Arabica Coffee Genotypes Research Articles

Optimized Multilayer perceptron for the geographical and genotypic classification of four genotypes of arabica coffee

<p>The climatic conditions of the coffee crop give special attributes to the beverage and could increase its value. However, it is essential to prove the geographical and genotype origin of the cultivar using reliable methods. Several statistical methods have been developed in an attempt to reproduce the human capability of pattern recognition. The multilayer perceptron (MLP) is an artificial neural network (ANN) with supervised learning that is widely used for pattern classification. This study aimed to develop a MLP to classify the geographic origin and the genotypic of the arabica coffee. For this purpose, spectra obtained in the Fourier transform infrared (FTIR) were analyzed using MLPs optimized by sequential simplex. The networks that used the range 1900-800 cm<sup>-1</sup> of the raw spectrum had lower mean squared error (MSE) and a higher percentage of correct classification for geographical (100%) and genotypic (77,74%) segmentation. After the results it was concluded that the optimized multilayer perceptrons were able to classify the samples of arabica coffee geographically. However, for genotypic classification the performance was not satisfactory. Also, the MLP developed for genotypic classification has a high number of synaptic weights, thus a large degrees of freedom database is necessary to produce a network with generalization capability. Therefore, to improve the genotype classification performance the authors suggest the use of other type of ANN and information from the near infrared.</p><p> </p><p>DOI: http://dx.doi.org/10.14685/rebrapa.v3i1.96</p>

Biomass production and distribution in seedlings of <i>Coffea Arabica</i> genotypes under contrasting nursery environments in southwestern Ethiopia

In Ethiopia, the natural forests with the occurrence of wild Arabica coffee gene pools are under constant threats, largely due to anthropogenic activities. The study was conducted to compare the variability among the wild arabica coffee genotypes in biomass assimilation and allocation patterns under varying light and irrigation conditions at the Jimma Research Center, southwestern Ethiopia. The treatments included irradiance (moderate and full sunlight), irrigation (well watered and water stressed) regimes and twelve coffee genotypes of different geographical areas. One-year-old seedlings were used to record dry mass of leaves, main stem, primary branches and root growth. Each organ was separately oven-dried and total dry matter production and allocation patterns were measured and analyzed. The results depicted highly significant differences between the contrasting irradiance and irrigation regimes as well as among coffee genotypes. Significantly the lowest and highest stems dry mass values recorded for Berhane-Kontir and Harenna genotypes, respectively. Most accessions had relatively lower assimilations in shade as compared to full sun light conditions. Likewise, coffee seedlings significantly differed in root dry mass and root to shoot ratio, dry matter partitioning due to the main and combined treatment effects. Overall, total biomass assimilation and partitioning were higher for unshaded, water stressed and Harenna genotypes from the respective treatment groups. Conversely, leaf dry matter, leaf share was significantly high under moderate shade environments. The total dry matter share varied for the seedling growth parts (root = 22%, leaf = 35%, stem = 43% and whole shoot = 78%). The root growth followed the order of Harenna > Yayu > Bonga > Berhane-Kontir populations. The reverse was true for the leaf and whole-shoots, demonstrating the completion between above and below ground growth parts and thus the need to consider both dry matter assimilation and partitioning patterns in identifying desirable genotypes and optimum environments for future breeding program in Ethiopia.

Evaluation of beverage quality and green bean physical characteristics of selected Arabica coffee genotypes in Kenya

