Metabolic Capacity Differentiates Plenodomus lingam from P. biglobosus Subclade ‘brassicae’, the Causal Agents of Phoma Leaf Spotting and Stem Canker of Oilseed Rape (Brassica napus) in Agricultural Ecosystems

In contrast to the long-lasting taxonomic classification of Plenodomus lingam and P. biglobosus as one species, formerly termed Leptosphaeria maculans, both species form separate monophyletic groups, comprising sub-classes, differing considerably with epidemiology towards Brassicaceae plants. Considering the great differences between P. lingam and P. biglobosus, we hypothesized their metabolic capacities vary to a great extent. The experiment was done using the FF microplates (Biolog Inc., Hayward, CA, USA) containing 95 carbon sources and tetrazolium dye. The fungi P. lingam and P. biglobosus subclade ‘brassicae’ (3 isolates per group) were cultured on PDA medium for 6 weeks at 20 °C and then fungal spores were used as inoculum of microplates. The test was carried out in triplicate. We have demonstrated that substrate richness, calculated as the number of utilized substrates (measured at λ490 nm), and the number of substrates allowing effective growth of the isolates (λ750 nm), showed significant differences among tested species. The most efficient isolate of P. lingam utilized 36 carbon sources, whereas P. biglobosus utilized 60 substrates. Among them, 25–29 carbon sources for P. lingam and 34–48 substrates for P. biglobosus were efficiently used, allowing their growth. Cluster analysis based on Senath criteria divided P. biglobosus into two groups and P. lingam isolates formed one group (33% similarity). We deduce the similarities between the tested species help them coexist on the same host plant and the differences greatly contribute to their different lifestyles, with P. biglobosus being less specialized and P. lingam coevolving more strictly with the host plant.

Optimizing Plant Disease Management in Agricultural Ecosystems Through Rational In-Crop Diversification

Biodiversity plays multifaceted roles in societal development and ecological sustainability. In agricultural ecosystems, using biodiversity to mitigate plant diseases has received renewed attention in recent years but our knowledge of the best ways of using biodiversity to control plant diseases is still incomplete. In term of in-crop diversification, it is not clear how genetic diversity per se in host populations interacts with identifiable resistance and other functional traits of component genotypes to mitigate disease epidemics and what is the best way of structuring mixture populations. In this study, we created a series of host populations by mixing different numbers of potato varieties showing different late blight resistance levels in different proportions. The amount of naturally occurring late blight disease in the mixture populations was recorded weekly during the potato growing seasons. The percentage of disease reduction (PDR) in the mixture populations was calculated by comparing their observed late blight levels relative to that expected when they were planted in pure stands. We found that PDR in the mixtures increased as the number of varieties and the difference in host resistance (DHR) between the component varieties increased. However, the level of host resistance in the potato varieties had little impact on PDR. In mixtures involving two varieties, the optimum proportion of component varieties for the best PDR depended on their DHR, with an increasing skewness to one of the component varieties as the DHR between the component varieties increased. These results indicate that mixing crop varieties can significantly reduce disease epidemics in the field. To achieve the best disease mitigation, growers should include as many varieties as possible in mixtures or, if only two component mixtures are possible, increase DHR among the component varieties.

A semantically enriched taxonomic revision of Gryonoides Dodd, 1920 (Hymenoptera, Scelionidae), with a review of the hosts of Teleasinae

Teleasinae are commonly collected scelionids that are the only known egg parasitoids of carabid beetles and therefore play a crucial role in shaping carabid populations in natural and agricultural ecosystems. We review the available host information of Teleasinae, report a new host record, and revise Gryonoides Dodd, 1920, a morphologically distinct teleasine genus. We review the generic concept of Gryonoides and provide diagnoses and descriptions of thirteen Gryonoides species and two varieties: G. glabriceps Dodd, 1920, G. pulchellus Dodd, 1920 (= G. doddi Ogloblin, 1967, syn. nov. and G. pulchricornis Ogloblin, 1967, syn. nov.), G. brasiliensis Masner & Mikó, sp. nov., G. flaviclavus Masner & Mikó, sp. nov., G. fuscoclavatus Masner & Mikó, sp. nov., G. garciai Masner & Mikó, sp. nov., G. mexicali Masner & Mikó, sp. nov., G. mirabilicornis Masner & Mikó, sp. nov., G. obtusus Masner & Mikó, sp. nov., G. paraguayensis Masner & Mikó, sp. nov., G. rugosus Masner & Mikó, sp. nov., G. uruguayensis Masner & Mikó, sp. nov. We treat Gryonoides scutellaris Dodd, 1920, as status uncertain. Gryonoides mirabilicornis Masner & Mikó, sp. nov. is the only known teleasine with tyloids on two consecutive flagellomeres, a well-known trait of Sparasionidae. An illustrated identification key to species of Gryonoides, a queryable semantic representation of species descriptions using PhenoScript, and a simple approach for making Darwin Core Archive files in taxonomic revisions accessible are provided.

