Nematicidal Activity of the Endophyte Serratia ureilytica against Nacobbus aberrans in Chili Plants (Capsicum annuum L.) and Identification of Genes Related to Biological Control

The genus Serratia is widely distributed in soil, water, plants, animals, invertebrates, and humans. Some species of this genus have antifungal, antibacterial, and nematicidal activity. In this work, the nematicidal activity of the endophytic strain of Serratia sp. in chili, Capsicum annuum L., is reported, where at a bacterial concentration of 4 × 109 cel/mL, the penetration of nematodes into the roots significantly decreased by 91 and 55% at 7 and 21 days after inoculation. This bacterial concentration also significantly decreased the number of galls, eggs, egg masses and reproduction factor produced by Nacobbus aberrans in Chili plants, with respect to the control where this bacterial strain was not applied. In the analysis of the genome of the strain, based on average nucleotide identity (ANI), the isolate could be affiliated to the species Serratia ureilytica. The size of the genome is 5.4 Mb, with a 59.3% content of GC. Genes related to the synthesis of chitinases, siderophores, proteases C, serralisins, hemolysin, and serrawettin W2 that have been reported for biocontrol of nematodes were identified in the genome. It is the first report of Serratia ureilytica with nematicidal activity. Based on these results of nematicidal activity, this strain can be evaluated in the field as an alternative in the biocontrol of Nacobbus aberrans in chili cultivation.

Effect of irradiation on the growth and rooting of a climbing rose in vitro

The article presents the influence of pulsed and continuous irradiation (400…780 nm) on in vitro growth of the climbing rose variety “Camelot” at the illumination of 80±5 mmol/(m2s), temperature - 24±10C, and the relative air humidity - 73±2%. It was found that the experimental led light (LED) pulsed phytoirradiator contributed to a significant increase in the leaf surface area during cultivation of climbing rose microstems in Gamborg’s nutrient medium, the average growth was 2.94 mm2 compared to 2.80 mm2 in the control. Pulse irradiation increases the reproducibility of climbing roses by 1.7 times, and also increases the rooting rate up to 96% compared to 82% in the control. Experimental LED phytoirradiator of continuous irradiation promoted an increase in the leaf surface area growth at the level of the control luminescent phytoirradiator, but also provided a significant increase in the reproduction factor and rooting rate of rose microstems. In the pulsed mode, phytoinstallations consume only 50% of the electricity compared to the continuous irradiation mode.

Reaction of grapevine rootstocks and cultivars to Meloidogyne incognita, M. arenaria and M. hapla

This study aimed to evaluate the reaction of six grapevine rootstocks (MGT 101-14, Ritcher 110, Paulsen 1103, K 5BB, SO4, Salt creek) and two cultivars (Quebranta and Torontel) to three species of the root-knot nematode (Meloidogyne incognita, M. arenaria and M.hapla). The experiment was performed as a completely randomized design with an 8 × 3 factorial scheme and six replicates per treatment. The experimental unit in each replicate comprised a grapevine cutting planted in 3 kg bags with sterilized soil. Cuttings were inoculated with 5000 eggs + juveniles (J2) of M. incognita, M. arenaria and M. hapla. Six months after inoculation, plants were removed from the bags, and the reaction was determined by evaluating the number of galls (NG), number of nematodes per gram of root (NNGR), and reproduction factor (RF). The evaluated rootstocks, MGT 101-14, Ritcher 110, Paulsen 1103, K 5BB, SO4 and Salt Creek, were resistant to M. incognita, M. arenaria and M. hapla, except for Salt creek, which was susceptible to the latter. The Quebranta and Torontel cultivars were susceptible to the Meloidogyne species under study.

