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Leaf senescence in plants is the last stage of leaf development and is characterized by a decline in photosynthetic activity, an active degeneration of cellular structures, and the recycling of accumulated nutrients to areas of active growth, such as buds, young leaves, flowers, fruits, and seeds. This process holds economic significance as it can impact yield, influencing the plant’s ability to maintain an active photosynthetic system during prolonged periods, especially during the grain filling stage, which affects plant weight and oil content. It can be associated with different stresses or environmental conditions, manifesting itself widely in the context of climate change and limiting yield, especially in crops of agronomic relevance. In this work, we study the stability of two widely described sunflower (Helianthus annuus L.) genotypes belonging to the INTA Breeding Program against differential N conditions, to verify their yield stability in control conditions and under N supply. Two inbred lines were utilized, namely R453 (early senescence) and B481-6 (late senescence), with contrasting nitrogen availability in the soil but sharing the same ontogeny cycle length. It was observed that, starting from R5.5, the B481-6 genotype not only delayed senescence but also exhibited a positive response to increased nitrogen availability in the soil. This response included an increase in intercepted radiation, resulting in a statistically significant enhancement in grain yield. Conversely, the R453 genotype did not show significant differences under varying nitrogen availability and exhibited a tendency to decrease grain yield when nitrogen availability was increased. The response to nitrogen can vary depending on the specific genotype.

Abstract Sunflower Verticillium Wilt and Leaf Mottle (SVW), caused by Verticillium dahliae (Kleb.; Vd), is a soil-borne disease affecting sunflower worldwide. A single dominant locus, known as V1, was formerly effective in controlling North-American Vd races, whereas races from Argentina, Europe and an emerging race from USA overcome its resistance. This emphasizes the need for identifying broad-spectrum genetic resistance (BSR) sources. Here we characterize two sunflower mapping populations (MPs) for SVW resistance: a biparental MP and the association MP from the National Institute of Agricultural Technology (INTA), under field growing conditions. Nine field-trials (FTs) were conducted in highly infested fields in the most SVW-affected region of Argentina. Several disease descriptors (DDs), including incidence and severity, were scored across four phenological stages. Generalized linear models were fitted according to the nature of each variable, adjusting mean phenotypes for inbred lines across and within FTs. Comparison of these responses allowed the identification of novel BSR sources. Furthermore, we present the first report of SVW resistance heritability, with estimates ranging from 35 to 45% for DDs related to disease incidence and severity, respectively. This study constitutes the largest SVW resistance characterization reported to date in sunflower, identifying valuable genetic resources for BSR-breeding to cope with a pathogen of increasing importance worldwide.

Regression models to predict leaf area and leaf weight in common bean (Phaseolus vulgaris) were fitted using the three leaflets of the leaves. A total of 1504 leaves from 40 genotypes were collected, covering a large range of leaf sizes. Width, length, area, and weight were measured for each leaflet. The total leaf area and weight was obtained by the sum of left, central, and right leaflets. The dataset was randomly divided into training and validation sets. The training set was used for model fitting and selection, and the validation dataset was used to obtain statistics for model prediction ability. The leaf area and leaf weight were modeled using different linear regression models based on the length and width of the leaflet. Polynomial regressions involving both length and width of the leaflet provided very good models to estimate the expected area (R2 = 0.978) and weight (R2 = 0.820) of leaves.

Na região fruti-ortícula do cinturião verde da cidade de Córdoba, Argentina, ocorre com frequência nos períodos de inverno e primavera o aparecimento de Polygomun aviculare. O objetivo do presente trabalho foi o de conhecer a fenologia desta espécie e as necessidades bioclimáticas de cada uma das etapas do seu ciclo de vida. Para estas análises conduziu-se um ensaio em uma propriedade do cinturião verde, na região Nordeste de Córdoba, durante os anos de 1988, 1989 e 1990. Determinrou-se as fases e subperíodos do ciclo evolutivo da espécie e parâmetros como altura e densidade de plantas e dados meteorológicos. O estudo permitiu estabelecer o fluxo estacional de emergência e determinar o tipo ecológico de planta daninha quanto à estação de crescimento. Os aspectos ecológicos levantados servirão de ferramentas para implementar estratégias de controle desta planta daninha."Knotweed", Polygonum aviculare is one of the most common weeds in the winter-spring period in the horticultural zone of Córdoba green belt. In order to know the phenology and climatic requirements of the species in each stage of its life cycle, an experiment was conducted in one of the green belt farms located in the NE of Córdoba outskirsts for three years (1988, 1989, 1990). Different phases and sub-periods of this life cycle, phenometric parameters (plant height and density) and meteorological observations were determined. The experiment enabled to establish the stational flow of emergency and corroborate the winterspring ecological type of the weed. These aspects of the bioecology, phenology and bioclimatology are necessary tools when implementing an integrated system of weed control.

Melhoramento no planejamento de testes de toxicidade envolvendo efeitos em larvas de peixes e crustáceos. Existem estudos toxicológicos que têm por objetivo avaliar o efeito de um tóxico na progênie de peixes ou crustáceos. O seguinte protocolo experimental é usualmente empregado: (1) Cria-se um conjunto de larvas originadas de várias fêmeas, o qual é dividido em dois grupos, por exemplo; um deles é exposto ao tóxico, sendo o outro o grupo controle. (2) Cada grupo é separado em diferentes subgrupos, recebendo estes um tratamento adicional (salinidade). Deve-se observar que: (a) Uma fêmea pode gerar mais larvas do que outra, e portanto estar mais representada no conjunto de larvas. (b) Existem duas etapas de casualização no experimento, não simultâneas. A primeira acontece ao destinar as concentrações do tóxico a cada grupo. A segunda, ao estabelecer as salinidades aos subgrupos. Uma alternativa poderia ser a de considerar um delineamento "split-plot", comumente empregado em experimentos agrícolas. Esse delineamento assume duas etapas de casualização e tem como benefício o incremento da sensibilidade para a avaliação dos efeitos do subtratamento (salinidade) e da interação destes com o tratamento principal (concentrações tóxicas). Palavras-Chave: planejamento de parcelas divididas, progênie, conjunto de larvas