scholarly journals Kasule, F Farmer Preference of Cassava Cultivars in Eastern Uganda: A Choice Beyond Disease Resistance

2020 ◽  
Vol 2 (2) ◽  
pp. p169
Author(s):  
Kasule Faizo ◽  
Peter Wasswa ◽  
Settumba Brasio Mukasa ◽  
Anthony Okiror ◽  
Selma Ndapewa Nghituwamhata ◽  
...  
Keyword(s):  
Disease Resistance ◽  
Sweet Taste ◽  
Mosaic Disease ◽  
Cassava Mosaic Disease ◽  
Viral Diseases ◽  
Eastern Region ◽  
Cassava Brown Streak Disease ◽  
Improved Cultivars ◽  
High Yields ◽  
Eastern Uganda

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 cultivar attribute preferences and CBSD, CMD prevalence on the preferred cultivars. A total of 150 cassava farmer fields (74 in Bukedea district and 76 in Kumi district) located in eastern Uganda were evaluated for farmers’ cultivars and attribute preferences, as well as prevalence of CBSD and CMD on the farmer selected cultivars. The eastern region was of interest in the study, due to it-being the major cassava producing area in the country. In addition, 30 cassava plants of different genotypes were chosen randomly along transects of each field and assessed for CBSD/CMD incidence and severity on preferred cultivars. Results showed that more than 64% of the farmers in eastern Uganda preferred NASE 03 due to its sweet taste and high yields, followed by NASE 14 (21%) because of its high yields. There was a significant (P≤0.001) correlation between cassava cultivars preferred and CBSD severity (r = -0.56), CBSD incidence (r = -0.53), CMD severity (r = -0.51) and CMD incidence (r = -0.39). In corroboration, the most preferred cultivar, NASE 03 was found most susceptible to CBSD and CMD in both Bukedea and Kumi districts with CBSD incidence of 62.2% and 52.7% and CMD incidence of 56.9% and 34.3% respectively. The results showed that CBSD and CMD are prevalent on farmer preferred cassava cultivars, and that farmer cultivar preference depends not only on disease resistance but also other attributes.

scholarly journals Genetic Gains for Yield and Virus Disease Resistance of Cassava Varieties Developed Over the Last Eight Decades in Uganda

2021 ◽  
Vol 12 ◽  
Author(s):  
Francis Manze ◽  
Patrick Rubaihayo ◽  
Alfred Ozimati ◽  
Paul Gibson ◽  
Williams Esuma ◽  
...  
Keyword(s):  
Disease Resistance ◽  
Virus Disease ◽  
Resistance Breeding ◽  
Mosaic Disease ◽  
High Yield ◽  
Cassava Mosaic Disease ◽  
Genetic Gains ◽  
Cassava Brown Streak Disease ◽  
Faster Development ◽  
Cassava Varieties

Achieving food security for an ever-increasing human population requires faster development of improved varieties. To this end, assessment of genetic gain for key traits is important to inform breeding processes. Despite the improvements made to increase production and productivity of cassava in Uganda at research level, there has been limited effort to quantify associated genetic gains. Accordingly, a study was conducted in Uganda to assess whether or not genetic improvement was evident in selected cassava traits using cassava varieties that were released from 1940 to 2019. Thirty-two varieties developed during this period, were evaluated simultaneously in three major cassava production zones; central (Namulonge), eastern (Serere), and northern (Loro). Best linear unbiased predictors (BLUPs) of the genotypic value for each clone were obtained across environments and regressed on order of release year to estimate annual genetic gains. We observed that genetic trends were mostly quadratic. On average, cassava mosaic disease (CMD) resistance increased by 1.9% per year, while annual genetic improvements in harvest index (0.0%) and fresh root yield (−5 kg per ha or −0.03% per ha) were non-substantial. For cassava brown streak disease (CBSD) resistance breeding which was only initiated in 2003, average annual genetic gains for CBSD foliar and CBSD root necrosis resistances were 2.3% and 1.5%, respectively. It’s evident that cassava breeding has largely focused on protecting yield against diseases. This underpins the need for simultaneous improvement of cassava for disease resistance and high yield for the crop to meet its current and futuristic demands for food and industry.

scholarly journals A New Type of Satellite associated with Cassava Mosaic Begomoviruses

2021 ◽  
Author(s):  
Catherine D. Aimone ◽  
Leandro De León ◽  
Mary M. Dallas ◽  
Joseph Ndunguru ◽  
José T. Ascencio-Ibáñez ◽  
...  
Keyword(s):  
Symptom Severity ◽  
Smallholder Farmers ◽  
Mosaic Disease ◽  
African Cassava Mosaic Virus ◽  
Cassava Mosaic Disease ◽  
Viral Diseases ◽  
Soil Conditions ◽  
Viral Dna ◽  
Single Stranded Dna ◽  
New Type