Intermediate resistance to nematode Meloidogyne paranaensis in Híbrido de Timor coffee genotypes

The aim of this study was to prove that Híbrido de Timor (HdT) accessions are resistance sources to Meloidogyne paranaensis. Two experiments were carried out in a greenhouse at IDR-Paraná (Londrina, Paraná State, Brazil). Open pollinated fruits were harvested from 10 accessions (HdT UFV 380-05, HdT UFV 408-10, HdT UFV 408-11, HdT UFV 408-28, HdT UFV 428-04, HdT UFV 439-14, HdT UFV 443-08, HdT UFV 445-70, HdT UFV 446-138, HdT UFV 448-75) from the EPAMIG/ UFV germplasm bank. Seeds of these accessions were sown to obtain seedlings to test the resistance to M. paranaensis. For each experiment, a completely randomized design was used with 11 treatments, eight replications and one plant per plot. Cultivar Mundo Novo IAC 376-4 was the susceptible check. Seedlings with three to four pairs of leaves were transplanted into plastic cups with a capacity of 700 mL and 1200 eggs. The J2 of M. paranaensis (IP) were inoculated after one month. The assessments were performed 134 days after inoculation, when the data of the number of eggs and J2 per gram of roots and the final population of nematodes (FP) were obtained. The reproduction factor (RF) was calculated using the formula: RF = IP / FP. To classify the resistance levels of the genotypes, the reproduction factor reduction (RFR) was used. It classified the levels from highly resistant to highly susceptible. Different levels of intermediate resistance between the accesses were observed, highlighting HdT UFV 408-28 that presented moderate resistance to M. paranaensis. HdT UFV 408-28 showed a high percentage of plants with intermediate resistance, which can be used in breeding programs aimed at resistance to M. paranaensis

IMPROVEMENT OF CLONAL MICROPROPAGATION OF BERRY CROPS

The aim of the study is to optimize the conditions for in vitro cultivation of blue honeysuckle, raspberry and strawberry. The work was carried out in 2012-2020. The Murasige-Skuga medium (1/2 MS) was the control for all cultures for the initiation of explants. Additionally, we used a modified nutrient medium 1/2 MS with a reduced NH4 content by 15 % compared to the base MS; and Woodi Plant Medium (1/2 WPM) for honeysuckle; for raspberries - Quoirin-Lepoivre (1/2 QL) and 1/2 Anderson; for strawberries - 1/2 MS. For micropropagation and rooting, the following media were used: honeysuckle - modified MS and WPM; raspberries - QL and Anderson; strawberries - MS modified by Siliplant and Boksyu; control for all - MS. The following growth regulators were added to the optimal each culture a nutrient medium: 6-benzylaminopurine (6-BAP), gibberellic acid (GA), waste products of the large wax moth larvae, indolyl-3-butyric acid (IBA), Siliplant, EcoFus, HB-101. The effect of LED-phytoirradiators with a combination of red, blue and white light in the spectrum 2: 1: 1, 1: 1: 1, 2: 1, respectively, and LED-irradiators with a changing spectrum and flashing were studied at the stages of micropropagation and rooting in all cultures. The survival rate of honeysuckle explants on 1/2 WPM medium was 62.2 % (control 27.9 %). The highest reproduction factor of 5.1 (control 2.6) was achieved when using LED 2 red : 1 blue : 1 white on MS modified + 6-BAP 1.0 mg/L + kinetin 0.5 mg/L, and high rooting rate of honeysuckle 89.0 % (76.0 % k) was achieved on MS modified + IBA 0.5 mg/L. Cultivation of red raspberries on QL + 6-BAP 1.0 mg/L + GA 0.5 mg/L and LED irradiation 2 red : 1 blue : 1 white provided a reproduction factor of 5.3 (control 2.7), addition of IBA 0.5 mg/L + HB-101 100 μL/L in QL and LED irradiation 1 red : 1 blue : 1 white contributed to 100 % rooting. The addition of 6-BAP 1.0 mg/L + IBA 0.2 mg/L + GA 0.5 mg/L in QL and LED lighting 1 red : 1 blue : 1 white increased the reproduction factor of remontant raspberries by 1.6 times (from 2, 6 to 4.1), and the use of QL + IBA 0.5 mg/L + HB-101 50 μL/L and LED 2 red : 1 blue : 1 white increased its rooting ability to 96 % (control 67 %). LED irradiation with a changing spectrum during cultivation of garden strawberries on MS + Siliplant + EcoFus at 0.5 ml/L provided a reproduction factor of 5.9 (control 3.8), and the reproduction factor of remontant strawberries on MS + HB-101 100 μl/L was 7.4 (control 5.6). The addition of IBA 0.5 mg/L + HB-101 100 μL/L to the MS promoted the rooting of garden strawberries of 100 % when using a LED irradiator with a changing spectrum, and remontant strawberries – with a blinking LED irradiator

