Advances and outlook of horticultural bioengineering

A Branch of modern biotechnology for creating unique relevant genotypes is bioengineering that harnesses a spectrum of plant genome modification technologies. The study aimed to analyse the current state of the art in genome modification of fruit and berry crops for more significant (vs. premium pure breeding varieties) deviations of norm in the traits and properties of biotic and abiotic resistance, productivity, fruit quality, etc. First horticultural crop transformation studies aimed at developing protocols based on selectable enzyme marker genes of phosphorylationmediated aminoglycoside antibiotics detoxification. Neomycin phosphotransferase nptII constitutes the most common system of transgenic fruit and berry crop selection. In pome crops, the transgenic selection priorities were resistance to scab (Venturia inaequalis (Wint.) Cke), rust (Gymnosporangium juniper-virginianae Schwein.) and bacterial blight (Erwinia amylovora Burrill, Winslow et al.), higher fruit quality, including bright colouring, and reduced enzymatic browning. In stone crops, it was tolerance to plum pox (PPV), papaya ringspot (PRSV) and Prunus necrotic ringspot (PNRSV) viruses. In berry crops — resistance to Sphaerotheca humuli (DC.) Burrill fungus, grey mould (Botrytis cinerea Pers.), root rot (Phytophthora cactorum (Lebert & Cohn) J.Schrot.) and powdery mildew (Oidium tuckeri Berkeley), as well as higher fruit quality. In citruses — resistance to bacterial canker (Xanthomonas citri sub sp.), citrus ulcer (Xanthomonas axonopodis pv citri), greening disease (Huanglongbing (HLB)) and fungi (Trichoderma harzianum Rifai). In tropical crops — resistance to papaya ringspot (PRSV) and banana streak (eBSV) viruses. Unique FT-phenotype transgenic fruit lines are leveraged in the new FasTrack breeding strategy. Nine fruit and berry transgenic crop lines have now been registered worldwide. Transgenic Arctic apples (Golden, Granny, Fuji), plums (Honey Sweet) and papaya (Rainbow, SunUp, Laie Gold) are industry-approved in fresh and processed form. The transgenic list regulated in the Russian Federation does not include fruit or berry crops.

Chitin Deacetylase, a Novel Target for the Design of Agricultural Fungicides

Fungicide resistance is a serious problem for agriculture. This is particularly apparent in the case of powdery mildew fungi. Therefore, there is an urgent need to develop new agrochemicals. Chitin is a well-known elicitor of plant immunity, and fungal pathogens have evolved strategies to overcome its detection. Among these strategies, chitin deacetylase (CDA) is responsible for modifying immunogenic chitooligomers and hydrolysing the acetamido group in the N-acetylglucosamine units to avoid recognition. In this work, we tested the hypothesis that CDA can be an appropriate target for antifungals using the cucurbit powdery mildew pathogen Podosphaera xanthii. According to our hypothesis, RNAi silencing of PxCDA resulted in a dramatic reduction in fungal growth that was linked to a rapid elicitation of chitin-triggered immunity. Similar results were obtained with treatments with carboxylic acids such as EDTA, a well-known CDA inhibitor. The disease-suppression activity of EDTA was not associated with its chelating activity since other chelating agents did not suppress disease. The binding of EDTA to CDA was confirmed by molecular docking studies. Furthermore, EDTA also suppressed green and grey mould-causing pathogens applied to oranges and strawberries, respectively. Our results conclusively show that CDA is a promising target for control of phytopathogenic fungi and that EDTA could be a starting point for fungicide design.

The Effect of Monochromatic LED Light Wavelengths and Photoperiods on Botrytis cinerea

Botrytis cinerea is a ubiquitous necrotrophic pathogen causing grey mould in economically important crops. Light effect in horticulture is undeniable and fungi also react to light. Selected specific light-emitting diodes (LEDs) and photoperiods can be used for fungal pathogen inhibition. This study aimed to evaluate how LED light wavelengths and photoperiods affect the growth parameters of B. cinerea. The morphological (mycelium appearance, sclerotia distribution) and phenotypic (conidia presence and size, mycelium growth rate, recovery) characteristics of the fungal pathogen B. cinerea were evaluated under royal blue 455 nm, blue 470 nm, cyan 505 nm, yellow 590 nm, and red 627 nm LED lights at various photoperiods (4, 8, 12, 16, 20, 24 h). The results revealed that the light conditions and photoperiods influenced the B. cinerea morphological and phenotypic characteristics. Overall, the highest B. cinerea inhibition was under yellow (590 nm) LED light at 4 and 8 h photoperiods. Conidia did not form under blue 455 nm at 8, 16, 20, and 24 h photoperiods. Therefore, it can be assumed that the phenotypic and morphological features of B. cinerea depend on the specific photoperiod and LED light wavelength. The results allowed an exploration of original research approaches, raised new scientific questions for further investigation, and suggested new green plant protection solutions.