Divergence in Corn Mycorrhizal Colonization Patterns Due to Organic Treatment

Excessive application of chemical fertilizers and other agrochemicals can cause large imbalances in soils and agricultural ecosystems. In this context, mycorrhizae represent a viable solution to mitigate these negative effects. Arbuscular mycorrhizae are vital symbionts due to the multiple benefits they bring to both crops and the entire agroecosystem. The main purpose of this study was to observe whether differentiated fertilization has an influence on mycorrhizal colonization patterns in corn. Observed frequencies and intensities of colonization varied widely between phenophases and treatments, with 20% variation for frequency and 14% for intensity, which implies the constant development of both partners during the vegetation period. Arbuscules and vesicles were present in all development stages, but the overall mean was lower than 4% for arbuscules and 1% for vesicles in the analyzed root fragments. Intensity was highly correlated with frequency of colonization compared with arbuscules, where the coefficient was 0.54, and vesicles, with a coefficient of 0.16. Both PCA and NMDS provided good graphical solutions, with a high resolution due to explained variance and good spatial position of vectors. The use of mycorrhizal maps permits the full exploration of colonization patterns and fungal strategy, and the assessment of mycorrhizae-free areas. For the untreated variant, the strategy was oriented toward a longitudinal colonization followed by an irregular development of hyphae with multiple non-colonized areas. Treatment acts to stimulate the appearance of mycorrhizal spots, which further develop radially.

Predation capacity and larval development of Ceraeochrysa claveri (Neuroptera: Chrysopidae) fed with Raoiella indica (Acari: Tenuipalpidae)

Ceraeochrysa claveri Navás (Neuroptera: Chrysopidae) is a predator found in several agricultural ecosystems and feeds on insects and phytophagous mites. Its high reproductive potential and forage capacity makes it a candidate for biological control of agricultural pests. Raoiella indica Hirst (Acari: Tenuipalpidae) is an important pest that can damage several species of palms, in particular, Cocos nucifera L. Given the scarcity of available knowledge about the biological aspects of Chrysopidae fed with phytophagous mites, the present work aimed to study the larval development of C. claveri fed mainly with R. indica, in order to obtain information that would be of help in the integrated management of this pest. The evaluation was performed in the F0 generation. Larva 3 is the instar that consumes the most mites (F value = 32.99; P > 0.0001) (L3: 46.80 ± 10.12 a; L2: 9.80 ± 1.23 b; L1: 9.40 ± 1.58 b). C. claveri did not complete larval development when fed only with R. indica. Larval instars L1, L2 and L3 lived 7.4 ± 2.2, 7.6 ± 1.9 and 9.0 ± 3.9 days, respectively. The larvae that reached the pupal stage failed to grow further. When adding Sitotroga cerealella Olivier (Lepidoptera: Gelechidae) eggs to the diet, the development lasted 7.9 ± 0.2, 7.4 ± 0.8, 6.5 ± 0.9 and 13.6 ± 0.9 days for L1, L2, L3 and pupae, respectively. The adults lived on average 6.7 ± 4.9 days. The sexual ratio was rt = 0.42. According to the conditions under which the experiment was carried out, it can be inferred is that C. claveri cannot complete its development by feeding only on R. indica, and that it thus consumes this mite as an occasional prey. Highlights: Ceraeochrysa claveri is a predator found in various agricultural ecosystems and feeds on insects and phytophagous mites. Raoiella indica is an important mite that can damage several species of palms, in particular Cocos nucifera Ceraeochrysa claveri does not complete its biological cycle by feeding only on indica. By adding another protein source to L3, it can reach the adult stage in 35.4±2.8 days. Ceraeochrysa claveri does not complete its cycle by feeding only on R. indica and consequently takes this mite as occasional prey.

The Regulation of Plant Vegetative Phase Transition and Rejuvenation: miRNAs, a Key Regulator

In contrast to animals, adult organs in plants are not formed during embryogenesis but generated from meristematic cells as plants advance through development. Plant development involves a succession of different phenotypic stages and the transition between these stages is termed phase transition. Phase transitions need to be tightly regulated and coordinated to ensure they occur under optimal seasonal, environmental conditions. Polycarpic perennials transition through vegetative stages and the mature, reproductive stage many times during their lifecycles and, in both perennial and annual species, environmental factors and culturing methods can reverse the otherwise unidirectional vector of plant development. Epigenetic factors regulating gene expression in response to internal cues and external (environmental) stimuli influencing the plant’s phenotype and development have been shown to control phase transitions. How developmental and environmental cues interact to epigenetically alter gene expression and influence these transitions is not well understood, and understanding this interaction is important considering the current climate change scenarios, since epigenetic maladaptation could have catastrophic consequences for perennial plants in natural and agricultural ecosystems. Here, we review studies focusing on the epigenetic regulators of the vegetative phase change and highlight how these mechanisms might act in exogenously induced plant rejuvenation and regrowth following stress.