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Gene action controlling cassava brown streak disease resistance and storage root yield in cassava

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Michael M Chipeta at Lilongwe University of Agriculture and Natural Resources
Michael M Chipeta
Rob Melis at University of KwaZulu-Natal
Rob Melis
Paul Shanahan at University of KwaZulu-Natal
Paul Shanahan
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Abstract and Figures

Cassava (Manihot esculenta Crantz) brown streak disease (CBSD) is currently one of the major constraints to sustained cassava production in Malawi. Its economic impact is mainly manifested in the storage roots where it causes pitting, necrosis and constriction. CBSD can effectively be managed by using resistant varieties as well as early harvesting especially if the varieties are early bulking (high storage root yield). However, development of resistant and high storage root bulking varieties requires an understanding of gene action controlling inheritance of the two traits. Currently, there is very little information in Malawi regarding the inheritance pattern and relative importance of general (GCA) and specific combining ability (SCA) of these two traits. Therefore, a study was conducted to determine mode of gene action as well as importance of GCA and SCA in the genetic control of CBSD resistance and storage root yield. Information generated is essential in the selection of parents and breeding strategies for an effective breeding programme. Thirty-six crosses were generated using a 6 × 6 North Carolina Design II and later evaluated for CBSD resistance and storage root bulking at two locations using a triple square lattice design. Data for the progenies were analysed using REML in Genstat (17th ed.) while family (crosses) data were analysed using a PROC Mixed procedure performed in SAS® 9.3 Software. The GCAf × location, GCAm × location and SCA × location interaction effects were highly significant (P < 0.01) for CBSDS and CBSDI. Pooled analysis across two locations showed highly significant (P < 0.01) variance among GCA due to females (GCAf) and GCA due to males (GCAm) for FSRY. These GCAf, GCAm and female × male interaction (SCA) effects accounted for 19.8, 33.4 and 46.7% of the sum of squares for CBSDS, respectively. The results suggested that additive gene effects predominantly controlled CBSD resistance and high storage root bulking. Four parental genotypes (Silira, Mulola, Phoso and Mkondezi) were identified as the best general combiners for the CBSD, high storage root bulking and other traits. Thirteen progenies exhibiting CBSD resistance and high storage root bulking were identified and selected for advancement.
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Gene action controlling cassava brown streak disease
resistance and storage root yield in cassava
Michael M. Chipeta .Rob Melis .Paul Shanahan
Received: 24 February 2017 / Accepted: 5 June 2018 / Published online: 14 June 2018
ÓSpringer Nature B.V. 2018
Abstract Cassava (Manihot esculenta Crantz)
brown streak disease (CBSD) is currently one of the
major constraints to sustained cassava production in
Malawi. Its economic impact is mainly manifested in
the storage roots where it causes pitting, necrosis and
constriction. CBSD can effectively be managed by
using resistant varieties as well as early harvesting
especially if the varieties are early bulking (high
storage root yield). However, development of resistant
and high storage root bulking varieties requires an
understanding of gene action controlling inheritance
of the two traits. Currently, there is very little
information in Malawi regarding the inheritance
pattern and relative importance of general (GCA)
and specific combining ability (SCA) of these two
traits. Therefore, a study was conducted to determine
mode of gene action as well as importance of GCA and
SCA in the genetic control of CBSD resistance and
storage root yield. Information generated is essential
in the selection of parents and breeding strategies for
an effective breeding programme. Thirty-six crosses
were generated using a 6 96 North Carolina Design
II and later evaluated for CBSD resistance and storage
root bulking at two locations using a triple square
lattice design. Data for the progenies were analysed
using REML in Genstat (17th ed.) while family
(crosses) data were analysed using a PROC Mixed
procedure performed in SAS
Ò
9.3 Software. The
GCA
f
9location, GCA
m
9location and SCA 9lo-
cation interaction effects were highly significant
(P\0.01) for CBSDS and CBSDI. Pooled analysis
across two locations showed highly significant
(P\0.01) variance among GCA due to females
(GCA
f
) and GCA due to males (GCA
m
) for FSRY.
These GCA
f
, GCA
m
and female 9male interaction
(SCA) effects accounted for 19.8, 33.4 and 46.7% of
the sum of squares for CBSDS, respectively. The
results suggested that additive gene effects predomi-
nantly controlled CBSD resistance and high storage
root bulking. Four parental genotypes (Silira, Mulola,
Phoso and Mkondezi) were identified as the best
general combiners for the CBSD, high storage root
bulking and other traits. Thirteen progenies exhibiting
CBSD resistance and high storage root bulking were
identified and selected for advancement.