Physical characteristics of green coffee bean have been reported to affect beverage quality to some extent. The objective of this study was to assess the beverage quality and green bean physical characteristics of forty two arabica coffee genotypes and to determine the relationship between the two attributes. Green bean physical characteristics were assesed through actual measurements, grading and weighing while beverage quality was determined by a panel of seven judges using the prescribed sensory evaluation procedures. Sensory data was used to calculate diversity in beverage quality among genotypes and to construct a dendrogram using the unweighted pair-group method with arithmetic average. Data were also subjected to analysis of variance and differences declared significant at 5% level based on Duncan's Multiple Range Test. Linear correlation was done to compare the relationship between variables. Cluster analysis results demonstrated 0 - 47% diversity in beverage quality among genotypes. There was close similarity among coffee tasters in ranking various beverage quality characteristics of the cultivars indicating that the panel was reliable in assessment of beverage quality. All sensory variables evaluated were positively and significantly correlated. However, correlations between the sensory variables and green bean physical characteristics were non-significant. (Resume d'auteur)

Comparison of SSR and AFLP analysis for genetic diversity assessment of Ethiopian arabica coffee genotypes

Knowledge of genetic diversity within and among genotypes of any crop is fundamental for estimation of the potential genetic gain in a breeding programme and effective conservation of available genetic resources. Currently, different molecular marker techniques are being developed for measuring genetic diversity. Comparison among molecular marker techniques is important for effective marker selection. However such types of efforts are rare for arabica coffee. This study was conducted to compare the efficiency of simple sequence repeat (SSR) analysis for determining genetic relationships of 28 Coffea arabica L. genotypes collected from different parts of Ethiopia with work previously done using amplified fragment length polymorphism (AFLP) analysis. A total of 22 SSR fragments were amplified and compared with 712 previously amplified AFLP fragments. AFLP and SSR markers were positively and significantly correlated (0.217) in estimating genetic similarity among genotypes. The average genetic similarity coefficient calculated using SSR markers was much lower (0.560 with a range of 0.286–1.000) compared to AFLP markers (0.915 with a range of 0.860–0.982) indicating the higher information content of SSR markers. AFLP markers distinguished all genotypes, while SSR markers distinguished 64.3% of the genotypes. Results indicated that AFLP markers were more efficient compared to SSR markers for characterization of the evaluated coffee genotypes.

AFLP analysis among Ethiopian arabica coffee genotypes

Knowledge of genetic diversity is vital for genetic improvement and germplasm conservation. The genetic relationship of 28 Coffea arabica genotypes from Ethiopia was assessed using 10 Amplified Fragment Length Polymorphism (AFLP) primer combinations. The level of polymorphism was 30.9% and 18 markers were unique to 10 genotypes. Pair-wise genetic similarity coefficients ranged from 0.851 to 0.982, AD1491 being the most divergent and AD5091 the most closely related to all genotypes. All genotypes were independently distinguished and did not cluster according to collection region, demonstrating the presence of coffee genetic resource diversity within each region. Results of this study will be utilised for germplasm collection, conservation as well as in variety development efforts.

Additional evidence for oligogenic inheritance of durable host resistance to coffee berry disease (Colletotrichum kahawae) in arabica coffee (Coffea arabica L.)

Breeding for host resistance to coffee berry disease (CBD) in arabica coffee (Coffea arabica) was initiated some 35–40 years ago in Kenya, Ethiopia and Tanzania in response to severe CBD epidemics. The release of CBD resistant cultivars to the coffee growers has been in progress since 1985. The resistance of cultivars like Ruiru 11 (Kenya) and Ababuna (and other cvs in Ethiopia) appears to be of a durable nature, since confirmed cases of a breakdown of host resistance under field conditions have not been reported over the past 20 years. Host resistance to the hemibiotrophic fungus Colletotrichum kahawae is of a quantitative nature, but nevertheless can be practically complete in some genotypes of arabica coffee. There is still no consensus on the genetics of CBD resistance, some claiming convincing evidence for oligogenes (1–3 major genes) and others for polygenes determining CBD resistance. Results from genetic studies with germplasm from the centre of genetic diversity for C. arabica in Ethiopia are presented here. These together with the recent identification of molecular markers associated with and the mapping of one major gene, provides additional evidence for oligogenic inheritance of CBD resistance. The development of cultivars combining yield and quality with durable host resistance to CBD has contributed greatly to increased sustainability of arabica coffee production in Africa. It has also considerable relevance to arabica coffee in Latin America and Asia, where CBD is still a quarantine disease but with a risk of becoming endemic one day, just as has happened earlier with coffee leaf rust (Hemileia vastatrix).

