Structure of African Populations of Pyricularia oryzae from Rice.

Rice blast, caused by the filamentous ascomycete Pyricularia oryzae, is one of the most devastating diseases of rice. Four genetic clusters were previously identified, and three have a large geographic distribution. Asia is the center of diversity and the origin of most migrations to other continents, and sexual reproduction persisted only in the South China-Laos-North Thailand region, which was identified as the putative center of origin of all P. oryzae populations on rice. Despite the importance of rice blast disease, little is known about the diversity and the population structure of the pathogen in Africa (including Madagascar). The present study was intended to describe the structure of African populations of P. oryzae and identify the relationship between African and worldwide genetic clusters. A set of 2,057 strains (937 African and 1,120 Madagascan strains) were genotyped with 12 simple sequence repeat markers to assess the diversity and the population structure of P. oryzae. Four genetic clusters were identified in Africa and Madagascar. All four clusters previously identified are present in Africa. Populations from West Africa, East Africa, and Madagascar are highly differentiated. The geographic structure is consistent with limited dispersion and with some migration events between neighboring countries. The two mating types are present in Africa with a dominance of Mat1.2, but no female-fertile strain was detected, supporting the absence of sexual reproduction on this continent. This study showed an unsuspected high level of genetic diversity of P. oryzae in Africa and suggested several independent introductions.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Genetic variation in blast resistance in rice germplasm from West Africa.

The genetic variation in resistance to blast (Pyricularia oryzae Cavara) in 195 rice accessions comprising 3 species of the AA genome complex (Asian rice [Oryza sativa L.], African rice [Oryza glaberrima Steud.] and wild rice [Oryza barthii]) was investigated based on their patterns of reaction to standard differential blast isolates (SDBIs) and SSR marker polymorphism data. Cluster analysis of the polymorphism data of 61 SSR markers identified 3 major clusters: cluster A (mainly Japonica Group or upland accessions), cluster B (mainly Indica Group or lowland accessions) and cluster C (O. glaberrima and O. barthii). The accessions were classified again into 3 resistance groups based on reactions to SDBIs: group Ia (susceptible), group Ib (middle resistance) and group II (high resistance). Group Ia included only a few differential varieties, susceptible controls and the Japonica Group cultivar Nipponbare. Accessions in clusters A and B included all 3 resistance groups and showed a wide variation in blast resistance, but cluster C contained only group Ib. These results demonstrated that variations in Asian rice (O. sativa) accessions in West Africa were skewed toward high resistance and that variations in O. glaberrima and O. barthii were limited and lower than the Asian rice accessions.

Volatile compounds profile and sensory evaluation of Beninese condiments produced by inocula of Bacillus subtilis.

BACKGROUND: Three Beninese food condiments (ABS1(24h), IBS2(48h) and SBS3(48h)) were produced by controlled fermentation of African locust beans using inocula of pure cultures of Bacillus subtilis, BS1, BS2 and BS3, respectively. Quantitative and qualitative assessments of the volatile compounds in the condiments produced have been performed using the Likens-Nickerson simultaneous distillation-extraction method and GC-MS analysis, followed by a sensory evaluation in comparison with the spontaneously fermented condiments. RESULTS: A total of 94 volatile compounds have been found including 53 compounds identified in relatively high concentrations and were subdivided into seven main groups with the predominance of four major groups: pyrazines, aldehydes, ketones and alcohols. Compared to the spontaneously fermented condiments, volatile compounds identified in controlled fermented condiments have been found in high number and in concentrations which varied according to the inoculum of B. subtilis used. The condiments produced with starter cultures scored significantly (P < 0.05) higher for odour than the spontaneously fermented condiments. But the overall acceptability (7/10) of the two types of condiments was similar. CONCLUSION: The investigated B. subtilis, BS1, BS2 and BS3 can be considered as potential starter cultures for the fermentation of African locust beans to produce good quality of Beninese food condiments.