Settumba B Mukasa

Makerere University · Department of Agricultural Production

Low hydrogen cyanide (HCN) concentration is a high-priority trait for cassava varieties targeting their fresh and dry product profiles. To be acceptable, varieties bred and developed for these market segments must meet international safety standards for maximum acceptable residual levels of cyanide in cassava food and food products. The discovery o...

The sweetpotato (Ipomoea batatas (L) Lam) seed system in Uganda is transiting from an informal to a formal setting, by integrating the use of certified sweetpotato seed (CSS) in the production system. Use of CSS enhances productivity by controlling the spread of the sweetpotato virus disease (SPVD) and seed degeneration. However, owing to the limit...

Understanding pollen and ovule fertility as factors influencing fruit and seed set is important in cassava breeding. Extended daylength with red light (RL) and plant growth regulators (PGRs) have been used to induce flowering and fruit set in cassava without any reference to effects on pollen viability or ovule fertilizability. This study investiga...

Understanding pollen and ovule fertility as factors influencing fruit and seed set is important in cassava breeding. Red light (RL) and plant growth regulators (PGRs) have been used to induce or enhance flowering and fruit set in cassava without any reference to effects on pollen viability or ovule fertilizability. This study investigated effects o...

Most banana improvement programs are restricted to using a sub-set of edible landraces for sexual hybridization as the majority are female sterile. This results from an array of factors that work in tandem and lead to sterility. Use of pollen germination media (PGM) during pollination significantly increases seed set, but it is a very small fractio...

The ipomoviruses (family Potyviridae) that cause cassava brown streak disease (cassava brown streak virus [CBSV] and Uganda cassava brown streak virus [UCBSV]) are damaging plant pathogens that affect the sustainability of cassava production in East and Central Africa. However, little is known about the rate at which the viruses evolve and when the...

Breeding for low-hydrogen-cyanide (HCN) varieties is a major objective of programs targeting boiled cassava food products. To enhance the breeding of low-HCN varieties, knowledge of genetic variation and trait heritability is essential. In this study, 64 cassava clones were established across four locations and evaluated for HCN using three HCN ass...

Opportunities for Ugandan farmers to undertake the production of sweet potato have resulted in certified sweet potato seed (CSS) innovations being pursued in recent times. The CSS and farmer-saved vine sources co-exist with the latter still predominant despite the formers’ on-farm superior performance as regards yields, disease reduction and promot...

Rice (Oryza sativa) bacterial blight (BB) is a direct threat to production in Africa. The extent of damage on the continent is not known. We conducted a genome-wide association study (GWAS) to seek out Quantitative trait loci (QTL) that confer the broad-spectrum resistance (BSR) to rice Xanthomonas oryzae pv. oryzae in the rice Multiparent advanced...

Flowering in cassava (Manihot esculenta Crantz) is crucial for the generation of botanical seed for breeding. However, genotypes preferred by most farmers are erect and poor at flowering or never flower. To elucidate the genetic basis of flowering, 293 diverse cassava accessions were evaluated for flowering-associated traits at two locations and se...

The use of certified sweetpotato (Ipomoea batatas) seed (CSS) was reported to unlock the yield potential of the crop leading to an over 80% yield increase. Despite the availability of elements of a formal CSS system, uptake in Uganda has remained dismal. Interdependence between farmer knowledge, perceptions, and purchase behaviors (PBs) is not well...

Flowering in cassava is crucial for generation of botanical seed for breeding. However, most farmer preferred genotypes are poor at flowering, exhibit great disparity in time and amount of flowering or never flower. To elucidate the genetic basis of such a flowering behaviour, 293 diverse cassava accessions were evaluated for flowering traits under...

This study focuses on meeting end‐users’ demand for cassava (Manihot esculenta Crantz) varieties with low cyanogenic potential (hydrogen cyanide potential [HCN]) by using near‐infrared spectrometry (NIRS). This technology provides a fast, accurate, and reliable way to determine sample constituents with minimal sample preparation. The study aims to...

