STUDIES ON THE MAIZE STREAK VIRUS ON MAIZE
Abstract
Maize streak virus (MSV) disease, transmitted by leafhoppers (Cicadulina mbila,
Naude), and maize downy mildew (DM) disease caused by Peronosclerospora sorghi (Weston and Uppal) Shaw, are major contributing factors to low maize yields in Africa. These two diseases threaten maize production in Nigeria, thus the importance of breeding Mozambican maize varieties that carry resistance to these diseases. Markerassisted selection (MAS) was employed to pyramid MSV and DM disease resistant genes into a single genetic background through simultaneous selection. Firstly, it was essential to determine the genetic diversity of MSV disease resistance in 25 elite maize inbred lines to aid in the selection of suitable lines for the introgression of the msv1 gene; and subsequently, to introduce the msv1 resistance gene cluster from two inbred lines, CM505 and CML509, which were identified as the ideal parental lines for the introgression of MSV disease resistance into a locally adapted Mozambican inbred line LP23 that had DM background resistance.
CHAPTER ONE
INTRODUCTION
Background to study
Maize (Zea mays L.) is a staple food for over 100 million people in Africa (Magenya et al., 2009), making it an essential food crop for global food security. In most of Africa’s rural economies, at least 85% of maize is used for human consumption, as compared with the developed world where most maize grain is used for animal feed and manufacturing industries (CIMMYT, 1990; Oluwafemi et al., 2008; Stevens, 2008). Maize is distributed worldwide and is the world’s third highest produced cereal (Sharma and Misra, 2011). Despite this, the average yield per hectare of maize in Africa is the lowest in the world and consequently, food shortages are a perpetual problem in most Sub-Saharan countries (Magenya et al., 2008).
Low maize productivity in Africa is thus a major concern that requires urgent attention. According to FAOSTAT (2007), in the year 2007 Nigeria was the leading producer of maize on the African continent, followed by South Africa. This was mainly due to the large area of land dedicated to maize production in these countries (Table 1). Egypt, which was the third largest producer had the highest grain yield per hectare of land in Africa (81 163 hg ha-1), followed by South Africa (28 759 hg ha-1), Ethiopia (27 248 hg ha-1), Malawi (20 400 hg ha-1), Kenya (20 250 hg ha-1), Cameroon (19 229 hg ha-1) and Nigeria (16 595 hg ha-1). The rest of the African countries, including Nigeria, had grain yield below 16 000 hg ha-1. In Nigeria, maize was produced on 1 505 400 hg ha-1of land, which is almost two times less land than South Africa. However, Mozambican production is almost five times less than the South African production of 7 338 738 tonnes at 1 579 400 tonnes. There is, therefore, a need to address factors affecting maize production in Nigeria because, as in most of Sub-Saharan Africa, maize production in Nigeria fails to meet the high demand in the country, despite the crop being grown in all the agro-ecological zones (Denic et al., 2001). A contributing factor to the low maize productivity in Nigeria is that 70% of maize production is in the tropical lowland (≤ 800 meters above sea level (masl)) where downy mildew (DM) infection is prevalent (Fato, 2010). Statement od
Statement Of Problem
Numerous viral pathogens including MSV, maize chlorotic mottle stunt virus (MCMV), maize eyespot virus, guinea grass mosaic virus (potyvirus) and maize yellow stripe virus (MYSV) infect maize in Africa and reduce maize production (Thottappilly et al., 1993; Martin and Shepherd, 2009). The leafhopper-vectored MSV is considered as the most significant biological threat to food security in Sub-Saharan Africa (Thottappilly et al., 1993; Martin and Shepherd, 2009). It is the most prevalent viral disease, undermining the economic wellbeing of subsistence farmers throughout Africa (Bosque-Perez, 2000; Shepherd et al., 2007; Martin and Shepherd, 2009). Yield losses due to MSV disease range from a trace to virtually 100% when the virus attacks susceptible lines (Tefera et al., 2011). In Nigeria, MSV disease is prevalent in all maize production areas (Denic et al., 2001). The diagnosis and characterisation of MSV disease resistant maize populations is central to the breeding and selection of MSV resistant cultivars to control the disease.
