To non-destructively and rapidly monitor the chlorophyll content of winter wheat leaves under COsub.2 microleakage stress, and to establish the quantitative relationship between chlorophyll content ...and sensitive bands in the winter wheat growing season from 2023 to 2024, the leakage rate was set to 1 L/min, 3 L/min, 5 L/min, and 0 L/min through field experiments. The dimensional reduction was realized, fractional differential processing of a wheat canopy spectrum was carried out, a multiple linear regression (MLR) and partial least squares regression (PLSR) estimation model was constructed using a SPA selection band, and the model’s accuracy was evaluated. The optimal model for hyperspectral estimation of wheat SPAD under COsub.2 microleakage stress was screened. The results show that the spectral curves of winter wheat leaves under COsub.2 microleakage stress showed a “red shift” of the green peak and a “blue shift” of the red edge. Compared with 1 L/min and 3 L/min, wheat leaves were more affected by COsub.2 at 5 L/min. Evaluation of the accuracy of the MLR and PLSR models shows that the MLR model is better, where the MLR estimation model based on 1.1, 1.8, 0.4, and 1.7 differential SPAD is the best for leakage rates of 1 L/min, 3 L/min, 5 L/min, and 0 L/min, with validation set Rsup.2 of 0.832, 0.760, 0.928, and 0.773, which are 11.528, 14.2, 17.048, and 37.3% higher than the raw spectra, respectively. This method can be used to estimate the chlorophyll content of winter wheat leaves under COsub.2 trace-leakage stress and to dynamically monitor COsub.2 trace-leakage stress in crops.
The essential oil (EO) of Thymbra capitata has been demonstrated to possess herbicidal activity and could be used as an alternative to synthetic herbicides with reduced persistence in soil and new ...mode of action. Nevertheless, it is necessary to determine the adequate doses for its use, the proper way for its application and the best phenological stage of weeds and crops in which the EO should be applied to obtain maximum efficacy against weeds without compromising crop production. In this work, T. capitata EO was tested at three different concentrations against weeds grown from a citrus orchard soil seedbank untreated with herbicides and against three important weed species grown in substrate to determine the efficacy of the concentrations on different weed species. All experiments were carried out under greenhouse conditions. To find out the best way for applying the EO, it was applied by irrigation and by spraying on the targeted weeds, and to verify the influence of timing, it was tested on Lolium rigidum at two different phenological stages and on wheat at a later phenological stage than weeds. The highest concentration tested (12 µL·mLsup.−1) showed the best performance to control weeds. The more effective mode of application was by spraying on dicotyledons and by irrigation on monocotyledons at the earliest phenological stage. T. capitata EO was phytotoxic for wheat. More trials in different crops are needed to determine the best conditions for its use.
One strategy presented as an alternative to avoid using chemical substances in soil disinfestation consists in the technique of biosolarization. The aim of the present study was to analyze the effect ...of seasonality on the effectiveness of biosolarization with different organic amendments for the control of Fusarium oxysporum f. sp. lactucae (FOLAC) on lettuce plants, and to compare the results obtained using a classical soil infectivity bioassay and a qPCR-based molecular technique. None of the plants subjected to biosolarization in the summer season (469-700 and 0-463 h with temperature > 42 °C at 15 and 30 cm soil depth, respectively) showed damage by the pathogen except the untreated control. Conversely, in autumn (3-5 and 0-0 h at temperature = 38-40 °C at 15 and 30 cm soil depth, respectively), only two biosolarization treatments (wheat + semi-composted manure, sunflower pellets) that reduced FOLAC inoculum in soil and plants did not show any disease at the lowest depth (15 cm) in the soil infectivity bioassay. This same result was only obtained at 30 cm soil depth in the biosolarization treatment with sunflower pellets. The number of FOLAC sequences per gram of soil determined with qPCR was null in the biosolarization treatments in summer at both soil depths and corresponded to the absence of disease in the soil infectivity bioassay. A threshold of 145 sequences per gram of soil determined by the qPCR-based molecular technique corresponded to the presence of 10% of diseased lettuce plants infected by FOLAC. Therefore, this molecular technique has been shown to be useful for establishing the soil inoculum thresholds required for crop infection by pathogens, while reducing the time and execution tasks necessary to perform soil infectivity bioassays.
Allohexaploid bread wheat and diploid barley are two of the most cultivated crops in the world. This book reports novel research and reviews concerning the use of modern technologies to understand ...the molecular bases for wheat and barley improvement. The contributions published in this book illustrate research advances in wheat and barley knowledge using modern molecular techniques. These molecular approaches cover genomic, transcriptomic, proteomic, and phenomic levels, together with new tools for gene identification and the development of novel molecular markers. Overall, the contributions for this book lead to a further understanding of regulatory systems in order to improve wheat and barley performance.
O objetivo foi avaliar os efeitos da inoculação de sementes de trigo (Triticum aestivum L.) com Azospirillum brasilense e doses de nitrogênio em cobertura no desempenho produtivo, índices de ...vegetação e clorofila e teores de nitrogênio na folha e no grão. Experimentos a campo foram conduzidos em delineamento experimental de blocos casualizados, esquema fatorial 2 x 5 com seis repetições. Avaliou-se a inoculação de sementes com Azospirillum brasilense (com e sem) e cinco doses de nitrogênio em cobertura (0, 30, 60, 90 e 120 kg ha-1), aplicadas por ocasião do perfilhamento. Foram avaliados: produtividade e massa de mil grãos, teor de nitrogênio na folha e grão, massa seca da parte aérea, índice de clorofila e de vegetação avaliados por ocasião do perfilhamento, elongamento do colmo e espigamento. Os dados foram submetidos à análise de variância, correlação e análise de regressão para doses, e comparação de médias pelo teste de Tukey a 5% para inoculação. O nitrogênio aplicado em cobertura no trigo cultivado após a soja não altera a produtividade, a massa de 1000 grãos e a massa seca da parte aérea, porém, o incremento das doses aumenta linearmente o teor de nitrogênio no grão e o índice de clorofila e de vegetação avaliado na fase de espigamento. A inoculação com Azospirillum brasilense aumenta o teor do nitrogênio no grão, mas não influencia as demais características avaliadas. O índice de vegetação por diferença normatizada (NDVI), avaliado no perfilhamento, elongamento do colmo e espigamento possui correlação positiva com a produtividade, quando avaliado no espigamento com o teor de nitrogênio da folha bandeira.
Com o objetivo de avaliar o efeito de diferentes lâminas de irrigação suplementar, densidades de semeadura e a interação destes fatores sobre a produtividade e qualidade de grãos de trigo (Triticum ...aestivum L.) conduziu-se um experimento em Argissolo Amarelo distrófico típico, no município de Santa Maria - RS, nas seguintes coordenadas geográficas: 29°42'55.30" S e 53°44'22.56" O. O delineamento experimental foi o de blocos ao acaso com parcelas subdivididas, com quatro repetições, onde as parcelas foram constituídas pelas lâminas de irrigação e as subparcelas pelas diferentes densidades de semeadura. Foram estabelecidas seis lâminas de irrigação: 0, 25, 50, 75, 100 e 125% da ETo e três densidades de semeadura: 250, 350 e 450 pl m-2. A produtividade mínima de 4165 kg ha-1 foi observada no tratamento sem irrigação na densidade de 450 pl m-2 e máxima de 6894 kg ha-1 na lâmina de 100% da ETo na densidade de 350 pl m-2. A lâmina de irrigação e densidade de semeadura influenciaram significativamente o número de espiguetas por espiga, número de espigas por metro quadrado e massa de mil grãos.
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