Combined effect of β-aminobutyric acid and silver nanoparticles on eggplants, Solanum melongena, infected with Meloidogyne javanica

Summary The acquired resistance of plants to root-knot nematodes (Meloidogyne spp.) can be achieved by applying chemical inducers, such as β-aminobutyric acid (BABA). Recently, the use of metal nanoparticles with multifunctional use against plant-parasitic nematodes has been presented. In this study, silver nanoparticles (AgNPs) were synthesised using the aqueous leaf extract of Malva sylvestris. The effect of different AgNPs concentrations on hatching and mortality of the second-stage juveniles (J2) of Meloidogyne javanica was investigated in vitro. The effects of AgNPs on eggplants infected with 0, 1, 2, 4 and 8 eggs (cm3 soil)−1 were investigated under glasshouse conditions. The combined effects of AgNPs and BABA on eggplants infected with 4 and 8 eggs (cm3 soil)−1 were investigated in another study. The results showed that increasing the concentration of AgNPs the hatching of M. javanica decreased and the mortality of J2 increased. The number of eggs, galls, egg masses and reproduction factor in plants treated with AgNPs infected with 4 eggs (cm3 soil)−1 decreased by 43.4, 24.7, 23.5 and 43.2%, and in plants infected with 8 eggs (cm3 soil)−1, decreased by 64.5, 25.5, 63.1 and 64.5%, respectively, compared to control plants. The reproduction factor in infected plants with 4 and 8 eggs (cm3 soil)−1 that were treated with BABA (1 mM) and AgNPs decreased by 51.6 and 55.9%, respectively, compared to control plants. The results of this study demonstrated the effects of BABA, AgNPs and the combination of these two substances in reducing the damage of different inoculum densities of M. javanica in eggplant.

Biological Control Agents in the Management of Different Initial Population Densities of Meloidogyne javanica in Tomato

The efficacy of single and combined application of Trichoderma harzianum and Pseudomonas fluorescens (CHA0) in the controlling of Meloidogyne javanica on tomato plants was evaluated under green house conditions. Seeds of the susceptible tomato cv. Early-Urbana were sown in clean plastic pots containing 1.5 kg steam sterilized soil. Four weeks after planting, the soil of each pot was infested with a suspension of 20 ml/kg soil of T. harzianum (106 spores/ ml) and a suspension of 15 ml/kg soil of P. fluorescens (CHA0) (108 CFU/ ml). Soil of other pots were infested with the two tested bio-agents together as a combined application. Seven days later, plants in all pots, except the controls, were inoculated with M. javanica at initial population densities of 1, 2 or 4 eggs/ cm3 soil. Sixty days after nematode inoculation, the parameters of plant growth and nematode reproduction were determined. Results showed that the nematode reproduction factor (Rf) on the plants infected with 1, 2 and 4 eggs/ cm3 decreased by 58, 63 and 31% after the single application of T. harzianum, 11, 33 and 12% after the single application of P. fluorescens (CHA0) and 43, 55 and 49% after the combined application of the bio-agents, respectively. Combined application of the two bio-agents was found to be the most effective in controlling the higher initial population density of the nematode (4 eggs/ cm3).

