Reaction of cotton and soybean cultivars to populations of Meloidogyne javanica and M. incognita in Zimbabwe

The response of common cotton (Gossypium hirsutum L.) and soybean [Glycine max L. (Merr.)] cultivars in Zimbabwe to infestation by Meloidogyne javanica (Treub) Chitwood and Meloidogyne incognita (Kofoid & White) Chitwwod races 1 and 3 was evaluated. This was done under greenhouse conditions in two separate experiments at Kutsaga Research Station, Zimbabwe, in a program aimed at identifying alternative rotation crops for root-knot nematode management in tobacco (Nicotiana tabacum L.). Seedlings of each cultivar were raised in sterilised soil in 15 cm diameter pots. The inoculum which was applied three weeks after sowing was a mixture of eggs and second stage juveniles (J2s). The dosage was 4000 mixed eggs and J2s per plant for the soybean trial while it was 5000 for cotton. Nine weeks after infestation, root gall indices, numbers of nematode egg masses and eggs per root system were recorded. The numbers of J2s per pot were also recorded. Reproduction factor (RF) was computed as final population (eggs + J2s) ÷ initial population inoculated. All the cotton cultivars were susceptible (RF>1 and abundant galling) to M. incognita Race 3 while they were all resistant (RF<1) to M. javanica. The cultivars, TE-94-4, FQ 92-19, CY889, AG4869 and DF885 were resistant to M. incognita Race 1. The other three cultivars which were susceptible to M. incognita Race 1 did not show any damage symptoms suggesting that assessing for resistance using this criterion alone may be inadequate. The soybean cultivars were all susceptible to the three species except SNK60 which was resistant to M. incognita race 1 (RF=0). The cultivar, however, produced galls further indicating the inadequacy of using damage functions of Meloidogyne species for host status evaluatio

Towards a collaborative research: A case study on linking science to farmers' perceptions and knowledge on Arabica coffee pests and diseases and its management

The scientific community has recognized the importance of integrating farmer's perceptions and knowledge (FPK) for the development of sustainable pest and disease management strategies. However, the knowledge gap between indigenous and scientific knowledge still contributes to misidentification of plant health constraints and poor adoption of management solutions. This is particularly the case in the context of smallholder farming in developing countries. In this paper, we present a case study on coffee production in Uganda, a sector depending mostly on smallholder farming facing a simultaneous and increasing number of socio-ecological pressures. The objectives of this study were (i) to examine and relate FPK on Arabica Coffee Pests and Diseases (CPaD) to altitude and the vegetation structure of the production systems; (ii) to contrast results with perceptions from experts and (iii) to compare results with field observations, in order to identify constraints for improving the information flow between scientists and farmers. Data were acquired by means of interviews and workshops. One hundred and fifty farmer households managing coffee either at sun exposure, under shade trees or inter-cropped with bananas and spread across an altitudinal gradient were selected. Field sampling of the two most important CPaD was conducted on a subset of 34 plots. The study revealed the following findings: (i) Perceptions on CPaD with respect to their distribution across altitudes and perceived impact are partially concordant among farmers, experts and field observations (ii) There are discrepancies among farmers and experts regarding management practices and the development of CPaD issues of the previous years. (iii) Field observations comparing CPaD in different altitudes and production systems indicate ambiguity of the role of shade trees. According to the locality-specific variability in CPaD pressure as well as in FPK, the importance of developing spatially variable and relevant CPaD control practices is proposed. (Résumé d'auteur

Gene expression in coffee

Coffee is cultivated in more than 70 countries of the intertropical belt where it has important economic, social and environmental impacts. As for many other crops, the development of molecular biology technics allowed to launch research projects for coffee analyzing gene expression. In the 90s decade, the first expression studies were performed by Northern-blot or PCR, and focused on genes coding enzymes of the main compounds (e.g., storage proteins, sugars, complex polysaccharides, caffeine and chlorogenic acids) found in green beans. Few years after, the development of 454 pyrosequencing technics generated expressed sequence tags (ESTs) obviously from beans but also from other organs (e.g., leaves and roots) of the two main cultivated coffee species, Coffea arabica and C. canephora. Together with the use of real-time quantitative PCR, these ESTs significantly raised the number of coffee gene expression studies leading to the identification of (1) key genes of biochemical pathways, (2) candidate genes involved in biotic and abiotic stresses as well as (3) molecular markers essential to assess the genetic diversity of the Coffea genus, for example. The development of more recent Illumina sequencing technology now allows large-scale transcriptome analysis in coffee plants and opens the way to analyze the effects on gene expression of complex biological processes like genotype and environment interactions, heterosis and gene regulation in polypoid context like in C. arabica. The aim of the present review is to make an extensive list of coffee genes studied and also to perform an inventory of large-scale sequencing (RNAseq) projects already done or on-going