Keywords Breeding strategies Combining ability
Necrosis Progenies Fresh storage roots
M. M. Chipeta (&)R. Melis P. Shanahan
African Centre for Crop Improvement, University of
KwaZulu-Natal, P. Bag X01, Scottsville,
Pietermaritzburg, Republic of South Africa
e-mail: chipetamichael@gmail.com
M. M. Chipeta
Lilongwe University of Agriculture and Natural
Resources, Bunda Campus, P.O BOX 219, Lilongwe,
Malawi
123
Euphytica (2018) 214:104
https://doi.org/10.1007/s10681-018-2196-1
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... However, challenges remain due to whitefly vectors, variations in virus strain, and environmental conditions that can impact the consistent and durable expression of resistance across generations [13]. The previous studies reported that the resistance to CBSD is controlled by additive gene action [14,15,16] and non-additive gene action as reported in previous studies [17,18]. Other related diseases/pests of importance to cassava, Cassava Mosaic Disease (CMD) was reported to be influenced by additive gene action [15] and non-additive [19], and resistance to Cassava green mites reported to be influenced by additive gene action [20] and the seventeen candidate genes associated with its resistance [21]. ...
... The substantial significance of specific combining ability (SCA) results, on the other hand, suggested the presence of dominance and epistatic effects. The observed significance of GCA across all the traits underscored the predominance of additive genes in the expression of the traits for CBSDLS, CBSDRS, and fresh yield (FRYLD) [17] , CBSDLI (Chipeta et al., 2018) and HI [23]. The non-significance of SCA for CBSDRI, CMDS, CMDI, HI and DMC indicated that parental interactions do not significantly influence the performance of their hybrids, suggesting a relatively stronger influence of additive gene effects compared to non-additive effects. ...
Unlocking CBSD Resistance in Cassava: Insight From Genetic Variability and Combining Ability
Preprint
Full-text available
  • Jul 2024
Cassava brown streak disease (CBSD) threatens cassava production in sub-Saharan Africa despite the availability of resistant varieties since extreme environmental factors weakens plant defenses hence reduce CBSD resistance. This study examined the inheritance of CBSD in cassava populations, assessed genetic variability and identified superior sources of resistance through F1, S1 and half-sib offspring of populations derived from resistant sources. The offsprings underwent field evaluation at two distinct sites from 2019 to 2021, and the symptoms free genotypes were analyzed using reverse transcription quantitative polymerase chain reaction (RT-qPCR). Resistance to CBSD was categorized as most resistant, resistant, most tolerant and tolerant based on symptoms and virus titer. The findings of the study indicate that the resistance to Cassava Brown Streak Disease (CBSD) is highly influenced by genotypes, F1/S1 types, and environmental conditions. The analysis of combining abilities revealed significant general combining abilities (GCA) for CBSD, cassava mosaic disease (CMD), and traits associated with yield. The heritability estimates for resistance to CBSD varied between 43.4% to 63.2% for foliar symptoms and 14.6% to 57.9% for root necrosis across locations. The inheritance pattern involved a combination of additive and recessive genes and selfed (S1) populations displayed stronger and effective resistance to the disease. There was a high prevalence of cassava brown streak virus (CBSV) and a low prevalence of Ugandan cassava brown streak virus (UCBSV). Four genotypes were identified to be highly resistant to Cassava Brown Streak Disease (CBSD) that could be used as key sources of resistance to CBSD.
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... The genetic observed variation within and between populations in this study emphasized the role of the selfed populations in enhancing selection breeding. The results indicated that resistance to CBSD was primarily controlled by an additive mode of gene action, consistent with the previous studies by Chipeta et al. [16] and Nduwumuremyi et al. [14]. Furthermore, identifying the genotypes most resistant to CBSD across various locations highlighted the importance of utilizing different locations in the selection process [31]. ...
Unlocking Cassava Brown Streak Disease Resistance in Cassava: Insights from Genetic Variability and Combining Ability
Article
Full-text available
  • Sep 2024
Cassava brown streak disease (CBSD) threatens cassava production in sub-Saharan Africa despite the availability of resistant varieties. Extreme environmental factors weaken plant defenses, reducing CBSD resistance. This study examined CBSD inheritance in cassava populations, assessed genetic variability, and identified superior sources of resistance using F1, S1, and half-sib offspring populations derived from resistant sources. The offspring underwent field evaluation at two distinct sites from 2019 to 2021, and the symptom-free genotypes were analyzed using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Resistance to CBSD was categorized as most resistant, resistant, most tolerant, or tolerant based on symptoms and virus titers. The findings indicated that the resistance to CBSD is highly influenced by genotypes, F1/S1 types, and environmental conditions. An analysis of combining abilities revealed significant general combining abilities (GCAs) for CBSD, cassava mosaic disease (CMD), and traits associated with yield. The heritability estimates for resistance to CBSD varied between 43.4% and 63.2% for foliar symptoms and 14.6% and 57.9% for root necrosis across locations. The inheritance pattern involved a combination of additive and recessive genes with selfed (S1) populations displaying stronger and more effective resistance to the disease. The cassava brown streak virus (CBSV) was highly prevalent, and the Ugandan cassava brown streak virus (UCBSV) was not prevalent. Four genotypes were highly resistant to CBSD and could be key sources of resistance to this disease.
