Cassava (Manihot esculenta Crantz) production is currently under threat from cassava brown streak disease (CBSD), a disease that is among the seven most serious obstacles to world’s food security. Three issues are of significance for CBSD. Firstly, the virus associated with CBSD, has co-evolved with cassava outside its center of origin for at least 90 years. Secondly, that for the last 74 years, CBSD was only limited to the low lands. Thirdly, that most research has largely focused on CBSD epidemiology and virus diversity. Accordingly, this paper focuses on CBSD genetics and/or breeding and hence, presents empirical data generated in the past 11 years of cassava breeding in Uganda. Specifically, this paper provides: 1) empirical data on CBSD resistance screening efforts to identify sources of resistance and/or tolerance; 2) an update on CBSD resistance population development comprising of full-sibs, half-sibs and S1 families and their respective field performances; and 3) insights into chromosomal regions and genes involved in CBSD resistance based on genome wide association analysis. It is expected that this information will provide a foundation for harmonizing on-going CBSD breeding efforts and consequently, inform the future breeding interventions aimed at combating CBSD.

Culinary cassava (Manihot esculenta L.) qualities that make a variety popular are a function of starch physicochemical properties. Hence, in response to inferior root qualities in some released cassava varieties in Uganda compared to the local germplasm, a study was undertaken to examine: (i) starch physicochemical characteristics in both introduced and local varieties; and (ii) the variation in the starch properties of their F 1 progenies. The local varieties included Bao, Nyaraboke, Kakwale, and Bamunanika; and the introduced genotypes SE/95/00036, NASE 10, NASE 12, TME 5, and TME 14. Of the generated 7000 F 1 seedlings, 1077 seedlings were selected, cloned (6-8 plants per genotype) and established in a single-row trial. Root samples were collected per clone and examined for starch physicochemical properties. Considerable variations were observed in the F 1 families compared to the parental lines with weak correlations in most starch properties (r < 0.25). Amylose content ranged from 10 to 25%, with the amylose: amylopectin ratio between 1:3 and 1:9. Among the F 1 families, solubility and swelling power ranged from 1-15g100g -1 and 40-140g100 g -1 starch at 60 o C, respectively. In the parents, it ranged between 1.3-8.6 and 50-67g100g -1 starch at 60 o C, respectively. Fresh root starch yield ranged from 18 to 34%, with dry matter content varying from 19-47% in both the F 1 families and the parents. Ash and lipid content varied among the F 1 families and parents with ranges 0.05-0.29% for ash and 0.1-0.32% for lipids. In both the parents and the F 1 families, the reducing sugar and protein content ranged between 0.7-1.7 and 0.23-0.43%, respectively. These findings demonstrate: (i) existence of considerable genetic variations in starch physicochemical properties in both local and introduced cassava genotypes and their progenies, and (ii) potential utilisation of cassava starches for various applications based on the inherent differences in physicochemical characteristics.Key Words: Amylose, cassava starch, Manihot esculenta, protein, reducing sugar RÉSUMÉLes qualités qui rendent le manioc culinaire (Manihot esculenta L.) une variété populaire sont fonction des propriétés physico-chimiques de l'amidon. Ainsi, en réponse aux qualités inférieures des racines dans certaines variétés de manioc diffusées en Ouganda en comparaison avec les matériels génétiques locaux, une étude avait était menée dans le but d'examiner: (i) les caractéristiques physico-chimiques de l'amidon aussi bien dans les variétés locales que dans les variétés exotiques introduites; en plus (ii) la variation dans les propriétés de l'amidon des progenies F 1 . Les variétés locales sont Bao, Nyaraboke, Kakwale, Bamunanika et les génotypes exotiques SE/95/ 00036, NASE 10, NASE 12, TME 5 et TME 14. De 7000 F 1 plantules générées, 1077 plantules ont été sélectionnées, clonées (6-8 plants par génotype) et établies dans un essai en ligne unique. Les échantillons des racines avaient été collectées par clone et examinées pour les propriétés physico...

