Use of near infrared reflectance and transmittance coupled to robust calibration for the evaluation of nutritional value in naked oats

A rapid accurate and precise method for simultaneous determination of β-glucan and protein content in naked oat samples, based on the coupling of near-infrared spectroscopy and chemometrics, is presented. In particular, three different spectroscopic approaches [near infrared reflectance (NIR) and transmittance (NIT) on flour and NIT on whole grains] and various spectral pretreatments were considered. To account for the possibility of outlying samples, a robust version of the PLS algorithm (namely partial robust M-regression) was used. All the models resulted as accurate as the reference methods, reflectance spectroscopy being the technique providing the best outcomes. Variable reduction by inclusion of the most relevant predictors only (as evaluated by VIP scores) resulted in simpler and, in one case, more parsimonious models, without loss in accuracy.     

Date of pruning of Guazuma ulmifolia during the rainy season affects the availability, productivity and nutritional quality of forage during the dry season

Guazuma ulmifolia was experimentally pruned to determine when pruning should begin during the rainy season in order to extend the production of green tree-forage during the dry season. Three prunings (P-1, P-2, and P-3) were performed (5 weeks apart) during the rainy season (August, September, and October) and four forage harvests (C-a, C-b, C-c, and C-d) (3 weeks apart) took place during the dry season (February, March, and April). Over 2 years, forage biomass production was evaluated as total biomass (g dry matter tree^?1), biomass of the morphological components (leaves, stems, and dead matter), and nutritional quality (crude protein, fiber, lignin, and digestibility). Date of pruning affected the production of total biomass (P = 0.001) with the earliest pruning (P-1) yielding the greatest forage quantity, while stems (P = 0.022) and dead matter (P = 0.032) varied due to a year by pruning interaction. Total biomass, leaves, stems, and dead matter varied by the interaction between forage harvest and year for all four variables (P < 0.037). In both years, the largest forage harvest occurred in C-b (P < 0.05), leaf production was highest in C-a and C-b (P < 0.001), stem production was greatest in C-b (P = 0.013) and dead matter was highest in C-b and C-d (P = 0.002). Leaf crude protein ranged between 10 and 19 %, and the interaction of pruning by forage harvest by year was significant (P = 0.035). Digestibility, neutral and acid detergent fiber and lignin differed significantly because of the interaction between forage harvest and year (P < 0.005), with February showing the lowest values for fiber and the highest digestibility. The best time to prune G. ulmifolia is in August so that the young trees will produce more total biomass with a higher crude protein content. The most suitable moment for forage harvest is in February when the trees have more leaves with greater digestibility and less fiber.     

Growth, herbivore distribution, and herbivore damage of timber trees in a tropical silvopastoral reforestation system

Context

The reforestation of degraded tropical pastures requires innovative tree planting systems that consider land user needs.

Aim

We established a silvopastoral reforestation system and assessed the effects of companion trees on the native timber tree Tabebuia rosea in Panama. Timber tree individuals were established in (1) solitary plantings (TSol) or in companion plantings with (2) Guazuma ulmifolia (TGua) or (3) the nitrogen-fixing Gliricidia sepium (TGli).

Methods

We quantified growth characteristics and herbivory of T. rosea, and analyzed leaf chemistry (including the stable isotopes ??¹⁵N and ??¹³C) and structure (leaf mass per area).

Results

Companion trees significantly affected stem diameter growth of T. rosea. Stem diameter growth was as high in TGli trees as in TSol trees but was reduced in TGua trees. Furthermore, TGua trees had higher leaf water content, and lower ??¹³C and lower leaf mass-to-area ratio than TGli trees, suggesting there were effects of shading by G. ulmifolia on T. rosea. Herbivory was high but not affected by planting regimes. Leafing phenology did not differ between planting regimes and G. sepium did not increase nitrogen content in T. rosea leaves.

Conclusion

Companion tree planting can support timber tree growth in silvopastoral reforestations, but adequate species selection is crucial for successful implementation of this planting system. Tree?Ctree interactions seem to be more relevant for timber tree growth than herbivory in the studied system.     