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... Results of this study showed that both GCA and SCA were significant for CBSD resistance. The Chigoma and Mulalei genotypes appeared as good candidates to be used as parental lines in breeding programs for CBSD resistance, while preserving other desired traits such as good yield and root characteristics [101] . ...
Breeding strategies for mitigating cassava brown streak disease in Africa
Article
Full-text available
  • Feb 2024
Cassava (Manihot esculenta Crantz), is an important staple crop for about 800 million people worldwide, and a key commodity for the starch industry. However, the potential cassava production is limited by several biotic constraints amongst which cassava brown streak disease (CBSD) is the most economically important disease in Africa. To date, the most sustainable strategy to control CBSD is the use of resistant varieties and the supply of disease-free planting materials to cassava farmers. CBSD breeding activities were initiated in Tanzania in the 1930's and Manihot glaziovii species was used as a donor parent to generate resistant hybrids. Joint regional initiatives through variety development and virus-elimination methods have been vital for CBSD management in the last two decades. While conventional breeding is tedious and sources of broad-spectrum resistance are not always available to improve cassava, new plant breeding technologies (NPBTs) appears as a valuable and complementary tool to generate virus resistance as well as to speed up and scale up cassava breeding efforts towards CBSD resistance. This review presents the breeding strategies which have so far been used to manage the CBSD disease and discusses the advantages of integrating NPBTs in current cassava breeding programs to rapidly deliver CBSD-resistant varieties to farmers in Africa.
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... These genetic gains for CBSD resistance within such a relatively short timeframe could be attributed to the concerted and systematic approaches taken to harness and utilize available genetic resources in cassava breeding (Abaca et al., 2012;Kaweesi et al., 2014;Pariyo et al., 2015;Kawuki et al., 2016;Okul et al., 2018;Ozimati et al., 2018). Predominance of additive gene effects for CBSD resistance (Kulembeka et al., 2012;Chipeta et al., 2018), which can be exploited through recurrent selection, have equally enabled consolidation of gains. ...
Genetic Gains for Yield and Virus Disease Resistance of Cassava Varieties Developed Over the Last Eight Decades in Uganda
Article
Full-text available
  • Jun 2021
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.
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Exploring the Quantitative Genetics of Essential Oil Components in Coriandrum sativum L. Under Different Water Regimes
Article
  • Dec 2022
Coriander is one of the most popular essential oil (EO) source in Apiaceae family and economically important. This study aimed to evaluate the genetic combining ability and inheritance nature in coriander for EO components. A set of 4 × 4 one-way diallel crosses were performed between four genetically divers genotypes. The plant materials (hybrids + parents) were evaluated under well-watered (WW) and water deficit stressed (WDS) irrigation regimes. Linalool (65.96% in WW; 69.45% in WDS) and geranyl acetate (12.92% in WW; 15.58% in WDS) composed a large percent of the total EO content in both irrigation regimes. WDS had an increasing effect on linalool, geranyl acetate, o-cymene and geraniol content. Significant genotypic and genotype × irrigation regime effects observed for EO components which are due to differences in the genome alleles content and alleles action. The significant general combining ability (GCA) and specific combining ability (SCA) effects for EO components reveal the presence of both additive and dominance gene actions. Genetic control pattern of o-cymene, γ-terpinene and citronellol in WDS regime were similar to WW while the preponderance of additive gene effects increased for α-pinene and linalool. In conclusion, consideration the GCA and SCA values and inheritance nature of the EO components, selection for high linalool, α-pinene and geranyl acetate content in segregating generations derived from H1×4 (a hybrid derived crossing between parent 1 and parent 4) hybrid should be delayed to F3 generation.
