Functional response of soil microbial communities to tillage, cover crops and nitrogen fertilization

© 2016 Elsevier B.V.Agricultural practices such as tillage, cover crops, and nitrogen (N) fertilization affect physico-chemical and biological soil parameters. However, these factors were often studied separately and their combined effects remain unclear, especially with respect to soil microbial functional diversity and carbon (C) and N content. Thereafter, we aim to assess the links between cropping systems and functional response of microbial communities by using a large range of soil chemical and biological measurements. A 5-yr field experiment was conducted in Northern France using a combination of three factors: i) no-till (NT) vs. conventional tillage (CT); ii) with or without winter cover crops (bare fallow; cover crops with a low prevalence of legumes; cover crop with a high prevalence of legumes); and iii) with or without N fertilization. C and N inputs from cover crops and crop residues, C and N content, enzyme activities, and microbial functional diversity in the topsoil (0–10 cm) were measured over an industrial crop rotation: wheat, pea, corn, wheat, flax. No-till combined with any of the cover crops was characterized by increased total soil organic C and N contents by more than 20% between 2010 and 2015. Dehydrogenase and urease activities were significantly greatest under NT, irrespective of the presence of cover crops. Cover crops without N fertilization under no-till led to higher microbial functional activity (faster carbohydrate and phenolic compound degradation) and diversity. Bare fallow had lower soil microbial functional diversity and C and N contents compared with soil under NT and cover crops. On the other hand, NT associated with cover crops allowed to maintain the soil in both C and N, and to promote microbial activities without N fertilization. In conclusion, winter cover crops and/or NT are sustainable agricultural practices resulting in a greater soil quality index. These results demonstrate that NT and use of standard cover crops or cover crops with legumes for 5 years under a low biomass return in industrial crop production have a positive effect on: i) upper soil C content and microbial enzymes, irrespective of N fertilization regime; ii) soil microbial functional diversity in the absence of N fertilization

Detection par la PCR des begomovirus de la tomate (Solanum lycopersicum L.) dans les zones de production du Togo

Les maladies virales causées par les Begomovirus transmis par l’insecte vecteur Bemisia tabaci Gennadius sur la tomate (Solanum lycopersicum L.) constituent une contrainte biotique majeure pour la production de ce légume fruit. Les pertes de rendement causées par ces virus peuvent atteindre 100%. Au Togo, très peu de données moléculaires existent sur les Begomovirus de la tomate. Afin d’avoir plus d’information sur ces Begomovirus que la présente étude a été menée afin de déterminer les Begomovirus de la tomate au Togo et de mieux la protéger. Pour atteindre ces objectifs, une collecte d’échantillons géoréférencés de feuilles présentant des symptômes typiques de virose a été effectuée dans les champs sur des plants de tomate et autres plantes (sauvages et cultivées) dans les préfectures d’Assoli, de Bassar, de Binah, de Cinkassé, de Doufelgou, du Golfe, de la Kozah, de Kpendjal, des Lacs, de l’Ogou , de Sotouboua, de Tchaoudjo, de Tone et de Zio. Au total 307 échantillons ont été collectés et analysés par PCR. Les résultats de la PCR ont révélé la présence de Begomovirus sur 25,40% des échantillons analysés dont 4% sur les plantes sauvages et autres plantes cultivées à savoir: Euphorbia heterophylla, Physalis angulata, Ageratum conyzoides, Synedrella nodiflora, Clerodendron sp, Solanum macrocarpon, Glycine max, et Abelmoschus esculentus. Les analyses statistiques ont révélé dans l’ensemble que la préfecture de Tchaoudjo, avait le taux de contamination le plus élevé (100%). Ces résultats suggèrent que les Begomovirus seraient associés à une grande diversité de plantes sauvages non encore connues au Togo. Mots clés: Begomovirus, PCR, Plantes sauvages, Tomate, Virose

Diagnostic de Begomovirus associes aux systemes de cultures a base du manioc (Manihot esculenta Crantz) par la PCR (Polymerase Chain Reaction) au Togo