Background: Xanthomonas oryzae pv. Oryzae (Xoo), the causal agent of rice bacterial blight disease has been extensively characterized and loci against different races identified. Many rice cultivars have been developed and utilized to combat the disease, however due to rapid evolution of Xoo, a number of resistances have broken-down. The continuous...

This study examined profitability of producing bioethanol and factors that drive farmers’ decisions to produce bioethanol from cassava. Although small scale production of bioethanol was found to be profitable, selling cassava dry chips was found to be more profitable. In addition, selling fresh cassava roots was also more profitable than small scal...

Background Cassava (Manihot esculenta Crantz) is staple food and major source of calories for over 500 million people in sub-Saharan Africa. The crop is also a source of income for smallholder farmers, and has increasing potential for industrial utilization. However, breeding efforts to match the increasing demand of cassava are impeded by its inab...

Cassava brown streak disease (CBSD) caused by cassava brown streak viruses and cassava mosaic disease (CMD) caused by different species of cassava mosaic geminiviruses (CMGs) are the two major viral diseases constraining cassava production in Uganda. Both diseases are spread through cuttings and are transmitted by whiteflies Bemisia tabaci. A numbe...

Rice yellow mottle virus disease, caused by Rice yellow mottle virus (RYMV), is the most important disease of lowland rice in Uganda. However, little is known, about its genetic diversity in Uganda and relationships with other strains elsewhere across Africa. A new degenerate primer pair that targets amplification of the entire RYMV coat protein ge...

Characterizing anti-virus genes in sweetpotato is a vital step in mitigating yield loss due to virus infections. This work lays an insight into the structure and expression of key anti-virus genes. Related plant-based anti-virus genes were used as reference to mine key sweetpotato genes from various databases. BLASTN and BLASTP for transcripts was...

Background: Cassava (Manihot esculenta Crantz) is staple food and major source of calories for over 500 million people in sub-Saharan Africa. The crop is also a source of income for smallholder farmers, and has increasing potential for industrial utilization. However, breeding efforts to match the increasing demand of cassava are impeded by its ina...

Introduction The intrinsic high heterozygosity of cassava makes conventional breeding ineffective for rapid genetic improvement. However, recent advances in next generation sequencing technologies have enabled the use of high-density markers for genome-wide association studies, aimed at identifying single nucleotide polymorphisms (SNPs) linked to m...

Background Xanthomonas oryzae pv. Oryzae (Xoo), the causal agent of rice bacterial blight disease has been extensively characterized and loci against different races identified. Many rice cultivars have been developed and utilized to combat the disease, however due to rapid evolution of Xoo, a number of resistances have broken-down. The continuous...

Background: Xanthomonas oryzae pv. Oryzae (Xoo), the causal agent of rice bacterial blight disease has been extensively characterized and loci against different races identified. Many rice cultivars have been developed and utilized to combat the disease, however due to rapid evolution of Xoo, a number of resistances have broken-down. The continuous...

This study employed an extended theory of planned behaviour to assess the socio-psychological factors influencing farmers’ willingness to continue participating (WTCP) in collaborative activities of community-based innovation platforms (CB-IPs). Using a structured questionnaire, data were obtained from a random sample of 231 farmers who had partici...

Sterility in edible bananas is as a result of a long history of anthropogenic-driven selection for sterile genotypes, since seed is not desirable in fruit pulp for human consumption. However, this poses a challenge to conventional genetic improvement by slowing breeding pipelines. In this study, we investigated whether pollen tubes reach all parts...

Sterility and low seed set in bananas is the main challenge to their conventional genetic improvement. The first step to seed set in a banana breeding program depends on pollination at the right time to ensure effective fertilization. This study aimed at determining bract opening time (BOT) to enhance efficient pollination and seed set in bananas....

Seed set in banana is influenced by weather, yet the key weather attributes and the critical period of influence are unknown. We therefore investigated the influence of weather during floral development for a better perspective of seed set increase. Three East African highland cooking bananas (EAHBs) were pollinated with pollen fertile wild banana...

