collected ∼15 years earlier at container nurseries. Survey responses revealed that nurseries were undertaking strategies that aimed to improve production efficiency, better recruit and retain employees, and secure other sources of labor to overcome this shortage. Specifically, more than 65% of surveyed US nurseries increased worker wages, and more than 55% of respondents adopted automation to address the labor shortage. Strategies in use by ≥23% of respondents may limit future growth or jeopardize long-term nursery survival. These include diversifying tasks of current employees, reducing production of labor-intensive plants, or delaying expansion plans. Survey results suggested that production tasks excluding irrigation were on average 31% automated or mechanized at container nurseries, an increase from 16% during the prior survey. Field nurseries were 35% automated or mechanized in 2020. Newly developed or yet-to-be developed automated and mechanized technology (AMT) that decision-makers perceive as being helpful were reported. This article explores linkages between nursery characteristics and AMT adoption and highlights research and extension programming initiatives that are needed to help growers make informed decisions regarding adopting automation.

Comparison of salinity tolerance between Avicenna marina and Rhizophora mucronata Karachi coast, Pakistan

Mangrove propagule size variation is an important factor in their survival. The main aim of this study was to determine the productivity and identify the comparison between Avicenna marina and Rhizophora mucronata. However, it is less studied about the comparison of mangrove species and their salt tolerance in terms of seedling establishment of propagules. We investigated the propagules size variation of Avicennia marina and Rhizophora mucronata from the Indus delta and were grown in the polythene bags of 5x10″ filled with silty soil from field nursery. We used salinity and nutrients treatments to propagules to identify the growth rate of mangrove species. The surveying technique was also used to collect the information of mangrove forest from local communities. We detected that Rhizophora mucronata had a higher productivity rate due to the given concentration of 50% sea water. While the Avicennia marina showed a lower decline ratios growth at 25% salinity level with further increases in salinity. Using diffusion porometers and infrared gas analyzers (IRGAs), we revealed that stomatal conductance was higher in Rhizophora mucronata, followed by Avicennia marina. Moreover, our outcomes showed a higher Sodium and chloride ions with the increase in salinity and also demonstrated a higher accumulation in Avicennia marina. Overall, its was found that Avicennia marina is the most salt resistant species and it’s a dominated species in littoral forest. Our outcomes can help us to better understand the green infrastructure design of mangroves, suggesting that selecting multiple techniques ensure many post-tsunami restoration initiatives are encountering problems.

Development of a molecular diagnostic to discriminate between Fomitiporia species and advancements in detection of the main grapevine decline‐related pathogens in propagating material and mature vines

AbstractA comprehensive study was conducted on the prevalence of grapevine trunk diseases in Greece, focusing specifically on contamination of grapevine propagation material by Phaeomoniella chlamydospora and black foot disease‐related species. Additionally, detection of esca pathogen Fomitiporia mediterranea, causing white rot in grapevine and other woody hosts, was assessed using a new PCR‐based assay that distinguishes F. mediterranea from F. punctata. Development of a nested PCR assay, combined with a cost‐effective DNA extraction protocol, revealed a high percentage of infection by P. chlamydospora (51%) and Ilyonectria species associated with black foot disease (28%) in different types of grapevine propagation material (dormant cuttings, field‐rooted benchgrafts and green‐growing plants). Interestingly, black foot disease‐related pathogens were more prevalent in nursery plants grown in the field for 6 months (57%) than in other types of propagation material and compared with P. chlamydospora (43%), indicating increased infection of propagation material during growth in the nursery field. The cost‐effective molecular method developed in this study could be used in mass inspections of propagation material for phytosanitary purposes. Finally, using primers specific for F. mediterranea and F. puncata developed in this study, combined with the universal ITS4 primer, a collection of Fomitiporia isolates from mature grapevine and other woody hosts from Greece and Italy (southern Europe) were characterized as F. mediterranea, whereas German and Swedish isolates from forest plants (central Europe) were classified as F. punctata. The developed primers can discriminate between the two Fomitiporia species, which are indistinguishable based on culture and morphological characteristics alone.

Incidence of Sheath Blight in Irrigated Rice and Associated Yield Losses in Northern India.