L’une des conséquences de la propagation des biotypes très polyphages de Bemisia tabaci, est probablement l’émergence de nouvelles espèces de Begomovirus associées aux changements climatiques. Cette étude a été initiée pour identifier ces agents pathogènes au sein des systèmes de cultures à base du manioc à travers tout le Togo afin d’avoir plus d’information sur les Begomovirus émergents. Ainsi des échantillons foliaires de manioc, de dix plantes associées au manioc en cultures mixtes et de diverses plantes sauvages collectés durant la période de 2013-2016, ont été soumis à un diagnostic PCR pour la détection des Begomovirus de façon générale et plus spécifiquement pour l’identification des Begomovirus de la mosaïque du manioc. À cet effet cinq couples d’amorces spécifiques ciblant le gène de la CP des Begomovirus ont été utilisés notamment JSP001/JSP002, JSP001/JSP003, JSP012/JSP013, ICMV-F2/ICMV-R2 et AC1048/AV494. Les résultats ont montré la présence effective de Begomovirus dans les cinq régions économiques du Togo. Avec l’amorce AC1048/AV494 des Begomovirus ont été identifié dans 50 % (soja), 26,31 % (piment), 19,15 % (manioc), 13,63 % (tomate), 9,09 % (corète potagère), et 5 % (plantes sauvages). Deux espèces de Begomovirus de la mosaïque du manioc ACMV et EACMV ont également été identifiées. Le taux d’incidence individuel de ACMV est de 36,17 % sur le manioc et celui de EACMV est de 20,21 % sur le manioc et 10.53 % sur le piment. C’est la première fois que des Begomovirus sont détectés dans des échantillons de la corète potagère et EACMV sur le piment au Togo. Cette étude contribuera à l’avancé des connaissances sur les maladies induites par des Begomovirus transmis par les mouches blanches, Bemisia tabaci.Mots clés:  Begomovirus, Bemisia tabaci, diagnostic, manioc, PCR, systèmeEnglish Title: Diagnosis of Begomoviruses associated with cassava  (Manihot esculenta Crantz)-based cropping systems by  PCR (Polymerase Chain Reaction) in TogoEnglish AbstractOne of the consequences of the spread of highly polyphagous Bemisia tabaci biotypes is probably the emergence of new begomovirus species associated with climate change. This study is conducted to identify theses pathogen agents within cassava based cropping systems throughout Togo in order to get more information about emerged begomoviruses. Thus, Foliar samples of cassava, ten intercropped plants with cassava in fields and various wild plants collected during the period 2013-2016 are submitted to PCR diagnosis for the detection of begomoviruses in general and more specifically for the detection of cassava mosaic begomoviruses. For this purpose, five specific primer pairs targeting begomoviruses CP gene were used, in particular JSP001/JSP002, JSP001/JSP003, JSP012/JSP013, ICMV-F2/ICMV-R2 and AC1048/AV494. Results showed the effective presence of begomoviruses in the five economic regions of Togo. With AC1048/AV494 primers begomoviruses are found in 50 % (soybean), 26.31 % (pepper), 19.15 % (cassava), 13.63 % (tomato), 9.09 % (jute), and 5 % (wild plants). Two species of cassava mosaic begomoviruses ACMV and EACMV are also identified. The individual incidence rate for ACMV is 36.17 % in cassava and EACMV is 20.21 % in cassava and 10.53 % in pepper. This is the first report of begomoviruses in jute samples and EACMV in pepper in Togo. This study will contribute to the advancement of knowledge on begomoviruses-induced diseases transmitted by whiteflies, Bemisia tabaci.Keywords: Begomovirus, Bemisia tabaci, diagnosis, cassava, PCR, syste

Cytokinin controls polarity of PIN1-dependent auxin transport during lateral root organogenesis

Plant science

Functional response of soil microbial communities to tillage, cover crops and nitrogen fertilization

© 2016 Elsevier B.V.Agricultural practices such as tillage, cover crops, and nitrogen (N) fertilization affect physico-chemical and biological soil parameters. However, these factors were often studied separately and their combined effects remain unclear, especially with respect to soil microbial functional diversity and carbon (C) and N content. Thereafter, we aim to assess the links between cropping systems and functional response of microbial communities by using a large range of soil chemical and biological measurements. A 5-yr field experiment was conducted in Northern France using a combination of three factors: i) no-till (NT) vs. conventional tillage (CT); ii) with or without winter cover crops (bare fallow; cover crops with a low prevalence of legumes; cover crop with a high prevalence of legumes); and iii) with or without N fertilization. C and N inputs from cover crops and crop residues, C and N content, enzyme activities, and microbial functional diversity in the topsoil (0–10 cm) were measured over an industrial crop rotation: wheat, pea, corn, wheat, flax. No-till combined with any of the cover crops was characterized by increased total soil organic C and N contents by more than 20% between 2010 and 2015. Dehydrogenase and urease activities were significantly greatest under NT, irrespective of the presence of cover crops. Cover crops without N fertilization under no-till led to higher microbial functional activity (faster carbohydrate and phenolic compound degradation) and diversity. Bare fallow had lower soil microbial functional diversity and C and N contents compared with soil under NT and cover crops. On the other hand, NT associated with cover crops allowed to maintain the soil in both C and N, and to promote microbial activities without N fertilization. In conclusion, winter cover crops and/or NT are sustainable agricultural practices resulting in a greater soil quality index. These results demonstrate that NT and use of standard cover crops or cover crops with legumes for 5 years under a low biomass return in industrial crop production have a positive effect on: i) upper soil C content and microbial enzymes, irrespective of N fertilization regime; ii) soil microbial functional diversity in the absence of N fertilization

