Search

In agriculture, new and sustainable strategies are increasingly demanded to integrate the traditional management of viral diseases based on the use of virus-free propagation materials and resistant or tolerant cultivars and on the control of insect vectors. Among the possible Integrated Pest Management (IPM) approaches, organic biostimulants have shown promising results in enhancing plant tolerance to virus infections by improving plant fitness and productivity and modulating metabolic functions. In this study, the combination of two organic biostimulants, Alert D-Max and Resil EVO Q, composed of seaweed and alfalfa extracts, enzymatic hydrolysates, and micronized zeolite, was applied on the leaves and roots of zucchini squashes, both healthy and infected by zucchini yellow mosaic virus (ZYMV). Four applications were scheduled based on ZYMV inoculation timing, and plant vegetative and reproductive parameters were recorded along with the virus titre and symptom severity. The modulation of the expression of specific genes potentially involved in pattern-triggered immunity (PTI), systemic acquired resistance (SAR), and oxidative stress defence pathways was also investigated. Besides increasing the general fitness of the healthy plants, the biostimulants significantly improved the production of flowers and fruits of the infected plants, with a potential positive impact on their productivity. The repeated biostimulant applications also led to a one-tenth reduction in ZYMV titre over time and induced a progressive slowdown of symptom severity. Genes associated with SAR and PTI were up-regulated after biostimulant applications, suggesting the biostimulant-based priming of plant defence mechanisms. Due to the observed beneficial effects, the tested biostimulant mix can be an effective component of the IPM of cucurbit crops, acting as a sustainable practice for enhancing plant fitness and tolerance to potyviruses. [ABSTRACT FROM AUTHOR]

The onion yellow dwarf virus (OYDV) represents a limiting biotic stress in onion (Allium cepa L.); little information is available regarding resistant varieties. In Italy, onion production is limited but represented by a wide diversity of ecotypes. A two-year trial was carried out to test the OYDV-susceptibility/tolerance of different Italian onion cultivars by rating symptom severity and plant growth parameters and assessing post-harvest secondary infections. The cultivar and ecotypes included in the study were characterized by simple sequence repeats (SSR) analysis, and the expression analysis of two genes (Eukaryotic translation initiation factors, EIFs) involved in potyvirus replication was also performed. Two susceptible and one tolerant cultivar were identified based on symptom expression and virus impact on plants. Although differences in growth parameters were limited to the first-year trial, the infection was correlated to a higher incidence of secondary infections in post-harvest, with altered water balance in infected bulbs. This correlation was also demonstrated during the long-term storage of bulbs. SSR analysis identified different clusters and only one gene isoform (EIF4eiso1) showed different expression levels in the OYDV/onion pathosystem. In conclusion, this study defines the genetic profile of Italian onion cultivars and provides evidence on susceptibility/tolerance features which will be useful in the future for the identification of viral resistance traits in onion. [ABSTRACT FROM AUTHOR]

In Europe and the Mediterranean region, 'Candidatus Liberibacter solanacearum' (Lso) is associated with emerging diseases of Apiaceae crops, mainly carrot. Emergency measures for import of carrot seed were set, requiring seed to be heattreated at 50°C or tested as Lso-negative by PCR. The germination response to heat treatment was assessed for 24 carrot cultivar and hybrid seed lots. Ten parsley, five fennel, and two celery seed lots were also analysed. Of these 41 seed lots, 21 were Lsoinfected. Water heat treatment significantly decreased germinability compared to dry heat treatment, indicating that dry heat treatment is a cheaper and less detrimental procedure. However, the dry heat treatment significantly decreased seed germination compared to untreated controls in four of 24 seed lots of carrot, four of ten parsley seed lots, three of five fennel seed lots, and one of two celery seed lots. For parsley, the heat treatment reduced germinability to a lesser extent in Lso-infected than Lso-free seed lots. These data show that heat treatment can affect the germination of Apiaceae seeds to varying degrees, depending on species or variety, the type of heat treatment, and the sanitary status of the seeds. [ABSTRACT FROM AUTHOR]

Bemisia tabaci (Hemiptera: Aleyrodidae) is responsible for severe damage to horticultural and ornamental crops worldwide, mainly for its role as virus vector. In Italy, the B. tabaci Mediterranean (MED) and Middle East-Asia Minor 1 (MEAM1) cryptic species are widespread in the Southern regions as well as in Sicily and Sardinia. During the last two decades, MED populations progressively increased, in those areas where intensive farming is applied. The recent introduction of the begomovirus Tomato leaf curl New Delhi virus (ToLCNDV) prompted extensive surveys of both vector and symptomatic plants. In 2016 and 2017, monitoring activities were carried out in Lazio region (Central Italy) where begomovirus epidemics had never occurred before and the presence of B. tabaci was thought to be only occasional. ToLCNDV-infected zucchini plants were found in Southern Lazio together with whitefly populations belonging only to the MED cryptic species. The MED-Q2 haplotype was the most abundant, likely favored by high temperatures and intensive agricultural practices. Single and mixed populations of MED and MEAM1 were found in Central and Northern Lazio, suggesting that agro-ecological factors still limit MED outbreaks in these areas. This preliminary survey indicates that B. tabaci is well established in Lazio, making ToLCNDV potentially able to spread to the rest of the region as well as to the nearby regions of Central Italy that have similar climatic and cultural conditions. The northward spread of B. tabaci is a critical issue for viral disease epidemiology and the management of whitefly-transmitted viruses in Central Italy, and must be kept under strict surveillance. [ABSTRACT FROM AUTHOR]