Biochemical and molecular characterization of Alternaria alternata isolates highly resistant to procymidone from broccoli and cabbage

Alternaria alternata, a causal agent of leaf blights and spots on a wide range of hosts, has a high risk of developing resistance to fungicides. Procymidone, a dicarboximide fungicide (DCF), has been widely used in controlling Alternaria leaf blights in China for decades. However, the resistance of A. alternata against DCFs has rarely been reported from crucifer plants. A total of 198 A. alternata isolates were collected from commercial fields of broccoli and cabbage during 2018–2019, and their sensitivities to procymidone were determined. Biochemical and molecular characteristics were subsequently compared between the high-level procymidone-resistant (ProHR) and procymidone-sensitive (ProS) isolates, and also between ProHR isolates from broccoli and cabbage. Compared with ProS isolates, the mycelial growth rate, sporulation capacity and virulence of most ProHR isolates were reduced; ProHR isolates displayed an increased sensitivity to osmotic stresses and a reduced sensitivity to sodium dodecyl sulfate (SDS); all ProHR isolates showed a reduced sensitivity to hydrogen peroxide (H2O2) except for the isolate B102. Correlation analysis revealed a positive cross-resistance between procymidone and iprodione, or fludioxonil. When treated with 10 μg/mL of procymidone, both mycelial intracellular glycerol accumulations (MIGAs) and relative expression of AaHK1 in ProS isolates were higher than those in ProHR isolates. Sequence alignment of AaHK1 from ten ProHR isolates demonstrated that five of them possessed a single-point mutation (P94A, V612L, E708K or Q924STOP), and four isolates had an insertion or a deletion in their coding regions. No significant difference in biochemical characteristics was observed among ProHR isolates from two different hosts, though mutations in AaHK1 of the cabbage-originated ProHR isolates were distinct from those of the broccoli-originated ProHR isolates.

Eucalypts for Tropical Rainforest (Af) climate

The equatorial region of the world includes areas of Tropical Rainforest (Af) and Tropical Monsoon (Am) climate zones, which are distinguished by high temperatures and high rainfall, but soils which are often deficient. Potential productivity of plantation forestry in this area is high, and so are the pest and disease dangers which threaten it. This paper describes the Eucalyptus and Corymbia species which are adapted to this situation and also resistant to the main diseases like leaf blights. Based on the highly adapted E. biterranea and E. deglupta and several more, hybridization combined with vegetative propagation is discussed as an excellent alternative to obtain quick gains in short rotations while maintaining wide genetic diversity in such plantations. Management remedies are given for the possible backlash of quick soil depletion.

Inhibitory Activity of Piper Caninum Leaf Extract against Curvularia Spotting Disease on Rice Plants

Rice is a plant that has been intensively breed, especially in Asia, most of the population’s staple food is rice. There were Many types of rice varieties have been developed for high yeald production. Different rice diseases arise that many treat to reduce production. Such as curvularia spotting disease caused by the fungus Curvularia sp. Infection of Curvularia species causing leaf spots, leaf blights, kernel root, grain deformation and other diseases are well known globally. It was discovered that the small brown oval spots on the Ciherang rice variety cultivated in Bali, Indonesia was caused by Curvularia verruculosa. This disease could reduce the rice yield up to almost 50%. The application of commercial fungicide by the local farmers has not been satisfactorily successful in term of controlling the disease but instead bring damages to the environment and the soil as well. Farmer’s safety is also another serious issue. The current studi develop a natural and green fungicide to check the efficacy of Piper caninum extract against the fungi. Research in the laboratory uses a completely randomized design and research in the field uses a randomized group design.The method of making leaf extracts uses maceration method. Diffusion well technique showed a strong inhibition of the abstract against the C. verruculosa with 22mm inhibition. Zone with a total inhibition of 4% extract concentration. The minimum inhibitory concentration (MIC) was low of 0.5%. Scanning electron images of the treated fungi showed hollow and wrinkled mycelia morphology indicating lysis of the cell has occurred. P. caninum leaf extract at a concentration of 3% provides the highest obstacle to the intensity of C. verruculosa disease, whereas in the treatment of leaf extract concentration p. caninum 4% intensity of C. verrucuosa disease has decreased because rice plants are toxic at a concentration of 4%. Further research is needed regarding the treatment of P. caninum leaf extract against C. verruculosa in rice fields.