Diagnostic de Begomovirus associes aux systemes de cultures a base du manioc (Manihot esculenta Crantz) par la PCR (Polymerase Chain Reaction) au Togo

One of the consequences of the spread of highly polyphagous Bemisia tabaci biotypes is probably the emergence of new begomovirus species associated with climate change. This study is conducted to identify theses pathogen agents within cassava based cropping systems throughout Togo in order to get more information about emerged begomoviruses. Thus, Foliar samples of cassava, ten intercropped plants with cassava in fields and various wild plants collected during the period 2013-2016 are submitted to PCR diagnosis for the detection of begomoviruses in general and more specifically for the detection of cassava mosaic begomoviruses. For this purpose, five specific primer pairs targeting begomoviruses CP gene were used, in particular JSP001/JSP002, JSP001/JSP003, JSP012/JSP013, ICMV-F2/ICMV-R2 and AC1048/AV494. Results showed the effective presence of begomoviruses in the five economic regions of Togo. With AC1048/AV494 primers begomoviruses are found in 50 % (soybean), 26.31 % (pepper), 19.15 % (cassava), 13.63 % (tomato), 9.09 % (jute), and 5 % (wild plants). Two species of cassava mosaic begomoviruses ACMV and EACMV are also identified. The individual incidence rate for ACMV is 36.17 % in cassava and EACMV is 20.21 % in cassava and 10.53 % in pepper. This is the first report of begomoviruses in jute samples and EACMV in pepper in Togo. This study will contribute to the advancement of knowledge on begomoviruses-induced diseases transmitted by whiteflies, Bemisia tabaci

Targeted cell elimination reveals an auxin-guided biphasic mode of lateral root initiation.

To sustain a lifelong ability to initiate organs, plants retain pools of undifferentiated cells with a preserved proliferation capacity. The root pericycle represents a unique tissue with conditional meristematic activity, and its tight control determines initiation of lateral organs. Here we show that the meristematic activity of the pericycle is constrained by the interaction with the adjacent endodermis. Release of these restraints by elimination of endodermal cells by single-cell ablation triggers the pericycle to re-enter the cell cycle. We found that endodermis removal substitutes for the phytohormone auxin-dependent initiation of the pericycle meristematic activity. However, auxin is indispensable to steer the cell division plane orientation of new organ-defining divisions. We propose a dual, spatiotemporally distinct role for auxin during lateral root initiation. In the endodermis, auxin releases constraints arising from cell-to-cell interactions that compromise the pericycle meristematic activity, whereas, in the pericycle, auxin defines the orientation of the cell division plane to initiate lateral roots

Functional response of soil microbial communities to tillage, cover crops and nitrogen fertilization

© 2016 Elsevier B.V.Agricultural practices such as tillage, cover crops, and nitrogen (N) fertilization affect physico-chemical and biological soil parameters. However, these factors were often studied separately and their combined effects remain unclear, especially with respect to soil microbial functional diversity and carbon (C) and N content. Thereafter, we aim to assess the links between cropping systems and functional response of microbial communities by using a large range of soil chemical and biological measurements. A 5-yr field experiment was conducted in Northern France using a combination of three factors: i) no-till (NT) vs. conventional tillage (CT); ii) with or without winter cover crops (bare fallow; cover crops with a low prevalence of legumes; cover crop with a high prevalence of legumes); and iii) with or without N fertilization. C and N inputs from cover crops and crop residues, C and N content, enzyme activities, and microbial functional diversity in the topsoil (0–10 cm) were measured over an industrial crop rotation: wheat, pea, corn, wheat, flax. No-till combined with any of the cover crops was characterized by increased total soil organic C and N contents by more than 20% between 2010 and 2015. Dehydrogenase and urease activities were significantly greatest under NT, irrespective of the presence of cover crops. Cover crops without N fertilization under no-till led to higher microbial functional activity (faster carbohydrate and phenolic compound degradation) and diversity. Bare fallow had lower soil microbial functional diversity and C and N contents compared with soil under NT and cover crops. On the other hand, NT associated with cover crops allowed to maintain the soil in both C and N, and to promote microbial activities without N fertilization. In conclusion, winter cover crops and/or NT are sustainable agricultural practices resulting in a greater soil quality index. These results demonstrate that NT and use of standard cover crops or cover crops with legumes for 5 years under a low biomass return in industrial crop production have a positive effect on: i) upper soil C content and microbial enzymes, irrespective of N fertilization regime; ii) soil microbial functional diversity in the absence of N fertilization