Incidence and Etiology of Postharvest Fungal Diseases Associated with Bulb Rot in Garlic (Alllium sativum) in Spain

In recent years, different postharvest alterations have been detected in garlic. In many cases, the symptoms are not well defined, or the etiology is unknown, which further complicates the selection of bulbs during postharvest handling. To characterize the different symptoms of bulb rot caused by fungi, garlic bulb samples were collected from six Spanish provinces in two consecutive years. Eight different fungal species were identified. The most prevalent postharvest disease was Fusarium dry rot (56.1%), which was associated with six Fusarium species. Fusarium proliferatum was detected in more than 85% of symptomatic cloves, followed by F. oxysporum and F. solani. Pathogenicity tests did not show a significant correlation between virulence and mycotoxin production (fumonisins, beauvericin, and moniliformin) or the mycelial growth rate. Penicillium allii was detected in 12.2% of the samples; it was greatly influenced by the harvest season and garlic cultivar, and three different morphotypes were identified. Stemphylium vesicarium and Embellisia allii were pathogenic to wounded cloves. Some of the isolated fungal species produce highly toxic mycotoxins, which may have a negative impact on human health. This work is the first to determine the quantitative importance, pathogenicity, and virulence of the causative agents of postharvest garlic rot in Spain.

Combined Influence of Chitosan and Calcium Chloride on Fusarium Dry Rot Disease Under Field Conditions

Background: Fusarium dry rot disease caused by Fusarium sambucinum Fuckel (F. sambucinum) can infect the potato tubers in the field and during storage. Yield losses by F. sambucinum reach 60%. Traditional methods to control Fusarium dry rot are fungicides application, which led to developing many isolates resistant to these fungicides. Objective: The aim of this study is to evaluate the effect of calcium chloride (CaCl2) and chitosan, alone or in combination, on plant development, tuber yield, and Fusarium dry rot disease incidence under field conditions. Methods: Soil inoculated with F. sambucinum before planting. We treated the seed tubers with CaCl2 (0.5 or 1%), chitosan 0.5%, or both. The foliage was sprayed twice with CaCl2 (0.5 or 1%), 0.1% chitosan, or both. During the vegetation period, growth parameters, such as germination (%), plant height (cm), and branches number per plant, were measured. At harvest, we calculated the total and the marketable number of tubers and tuber yield. In addition, during storage, we assessed the incidence of Fusarium dry rot disease on tubers. Results: Results revealed that combined pre-planting application with 1% CaCl2 and 0.5% chitosan with 2 hours intervals, then spraying foliar with 1% CaCl2 and 0.1% chitosan twice with ten days intervals starting at 40 days after planting resulted in: a) increasing the germination, enhancing the growth parameters such as plant height and branches number per plant; b) enhancing the marketable tuber yield by 75.2 and 97.6% in Sante and Kolobok varieties, respectively; c) reducing Fusarium dry rot disease incidence by 61.9-72.7%. Conclusion: The work highlighted that the combined pre-planting and foliar application of CaCl2 and chitosan might be recommended for potato producers to reduce the incidence of Fusarium dry rot disease and augment yields.

The Effect of Endophytic Bacteria Bacillus subtilis and Salicylic Acid on Some Resistance and Quality Traits of Stored Solanum tuberosum L. Tubers Infected with Fusarium Dry Rot

The effect of endophytic Bacillus subtilis (strains 10-4, 26D) and their compositions with salicylic acid (SA) on some resistance and quality traits of stored potatoes infected with Fusarium dry rot were studied. The experiments were carried out on hydroponically grown Solanum tuberosum L. tubers that were infected before storage with Fusarium oxysporum and coated with B. subtilis 10-4, 26D with and without exogenous SA, and then stored for six months. It has been shown that 10-4, 26D, 10-4 + SA, and 26D + SA reduced in different levels (up to 30–50%) the incidence of F. oxysporum-caused dry rot (with the highest effect for 10-4 + SA). SA notably enhanced the positive effect of 10-4, while for 26D, such an effect was not observed. All of the tested treatments increased amylase (AMY) and AMY inhibitors activity in infected tubers, while decreased Fusarium-induced protease activity (except in the case of 10-4 + SA, which promoted a slight increase) was revealed. 10-4, 26D, and their compositions with SA decreased (in different degrees) the pathogen-caused lipid peroxidation, proline, and reducing sugars accumulation in potatoes after long-term storage. It was also discovered 10-4 and 26D, regardless of SA presence, decrease pathogen-induced glycoalkaloids α-Solanine and α-Chaconine accumulation and preserved increased levels of starch and total dry matter in infected stored potatoes. The findings indicate endophytic B. subtilis and its compositions with SA is a promising eco-friendly and bio-safe approach to cope with postharvest decays of potato during long-term storage; however, when developing preparations-compositions it should take into account the strain-dependent manner of B. subtilis action together with SA.

Identification of Fusarium spp. Associated with Potato Tubers in Upper Egypt by Morphological and Molecular Characters

Potato (Solanum tuberosum L.) is an important crop which holds promise for food security considering the global population growth rate. Fusarium dry rot is one of the most significant diseases of potato. To build up strategies for the control of this disease, it ought to be made primarily a correct diagnosis and identification of the pathogen. A total of 504 Fusarium isolates were recovered from potato tubers collected from Upper Egypt. Fusarium isolates were identified based on morphology and partial DNA sequencing of β-tubulin (TUB) genes. 62.5% of the isolates were identified as F. sambucinum, followed F. oxysporum (57.5%), then F. verticillioides (56.25%) and F. incarnatum (47.5%). All the tested Fusarium species were able to produce amylase. The pathogenicity of the isolates was tested by inoculation of healthy potato tubers; all of the tested isolates were pathogenic to healthy potato tubers. F. sambucinum had a highly virulent effect.