The Ethiopian staple food crop enset (Ensete ventricosum) assessed for the first time for resistance against the root-lesion nematode Pratylenchus goodeyi

Summary Pratylenchus goodeyi appears to be the most prevalent nematode pest of enset in Ethiopia, where it can occur in extremely high densities. However, the damage to yield or how different enset cultivars react to the nematode has yet to be determined. The current study therefore sought to establish a first assessment of these reactions by enset to P. goodeyi infection. Determining pest-resistant cultivars is an important task in developing management strategies. Our study evaluated nine enset cultivars to establish host response and identify potential sources of resistance. In addition, the pathogenicity of P. goodeyi was assessed on three enset cultivars. After 9 months’ growth, significant differences in final population densities (Pf) and reproduction factor (RF) were observed amongst the nine cultivars, with ‘Gefetanuwa’ the most susceptible (Pf = 25 799 and RF = 12.9), and similarly in a repeat experiment for 4.5 months (Pf = 126 534 and RF = 63.3). ‘Maziya’ and ‘Heila’ were the most resistant in the first experiment (Pf < 455 and RF < 0.2) as well as in the repeat, together with ‘Kellisa’ (Pf < 5255 and RF < 2.6). In the pathogenicity experiment four inoculum densities significantly affected the Pf and RF but not among the three cultivars ‘Maziya’, ‘Arkiya’ and ‘Heila’. This is the first known study to assess genotype reaction to P. goodeyi, which shows that there are significant differences in the reactions of different cultivars and that resistance appears to be present in enset.

Super-Spreaders Out, Super-Spreading In: The Effects of Infectiousness Heterogeneity and Lockdowns on Herd Immunity

Recently, [8] has proposed that heterogeneity of infectiousness (and susceptibility) across individuals in infectious diseases, plays a major role in affecting the Herd Immunity Thresh-old (HIT). Such heterogeneity has been observed in COVID-19 and is recognized as overdis-persion (or “super-spreading”). The model of [8] suggests that super-spreaders contribute significantly to the effective reproduction factor, R, and that they are likely to get infected and immune early in the process. Consequently, under R0 ≈ 3 (attributed to COVID-19), the Herd Immunity Threshold (HIT) is as low as 5%, in contrast to 67% according to the traditional models [1, 2, 4, 10].This work follows up on [8] and proposes that heterogeneity of infectiousness (susceptibility) has two “faces” whose mix affects dramatically the HIT: (1) Personal-Trait-, and (2) Event-Based-Infectiousness (Susceptibility). The former is a personal trait of specific individuals (super-spreaders) and is nullified once those individuals are immune (as in [8]). The latter is event-based (e.g cultural super-spreading events) and remains effective throughout the process, even after the super-spreaders immune. We extend [8]’s model to account for these two factors, analyze it and conclude that the HIT is very sensitive to the mix between (1) and (2), and under R0 ≈ 3 it can vary between 5% and 67%. Preliminary data from COVID-19 suggests that herd immunity is not reached at 5%.We address operational aspects and analyze the effects of lockdown strategies on the spread of a disease. We find that herd immunity (and HIT) is very sensitive to the lock-down type. While some lockdowns affect positively the disease blocking and increase herd immunity, others have adverse effects and reduce the herd immunity.

Respuesta del perejil crespo a diferentes densidades de población de Meloidogyne arenaria

The effect of initial population density (Pi) of the peanut root-knot nematode, Melodoigyne arenaria, on curly leaf parsley growth was assessed in this study. The population densities of M. arenaria ranged from 0 to 64 eggs + second-stage juveniles (J2)/cm3 soil in sterile sandbags. The root gall index (RGI), reproduction factor (RF), fresh leaf weight (FLW), dry leaf weight (DLW), root fresh weight (RFW), root length (RL), leaf height (LH), and chlorophyll index (SPAD) were determined at 90 days after inoculation. FLW, DLW, RFW, LH, and SPAD data were fitted to the Seinhorst equation, y = m + (1 - m) zPi-T, to determine the tolerance limit T = 0.25 eggs +J2/cm3 soil for FLW, DLW, RFW, and LH, with relative means (m) of 0.52, 0.24, 0.22, and 0.4 respectively; conversely, the T value for SPAD was 0.125 eggs + J2/cm3 soil and with a m of 0.26. All biometric variables decreased with an increase in the initial population density (Pi). Nevertheless, the highest RF of M. arenaria in parsley was 78.92 for a Pi = 8 eggs + J2/cm3 soil, with an RGI value of 5 from Pi = 1 eggs + J2/cm3. Curly leaf parsley growth decreased with an increase in Pi of M. arenaria.