The sweet popcorn aroma conferred by 2-acetyl-1-pyrroline (2AP) is a highly economic trait of rice grain attracting premium price worldwide. This research study was conducted to determine the levels of 2AP in Ugandan rice lines with the aim of establishing a better understanding on the level and classes of 2AP and aroma phenotype. Concentration of 2AP was assayed using two-dimensional gas chromatography-time-of-flight mass spectrometry (GC × GC-TOF-MS) in tandem with sensory evaluation. Substantial variations in aroma intensity within and between the Uganda rice families were recorded. However, the levels of aroma variation were strongly influenced by the type of rice, and the breeding population it was derived from. Hence, three aroma based categories, namely, nonaromatic, moderately aromatic and highly aromatic were identified. GC with complementary sensory evaluation suggested a highly complex nature of rice aroma, as several rice lines were reclassified on the basis of this study. The 2AP contents and aroma intensity for genotypes with O. glaberrima were low compared to O. sativa and O. barthi. Genotypes of Supa 5, Supa 1052, Yasmin aromatic and MET 3 contained high 2AP levels whereas MET 16, MET 6, AGRA 78, AGRA 55, AGRA 41 and Sande TXD 306 exhibited moderate 2AP contents. Therefore, in developing an optimal breeding strategy aimed at improving the aroma in rice, quantitative information about 2AP and complementary sensory evaluation are a prerequisite.

This study aimed to identify cassava quality attributes preferred by users along the food chain, in order to provide breeders with criteria for prioritization. Survey, and consumer-testing studies were conducted within Apac and Luwero districts in Uganda. Additionally, sensory evaluation by trained panelists was conducted to determine descriptors for assessing quality of boiled roots. Results revealed softness of boiled roots and in-ground storability as key attributes influencing varietal preference besides high yield, non-bitter roots, disease resistance, early maturity and drought resistance. For some attributes like in-ground storability, preference differed significantly between locations, and showed differentiation by gender. Local varieties were found to be superior in quality attributes. From sensory evaluation, 21 descriptors associated with appearance, texture, taste and aroma of boiled roots were determined. Findings from this study are vital for breeders to adopt gender-responsive approaches in order to develop varieties that meet the needs and preferences of end-users.

Although breeders have made significant progress in the genetic improvement of cassava (Manihot esculenta Crantz) for agronomic traits, lack of information on heritability and limited testing of highthroughput phenotyping methods are major limitations to improving root quality traits, such as softness after cooking, which rank high among Ugandan consumers. The objectives of this study were to determine heritability for softness of cooked cassava roots, and quantify the relationship between penetrometer and consumer testing methods for phenotyping softness of cassava roots. Softness defined as the maximum force (N) needed to penetrate cooked root samples using a penetrometer, was evaluated at four cooking time intervals: 15, 30, 45, and 60 min on 268 cassava genotypes. Estimates of broad-sense heritability (repeatability) ranged from 0.17 to 0.37, with the highest value observed at 45 min of cooking time interval. In the second study involving 135 cassava consumers from Kibaale district in Uganda, penetrometer measurements of cooked roots from six cassava varieties were found to be in strong agreement (r 2 = 0.91; P-value = 0.003) with ordinal scores of root softness from consumer testing. These results suggest that: (a) softness of cooked cassava roots is a trait amenable for evaluation and selection; and (b) a penetrometer can readily be used for assessment of cooked root softness. These findings form the basis for operationalising the routine assessment of root softness in cassava breeding trials, an output that will enhance ongoing efforts to breed for desired end-user root quality traits.

The review aimed to identify the different high-throughput phenotyping (HTP) techniques that used for quality evaluation in cassava and yam breeding programmes, and this has provided insights towards the development of metrics and their application in cassava and yam improvements. A systematic review of the published research articles involved the use of NIRS in analysing the quality traits of cassava and yam was carried out, and Scopus, Science Direct, Web of Sciences and Google Scholar were searched. The results of the review established that NIRS could be used in understanding the chemical constituents (carbohydrate, protein, vitamins, minerals, carotenoids, moisture, starch, etc.) for high-throughput phenotyping. This study provides preliminary evidence of the application of NIRS as an efficient and affordable procedure for HTP. However, the feasibility of using mid-infrared spectroscopy (MIRS) and hyperspectral imaging (HSI) in combination with the NIRS could be further studied for quality traits phenotyping.

Early detection of crop disease is an essential step in food security. Usually, the detection becomes possible in a stage where disease symptoms are already visible on the aerial part of the plant. However, once the disease has manifested in different parts of the plant, little can be done to salvage the situation.Here, we suggest that the use of visible and near infrared spectral information facilitates disease detection in cassava crops before symptoms can be seen by the human eye. To test this hypothesis, we grow cassava plants in a screen house where they are inoculated with disease viruses. We monitor the plants over time collecting both spectra and plant tissue for wet chemistry analysis. Our results demonstrate that suitably trained classifiers are indeed able to detect cassava diseases. Specifically, we consider Generalized Matrix Relevance Learning Vector Quantization (GMLVQ) applied to original spectra and, alternatively, in combination with dimension reduction by Principal Component Analysis (PCA). We show that successful detection is possible shortly after the infection can be confirmed by wet lab chemistry, several weeks before symptoms manifest on the plants.

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