AbstractCassava mosaic disease (CMD), which is caused by single-stranded DNA begomoviruses, severely limits cassava production across Africa. A previous study showed that CMD symptom severity and viral DNA accumulation increase in cassava in the presence of a DNA sequence designated as SEGS-2 (sequence enhancing geminivirus symptoms). We report here that when SEGS-2 is co-inoculated with African cassava mosaic virus (ACMV) onto Arabidopsis thaliana, viral symptoms increase. Transgenic Arabidopsis with an integrated copy of SEGS-2 inoculated with ACMV also display increased symptom severity and viral DNA levels. Moreover, SEGS-2 enables Cabbage leaf curl virus (CaLCuV) to infect a geminivirus resistant Arabidopsis accession. Although SEGS-2 is related to cassava genomic sequences, an earlier study showed that it occurs as episomes and is packaged into virions in CMD-infected cassava and viruliferous whiteflies. We identified SEGS-2 episomes in SEGS-2 transgenic Arabidopsis. The episomes occur as both double-stranded and single-stranded DNA, with the single-stranded form packaged into virions. In addition, SEGS-2 episomes replicate in tobacco protoplasts in the presence, but not the absence, of ACMV DNA-A. SEGS-2 episomes contain a SEGS-2 derived promoter and an open reading frame with the potential to encode a 75-amino acid protein. An ATG mutation at the beginning of the SEGS-2 coding region does not enhance ACMV infection in Arabidopsis. Together, the results established that SEGS-2 is a new type of begomovirus satellite that enhances viral disease through the action of a SEGS-2 encoded protein that may also be encoded in the cassava genome.IMPORTANCECassava is an important root crop in the developing world and a food and income crop for more than 300 million African farmers. Cassava is rising in global importance and trade as the demands for biofuels and commercial starch increase. More than half of the world’s cassava is produced in Africa, where it is primarily grown by smallholder farmers, many of whom are from the poorest villages. Although cassava can grow under high temperature, drought and poor soil conditions, its production is severely limited by viral diseases. Cassava mosaic disease (CMD) is one of the most important viral diseases of cassava and can cause up to 100% yield losses. We provide evidence that SEGS-2, which was originally isolated from cassava crops displaying severe and atypical CMD symptoms in Tanzanian fields, is a novel begomovirus satellite that can compromise the development of durable CMD resistance.

Marker-Assisted Breeding for Cassava Mosaic Disease Resistance

2013 ◽  
pp. 291-325 ◽  
Author(s):  
E. Okogbenin ◽  
I. Moreno ◽  
J. Tomkins ◽  
C. M. Fauquet ◽  
G. Mkamilo ◽  
...  
Keyword(s):  
Disease Resistance ◽  
Mosaic Disease ◽  
Cassava Mosaic Disease ◽  
Marker Assisted Breeding

scholarly journals Field Evaluation of Some Cassava Cultivars against the African Cassava Mosaic Disease in the Humid Forests of Cameroon

2019 ◽  
pp. 1-8
Author(s):  
A. Mogo ◽  
J. Fomekong Nopogwo ◽  
E. L. Ngonkeu Mangaptche ◽  
R. Ghogomu Tamouh ◽  
E. Temgoua ◽  
...  
Keyword(s):  
Large Scale ◽  
Block Design ◽  
Field Evaluation ◽  
Mosaic Disease ◽  
Annual Production ◽  
Cassava Mosaic Disease ◽  
Yield Performance ◽  
Randomized Complete Block Design ◽  
Cassava Production ◽  
Improved Cultivars

There is a considerable deficit in the annual production of cassava in Cameroon of about 31 million tons, and this has been mainly due to constraints related to pest attacks and most especially diseases like the African Cassava Mosaic Disease (ACMD). This study was therefore undertaken on three sites in the locality of Bityili (South Region of Cameroon), to determine amongst improved and local cassava cultivars those that provide resistance to the development of the ACMD. The severity and incidence of this disease was evaluated and its impact on cassava yield. In each site, cassava was grown in a randomized complete block design. The local cultivars (Ekobele and Ngon kribi) showed higher severity (76-100%) and incidence of ACMD compared to the improved cultivars (TMS 92/0326 and TMS 96/1414) of 0-25% and 0-10%, respectively. Strong inverse correlations were observed between ACMD severity and yield performance, measured in terms of number of tubers/plant and weight of fresh tubers. The improved cultivars, TMS 92/0326 and TMS 96/1414, could, therefore, be recommended for large-scale planting in a bid to promote cassava production in the South Region of Cameroon.

scholarly journals Effective isolation distance for prevention of cassava virus infections in Uganda