Rice-growing districts in Uttar Pradesh, India, were surveyed during the months of July and October to record the frequency of occurrence and disease incidence of sheath blight caused by Rhizoctonia solani in paddy. A total of 180 paddy fields were surveyed at the block level of 21 districts, where almost all the rice varieties were found highly susceptible to R. solani and exhibited severe yield loss compared with low-infested fields. The district Muzaffarnagar had the highest rate of disease occurrence, while maximum disease severity was recorded in the district Saharanpur. This district also had the highest soil population of R. solani, followed by Mathura, Muzaffarnagar, Barabanki, Aligarh, Sultanpur, Mainpuri, and Rampur. The greatest relative yield loss attributed to sheath blight infestation was recorded in Mathura (40%). The yield loss was linearly correlated with soil population of R. solani and disease incidence. Disease occurrence, incidence, severity, and yield loss to paddy were all significantly greater in the area which experienced relatively higher temperatures (25 to 38°C) and relative humidity (49 to 100%) during the months of June to August. Furthermore, the fields applied with a total dose of 250 to 280 kg nitrogen/ha exhibited higher disease severity (2.9 to 3.3 score) compared with fields that received a moderate dose of 140 to 180 kg N/ha (0.9 to 1.8 disease severity score). The rice nursery fields were found almost free from the sheath blight, but the disease was quite prevalent in the paddy fields with 7.2 to 38.9% disease incidence which resulted in 14.3 to 39.7% yield loss to rice.

The Zoige pioneer plant Leymus secalinus has different endophytic bacterial community structures to adapt to environmental conditions.

Leymus secalinus is a pioneer plant grown in the Zoige desertified alpine grassland and it is also one of the dominant plant species used for environmental remediation. L. secalinus plays a large role in vegetation reconstruction in sandy land, but the abundance and diversity of its endophytes have not yet been investigated. This study was performed to investigate the changes in the endophytic bacterial community structure of L. secalinus under different ecological environments and to analyze the effects of environmental changes and different plant tissues on the L. secalinus endophytic bacteria. Leaf, stem, and root tissue samples of L. secalinus were collected from Zoige Glassland (Alpine sandy land) and an open field nursery (Control). DNA was extracted and the 16S ribosomal DNA was amplified. The sequence library was sequenced on an Illumina MiSeq platform and clustered by operational taxonomic units (OTUs). α-diversity and β-diversity analyses, species diversity analyses, functional prediction, and redundancy (RDA) analyses for the soil physicochemical properties were conducted. α-diversity and β-diversity analyses showed that the endophytic bacteria in L. secalinus varied in different areas and tissues. The abundance of Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium, which is related to nitrogen fixation, increased significantly in the L. secalinus found in the Zoige Grassland.Moreover, the abundance of nutrition metabolism and anti-stress abilities increased in functional prediction in the desert samples. The soil physicochemical properties had an insignificant influence on bacterial diversity. The changes in the endophytic bacterial community structure in L. secalinus were significant and were caused by environmental alterations and plant choice. The endophytic bacteria in L. secalinus grown in alpine sandy land may have greater anti-stress properties and the ability to fix nitrogen, which has potential value in environmental remediation and agricultural production.

Endophytic Bacterium Lysobacter firmicutimachus Strain 5-7 Is a Promising Biocontrol Agent Against Rice Seedling Disease Caused by Pythium arrhenomanes in Nursery Trays.

Rice root rot disease caused by Pythium spp. is a highly destructive disease in rice nurseries. Biocontrol with endophytic bacteria was developed in this study to control rice seedling diseases. An in planta screening assay revealed that two bacterial endophytes, strains 5-7 and 6-4, displayed strong protection of rice seedlings from attack by Pythium arrhenomanes. Phylogenetic analysis indicated that strain 5-7 is Lysobacter firmicutimachus, while strain 6-4 belongs to the Kitasatospora genus. To quickly evaluate the disease severity of the root system damaged by Pythium spp. in nursery trays, a root surface area measurement assay was developed. By using this measurement, the control efficacy in nursery trays was evaluated, and L. firmicutimachus 5-7 showed promising biocontrol activity against Pythium disease. In a field trial, the two endophytes exhibited significant disease control efficacy on rice brown spot disease caused by Bipolaris oryzae naturally occurring in a commercial nursery field. The two endophytes exhibited multiple enzymatic activities and broad-spectrum antagonistic activities against multiple rice pathogens. The two endophytes colonized the root surface and inside of the root. L. firmicutimachus 5-7 primarily colonized the intercellular space and aerenchyma. Antibiosis is the major mechanism used by strain 5-7 to cause Bipolaris hyphal swelling and inhibit Pythium zoospore germination and sporangium formation, while a hyperparasitism-like phenomenon was found in the interaction of strain 6-4 with Pythium and Bipolaris hyphae. In conclusion, we report the promising biocontrol agent L. firmicutimachus 5-7 and the potential biocontrol agent Kitasatospora sp. 6-4 for disease control of rice seedlings in commercial nursery trays and their possible mechanisms of action.

