Ultrasonido de baja frecuencia como potenciador para el proceso de germinación de Stizolobium pruriens

Mucuna (Stizolobium pruriens) is widely used in agriculture as a green allowance and in croprotation, due to its ability to fix nitrogen and recover degraded areas; without embargo, there is aslow and uneven germination. This study used some classical methods, together with the use oflow-frequency ultrasound to accelerate and homogenize the germination and emergence of theseeds.TheexperimentwascarriedoutatthePlantTissueCultivationLaboratoryoftheIlhaSolteiraCampus,SãoPaulo,Brazil.Thedesignusedwasacompletelyrandomizedone,withfivereplications, in a 3x6 factorial scheme, the factors being: three pre-treatments for latency break:mechanicalscarification,thermalscarification,andwithoutscarificationwithsixlevelsofultrasoundexposure:0,1,2,3,5,8min,totaling18treatments.Foreightdaysthegerminationandtheinitialstagesoftheseedlingswerecontrolled.Themethodwithoutscarificationsubjectedto4.5 min of ultrasound can become an excellent alternative, since it presented greater germinationvigor, while 3.14 min of exposure to ultrasound were enough to improve the emergence speed, regardless of the method used in the preparation of seeds. In conclusion, only with the use of low-frequencyultrasound,itispossibletoimproveboththegerminationspeedindexandthegerminationvigor, with out the need for additional treatments.La mucuna (Stizolobium pruriens) se usa ampliamente en agricultura como abono verde y en rotación de cultivos, debido a su capacidad para fijar nitrógeno y recuperar áreas degradadas; sin embargo, tiene una germinación lenta y desigual. Este estudio utilizó algunos métodos clásicos, junto con el uso de ultrasonidos de baja frecuencia para acelerar y homogeneizar la germinación y emergencia de las semillas. El experimento se realizó en el Laboratorio de Cultivo de Tejidos Vegetales del campus Ilha Solteira, São Paulo, Brasil. El diseño utilizado fue un completamente al azar, con cinco repeticiones, en un esquema factorial 3x6, siendo los factores: tres pre-tratamientos para ruptura de la latencia: escarificación mecánica, térmica, y sin escarificación con seis niveles de exposición a ultrasonido: 0, 1, 2, 3, 5, 8 min, totalizando 18 tratamientos. Durante ocho días se controló la germinación y las etapas iniciales de las plántulas. El método sin escarificación sometido a 4.5 min de ultrasonido puede convertirse en una excelente alternativa, ya que presentó mayor vigor de germinación, mientras que 3.14 min de exposición a ultrasonido fueron suficientes para mejorar la velocidad de emergencia, independientemente del método utilizado en la preparación de semillas. En conclusión, solo con el uso de ultrasonidos de baja frecuencia es posible mejorar tanto el índice de velocidad de germinación como el vigor de germinación, sin necesidad de tratamientos adicionales

Dry Rot Caused by the Complex <i>Colletotrichum falcatum</i> and <i>Thielaviopsis paradoxa</i> Emerges as a Key Stalk Disorder in Newly Expanded Sugarcane Plantations from Northwestern São Paulo, Brazil

Sugarcane dry rot emerged as an important stalk disorder in newly expanded plantations in northwestern São Paulo, Brazil, under the current no-burning fully mechanical harvest policy gradually implemented in the past 20 years. This emergence was probably due to a considerable increase in both pathogen inocula and insect pest populations in sugarcane crop residues kept in the field. In this study, we surveyed the incidence of three stalk-related disorders in commercial sugarcane fields in six municipalities in northwestern São Paulo and the corresponding yield losses. The three stalk-related disorders surveyed were as follows: the red rot disease caused by the fungal pathogen Colletotricum falcatum, the spittlebug-induced shoot stunting, and the stem dry rot, which is associated with the simultaneous infection of C. falcatum and Thielaviopsis paradoxa, the pineapple set rot pathogen. Red rot disease was detected in 88.2% of the fields surveyed, while the spittlebug-induced shoot stunting disorder and the internal stem dry rot were found in 97.1% of the fields. Stem dry rot had the highest incidence and resulted in the highest yield losses. Total sugarcane yield losses were estimated at 20.1%, with an average of 14.2 (±3.8) t·ha−1 per field. The multiple regression model constructed to determine which of the three stem-related disorders contributed the most to total yield losses was not significant. Subsequently, the performance analyses of single-variable polynomial regression models indicated that the simple linear model was the best fit in terms of independently predicting sugarcane yield losses based on each stem-related disorder. Positive and significant correlations were only detected between sugarcane yield losses in t·ha−1 and the incidence of red rot disease or leafhopper-induced shoot stunting. We concluded that the stalk’s internal dry rot, as a disease complex associated with both C. falcatum and T. paradoxa, was the most important disorder in sugarcane fields in the northwest region of São Paulo state. A sustainable pest management program is needed to reduce the impact of all three stalk-associated disorders on regional sugarcane production