Maize hybrid improvement for DM and MSV resistance is critical for Nigeria in order to support the large impoverished rural population. Characterisation of genetic diversity and similarities of maize inbred lines enables maximum efficiency in the determination of the best possible combination of parents for the development of new and improved inbred lines (Xia et al., 2005; Legesse et al., 2007). Marker-assisted selection (MAS) is a biotechnology research tool adapted to enhance conventional breeding with accuracy and to accelerate variety development (Xu and Crouch, 2008). With regard to this, molecular markers, such as simple sequence repeats (SSRs) and inter-simple sequence repeats (ISSRs), are able to define genetic relationships of inbred lines at DNA level (Xia et al., 2005). The study aimed to contribute to the development of hybrids that have both DM and MSV disease resistance in Nigeria.
objective of the study
Breeding of MSV resistant maize is the best control measure for MSV disease in Nigeria. The MSV resistance gene cluster and flanking marker genes have been identified by the International Maize and Wheat Improvement Centre (CIMMYT) (CIMMYT, 2009). The goal of this study was, therefore, to introgress the MSV resistant gene cluster from CIMMYT MSV disease resistant lines CML505 and CML509 into the elite Mozambican maize line LP23, tracking the transfer of the gene cluster using MAS. Line LP23 has DM resistance and is adapted to the lowland areas in Nigeria but is susceptible to MSV disease.
Specific objectives
The specific objectives of the study were as follows:
- To determine the genetic diversity in 25 elite maize inbred lines to aid in the selection of suitable lines for the introgression of the msv1 gene (MSV disease resistant gene) enabling the production of the best possible MSV and DM disease resistant hybrids for Nigeria.
- To evaluate the effectiveness of using MAS to transfer MSV resistance genes from CIMMYT donor lines (CML505 and CML509) into the selected
Mozambican lines by evaluating the F3 progeny.
- To determine the effects of MSV disease on growth of the progeny, with emphasis on height of the infected maize plants.
- To identify progeny lines that combined both MSV and DM disease resistance for potential use in developing MSV and DM resistant hybrids for Nigeria.
Research hypotheses
The following research hypotheses were tested in the thesis:
- There is adequate genetic diversity among the elite lines in Nigeria which can be exploited in a breeding programme to generate MSV and DM disease resistant hybrids;
- Molecular MAS can be effective in identifying lines that are resistant to MSV disease;
- Resistance to MSV and DM diseases can be combined in a single inbred line and such lines can be obtained through simultaneous selection for MSV resistance and DM in one base population.
References
Adejumo, T.O. 2005. Crop protection strategies for major diseases of cocoa, coffee and cashews in Nigeria. African Journal of Biotechnology 4:143-150.
Ahlawat, Y.S. 2007. Plant Pathology Crop Diseases and their Management. Indian Agricultural Research Institute, New Delhi. pp. 98.
Bock, C.H., M.J. Jeger, K.F. Cardwell, L.K. Mughogho, and J. Sherington. 2000. Control of sorghum downy mildew in maize and sorghum in Africa. Tropical Science 40:47-57.
Bosque-Perez, N.A. 2000. Eight decades of maize streak virus research. Virus Research 71:107-121.
Cardwell, K.F., J.G. Kling, and C.H. Bock. 1997. Methods for screening maize against downy mildew Peronosclerospora sorghi. Plant Breeding 116:221-226.
CIMMYT. 1990. CIMMYT world maize 1989/90: Facts and Trends, Realizing the Potential of Maize in Sub-Saharan Africa. CIMMYT, Mexico.
http://pdf.usaid.gov/pdf_docs/PNABT192.pdf (Accessed 15 Nov. 2010).