Costs and benefits associated with the adoption of tomato and sweet pepper nursery seed propagation technologies in Arumeru and Mvomero districts in Tanzania

Seed propagation technologies are becoming increasingly popular among vegetable producers in developing countries due to their ability to provide benefits by lowering production costs. We assessed the costs and benefits of seed propagation technology adoption for tomato and sweet pepper production using a partial budget approach for seedling trays or field nursery technologies in the districts of Arumeru and Mvomero in Tanzania. We applied Net Present Value, Cost–Benefit Ratio (CBR) and Internal Rate of Return (IRR) to choose the best seed propagation technology that can be adopted by farmers and especially those producing vegetable seedlings as their core business and for commercial purposes. We collected the data using a household survey questionnaire, interviews, and focus group discussions. The results show that switching from field nurseries to seedling trays is economically beneficial by increasing the rate of return value to 3.02, which is greater than one, implying a rate of return of 302 %, which is greater than the costs of new investments. Overall, we can conclude that farmers were less likely to grow vegetable seedlings in seedling trays due to the fact that seedling tray technology was considerably more expensive than field nursery technology. As a result, we recommend that policymakers at all levels of local and central governments promote extension agent training in this technology to promote seedling tray propagation among vegetable farmers and make the technology affordable to farmers in order to increase agricultural productivity, income, and well-being.

Neem Oil to Reduce Zeatin Use and Optimize the Rooting Phase in Olea europaea L. Micropropagation.

Micropropagation is an in vitro propagation technique, established in the nursery field sector for numerous species, which offers several advantages compared to traditional agamic propagation techniques. In the case of the olive tree, however, despite the advances made through research, it is still little used, due to the recalcitrance to in vitro proliferation and/or rooting of many olive cultivars and the high cost of zeatin, the only cytokinin that makes it possible to achieve a satisfactory proliferation rate in this species. In this context, numerous attempts have been made to identify alternative cytokinin compounds able to improve the proliferation rate of olive tree explants and thus reduce the unitary production cost. In particular, there is a growing interest in the use of natural substances (called in some cases "complex mixtures"), which, when added to the in vitro cultivation substrates, seem to be able to improve proliferation rates. In the present study, neem oil was added to the propagation substrates (partially/totally replacing zeatin) and in the rooting phase for the olive cultivar Moraiolo. In particular, in the proliferation phase, the effect of neem oil (0.1 mL L-1) in substrates containing different zeatin concentrations (0, 1, 2, and 4 mg L-1) was evaluated. For the rooting phase, agarized substrate and soil were used with shoots derived from a standard proliferation substrate (4 mg L-1 zeatin) and from the substrate that gave the best results in the proliferation phase (2 mg L-1 zeatin and 0.1 mL L-1 neem oil). In the proliferation phase, the addition of neem oil in the substrates with low zeatin concentration (1 and 2 mg L-1) induced an increase in the number of adventitious shoots and shoots length. On the contrary, the addition of neem oil in the rooting substrates did not positively influence the rooting phase, but positive results especially in terms of root number and length were observed in explants derived from a neem oil-enriched proliferation substrate compared to the control substrate. Therefore, the present study demonstrated for the first time the positive role of neem oil in the proliferation of olive in vitro with low zeatin concentrations.

First report of Pythium aristosporum causing root rot on rice seedling in Taiwan.

