Articles publicats (Ciència i Enginyeria Forestal i Agrícola)

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    Open Access
    Wheat yield is not causally related to the duration of the growing season.
    (Elsevier, 2023) Slafer, Gustavo A.; Savin, Roxana; Sadras, Víctor O.
    A common conceptual model for crop growth analysis assumes biomass is proportional to the accumulation of radiation intercepted by the canopy during the growing season, and yield is the product of biomass and harvest index. This model assumes that biomass and harvest index are independent, and that biomass has the same value for yield across developmental stages; here we focus on the latter assumption. A corollary of this model is that yield and duration of the growing season are causally related. In this article, we analyse the evidence for and against this causal relationship. We use both a physiological perspective and agronomic evidence to challenge this causality. An alternative, phenology-focused model is outlined that is based on the following principles: crops accommodate environmental variation through grain number, grain number is defined in a species-specific critical developmental period, and grain number is a function of three traits in the critical period: duration, growth rate, and partitioning to reproduction. Against this framework, we analyse dual purpose wheat, where a substantial part of the biomass is removed, effectively shortening the growing season, with little or no effect on yield; timing of nitrogen fertilisation, where delayed application reduces the growth rate early in the season, with little or no effect on yield; and the correlation between season length and yield of winter wheat and spring wheat - wheat yield in Southern Chile, with a sowing-to-maturity season of ∼ 5 months, could be as high as that of winter wheat in the UK, with a sowing-to-maturity season of ∼ 10 months. Physiological principles and agronomic evidence support the conclusion that the duration of, and growth rate and partitioning during the critical period, rather than the duration of the growing season, are the drivers of wheat yield.
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    Open Access
    Awned versus awnless wheat spikes: does it matter?
    (Elsevier, 2023) Sanchez-Bragado, Rut; Molero, Gemma; Araus Ortega, José Luis; Slafer, Gustavo A.
    Awnless and awned wheat is found across the globe. Archeological and historical records show that the wheat spike was predominantly awned across the many millennia following domestication. Thus, ancient farmers did not select against awns at least until the last millennium. Here, we describe the evolution and domestication of wheat awns, quantifying their role in spike photosynthesis and yield under contrasting environments. Awns increase grain weight directly (increasing the size of all grains) or indirectly (increasing the failure of distal grains), but not as a consequence of additional spike photosynthesis. However, a trade-off is produced through decreasing grain number. Thus, favorable effects of awns on yield are not consistently found across environments.
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    Open Access
    Pre-anthesis spike growth dynamics and its association to yield components among elite bread wheat cultivars (Triticum aestivum L. spp.) under Mediterranean climate
    (Elsevier, 2023) Roychowdhury, Rajib; Zilberman, Orian; Chandrasekhar, Kottakota; Curzon, Arie Yehuda; Nashef, Kamal; Abbo, Shahal; Slafer, Gustavo A.; Bonfil, David J.; Ben-David, R.
    Context Wheat (Triticum spp.) grain yield (GY) is highly associated with grain number per unit area (GN m-2). Biomass accumulation and partitioning are essential to understand pre-anthesis spike growth dynamics which determines spike dry matter at anthesis (SDMa) - a GN determinant. Spike growth takes place during the stem elongation period (SE), from terminal spikelet to anthesis, following leaf and spikelet initiation (LS) from sowing to terminal spikelet. Objective In this study, bread wheat cultivars were examined under Mediterranean semi-arid conditions to determine (i) the varietal differences in pre-anthesis phase duration, (ii) whether this variability influences biomass partitioning and spike-related traits, and (iii) to what extent, the genotypic variations in pre-anthesis phase duration and spike growth are associated with yield components. Methods A panel of Israeli commercial bread wheat cultivars were grown in the field during 2016-17 (three environments) and 2017-18 (two environments) and characterized for pre-anthesis phases, floral conditions and spike fertility via histological measurements; spike traits, dry matter accumulation, partitioning at anthesis and maturity and for yield components. Results Significant variability in the timing of pre-anthesis phases was detected within the tested panel for both LS and SE phases. LS duration was positively associated with growing degree days (GDD) to anthesis across environments (0.72-0.90) while variation in SE was related with differences in GDD to anthesis but to a lesser extent and not in all environments (0.47-0.79). In addition, LS duration, and occasionally SE, were favourably related with a higher dry matter of fertile florets spike-1 (at anthesis) and SDM (at both anthesis and maturity). Principal component analysis (PCA) clearly separates environments and to a lesser extent cultivars within each environment. Two cultivar pairs 'Zahir-Yuval' and 'Negev-Gedera', which flowered concurrently, showed significant differences in the durations of LS and SE phases across most of the environments. Longer LS, in cultivars Zahir and Negev, exhibited increased spikelets spike-1, whereas longer SE (e.g., in Yuval and Gedera) enhanced spike fertility through improving the survival rate of floret primordia (FSR%) of central spikelets. However, there was a trade-off for FSR at the proximal and distal spike portions, resulting in lower grain set (%) leading to reduction of final GN (or GY) in cultivars with longer SE. Conclusions In the tested panel and under our environmental conditions characterized by growing cycle and Mediterranean climate, the duration of both LS and SE contribute to spike fertility, but LS duration seemed a stronger driver than SE for GN and yield enhancement. Implications Our results highlight the importance of pre-anthesis phases, especially the role of LS in wheat yield increment during the short growing cycle. The varietal combination with variable LS and SE duration could be implemented in breeding pipelines and used as pre-breeding materials for GN improvement. Furthermore, the findings will encourage pre-anthesis traits adoption in Mediterranean bread wheat future breeding programs.