Genetic diversity and correlation of bean caffeine content with cup quality and green bean physical characteristics in coffee (Coffea arabica L.)

AbstractBACKGROUND:Although people began to consume coffee for its stimulating effect, the demand for decaffeinated coffee is increasing and now accounts for 10% of the total amount of coffee consumed in the world. Forty‐two arabica coffee genotypes originating from Ethiopia were tested to assess caffeine content variability among them, and the correlation of caffeine content with cup quality and green bean physical characteristics.RESULTS:Green bean caffeine content was measured using high‐performance liquid chromatography, while cup quality was determined by professional coffee tasters. Caffeine content ranged from 9.1 to 13.2 g kg−1 on dry mass basis (d.m.b.). Six genotypes—AD0291, AD0591, AD2491, AD2691, AD2791 and AD2891—had a caffeine content of less than 10.0 g kg−1. Caffeine content showed negative and statistically significant correlations with cup quality attributes. Correlations between caffeine content and green bean physical characteristics were non‐significant.CONCLUSIONS:Simultaneous selection for low caffeine content and good cup quality is possible. Some accessions had low caffeine content, and may serve as a source of desirable genes for variety development of types with relatively low caffeine content. Copyright © 2008 Society of Chemical Industry

Reproducibility of the RAPD marker and its efficiency in coffee tree genotype grouping analysis

The genetic diversity of Coffea arabic L. cultivars is relatively narrow and its assessment and increase is important for breeding. Fifty two arbitrary primers were used to evaluate the reproducibility and the influence of the number of RAPD (Random Amplified Polymorphic DNA) markers on the estimation of genetic distances among 40 genotypes of Coffea spp. The average number of polymorphic bands was 6.69 per primer among all genotypes, and 1.27 among arabica coffee genotypes. RAPD markers were efficient in estimating the genetic distances among the genotypes. The increase in RAPD loci number during grouping analysis did not affect the major groups’ composition; however, it affected the composition of subgroups. Marker reproducibility was 76.88% and replicated data was recommended for distinguishing genotypes with the same genetic background.

Somatic Embryogenesis in Commercial Crops—An Overview

Many researchers regard somatic embryogenesis as a system of choice for in vitro propagation of superior varieties of crops such as coffee, mango, datepalm, and rose. While there are advantages, commercialization has not been possible so far in coffee, mango, and rose. The work highlights some reasons for this and feasible alternatives. We have established somatic embryogenesis in four elite Indian arabica coffee genotypes. Plantlets (3500) of all the four varieties are now being field-evaluated. The cost of producing these propagules is 15 times the seedling cost at present. A major constraint is the long time (6 months) needed to reach the five-leaf stage in vitro prior to release for acclimatization. This period can be reduced to 2 months using exvitro development after the two leaf stage. There are many reports of somatic embryogenesis in mango. Results on establishing free-living plantlets have not been encouraging.We found a number of abnormalities in the shape of the somatic embryos in cv. Rumani. However, except for the “rod”-shaped ones (that lacked cotyledonary expansion), all embryos germinated satisfactorily (75% rooting).We have encouraging results in reducing the time required to generate suitable plantlets for field acclimatization and in standardizing the procedures for grafting. Our laboratory has developed methods for ex vitro germination of mature embryos in datepalm,which yield more numbers of free-living plantlets (50%–60%) in only 3 months with an average of four leaves per plant. This compared favorably with in vitro germination that takes 6 months and produces plantlets with one or two leaves only. A novel protocol for obtaining somatic embryogenesis in rose from petal derived calli was developed by us (Murali et al., 1996). The number of embryos induced was too low for commercial application. [Murali et al., 1996. Euphytica 91:271–275].