Rice (Oryza sativa L.) is the principle staple crops in the World and its production can be severely damaged by Pythium species. Several Pythium species including P. afertile, P. arrhenomanes, P. dissotocum, P. elongatum, P. spinosum, have been recorded to cause rice seedling root rot in Taiwan (List of Plant Diseases in Taiwan edited by Tzean et al., 2019). During the survey of rice seedling diseases, we identified a new species of Pythium that causes seedling root rot on rice in commercial nursery trays in two nursery fields in 2019 in Taichung, Taiwan. Stunting and root rot symptom were found on the affected plants and up to 20% seedlings in a nursery tray showed similar symptoms. To isolate the pathogen, symptomatic roots were surface sterilized with 75% ethanol for 1 min and rinsed in sterile water. The margin of lesion was cut off, placed on 1.5% water agar and incubated at 28 ℃. After 24 h, the hyphal tips of a white colony growing from the diseased region were transferred to potato dextrose agar (PDA) medium. Koch's postulates were fulfilled by inoculating the germinated rice seeds with mycelia. Rice seeds of O. sativa var. Tainan11 (TN11) were treated with 75% ethanol and then 1.2% NaOCl for 15 min. The sterilized seeds were soaked in sterile water under dark condition for 3 days and the water was replaced every day. Five of the pre-germinated seeds with 2~5 mm embryonic shoot were placed in a sterile petri-dish and inoculated with 3-ml mycelial suspension (OD600 = 0.045) prepared by blending the mycelia of a 3-days PDA culture using an Oster 10 speed blender 6640 (Oster, USA). The seeds-mycelia were then covered with sterilized soil mixture of Akadama soil and rice husk (1:1, volume to volume) and incubated in a growth chamber at 28 ℃. Seven days post-inoculation, the inoculated seedlings showed stunting with short and necrotic roots (Fig. S1). The pathogen was reisolated from the diseased seedlings and identified with morphology and molecular methods. For morphological characterization, the pathogen was cultured on V8 agar to produce oogonia and zoospore (Chamswarng and Cook 1985). Globose oogonia with multiple antheridia (1-5 per oogonium), inflated filamentous sporangia, vesicle with abundant zoospores, main hypha with up to 6.57 μm wide and mature aplerotic oospores with diameter 24.35-30.81 μm (average= 27.22 μm; n=20) were observed (Fig. S1) that are similar to the descriptions for P. aristosporum (van der Plaats-Niterink 1981). Genomic DNA was extracted with CTAB method (Wang and White 1997) and the sequences of the internal transcribed spacer (ITS) region and gene region of β-tubulin (tub) and cytochrome c oxidase subunit II (cox II) were amplified with published primers (Villa et al., 2006). The obtained sequences were submitted to GenBank (accession nos: OL701302 (ITS), OL763269 (tub), and OL763270 (cox II); Fig. S2). Phylogenetic relationships between this Pythium pathogen and other 55 Pythium isolates, including the type species of P. aristosporum (ATCC11101), were conducted with the concatenated sequences of tub and cox II and analyzed by Bayesian interference (Fig. S3). Based on the tree built with tub and cox II sequences, this pathogen was identified as P. aristosporum that has not been reported in rice and other plants in Taiwan. It was observed in laboratory assays that this pathogen caused significant root-rot symptoms on several major rice varieties grown in Taiwan, including TN11, Tainung67 and Kaoshiung139. It may potentially cause severe crop loss in rice production, especially in nurseries. This identification provides important information on rice disease management.

Production of High-Quality Tomato Seedlings in the Open Field Nurseries

The aim of the study is to produce tomatoes seedlings with good characteristics for summer and fall seedlings seasons in field nurseries by investigating three plant distances (10, 15, 20 cm), inaddition to scatteringand two levels of seed rate (100 and 150% of the recommended rates).The experiment was carried out using completely random plots using split plot designs in three replications, and the levels of each factor were randomly distributed within the plots withcultivation of two seedbeds. Planting tomato seedlings at a 20 cm distance can improve tomato seedlings' growth in open field nurseries. Finally, more researches are needed to determine the optimal seed rates as well as planting distances in open field nurseries production under Al-Jabal Al-Khader conditions.

Effective decontamination and multiplication of Croton membranaceus in vitro

Abstract. Adukonu IA, Ayeh KO, Acheampong E. 2022. Effective decontamination and multiplication of Croton membranaceus in vitro. Cell Biol Dev 6: 68-81. Croton membranaceus Müll. Arg. is a useful herb with medicinal properties, and its leaves, roots, and bark are used to treat diverse ailments. However, the harvesting method by traditional medical practitioners without replacement exposes it to extinction. Therefore, the only means of propagating is by relatively slow use of seeds, and an alternative propagation method is needed for field establishment and nursery. Therefore, this study aims at determining an effective propagation by sterilization regime and subsequent in vitro regeneration using different explants; intact seeds, isolated embryos, coatless seeds, and nodal-cutting. The explants were decontaminated using double sterilization; the best was achieved by pre-treatment with 70% ethanol for 3 min before immersion in sodium hypochlorite (NaOCl). Intact seeds were effectively decontaminated by immersion in 15% NaOCl solution for 20 min, then by 10% NaOCl for 15 min. Conversely, coatless seeds were effectively decontaminated when isolated from intact seeds immersed in 20% NaOCl solution for 20 min and 15% NaOCl for 15 min. Further, embryos isolated from intact seeds were effectively decontaminated in 20% NaOCl for 15 min, then by 15% NaOCl for 10 min sequentially. These sterilization regimes successfully decontaminated 86% intact seeds, 100% isolated embryos, and 80% coatless seeds. Nodal-cutting explants were best decontaminated by immersion in 20% NaOCl solution for 15 min, followed by 15% NaOCl for 10 min sequentially without ethanol pre-treatment. This sterilization regime successfully decontaminated 100% of the nodal-cutting explants. However, the development of shoot explants varied in response to sterilization. Intact seeds did not develop into shoots, while isolated embryos, coatless seeds, and nodal-cutting explants developed into shoots independent of the sterilization regime. Shoot development was highest with the medium’s shoot-tip explants added with BAP, NAA, and GA3. Shoot multiplication was best achieved on an MS basal medium with 5.0 ?M BAP, 0.5 ?M NAA, and 5.0 ?M GA3 amendment.