The yield and protein performance in a soybean genotype result from its interaction with the prevailing environmental conditions. This makes selecting the best genotypes under varied target production environments more complex. This study’s objectives were to determine protein content and protein stability of 30 elite soybean genotypes in major soy...

Seed set in East African Highland Cooking bananas (EAHBs) is extremely low and therefore hampers breeding. Pollen–pistil interaction is a key contributing factor. We assessed the effect of pollen germination media (PGM) on seed set in EAHBs. Five EAHB cultivars were pollinated with pollen from the wild banana ‘Calcutta 4’. Glucose-based PGM sprayed...

Low female fertility in bananas is the biggest hurdle for banana breeding. The aim of this study was to determine seed set patterns in East African Highland Cooking bananas (EAHBs) to inform future decisions on a more targeted approach of increasing seed set and subsequently banana-breeding efficiency. Matooke (AAA) and Mchare (AA) bananas are gene...

The cassava breeding program in Uganda has released many improved cultivars resistant/tolerant to cassava brown streak disease (CBSD) and cassava mosaic disease (CMD). However, many farmers have continued to use cultivars that are susceptible to these major viral diseases but with diverse attributes. There is a need to understand farmers' cassava c...

Potatoes are prone to attack by multiple viruses, which contribute greatly to yield and quality decline depending on the cultivar and the virus involved. This study investigated the effect of co-infection involving Potato virus Y (potyvirus) and Potato leafroll Virus (pelero virus) on productivity of five potato cultivars in Uganda and the nature o...

Cassava brown streak disease (CBSD) and cassava mosaic disease (CMD) are the major viral diseases of cassava in Uganda. Although isolation distance of “50 m” has been recommended by MAAIF in Uganda for prevention of virus infections in crops, the minimum isolation distance has not been verified for effectiveness in cassava. This study assessed the...

Background: Seed set in banana (Musa spp.) is influenced by weather but the most critical weather attribute(s) and the critical period are unknown. Such information is of paramount importance to increase seed set for banana breeding programs. Three female fertile East African cooking bananas (EACBs), ‘Enzirabahima’ (AAA), ‘Mshale’ (AA), and ‘Nshono...

Background: Low female fertility in bananas is the biggest hurdle for banana breeding. The aim of this study was to determine seed set patterns in East African cooking bananas EACBs to inform future decisions on a more targeted approach of increasing seed set and subsequently banana breeding efficiency. Matooke (AAA) and Mchare (AA) bananas are gen...

Poor stigma receptivity is one of the limitations to seed set in East African Highland Bananas (EAHBs) that constrains their improvement through conventional breeding. This study was aimed at identifying a suitable pollen germination media (PGM) for faster germination of banana pollen both in vitro and in vivo. PGM was prepared by dissolving 0.01g...

Viruses limit sweetpotato (Ipomoea batatas) production worldwide. Many sweetpotato landraces in East Africa are, however, largely virus‐free. Moreover, some plants infected by the prevalent Sweet potato feathery mottle virus (SPFMV) may be able to revert to virus‐free status. In this study, we analysed reversion from SPFMV, Sweet potato virus C, Sw...

Sweetpotato virus disease (SPVD) causes more than 90 percent yield decline, especially in areas with high disease pressure. In central Uganda region, Ejumula, an SPVD susceptible variety almost disappeared on farmers' fields due to SPVD by fourth implementation year HarvestPlus project in 2010. In response, research-development partnerships conduct...

Here, we present the first near-complete genome of Ugandan Passiflora virus (UPV) sequenced from a symptomatic sample of KH7 passion fruit (Passiflora edulis Sims) variety. UPV had limited amino acid identity with other potyviruses known to cause passion fruit woodiness disease (PWD). The closest relationship (71.2% amino acid similarity) was with...

Here, we present the first near-complete genome of Ugandan Passiflora virus (UPV) sequenced from a symptomatic sample of KH7 passion fruit ( Passiflora edulis Sims) variety. UPV had limited amino acid identity with other potyviruses known to cause passion fruit woodiness disease (PWD). The closest relationship (71.2% amino acid similarity) was with...

