Effects of temperature and nitrogen source on tomato genotypes response to Meloidogyne incognita infection

A été testée la réaction de cultivars de tomate sensible ("Rutgers") et résistant ("VFN-8") à des populations de #Meloidogyne incognita agressives ou non, à 24 ou 28°C, cultivars alimentés avec une solution de Hoagland (HS) sans azote, ou additionnée, comme source d'azote, de NO3, NH4, NH4NO3, ou avec de l'eau (témoin). Pour chaque expérience, et pour chaque cultivar, il a été utilisé 40 plants agés d'une semaine ayant poussé dans des pots en polystyrène expansé contenant 286 g de sable argileux. La moitié des plants des Expériences I et II ont été inoculés avec 1000 juvéniles de deuxième stade (J2) de la population agressive de #M. incognita, et la moitié des plantes des Expériences III et IV avec 500 J2 de la population non agressive. Ont été déterminés le nombre et le stade de développement des nématodes à la fin des expériences, qui ont toutes duré 28 jours, sauf l'Expérience III qui a duré 15 jours. La croissance des plants des deux cultivars a été plus rapide à 24 qu'à 28°C, et meilleure avec les traitements au NH4 ou au NH4NO3. Les niveaux d'infestation des plants sont semblables chez le cultivar sensible, et ce quelle que soit leur taille, alors que les niveaux d'infestation sont moins élevés chez les plants les plus grands du cultivar résistant. Les plants du cultivar résistant contiennent moins de nématodes lorsqu'ils sont traités avec NH4 ou NH4NO3 qu'avec NO3. Les deux populations ont une multiplication plus faible chez le cultivar résistant que chez le cultivar sensible, ceci suggérant que même si la résistance peut se dégrader, il s'agit d'un processus graduel. Cette étude démontre, qu'en plus de la température, la source d'azote peut jouer un rôle dans la suppression de la résistance liée au gène Mi. La relation inverse entre taux de multiplication des nématodes et taille des plants du cultivar résistant suggère que des processus de régulation peuvent moduler le comportement du gène de résistance chez la plante. (Résumé d'auteur

Застосування рівняння Віганда–Снайдера до термодинамічної інтерпретації високоеластичної деформації гладеньких м'язів шлунка

Iз застосуванням рiвняння Вiганда–Снайдера здiйснено термодинамiчний аналiз високоеластичної деформацiї (Δl) кiльцевих гладеньких м’язiв антрального вiддiлу шлунка щурiв. Показано, що малi (Δl/l0 ≈ 20%) розтягування гладеньком’язових смужок шлунка щурiв (дiапазон температур 22–48 °С) не супроводжуються змiнами у впорядкованостi тензометричної системи (ΔS = 0). Такий самий феномен маємо i у випадку значних розтягувань (Δl/l0 ≈ 50%), але у бiльш вузькому дiапазонi температур: понад 30 °С i менше 40 °С. При великих розтягуваннях гладеньком’язових смужок шлунка (Δl/l0 ≈ 50%) як при вiдносно низьких (22–30 °С), так i при вiдносно високих (понад 37 °С) температурах мають мiсце iстотнi структурнi змiни в тензометричнiй системi. За цих умов спостерiгається iнверсiя знаку ентропiйних ефектiв: ΔS > 0 при T 37 °С. Обговорюється зв’язок мiж виявленими термодинамiчними ефектами i фiзiологiчними механiзмами регуляцiї функцiонування травного тракту.Применение уравнения Виганда–Снайдера проведен термодинамический анализ высокоэластичной деформации кольцевых гладких мышц антрального отдела желудка крыс. Показано, что малые (Δl/l0 ≈ 20%) растягивания гладкомышечных полосок желудка крыс (диапазон температур 22–48 °С) не сопровождаются изменениями в упорядоченности тензометрической системы (ΔS = 0). Такой же феномен наблюдается и при значительных растягиваниях (Δl/l0 ≈ 50%), но в более узком диапазоне температур: выше 30 °С и ниже 40 °С. При больших растяжениях гладкомышечных полосок желудка (Δl/l0 ≈ 50%) как при относительно низких (22–30 °С), так и при относительно высоких (выше 37 °С) температурах имеют место существенные структурные изменения в тензометрической системе. В этих условиях наблюдается инверсия знака энтропийных эффектов: ΔS > 0 при T 37 °С. Обсуждается связь между выявленными термодинамическими эффектами и физиологическими механизмами регуляции функционирования пищеварительного тракта.With using the Wiegand–Snyder equation, the thermodynamic analysis of a viscoelastic deformation of circular smooth muscle strips of rat’s stomach (antral part) is performed. It is shown that a small (Δl/l0 ≈ 20%) stretch of rat stomach smooth muscle strips (temperature range 22–48 °С) is not accompanied by changes in the ordering of the tensometric system (ΔS = 0). The same phenomenon is observed with a considerable stretching (Δl/l0 ≈ 50%), but in a narrower tempera- ture range: above 30 °C and below 40 °C. For large strains, gastric smooth muscle strips (Δl/l0 ≈ 50%) at relatively low (22–30 °C) and at relatively high (above 37 °C) temperatures undergo substantial structural changes in the ordering of the tensometric system. Under these conditions, there is the inversion of the sign of entropy effects: ΔS > 0 at temperatures below 31 °C and ΔS < 0 at temperatures above 37 °C. The relation between the identified thermodynamic effects and the physiological mechanisms of regulation of the functioning of the digestive tract is discussed