Spatial and temporal patterns at small scale in Austrocedrus chilensis diseased forests and their effect on disease progression

Austrocedrus chilensis is an endemic conifer of Patagonia that suffers a widespread mortality whose causes are a topic of discussion. Since Phytophthora austrocedrae is the most probable cause, we proposed that the spatial and temporal patterns of disease at small scale should reflect pathogen behavior. We aimed at characterizing the spatial and temporal patterns of diseased trees in different soil types and the effect of microsite variability on diseased trees spatial pattern. The spatial pattern of disease was influenced by soil type and tree density. In clay soils with low disease incidence (ca. 25%), the spatial pattern was random and not influenced by abiotic microsite conditions. When disease incidence increased (ca. 70%), concurring with denser plots, the spatial pattern was clustered, as a result of an infection process, and it was independent of microsite variability. In soils with better drainage conditions, that is, alluvial soils with volcanic ash input and coarse textured volcanic soils, the disease was clustered and associated with flat microtopographies. The progression of the disease at small scale was influenced by soil, precipitation and tree density. The spatial and temporal patterns of disease progression were associated with a contagion process and with environmental variables that affect drainage, coinciding with Phytophthora biology and requirements. Our results concur in pointing at Phytophthora as the cause of A. chilensis disease in the study area. Management practices should be urgently applied in order to minimize the spread of the inoculum.     

Effects of X-rays on Tuta absoluta for use in inherited sterility programmes

Tuta absoluta is a key pest of tomato crops originating from South America. The consequences of X-radiation on this species were studied under laboratory controlled conditions. The effect of radiation on adult emergence was evaluated exposing male and female pupae to increasing X-rays. Adult emergence decreased as doses of X-radiation increased, with the appearance of deformities such as malformed wings and bent legs at doses ≥350?Gy. Besides, males and females obtained from irradiated pupae were out crossed with untreated counterparts to explore the effects of X-radiation on inherited sterility. (a) Irradiated male?×?untreated female crosses. Both fecundity and fertility of the untreated females were reduced by radiation, and the effect was stronger as the doses increased. Neither the longevity of parental males and F1 adults nor the sex ratios of the F1 and F2 generations were affected by X-radiation (F1 and F2: first and second generation of descendants of irradiated adults). Inherited sterility effects were manifested by a significant reduction in the F1 fecundity, F1 fertility, and the amount of larvae and pupae produced. Doses of 200–250?Gy could be used to induce inherited sterility in T. absoluta males. (b) Untreated male?×?irradiated female crosses. The minimum dose at which irradiated females were completely sterile was 200?Gy. The present study is the first study in T. absoluta that provides the starting point for implementing the inherited sterility in this species.     

A review on <Emphasis Type="Italic">Trioza erytreae</Emphasis> (African citrus psyllid), now in mainland Europe,and its potential risk as vector of huanglongbing (HLB) in citrus

The African citrus psyllid (AfCP), Trioza erytreae (Del Guercio) (Hemiptera, Triozidae), recently has been found in northwestern Iberian Peninsula (Spain and Portugal). The insect is an important citrus pest because it transmits the phloem-limited bacteria Candidatus liberibacter spp., the causal agents of huanglongbing (HLB), the most devastating disease affecting citrus. The bacteria can be acquired by both AfCP nymphs and adults, but only adults can spread the pathogen. HLB has been detected neither in the Iberian Peninsula nor in Madeira and the Canary Islands, where the psyllid was recorded more than a decade ago. In the latter European islands, the eradication programmes of AfCP failed. Chemical-based control strategies are costly, could trigger increases of other pests and may have negative impact on the environment. The adoption of rigorous quarantine measures is extremely important for areas free of the psyllid. These measures likely represent the most effective prevention strategies for psyllid containment, because the geographic expansion of psyllids in citrus is mainly due to human activities, especially by the transport of plants and freshly harvested fruits from infested to uninfested areas. Many natural enemies may contribute to the reduction of its populations and consequent spread; hence, conservation biological control should be emphasised, especially in areas where the psyllid is not abundant. Classical biological control programmes should also be implemented in HLB-free areas by introducing effective AfCP parasitoids. In areas where HLB is detected, biological control is difficult to apply, and a rigorous chemical control program targeting the psyllid could complement this strategy. This report is an updated review of AfCP and strategies for its control in anticipation of its possible further spread in Europe and the Mediterranean Basin.