CIMMYT. 2009. CIMMYT Maize Inbred Lines (CML). CIMMYT International Maize and Wheat Improvement Center, Mexico.
http://www.cimmyt.org/en/component/content/article/459-international-maizeimprovement-network-imin/434-cimmyt-maize-inbred-lines-cml (Accessed 29 Oct. 2010).
Denic, M.P., C. Chauque, M. Jose, D. Langa, Mariote, P. Fato, and W. Haag. 2001. Maize screening for multiple stress tolerance and agronomic traits. Eastern and Southern Africa Regional Maize Conference 7:88-91.
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STUDIES ON THE MAIZE STREAK VIRUS ON MAIZE.docx
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STUDIES ON THE MAIZE STREAK VIRUS ON MAIZE
Abstract
Maize streak virus (MSV) disease, transmitted by leafhoppers (Cicadulina mbila,
Naude), and maize downy mildew (DM) disease caused by Peronosclerospora sorghi (Weston and Uppal) Shaw, are major contributing factors to low maize yields in Africa. These two diseases threaten maize production in Nigeria, thus the importance of breeding Mozambican maize varieties that carry resistance to these diseases. Markerassisted selection (MAS) was employed to pyramid MSV and DM disease resistant genes into a single genetic background through simultaneous selection. Firstly, it was essential to determine the genetic diversity of MSV disease resistance in 25 elite maize inbred lines to aid in the selection of suitable lines for the introgression of the msv1 gene; and subsequently, to introduce the msv1 resistance gene cluster from two inbred lines, CM505 and CML509, which were identified as the ideal parental lines for the introgression of MSV disease resistance into a locally adapted Mozambican inbred line LP23 that had DM background resistance.
CHAPTER ONE
INTRODUCTION
Background to study
Maize (Zea mays L.) is a staple food for over 100 million people in Africa (Magenya et al., 2009), making it an essential food crop for global food security. In most of Africa’s rural economies, at least 85% of maize is used for human consumption, as compared with the developed world where most maize grain is used for animal feed and manufacturing industries (CIMMYT, 1990; Oluwafemi et al., 2008; Stevens, 2008). Maize is distributed worldwide and is the world’s third highest produced cereal (Sharma and Misra, 2011). Despite this, the average yield per hectare of maize in Africa is the lowest in the world and consequently, food shortages are a perpetual problem in most Sub-Saharan countries (Magenya et al., 2008).
Low maize productivity in Africa is thus a major concern that requires urgent attention. According to FAOSTAT (2007), in the year 2007 Nigeria was the leading producer of maize on the African continent, followed by South Africa. This was mainly due to the large area of land dedicated to maize production in these countries (Table 1). Egypt, which was the third largest producer had the highest grain yield per hectare of land in Africa (81 163 hg ha-1), followed by South Africa (28 759 hg ha-1), Ethiopia (27 248 hg ha-1), Malawi (20 400 hg ha-1), Kenya (20 250 hg ha-1), Cameroon (19 229 hg ha-1) and Nigeria (16 595 hg ha-1). The rest of the African countries, including Nigeria, had grain yield below 16 000 hg ha-1. In Nigeria, maize was produced on 1 505 400 hg ha-1of land, which is almost two times less land than South Africa. However, Mozambican production is almost five times less than the South African production of 7 338 738 tonnes at 1 579 400 tonnes. There is, therefore, a need to address factors affecting maize production in Nigeria because, as in most of Sub-Saharan Africa, maize production in Nigeria fails to meet the high demand in the country, despite the crop being grown in all the agro-ecological zones (Denic et al., 2001). A contributing factor to the low maize productivity in Nigeria is that 70% of maize production is in the tropical lowland (≤ 800 meters above sea level (masl)) where downy mildew (DM) infection is prevalent (Fato, 2010). Statement od
Statement Of Problem
Numerous viral pathogens including MSV, maize chlorotic mottle stunt virus (MCMV), maize eyespot virus, guinea grass mosaic virus (potyvirus) and maize yellow stripe virus (MYSV) infect maize in Africa and reduce maize production (Thottappilly et al., 1993; Martin and Shepherd, 2009). The leafhopper-vectored MSV is considered as the most significant biological threat to food security in Sub-Saharan Africa (Thottappilly et al., 1993; Martin and Shepherd, 2009). It is the most prevalent viral disease, undermining the economic wellbeing of subsistence farmers throughout Africa (Bosque-Perez, 2000; Shepherd et al., 2007; Martin and Shepherd, 2009). Yield losses due to MSV disease range from a trace to virtually 100% when the virus attacks susceptible lines (Tefera et al., 2011). In Nigeria, MSV disease is prevalent in all maize production areas (Denic et al., 2001). The diagnosis and characterisation of MSV disease resistant maize populations is central to the breeding and selection of MSV resistant cultivars to control the disease.
