Coffee wilt disease

In the early 20th century, coffee wilt disease (CWD) caused by the vascular wilt pathogen, Fusarium xylarioides, spread across Africa destroying coffee trees, reducing yields and significantly impacting producer livelihoods. Through systematic sanitation and establishment of breeding programmes in affected countries, CWD appeared to decline. However, the disease re-emerged and increased to epidemic proportions in the 1990s affecting robusta coffee in DRC, Uganda and Tanzania and arabica coffee in Ethiopia. In 1999, 14.5 million robusta coffee trees were estimated to have been destroyed in Uganda alone. This chapter discusses the history, impact, symptoms, cause and spread of CWD. A summary of the Regional Coffee Wilt Programme (RCWP) which examined many aspects of the disease and its management is also provided. . Future research trends include host specificity, underlying resistance mechanisms and the role of alternative hosts. Investigation of pathogen ecology is needed to allow greater focus on agroecological management practices.

Genotype by year interaction for selected quantitative traits in hybrid lines of Triticum aestivum L. with Aegilops kotschyi Boiss. and Ae. variabilis Eig. using the additive main effects and multiplicative interaction model

This study estimated the genotype × environment interactions for ten yield associated traits in advanced generation hybrids of several cultivars of common wheat (Triticum aestivum L.) with Aegilops kotschyi Boiss. and A. variabilis Eig. using the additive main effects and multiplicative interaction (AMMI) models. Tests were ran over five years at one location in replicated field trials. The AMMI model showed significant genotypic and environmental effects for all analysed traits. A majority of the hybrid lines were less stable in the analysed traits than their parental wheats. The older wheat cultivars, with lower environmental sensitivity, were the most stable. The best total genotype selection index, for all ten traits combined, was observed for the oldest cvs. Gama and Rusałka, and among the hybrid lines, for Ae. kotschyi/Rusałka//Smuga and Ae. kotschyi/Rusałka//Muza. The lines Ae. kotschyi/Rusałka//Smuga, Ae. kotschyi/Rusałka//Muza, Ae. kotschyi/Rusałka//Korweta, Ae. kotschyi/Rusałka//Begra///Smuga, and Ae. kotschyi/Rusałka//Begra///Turnia are recommended for inclusion in breeding programmes due to their greater stability and the good average values for the observed traits.

A method for partitioning trends in genetic mean and variance to understand breeding practices

Quantifying the sources of genetic change is essential for optimising breeding programmes. However, breeding programmes are often complex because many breeding groups are subject to different breeding actions. Understanding the contribution of these groups to changes in genetic mean and variance is essential to understanding genetic change in breeding programmes. Here we extend the previously developed method for analysing the contribution of groups to changes in genetic mean to analysing changes in genetic variance. We, expectedly, show that the contribution of females and males to change in genetic variance can differ and are not independent, indicating we should not look at the contributions in isolation.

Morphological variations in Nigerian Apis mellifera Linnaeus, 1758 populations in Guinea savannah agro-ecological zone

Apis mellifera Linnaeus, 1758 is one of the most economically valuable insects which plays significant role in human medicine, nutrition and crop pollination. The morphometric variations of honeybee from different locations of the southern guinea and northern guinea savannah ecological zone of Nigeria were studied. Fifteen morphological traits were measured for variation on six hundred (600) worker honeybee samples purposively collected from ten different locations within the ecological zone. Data collected were subjected to one-way Analysis of Variance (ANOVA), SNK test (α=0.05) and Pearson correlation between morphometric characters were determined. At the same time a dendrogram of morphological proximity based on the fifteen morphological features was constructed. Results showed that morphometry variation (p<0.05) existed within the honeybee population in the guinea savannah agro-ecological zone of Nigeria, high morphological similarities were observed in the tibia length of the hind leg and the thorax length. The honeybee samples were classified into two distinct morphoclusters (A and B). Honeybee samples within morphocluster A were closely related in terms of the examined morphometric features and geographic distance (CV=1.65). In contrast, within cluster B, honeybee samples were closely related despite the vast geographical distance (CV=3.30, p<0.05). The body length was significantly positively correlated with the leg size, while hind wing length was positively associated with the proboscis, abdominal, thoracic, body length and hooks. Morphometric variations found in A. mellifera of guinea agro-ecological zone could significantly impact conservation and future bee breeding programmes of Nigeria.