2020 ◽  
Vol 28 (s1) ◽  
pp. 1-13
Author(s):  
F. Kasule ◽  
P. Wasswa ◽  
S.B. Mukasa ◽  
A. Okiror ◽  
A.W. Mwang’ombe
Keyword(s):  
Tissue Culture ◽  
Agricultural Research ◽  
Block Design ◽  
Mosaic Disease ◽  
Cassava Mosaic Disease ◽  
Viral Diseases ◽  
Virus Infections ◽  
Isolation Distance ◽  
Isolation Distances ◽  
Research Institute

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 effective isolation distance for management of viral diseases in cassava. Virus-clean cassava cultivars (NASE 03, NASE 14 and NAROCASS 1) from farmers’ fields were used as field sourced (FS) planting materials. Tissue culture (TC) material of the same cultivars were sourced from the National Crops Resources Research Institute and Makerere University Agricultural Research Institute tissue culture laboratories. Both FS and TC materials were tested at isolation distances of 50, 100, 150 and 250 m for virus prevention. The experiment was laid out in a randomised complete block design and was run for 12 months after planting (MAP). Mean CBSD/CMD prevalence significantly varied (P<0.05) among isolation distances in both FS and TC plants, and the 250 m isolation distance was the most effective in reducing disease prevalence. Across cultivars and planting material category at 12 MAP, the 50 m isolation distance had the highest foliar incidence for CBSD (29.2%) and CMD (16.1%); while severity for CBSD was 1.4 and 1.2 for CMD. At 250 m, all FS and TC plants had CBSD/CMD severity of 1.0 and 0% incidence. These results show that 250 m isolation distance can provide an option to disseminate popular, but CBSD/CMD susceptible cassava cultivars thereby manage CBSD/CMD.  

Disease resistance characterisation of improved cassava genotypes to cassava mosaic disease at different ecozones

2015 ◽  
Vol 48 (6) ◽  
pp. 504-518 ◽  
Author(s):  
Oluwole A. Ariyo ◽  
Alfred G.O. Dixon ◽  
Gabriel I. Atiri ◽  
Emma W. Gachomo ◽  
Simeon O. Kotchoni
Keyword(s):  
Disease Resistance ◽  
Mosaic Disease ◽  
Cassava Mosaic Disease

scholarly journals Evaluation of Newly Released Cassava Varieties for Yield Performance, Reactions to Cassava Diseases and Farmers’ Preference in Adjumani District of Uganda

2021 ◽  
Vol 13 (4) ◽  
pp. 84
Author(s):  
Alex Abaca ◽  
Emmanuel Odama ◽  
Alfred Komakech ◽  
Baron Asiku ◽  
Andema A. Andrews ◽  
...  
Keyword(s):  
Mosaic Disease ◽  
Cassava Mosaic Disease ◽  
Yield Performance ◽  
Foliar Symptoms ◽  
Information Gap ◽  
Root Necrosis ◽  
Cassava Brown Streak Disease ◽  
New Varieties ◽  
Rot Disease ◽  
Cassava Varieties

Cassava viral diseases particularly cassava brown streak disease (CBSD) and cassava mosaic disease (CMD) have put pressure on cassava breeders to develop varieties that are resistant/tolerant to them. Several cassava varieties have been rolled out to farmers with the latest being NAROCASS series that are tolerant to these diseases. The yield performance of these new varieties have not been documented in some sub zones like Adjumani district that falls within a major West Nile agro-ecology of Uganda. Therefore this study sought to established yield performances of, reactions to major diseases, and farmers&rsquo; preference to these newly released cassava varieties in Adjumani. Results showed significant (P &le; 0.05) differences among cassava varieties and experimental sites for all the parameters evaluated. Average yield performance by varieties were in the order of a local cassava&mdash;Alifasia (8.7 t/Ha) lowest, NAROCASS 2 (18.55 t/Ha), NASE 14 (33.97 t/Ha), NASE 19 (41.26 t/Ha), and NAROCASS 1 (41.71 t/Ha) highest. CMD foliar symptom was present at all sites on a local cassava&mdash;Alifasia, and on NAROCASS 1 in Ayiri parish, Ukusijoni sub-county. CBSD foliar symptoms were observed on off-types (TME 14) in the plot of NASE 14 in Miniki Parish only whereas CBSD root necrosis was observed at all sites on the local cassava&mdash;Alifasia, and on NASE 19 in Maaji parish, Ukusijoni sub-county. Cassava root rot disease was localised in Ukusijoni sub-county only. Farmers&rsquo; preferences to these newly released cassava varieties were in the order of NASE 19 (40.96%), NAROCASS 1 (24.86%), NAROCASS 2 (15.82.28%), NASE 14 (15.54%), and a Local cassava&mdash;Alifasia (2.83%). Result from this study strengthens the information gap in the breeding process towards developing a cassava variety with farmer-preferred attributes, and can also inform the utilisation of these improved cassava varieties in Adjumani district.

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