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Conventional breeding, marker-assisted selection, genomic selection and inbreeding in clonally propagated crops: a case study for cassava
Article
Full-text available
  • Jun 2015
  • THEOR APPL GENET
Key message: Consolidates relevant molecular and phenotypic information on cassava to demonstrate relevance of heterosis, and alternatives to exploit it by integrating different tools. Ideas are useful to other asexually reproduced crops. Asexually propagated crops offer the advantage that all genetic effects can be exploited in farmers' production fields. However, non-additive effects complicate selection because, while influencing the performance of the materials under evaluation, they cannot be transmitted efficiently to the following cycle of selection. Cassava can be used as a model crop for asexually propagated crops because of its diploid nature and the absence of (known) incompatibility effects. New technologies such as genomic selection (GS), use of inbred progenitors based on doubled haploids and induction of flowering can be employed for accelerating genetic gains in cassava. Available information suggests that heterosis, non-additive genetic effects and within-family variation are relatively large for complex traits such as fresh root yield, moderate for dry matter or starch content in the roots, and low for defensive traits (pest and disease resistance) and plant architecture. The present article considers the potential impact of different technologies for maximizing gains for key traits in cassava, and highlights the advantages of integrating them. Exploiting heterosis would be optimized through the implementation of reciprocal recurrent selection. The advantages of using inbred progenitors would allow shifting the current cassava phenotypic recurrent selection method into line improvement, which in turn would allow designing outstanding hybrids rather than finding them by trial and error.
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The viruses and virus diseases of cassava.
Chapter
  • Mar 2002
This multi-author book covers all aspects of cassava biology, breeding, production, crop protection and utilization. The first section of the book is on the origins, distribution and economic importance of cassava, and includes chapters on cassava in South America and the Caribbean, Africa, and Asia and the Pacific. Three chapters in the second section cover botany and physiology, agronomy and cropping systems, and mineral nutrition and fertilization. The section on genetics and crop improvement includes chapters on breeding, genetic resources and conservation, and cassava biotechnology. A crop protection section has chapters on arthropod pests, virus diseases, and bacterial, fungal and nematode diseases. The final two chapters are concerned with utilization, storage and processing of cassava.
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Early storage root bulking index and agronomic traits associated with early bulking in cassava
Article
  • Sep 2016
  • FIELD CROP RES
One of the attempts by farmers in counteracting the devastating effects of cassava brown streak disease(CBSD) on yield and quality of cassava is early harvesting. However, most varieties grown by farmersare often late bulking which increases the disease severity while on the other hand early harvestingresults in significant yield losses. Farmers, therefore, need early storage root bulking cassava varieties inorder to reduce the time to harvest leading to a faster rate of return to investment, while at the sametime avoiding devastating effects of CBSD on yield and quality of cassava. The study was, therefore,conducted to identify high-yielding and early storage root bulking cassava genotypes as well as traitsassociated with early storage root bulking and estimate yield loss if any due to early harvesting. Theoverall aim was to generate information that would guide future improvement programmes for high-yielding and early-bulking cassava varieties in Malawi and other countries facing similar challenges. Trialswere implemented using a square lattice design with three replications at two locations for two growingseasons with three harvest intervals (6, 9 and 12 months after planting, MAP). High yields were obtainedof up to 9.5 t/ha at 6 and 17.8 t/ha at 9 MAP. Furthermore, the study revealed that yields obtained at 9MAP were higher than those obtained at 12 MAP for some genotypes which suggests that such genotypeswould be considered as early storage root bulking. Simple correlation analysis identified harvest index,storage root number, storage root diameter and storage root length as the selection criteria to achievehigh fresh storage root yield (t/ha) and dry mass yield (t/ha). Path coefficient analysis allocated harvestindex and shoot mass as the major selection criteria in improving fresh storage yield and dry mass yield.The study suggests that both source and sink capacities were important for determining early yield.Therefore, these two traits are the key determinants of early storage root bulking and should be usedwhen selecting early-bulking cultivars and indirectly selecting for storage root number, storage rootdiameter and storage root length.
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Farmers' knowledge of cassava brown streak disease and its management in Malawi
Article
  • Apr 2016
There is little information on farmers’ knowledge about cassava (Manihot esculenta Crantz) brown streak disease (CBSD), despite extensive studies on incidences and severities. The objective of this study was to assess farmers’ knowledge of CBSD diagnosis and management. The study was conducted in three districts of Malawi by administering semi-structured interviews in combination with disease incidence and severity surveys. Farmers’ knowledge of disease diagnosis and management was associated with CBSD incidence and severity. High levels of knowledge about CBSD were observed in areas with high disease incidence. Only 10.1% of the farmers were capable of identifying the foliar symptoms of the disease. On average, 75.0% and 71.7% of the farms had leaf and storage root incidences, respectively. At harvest, 88.3% of the farmers’ fields exhibited storage root necrosis. CBSD leaf and storage root severities differed significantly (P < 0.001) from one district to the other and between varieties. Most farmers were found to lack a source of clean planting material. High needs for extension services on cassava cultivation methods and pest management were identified, but few farmers received such services. The lack of new improved varieties was reported as the most important constraint of cassava production, beyond CBSD. Education of farmers on the efficient management of this viral disease through selection of clean planting material should be provided. Additionally, the development of early root bulking cultivars as a long-term solution in avoiding CBSD impact should be supported.
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