Captive husbandry and breeding of the Nguru spiny pygmy chameleon Rhampholeon acuminatus

The Nguru spiny pygmy chameleon (Rhampholeon acuminatus) is endemic to the Nguru mountains in Tanzania. It is assessed as Critically Endangered and is collected from the wild for the pet trade. An ex-situ population of this species was recently established at The Wild Planet Trust, Paignton Zoo, in the hope of learning more about the husbandry and biology of this species. We report on the captive husbandry of adults and the successful breeding, hatching and rearing of juveniles. Females carried four eggs but laid them in pairs. When eggs were incubated at 19.2-22.8 °C, hatchlings emerged roughly 180 days after laying. The hatchlings had a total length of about 30 mm and weighed 0.2-0.3 g. To our knowledge, this is the first published account of captive breeding for this species. The husbandry methods described could be used to establish populations of this and other Rhampholeon species in captivity, which in turn would reduce the demand for wild caught (Rhampholeon), as well as inform future conservation breeding programmes for this species.

Reference genome-assisted identification of stem rust resistance gene Sr62 encoding a tandem kinase

The wild relatives and progenitors of wheat have been widely used as sources of disease resistance (R) genes. Molecular identification and characterization of these R genes facilitates their manipulation and tracking in breeding programmes. We developed a reference-quality genome assembly of the wild diploid wheat relative Aegilops sharonensis and used positional mapping, mutagenesis, RNA-Seq and transgenesis to identify the stem rust resistance gene Sr62, which was also transferred to common wheat. This gene encodes a tandem kinase, homologues of which exist across multiple taxa in the plant kingdom. Stable Sr62 transgenic wheat lines showed high levels of resistance against diverse isolates of the stem rust pathogen, highlighting the utility of Sr62 for deployment as part of a polygenic stack to maximize the durability of stem rust resistance.

Analysis of genetic diversity in selected sugarcane (Saccharum officinarum L.) accessions using inter simple sequence repeat (ISSR) markers

<p class="042abstractstekst"><span lang="EN-US">Genetic diversity information among a population is important in exploiting heterozygosity for the improvement of crop species through breeding programmes. This study was therefore, conducted to assess genetic diversity and establish molecular relationships among 20 selected exotic sugarcane accessions from the Unilorin Sugar Research Institute germplasm using Inter Simple Sequence Repeat (ISSR) molecular markers. Genomic DNA was extracted from the sugarcane leaf. Fragments amplification was then performed by polymerase chain reaction (PCR) with ISSR markers and the data obtained were analyzed using MEGA 4 software. Analysis of the electropherogram showed a total of 39 loci consisting of 369 bands, out of which 95.8% were polymorphic. The biplot analysis showed all the markers contributed to the observed diversity with the least achieved with ISSR6. The principal co-ordinate analysis grouped the accessions into four clusters, comprising mixtures of all the six collection sites. The polymorphism obtained in the present study showed that the ISSR markers are effective for assessment of genetic diversity of the sugarcane accessions as it reveals the genetic similarity or divergence of the accessions regardless their place of origin or cultivation.</span></p>

Efficient High-throughput Techniques for the Analysis of Disease-Resistant Plant Varieties and Detection of Food Adulteration