Leaf Spots and Leaf Blights of Palm

This fact sheet is limited to those diseases where the pathogens only infect (invade) and cause spots and blights of the leaf blade. Other diseases may cause death of leaflets and leaf segments but are actually the result of a pathogen infecting the leaf petiole or rachis. Petiole/rachis blight diseases are discussed separately at http://edis.ifas.ufl.edu/pp145. This document is PP-218, one of a series of the Plant Pathology Department, UF/IFAS Extension. Original publication date Janurary 2006. PP-218/PP142: Leaf Spots and Leaf Blights of Palm (ufl.edu)

Addition of mancozeb to the fungicide mixtures DMI + QoI and SDHI + QoI on the control of wheat leaf blights

ABSTRACT Wheat leaf blights caused by Drechslera siccans, D. tritici-repentis, especially D. tritici-repentis, are difficult to be controlled by site-specific fungicide mixtures. Due to development of resistance, the use of double site-specific mixtures has shown control inferior to 50%. In an experiment conducted in the field with the wheat cultivar Jadeite 11, in 3 x 6 m plots and four replicates, the effect of a muli-site fungicide added to fungicide mixtures on the control of leaf blights was evaluated. The effect of the following mixtures was evaluated: picoxystrobin + cyproconazole, kresoxim-methyl + epoxiconazole, azoxystrobin + cyproconazole, pyraclostrobin + epoxiconazole, pyraclostrobin + fluxapyroxad, trifloxystrobin + prothioconazole and azoxystrobin + propiconazole, added of five mancozeb levels, 0; 1.5; 2.0; 2.5 and 3.0 kg/ha. The first application occurred after 30% leaf incidence, and the remaining two occurred at 15 and 18-day intervals. The fungicides were applied with a backpack sprayer pressurized by CO2, delivering 180 L/ha. Leaf blights severity was quantified, control was calculated, the percentage of chlorophyll in flag leaves was determined, and grain yield was assessed. The mean control of leaf blights by the mixtures without addition of the multi-site fungicide was 44%. The disease severity reduced as a function of the addition of mancozeb levels for all treatments. Control superior to 80% was obtained with the mixtures kresoxim methyl + epoxiconazole and pyraclostrobin + epoxiconazole, both added at least 2.0 kg/ha mancozeb. There was a positive reflex on the increase in wheat grain yield as a function of control, varying from 3005 kg/ha for the best treatment to 2026 kg/ha for control.

Türkiye’de Orman, Park ve Fidanlıklarda Görülen Phytophthora Kök Çürüklüğü Hastalıkları ve Korunma Önlemleri

Phytophthora species, as a member of Oomycetes are important plan diseases occurring on almost all of the annual and perennial plants and rapidly killing the plants by producing root, collar rots and leaf blights. The first Phytophthora study on forest trees in Turkey was made on oak species which is the most widespread tree in the country. Seven Phytophthora species, namely P. cinnamomi, P. citricola, P. cryptogea, P. gonapodyides, P. quercina, Phytophthora sp. 1 and Phytophthora sp. 2’ were found to cause dieback and death on oaks, P. quercina being the most frequently encountered. The second most common tree having Phytophthora infections is sweet chestnut and root rots caused by Phytophthora were determined everywhere chestnut grow in the country. Four species were found on chestnut and the most frequently occurring two species are P. cambivora and P. cinnamomi occurring in the inner part and in the coastal areas of the country respectively. The third and fourth species, P. plurivora and P. cryptogea were observed in the decreasing order respectively. From the above mentioned species, P. cambivora and P. cryptogea were also reported from black pine at one location in the newly reforested location. From the other forest trees; various Phytophthora species were reported; P. lacustris from narrow leaved ash, P. plurivora, P. occultans from boxwood, P. citrophthora and P. cactorum from horse chestnut, P. nicotianae from Ailanthus sp. Phytophthora diseases were also found in a few nurseries growing forest an ornamental trees. P. cinnamomi, P. cryptogea, P. cactorum, P. citricola, P. megasperma and P. syringae were found to cause disease on various forest tree saplings. Elaborate information on Phytophthora diseases is being given in the review.

Irrigation and fungicide application on disease occurrence and yield of early and late sown sunflower

The objective of this study was to evaluate the effect of irrigation and fungicide application on the occurrence of diseases and cypsela yield of two genotypes of sunflower. The experiments were carried out in Santa Maria-RS, during the regular season in 2007 and the late season, in 2008. Plants were sown on 04/09/2007 and 21/01/2008, in a completely randomized design, with four replicates. A 2 x 6 factorial scheme was used, with the sunflower genotypes Aguará 03 and Hélio 358 and six fungicide application schemes, which were determined by the FAST forecasting system, as follows: FAST 16, FAST 22 and FAST 28, without irrigation, FAST 16 IRR under irrigated condition, in addition to irrigated control (CONTROL IRR) and control (CONTROL). Disease progress was analyzed based on weekly observations of the severity of the symptoms. It was verified that irrigation increases sunflower cypsela yield in the regular season, provided that weather conditions are not favorable for the occurrence of alternaria and septoria leaf blights or that fungicides are applied. In the late season, under irrigated condition, fungicide application is necessary to control alternaria and septoria leaf blights.