ABSTRACT
Cassava anthracnose is a plant disease that affects cassava stems, petioles and fruits. The aim of this study was to analyze the diversity of cassava anthracnose symptoms in Ivory Coast and then to identify and characterize the associated fungal genera. Surveys were carried out in all agricultural zones of the country from July to November, in 2014, 2015, 2016 and 2017. Infected samples consisting of stems cut with a small number of superficial cankers (0.3%), distorted stems (25.77%), and necrotic stems and petioles (65.18%) were collected. Also, withered and dried apical buds (8.76%) were harvested. Fungal pathogens derived from samples were Colletotrichum gloeosporioides (35.08%), Fusarium sp. (27.19%) and Botrytis sp. (19.73%) genera and undetermined strains (17.98%). Genera were characterized by morphological and microscopic characteristics. Parasitic pressure increased to 80 and 100% respectively for Botrytis sp. genus and Colletotrichum gloeosporioides and Fusarium sp genera. Fungal genera have caused lesions on stem and petioles in green house with diameters sizes 46, 71 and 72 mm respectively for genera Botrytis sp, Fusarium sp and Colletotrichum gloeosporioides. Aggressiveness index of Botrytis sp. genus was 3 and 4 respectively for Colletotrichum gloeosporioides and Fusarium sp. genera. The mycoflora of cassava aerial organs alteration, linked to the symptoms of anthracnose, is composed of genera of great economic importance and scientific interest.
ABSTRACT
Rice (Oryza spp) is one of the most important crops produced in the world. Rice production is dampered by environmental and biological factors including mainly pathogens, such as Rice yellow mottle virus (RYMV), which is the most rice devastating viral disease in Africa: whereas, These factors can be overcome by using different methods such as mineral fertilization supplying. To identify nutrients for this constraint management, a study was carried out in controlled condition in a greenhouse situated at Felix Houphouët-Boigny University station at Bingerville. The rice variety named Bouake 189 was sown in pots using local soil as substrate. Fourteen days old seedlings were inoculated mechanically with isolate of RYMV. Fertilizers N, P, K 12, 24, 18 (200 kg/ha) and 100 kg/ha of urea (46% N) were applied respectively. The concentrations of N, P, K, Ca and Mg as well as protein content in leaves were determined likely. Chlorophyll measurement was obtained using Spad-505. The severity and the (AUSPC) of the RYMV were evaluated. The presence of the RYMV in the infected leaves was confirmed by serological analysis. The averages of the various parameters were compared by ANOVA 2 with software STATISTICA version 7.1. Results showed significant difference (p < 0.001) between the seedlings according to infection levels and highest concentrations of P (0.40%), K (1.10%), Ca (1.49%), Mg (0.39%) and chlorophyll (37.37) were recorded in the leaves of non-infected seedlings whereas those related to infected seedlings were of 0.39%; 0.75%; 0.67%; 0.24% and 21.23 respectively. This was contrasting with N and protein contents recording 2.41% and 15.04 for the inoculated plants and 1.75% and 10.95 for the healthy plants respectively. The average severity and viral load of Rice yellow mottle disease were reduced respectively from 6.22 to 3.88 and from 2.132 to 1.577 under the action of the mineral fertilization (NPK), hence improving rice growth and yield to be targeted.