Biological Characteristics and Genetic Diversity of Phomopsis asparagi, Causal Agent of Asparagus Stem Blight

Asparagus stem blight is a regional disease. In the present study, we compared strains of Phomopsis asparagi from six different provinces to determine their biological characteristics and genetic diversity, differences in the pycnidium and conidium production, pathogenicity, and growth rate. Considerable differences were established in the pycnidium and conidium production among the P. asparagi strains from the six studied provinces. The largest pycnidium and conidium production had the strains from Fujian, followed by those from Hainan. The virulence of P. asparagi strains was significantly different but without a correlation with the geographical source of the strain. FJ2 had the highest virulence, followed by HN2, SD4, and SD5, whereas SD5 had the lowest virulence. The colony diameter and dry weight of the strains of asparagus stem blight fungus from the six provinces were substantially different. The colonies of HN1-5 had the largest diameters, whereas those of XT1-5, LT1-3, FJ1-5, and SX6 had smaller diameters. Four primers with good repeatability and strong specificity were selected from 100 intersimple sequence repeat (ISSR) primers. ISSR-PCR amplification was performed on 36 strains of asparagus stem blight fungus, and a large number of repeatable DNA fingerprints were obtained. Most of the amplified fragments were within 300 to 500 bp. In all, 69 total points, 64 multiple points, and 92.75% polymorphism points were established. The number of ISSR gene sites detected by four primers ranged from 14 to 20, with an average of 16 multiple sites. The copolymerization was divided into three groups: XT1-5, LT1-3, and FJ1-5, which were clustered into the first group; SD1-6, SX1-6, and HB1-6, clustered into the second group; and HN1-5 in the third group. The results of the cluster analysis revealed that the strains of the neighboring provinces had a nearer phylogenetic relationship than that between distant ones. Therefore, the system evolution of P. asparagi is related to the geographical distribution of its strains.

Evaluation ofTrichoderma atroviride and Trichoderma citrinoviride growth profiles and their potentials as biocontrol agent and biofertilizer

BackgroundTwo Trichoderma species (T. atroviride and T. citrinoviride) were evaluated for their potential to have Trichoderma-based biological control agent and biofertilizer properties.Materials and MethodsEight Trichoderma spp. were identified by molecular methods. The mycoparasitic activities against different phytopathogenic fungi and their capacity to produce extracellular lytic enzymes were investigated. Furthermore, indole-3-acetic acid production and phosphate solubilization capabilities of Trichoderma spp. were evaluated together with the effect of some physical parameters and different carbon:nitrogen sources on mycelial growth and conidium production.Results and DiscussionAll strains exhibited lytic enzymes and indole-3 acetic acid production as well as phosphate solubility characteristics. Trichoderma citrinoviride demostrated more mycoparasitic activity against Fusarium oxysporium than T. atroviride whereas T. atroviride was found more effective against Rhizoctonia solani. In particular, at lower temperatures, conidium production of T. atroviride strains were significantly higher than T. citrinoviride strains. Both strains grew well on all carbon sources tested. The effect of organic nitrogen sources on growth were notably higher than inorganic nitrogen sources.ConclusionThe results provided valuable insight in both the highest mycelial growth and conidia production conditions of these cultures for further similar studies related to development of Trichoderma-based new commercial biological control and biofertilizer formulations in different agro-climatic regions.

Neonectria ditissima conidium production and release in planta

Neonectria ditissima, the causal agent of European canker in apples, conidia are available year-round in the Tasman region of New Zealand. Spore production and release in apple trees were quantified during natural and artificial rain events. Rain traps captured spores over 18 rain events (July—August 2017) from European canker lesions (excised and in planta) derived from ‘Royal Gala’ picking wound and rasp wound infections. Rain traps were monitored regularly to determine spore release over time. Differences in the number of conidia produced from lesions on the tree and excised lesions re-mounted in the tree were not significant. Lesions arising from picking wounds produced 7.2 times more spores on average than lesions arising from rasp wounds. Most spores were released within the first hour of rain and total spore release followed a logarithmic curve. Rain duration × volume of water determined the rate of conidia release. Excised lesions are suitable to study the effect of biotic and abiotic drivers on spore production.

GFP-fluorescent protein on the study of blister spot in coffee plants

In Brazil, Colletotrichum gloeosporioides is associated with a complex of symptoms in coffee culture. Although this pathogen had its pathogenesis observed and identified, its importance has still been questioned due to its several endophytic forms, raising doubts as to the real importance of the pathosystem. The aim of this study was to demonstrate, by using an isolate transformed with the gene gfp, the infection and colonization capability of C. gloeosporioides in coffee seedlings. After the fourth day of inoculation, manifestation of symptoms as punctual necrosis could be observed, which progressed during the evaluation period, culminating in the death of seedlings. Epifluorescence microscopy confirmed the presence of the pathogen in the seedlings, as well as the visualization of internal colonization of tissues, acervulus formation and conidium production, confirming that it was responsible for the observed symptoms.

Pathogenicity of field and laboratorygrown inoculum of Neonectria galligena on potted apple trees

European canker caused by Neonectria galligena is an important disease of apple trees worldwide In this study methods were developed for conidium production in culture and for testing the pathogenicity of N galligena Conidia produced in culture were one or twocelled while conidia collected from cankers were multicelled Isolate ICMP9472 produced enough conidia in culture to produce inoculum (210 5 conidia/ml) to test the pathogenicity in comparison with that of conidia harvested from apple cankers from Motueka (field inoculum) and a twodayold suspension of conidia from Motueka apple cankers on potted Royal Gala trees in a glasshouse under continual misting The germination rates of the three inocula were similar (5079) Two months after inoculation all inoculated wounds were infected regardless of inoculum source However cankers caused by field inoculum (fresh and two dayold) were significantly larger (average 108 mm and 106 mm respectively) than those caused by isolate ICMP9472 (51 mm) Six months after inoculation cankers caused by fresh field inoculum were significantly larger than those caused by 2dayold inoculum which were significantly larger than those caused by isolate ICMP9472 In addition cankers caused by fresh field inoculum were significantly more active than those caused by older field inoculum or isolate ICMP9472

Enhancement of In Vitro Conidia Production in Monilinia vaccinii-corymbosi (Reade) Honey by Cellulose Acetate Membranes

In vitro conidia production by Monilinia vaccinii-corymbosi (Reade) Honey, the cause of mummy berry disease in blueberry, was significantly enhanced by cellulose acetate membranes placed on the surface of V-8 juice agar for most of the pathogen isolates tested, compared to V-8 juice agar alone. Temperature and light affected conidia production, but the effects were not consistent. Higher temperature (22 vs. 15 °C) yielded better sporulation, but the effects of light environment were variable. When 55 isolates from various sources were rated visually for sporulation on cellulose acetate membranes at 22 °C under ambient light/dark cycles, a wide range of conidium production was observed, and three of 55 isolates (6%) were identified as having very high conidia production.