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    Open Access
    Looking behind occlusions: A study on amodal segmentation for robust on-tree apple fruit size estimation
    (Elsevier, 2023) Gené Mola, Jordi; Ferrer Ferrer , Mar; Gregorio López, Eduard; Blok, Pieter M.; Hemming, Jochen; Morros Rubió, Josep Ramon; Rosell Polo, Joan Ramon; Vilaplana Besler, Verónica; Ruiz Hidalgo, Javier
    The detection and sizing of fruits with computer vision methods is of interest because it provides relevant information to improve the management of orchard farming. However, the presence of partially occluded fruits limits the performance of existing methods, making reliable fruit sizing a challenging task. While previous fruit segmentation works limit segmentation to the visible region of fruits (known as modal segmentation), in this work we propose an amodal segmentation algorithm to predict the complete shape, which includes its visible and occluded regions. To do so, an end-to-end convolutional neural network (CNN) for sim ultaneous modal and amodal instance segmentation was implemented. The predicted amodal masks were used to estimate the fruit diameters in pixels. Modal masks were used to identify the visible region and measure the distance between the apples and the camera using the depth image. Finally, the fruit diameters in millimetres (mm) were computed by applying the pinhole camera model. The method was developed with a Fuji apple dataset consisting of 3925 RGB-D images acquired at different growth stages with a total of 15,335 annotated apples, and was subsequently tested in a case study to measure the diameter of Elstar apples at different growth stages. Fruit detection results showed an F1-score of 0.86 and the fruit diameter results reported a mean absolute error (MAE) of 4.5 mm and R2 = 0.80 irrespective of fruit visibility. Besides the diameter estimation, modal and amodal masks were used to automatically determine the percentage of visibility of measured apples. This feature was used as a confidence value, improving the diameter estimation to MAE = 2.93 mm and R2 = 0.91 when limiting the size estimation to fruits detected with a visibility higher than 60%. The main advantages of the present methodology are its robustness for measuring partially occluded fruits and the capability to determine the visibility percentage. The main limitation is that depth images were generated by means of photogrammetry methods, which limits the efficiency of data acquisition. To overcome this limitation, future works should consider the use of commercial RGB-D sensors. The code and the dataset used to evaluate the method have been made publicly available at https://github.com/GRAP-UdL-AT/Amodal_Fruit_Sizing.
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    Open Access
    Stage-specifi c vulnerability of Harmonia axyridis (Coleoptera: Coccinellidae) to intraguild predation
    (Czech Academy of Sciences, 2023) Labrie, Geneviève; Meseguer, Roberto; Lucas, Eric
    The multicoloured Asian ladybeetle, Harmonia axyridis (Pallas), is a widespread invasive ladybird. It is considered a top predator among the aphidophagous coccinellids in North America and Europe; thus, it is supposed to be free from predation pressure by other members of the guild. Our study aims to evaluate the stage-specifi c vulnerability of H. axyridis to intraguild predation (IGP) by the indigenous Coleomegilla maculata lengi Timberlake and the invasive Propylea quatuordecimpunctata Linnaeus. We hypothesised that (1) H. axyridis stages will be less susceptible to IGP than the two other species, (2) vulnerability to IGP will decrease with the age of the larvae and (3) vulnerability to IGP will increase with increased weight difference between intraguild predator (IGPredator) and intraguild prey (IGPrey). Eggs, 1st and 2nd instars of H. axyridis were susceptible to IGP by both C. maculata and P. quatuordecimpunctata adults and larvae, but less vulnerable than the other beetles when facing the same IGPredator. Vulnerability to IGP for the three species was reduced with increased age of larvae and with decreased weight difference. Overall, H. axyridis was less vulnerable to IGP than the two other species, but the results confi rm the fact that the status of IGPrey or IGPredator of H. axyridis will be determined by the stages of both species during the interactions.