Over the past two decades, the advances in the next generation sequencing (NGS) platforms have led to the identification of numerous genes/QTLs at high-resolution for their potential use in crop improvement. The genomic resources generated through these high-throughput sequencing techniques have been efficiently used in screening of particular gene of interest particularly for numerous types of plant stresses and quality traits. Subsequently, the identified-markers linked to a particular trait have been used in marker-assisted backcross breeding (MABB) activities. Besides, these markers are also being used to catalogue the food crops for detection of adulteration to improve the quality of food. With the advancement of technologies, the genomic resources are originating with new markers; however, to use these markers efficiently in crop breeding, high-throughput techniques (HTT) such as multiplex PCR and capillary electrophoresis (CE) can be exploited. Robustness, ease of operation, good reproducibility and low cost are the main advantages of multiplex PCR and CE. The CE is capable of separating and characterizing proteins with simplicity, speed and small sample requirements. Keeping in view the availability of vast data generated through NGS techniques and development of numerous markers, there is a need to use these resources efficiently in crop improvement programmes. In summary, this review describes the use of molecular markers in the screening of resistance genes in breeding programmes and detection of adulterations in food crops using high-throughput techniques.

Morphometric and morphological characterization of chicken resources adapted to pastoral and agropastoral areas of southern Ethiopia

Thirteen qualitative and six quantitative variables taken from 303 adult chickens (95 cocks and 208 hens) from three locations/districts were used to phenotypically characterize the indigenous chicken populations in pastoral areas of South Omo Zone, Ethiopia. The studied traits were influenced by the effect of location and sex, where chicken populations from Hamer district and females of all districts were the smallest and lightest. Qualitative characteristics of the studied chicken populations such as normal feather morphology and distribution, plain plumage pattern, flat head shape, triangular body shape, and dominant red eye, earlobe and plumage colour suggest that they constitute previously undescribed populations. Chest circumference, wingspan and body length were the three most important morphometric traits used in discriminating the studied chicken populations. On average, 61% of the sampled populations were classified correctly into their respective locations. The multivariate analysis results discriminate the chicken populations into two groups: the Hamer group and the Omo group (chickens from Bena Tsemay and Male districts). However, such grouping should be confirmed and advanced to ecotype level using further genetic characterization studies as the observed phenotypic differences might be due to genetic or environmental variations. Such confirmation is important to design breeding programmes (for sustainable utilization) specific to each ecotype.

Genome-Wide Association Study of Root Mealiness and Other Texture-Associated Traits in Cassava

Cassava breeders have made significant progress in developing new genotypes with improved agronomic characteristics such as improved root yield and resistance against biotic and abiotic stresses. However, these new and improved cassava (Manihot esculenta Crantz) varieties in cultivation in Nigeria have undergone little or no improvement in their culinary qualities; hence, there is a paucity of genetic information regarding the texture of boiled cassava, particularly with respect to its mealiness, the principal sensory quality attribute of boiled cassava roots. The current study aimed at identifying genomic regions and polymorphisms associated with natural variation for root mealiness and other texture-related attributes of boiled cassava roots, which includes fibre, adhesiveness (ADH), taste, aroma, colour, and firmness. We performed a genome-wide association (GWAS) analysis using phenotypic data from a panel of 142 accessions obtained from the National Root Crops Research Institute (NRCRI), Umudike, Nigeria, and a set of 59,792 high-quality single nucleotide polymorphisms (SNPs) distributed across the cassava genome. Through genome-wide association mapping, we identified 80 SNPs that were significantly associated with root mealiness, fibre, adhesiveness, taste, aroma, colour and firmness on chromosomes 1, 4, 5, 6, 10, 13, 17 and 18. We also identified relevant candidate genes that are co-located with peak SNPs linked to these traits in M. esculenta. A survey of the cassava reference genome v6.1 positioned the SNPs on chromosome 13 in the vicinity of Manes.13G026900, a gene recognized as being responsible for cell adhesion and for the mealiness or crispness of vegetables and fruits, and also known to play an important role in cooked potato texture. This study provides the first insights into understanding the underlying genetic basis of boiled cassava root texture. After validation, the markers and candidate genes identified in this novel work could provide important genomic resources for use in marker-assisted selection (MAS) and genomic selection (GS) to accelerate genetic improvement of root mealiness and other culinary qualities in cassava breeding programmes in West Africa, especially in Nigeria, where the consumption of boiled and pounded cassava is low.