EFFECT OF CHITOSAN PRETREATMENT ON THE QUALITY OF STRAWBERRIES DURING COLD STORAGE

The paper is focused on improving the technology of storing strawberries. It has been investigated how pretreatment of berries with aqueous solutions of low-molecular-weight chitosan of three concentrations (0.1%, 0.3%, 0.5%) affects the quality parameters of strawberries during refrigeration. The treated berries and the reference (untreated sample) were stored in 500 g perforated plastic containers at 0±2°C for 14 days. It has been found that strawberries treated with chitosan solutions had significantly smaller weight loss than the reference. At the end of storage, this parameter was 9.7% in the reference and 7.0–8.6% in the treated berries. It has been established that the respiration rate of the strawberries decreased sharply on the first day, which was caused by refrigerated storage, and continued to decline until the end of storage. Finally, this parameter attained the value 3.3 mg CO2/kg-1h-1in the reference and 2.2–3.0 mg CO2/kg-1h-1 in the treated berries. The hardness of the strawberries at the end of storage was 0.10–0.14 kg/cm2. The change in the lustre level of the berries has been observed. It has been established that on the 14th day of storage, the surface of the untreated berries was dull. The best characteristics have been observed for treatment at the chitosan concentration 0.5%. The effect of chitosan films on the sensory characteristics of berries has been investigated. It has been found that the pretreatment did not impair the taste of the berries. The results of the tasting evaluation indicate that the taste, aroma, and colour were better in the variants with the treatment concentrations 0.3 and 0.5%. However, as for the appearance and consistency, the experts preferred the berries treated at the concentration 0.5%. After two weeks’ storage, the strawberries have been found to be damaged by four fungal diseases. The infections found in the samples were Botrytis cinerea (grey mould), Rhizopus stolonifer (black mould), Whetzelinia sclerotiorum (white mould), and Penicillium spp. It has been established that pretreatment of strawberries with chitosan solutions reduces the development of phytopathogenic diseases. It has been shown that chitosan-based edible coatings have a positive effect on strawberries, increasing their shelf life and improving their quality. A conclusion has been drawn about the technology of application of chitosan solutions and about their concentrations.

Role of the tomato fruit ripening regulator MADS-RIN in resistance to Botrytis cinerea infection

Tomato MADS-RIN (RIN) transcription factor has been shown to be a master activator regulating fruit ripening. Recent studies have revealed that in addition to activating many other cell wall genes, it also represses expression of XTH5, XTH8 and MAN4a, which are positively related to excess flesh softening and cell wall degradation, which might indicate it has a potential role in pathogen resistance of ripening fruit. In this study, both wild type (WT) and RIN-knockout (RIN-KO) mutant tomato fruit were infected with Botrytis cinerea, to investigate the function of RIN in defence against pathogen infection during ripening. The results showed that RIN-KO fruit were much more sensitive to B.cinerea infection with larger lesion sizes. Transcriptiome data and qRT-PCR assay indicate genes of phenylalanine ammonialyase (PAL) and chitinase (CHI) in RIN-KO fruit were reduced and their corresponding enzyme activities were decreased. Transcripts of genes encoding pathogenesis-related proteins (PRs), including PR1a, PRSTH2 and APETALA2/Ethylene Response Factor (AP2/ERF) including ERF.A1, Pti5, Pti6, ERF.A4 were reduced in RIN-KO fruit comparing to WT fruit. Moreover, in the absence of RIN the expression of genes encoding cell wall modifying enzymes XTH5, XTH8, MAN4a has been reported to be elevated, which is potentially correlated with cell wall properties. When present, RIN represses transcription of XTH5 by activating ERF.F4 a class II (repressor class) ERF gene family member and ERF.F5. These results support the conclusion that RIN enhances ripening-related resistance to grey mould infection by upregulating pathogen-resistance genes and defense enzyme activies as well as reducing accumulation of transcripts encoding some cell wall enzymes.

Covering Norway spruce container seedlings with reflective shading cloth during field storage affects seedling post-planting growth

The field storage of container seedlings is often a necessity after the seedlings have been transported from nurseries close to the regeneration area. Suboptimal storage conditions can lead to reduced growth or even seedling mortality. Supporting favourable conditions for the seedlings during storage requires labour, especially for the watering of seedlings, and therefore increases the costs of forest regeneration. In this study, we examined the effects of covering Norway spruce container seedlings with a reflective shading cloth and neglecting the watering during field storage. This was done by measuring the drying of the seedlings during field storage, the rooting of the seedlings when planting, and the subsequent survival and performance in the field two and three growing seasons after planting. The study comprised one-year-old Norway spruce container seedlings covered with reflective shading cloth and seedlings with no cover (subject to rainfall) in 2012 and 2013; additionally, in 2013, replicates from both treatments were stored in conditions where rainfall was impeded. The stem water potential was measured, a rooting test was carried out, and the seedlings were planted in the test field weekly over 42 days of field storage without watering. As a novel finding, the results indicate that covering the seedlings with a reflective shading cloth during the field storage increased the risk of grey mould in summer storage and led to negative effects regarding post planting seedling development. The application of a shading cloth directly on the seedlings cannot be recommended to prolong the watering intervals during field storage in the current climatic conditions in Southern Finland, where the risk of grey mould is high.

Indigenous Aureobasidium pullulans Strains as Biocontrol Agents of Botrytis cinerea on Grape Berries

Aureobasidium pullulans is a yeast-like fungus found on the surface of the grape berries that has been proven to act as a biocontrol agent for the management of grey mould disease caused by Botrytis cinerea. In this work, an indigenous strain of A. pullulans isolated from grape berries and selected according to the in vitro activity against B. cinerea, was used in vineyards of the winery where it originated, in comparison with a commercial product containing two A. pullulans strains with the aim of assessing its effectiveness as a biocontrol agent. The experimental design included daily meteorological data registration and the early defoliation of grapevines as treatments. The monitoring of A. pullulans strains on grape berries by plate counts and molecular methods as well as of B. cinerea symptoms on grape bunches was performed in the different trials from the end of flowering to the harvest time. Results highlighted that although no significant differences (p < 0.05) in the occurrence of B. cinerea were detected according to different treatments, the mean incidence of symptomatic berries ranged from 7 to 16%, with the lowest values recorded in bunches treated with the indigenous A. pullulans strain. The efficacy of the biocontrol agent was affected more by meteorological conditions than the defoliation practice.