A Nematode Community-Based Integrated Productivity Efficiency (IPE) Model That Identifies Sustainable Soil Health Outcomes: A Case of Compost Application in Carrot Production

Percent soil organic matter (SOM), pH and crop yield are among the biophysicochemical process-driven soil health indicators (SHIs). However, identifying sustainable soil health conditions using these SHIs is limited due to the lack of Integrated Productivity Efficiency (IPE) models. We define IPE as a concept that identifies best-to-worst-case soil health outcomes by assessing the effect of agronomic practices on weighted abundance of functional guilds (WAFG) of beneficial soil organisms and SHIs simultaneously. Expressing WAFG of all beneficial nematodes (x-axis) and SHIs (y-axis) as a percent of untreated control and regression of x and y reveals four quadrants describing worst-to-best-case outcomes for soil health and sustainability. We tested the effects of composted cow manure (AC) and plant litter (PC) applied at 135 (1×), 203 (1.5×), and 270 (2×) kg N/ha on WAFG, SOM, pH, and yield in a sandy clay loam field of a processing carrot cultivar over three growing seasons. Untreated control and urea at 1× served as experimental controls. Data that varied by time and were difficult to make sense of were separated into sustainable, unsustainable, or requiring specific modification to be sustainable categories by the IPE model. Within the sustainable category, all AC treatments and 2× rate of PC treatments had the best integrated efficiency outcomes across the SHIs. The IPE model provides a platform where other biophysicochemical process-driven SHIs could be integrated. View Full-Tex

Effects of integrated application of plant-based compost and urea on soil food web, soil properties, and yield and quality of a processing carrot cultivar

Soil nutrient management system characterized by reduced input of inorganic fertilizers integrated with organic amendments is one of the alternatives for reducing deleterious environmental impact of synthetic fertilizers, suppressing soil-borne pests and diseases, and improving soil health and crop yield. A hypothesis of the present study was that lower rates of urea mixed with higher rates of plant compost (PC) would improve nematode community structure, soil food web condition, soil biological, and physiochemical properties, and yield and quality of a processing carrot (Daucus carota) cultivar. Urea and PC were each applied at 135kg nitrogen (N)/ha alone or at 3:1, 1:1, and 1:3 ratios annually during the 2012 to 2014 growing seasons. A non-amended check served as a control. Nematode community was analyzed from soil samples collected approximately 4-week intervals from planting to 133 days after planting each year. Soil respiration, as a measure of soil biological activity, and soil physiochemical properties were determined from soils collected at planting and at harvest in 2012 and 2013. Results showed that PC alone, and U1:PC1 resulted in soil food web structure significantly above 50 at harvest in 2014. Urea significantly decreased end-ofseason soil pH, but increased NO3-N compared with the other treatments. While the herbivore population density was low, abundances of Tylenchus and Malenchus were negatively correlated with carrot fresh weight of marketable carrot. Overall, results suggest that integrating lower rates of urea and higher rates of PC are likely to increase soil biological activity, soil pH, and phosphorus content

In vitro co-cultures of Pinus pinaster with Bursaphelenchus xylophilus: a biotechnological approach to study pine wilt disease

Abstract Main conclusion Co-cultures of Pinus pinaster with Bursaphelenchus xylophilus were established as a biotechnological tool to evaluate the effect of nematotoxics addition in a host/parasite culture system. The pinewood nematode (PWN), Bursaphelenchus xylophilus, the causal agent of pine wilt disease (PWD), was detected for the first time in Europe in 1999 spreading throughout the pine forests in Portugal and recently in Spain. Plant in vitro cultures may be a useful experimental system to investigate the plant/nematode relationships in loco, thus avoiding the difficulties of field assays. In this study, Pinus pinaster in vitro cultures were established and compared to in vivo 1 year-old plantlets by analyzing shoot structure and volatiles production. In vitro co-cultures were established with the PWN and the effect of the phytoparasite on in vitro shoot structure, water content and volatiles production was evaluated. In vitro shoots showed similar structure and volatiles production to in vivo maritime pine plantlets. The first macroscopic symptoms of PWD were observed about 4 weeks after in vitro co-culture establishment. Nematode population in the culture medium increased and PWNs were detected in gaps of the callus tissue and in cavities developed from the degradation of cambial cells. In terms of volatiles main components, plantlets, P. pinaster cultures, and P. pinaster with B. xylophilus co-cultures were all b- and a-pinene rich. Cocultures may be an easy-to-handle biotechnological approach to study this pathology, envisioning the understanding of and finding ways to restrain this highly devastating nematode. Keywords Maritime pine ! Monoxenic culture ! Pinewood nematode ! Relative water content ! Shoots structure ! Volatiles Abbreviations BAP 6-Benzylaminopurine DAI Days after inoculation EPPO European and Mediterranean Plant Protectio