In sweet potato, an anti-virus defense mechanism termed reversion has been postulated to lead to virus freedom from once infected plants. The objectives of this study were to identify anti-virus defense genes and evaluate their segregation in progenies. Reference genes from different plant species were used to assemble transcript sequences of each...

Sweetpotato is usually propagated in Uganda by vine cuttings from mature crops, but sometimes sprouts from storage roots are used, especially in drought-prone areas. No information is available on whether the storage of roots of Ugandan cultivars are infected with the viruses and whether the sprouts on them express symptoms so that farmers can elim...

Cowpea (Vigna unguiculata L. Walp) grain constitutes an important source of protein for several households in Sub-Saharan Africa. However, widespread occurrence of viral diseases is a serious constraint to productivity of the crop and its nutritional value in terms of grain protein content. This study was carried out to identify cowpea genotypes wi...

We present here the first complete genome sequence of Cowpea aphid-borne mosaic virus (CABMV) isolated from cowpea in Uganda and compare it with five CABMV complete genome sequences from Brazil (2), India (2), and Zimbabwe (1). It most resembled the genomes of two Brazilian isolates (MG-Avr and BR1) and one Indian isolate (RR3).

Illumina sequencing of RNA from a cassava cutting from northern Malawi produced a genome of Ugandan cassava brown streak virus (UCBSV-MW-NB7_2013). Sequence comparisons revealed stronger similarity to an isolate from nearby Tanzania (93.4% pairwise nucleotide identity) than to those previously reported from Malawi (86.9 to 87.0%).

The incidence and severity of sweetpotato virus disease (SPVD) was reported to be highly variable under different agroecological zones in Uganda, a situation that could be partly attributable to differences in temperature. This raised a need for understanding the effect of temperature on the biology of SPVD causative agents which ultimately influen...

Background Cassava brown streak disease is emerging as the most important viral disease of cassava in Africa, and is consequently a threat to food security. Two distinct species of the genus Ipomovirus (family Potyviridae) cause the disease: Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV). To understand the evolutio...

Viruses infecting wild flora may have a significant negative impact on nearby crops, and vice-versa. Only limited information is available on wild species able to host economically important viruses that infect sweetpotatoes (Ipomoea batatas). In this study, Sweet potato chlorotic fleck virus (SPCFV; Carlavirus, Betaflexiviridae) and Sweet potato c...

Number of plants sampled from wild species and cultivated sweetpotato for detection of SPCFV in different agro-ecological zones of Uganda in 2004 and 2007. (DOC)

Nucleic acid–binding protein (NaBP) nucleotide sequence (399 nt, upper diagonal) and amino acid sequence (133 aa, lower diagonal) identities (%) of 32 SPCFV isolates. (DOC)

3′-untranslated region (3′-UTR) nucleotide sequence identities (%) of 32 SPCFV isolates. (DOC)

Coat protein (CP) nucleotide sequence (897 nt, upper diagonal) and amino acid sequence (299 aa, lower diagonal) identities (%) of 38 SPCFV isolates. (DOC)

Cowpea is important for food and income for many households in drought prone areas of Uganda. The seed is a rich source of dietary protein (23-32%), minerals and vitamins. The crop improves soil fertility through nitrogen fixation as well providing nutritious fodder for livestock. Viral infection of cowpea greatly reduces both productivity and nutr...

Artificial miRNAs (amiRNA) were generated targeting conserved sequences within the genomes of the two causal agents of Cassava brown streak disease (CBSD): Cassava brown streak virus (CBSV) and Ugandan cassava brown streak virus (UCBSV). Transient expression studies on ten amiRNAs targeting 21 nt conserved sequences of P1(CBSV and UCBSV), P3(CBSV a...

Use of plant growth hormones either singly or in combination is vital for rapid multiplication of virus-free in-vitro potato (Solanum tuberosum L. ) plantlets for the production of clean seed potato. This study was carried out at Kachwekano Zonal Agricultural Research and Development Institute, Kabale district in south-western Uganda to identify a...