Maize hybrid improvement for DM and MSV resistance is critical for Nigeria in order to support the large impoverished rural population. Characterisation of genetic diversity and similarities of maize inbred lines enables maximum efficiency in the determination of the best possible combination of parents for the development of new and improved inbred lines (Xia et al., 2005; Legesse et al., 2007). Marker-assisted selection (MAS) is a biotechnology research tool adapted to enhance conventional breeding with accuracy and to accelerate variety development (Xu and Crouch, 2008). With regard to this, molecular markers, such as simple sequence repeats (SSRs) and inter-simple sequence repeats (ISSRs), are able to define genetic relationships of inbred lines at DNA level (Xia et al., 2005). The study aimed to contribute to the development of hybrids that have both DM and MSV disease resistance in Nigeria.
objective of the study
Breeding of MSV resistant maize is the best control measure for MSV disease in Nigeria. The MSV resistance gene cluster and flanking marker genes have been identified by the International Maize and Wheat Improvement Centre (CIMMYT) (CIMMYT, 2009). The goal of this study was, therefore, to introgress the MSV resistant gene cluster from CIMMYT MSV disease resistant lines CML505 and CML509 into the elite Mozambican maize line LP23, tracking the transfer of the gene cluster using MAS. Line LP23 has DM resistance and is adapted to the lowland areas in Nigeria but is susceptible to MSV disease.
Specific objectives
The specific objectives of the study were as follows:
Mozambican lines by evaluating the F3 progeny.
Research hypotheses
The following research hypotheses were tested in the thesis:
References
Adejumo, T.O. 2005. Crop protection strategies for major diseases of cocoa, coffee and cashews in Nigeria. African Journal of Biotechnology 4:143-150.
Ahlawat, Y.S. 2007. Plant Pathology Crop Diseases and their Management. Indian Agricultural Research Institute, New Delhi. pp. 98.
Bock, C.H., M.J. Jeger, K.F. Cardwell, L.K. Mughogho, and J. Sherington. 2000. Control of sorghum downy mildew in maize and sorghum in Africa. Tropical Science 40:47-57.
Bosque-Perez, N.A. 2000. Eight decades of maize streak virus research. Virus Research 71:107-121.
Cardwell, K.F., J.G. Kling, and C.H. Bock. 1997. Methods for screening maize against downy mildew Peronosclerospora sorghi. Plant Breeding 116:221-226.
CIMMYT. 1990. CIMMYT world maize 1989/90: Facts and Trends, Realizing the Potential of Maize in Sub-Saharan Africa. CIMMYT, Mexico.
http://pdf.usaid.gov/pdf_docs/PNABT192.pdf (Accessed 15 Nov. 2010).
CIMMYT. 2009. CIMMYT Maize Inbred Lines (CML). CIMMYT International Maize and Wheat Improvement Center, Mexico.
http://www.cimmyt.org/en/component/content/article/459-international-maizeimprovement-network-imin/434-cimmyt-maize-inbred-lines-cml (Accessed 29 Oct. 2010).
Denic, M.P., C. Chauque, M. Jose, D. Langa, Mariote, P. Fato, and W. Haag. 2001. Maize screening for multiple stress tolerance and agronomic traits. Eastern and Southern Africa Regional Maize Conference 7:88-91.
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