Marker-assisted Screening of Cotton Cultivars for Bacterial Blight Resistance Gene

Bacterial blight or leaf blight is a common disease of cotton in almost all cotton growing countries, including Tanzania. Bacterial blight is caused by infection of plants with the bacteria (Xanthomonas axonopodis pv. malvacearum) and the use of resistant cultivars is the most effective long-term strategy to manage the disease. The strategy starts with identification of resistant individuals, which can be identified either phenotypically by inoculation or by use of molecular markers linked to genes that confer resistance. The B12 gene is known to confer a high level of resistance to all Xanthomonas axonopodis pv. malvacearum races found in USA and Africa. Four Brazilian and three local cultivars were screened for the presence of SSR (CIR246) and SNP NG0207155 markers linked to B12. The SNP marker showed the greatest frequency of resistance-linked alleles in the cultivar UK08 (85.71%) followed by UK91 (75%),UKM08 and Ipê (25%), Araça(8.33%),Aroeira (7.1%) and the least in Cedro (0%). Comparable results were recorded for SSR marker where the cultivar UK08 presented relatively higher frequency of resistance alleles (85.71%) of samples tested followed by UK91 (68.75%), UKM08 (25%), Ipê, Aroeira and Araça (8%) and the last was Cedro (0%). The results suggest the potential utility of Tanzanian germplasm in breeding for resistance to Xanthomonas axonopodis pv. malvacearum race 18 and the need to purify the same germplasm by marker assisted selection.Key words: Bacterial Blight, Cotton, Resistant cultivars, Tanzania

Use of simple sequence repeat (SSR) markers for screening blue disease resistance in cotton germplasm exchange

Blue disease of cotton is an economically important disease of the crop first described from the Central African Republic and spread to other countries. Brazil and other South American countries record crop losses of up to 80% from infection but no cases of the disease have been reported in Tanzania. Resistance to the disease has been found in African germplasm and transferred to crop cultivars worldwide. Molecular markers linked to blue disease resistance genes have been identified presenting useful tools to identify resistant germplasm. All plants of three Tanzanian cotton cultivars (Gossypium hirsutum L.) UK91, UK08 and UKM08 showed resistance alleles for both the simple sequence repeat (SSR) (DC20027-202 bp) and single nucleotide polymorphisms (SNP) (NG0204310-C) markers but some plants of the Brazilian cultivars (G. hirsutum L.); Ipê, Cedro, Aroeira and Araça lacked resistance alleles. The findings suggest the need for caution to be taken during introduction of exotic germplasm and recognize the value of resistance trait to susceptible Brazilian germplasm when  breeding for blue disease resistance.Key words: Cotton blue disease, cotton single nucleotide polymorphisms (SNPs), simple sequence repeat(SSR), resistant alleles in cotton

Building sustainable market linkages through innovations platforms for technology adoption: Case studies from Uganda, Kenya and Tanzania.

Finding and sustaining markets for Orange-fleshed sweetpotatoes is a challenge in many parts of East Africa. Farmers face numerous difficulties in identifying credible business partners, while traders and other market chain actors are frustrated by inconsistencies in supply. In the Dissemination of New Agricultural Technology in Africa (DONATA) OFSP project, Innovation Platforms for Technology Adoption (IPTAs) in Ethiopia, Kenya, Rwanda, Tanzania and Uganda have brought together relevant value chain stakeholders to develop institutional mechanisms which have supported the up-scaling of OFSP technologies (e.g. new varieties, agronomic practices, and post-harvest activities) and marketing strategies. This paper presents key strides attained in accessing equitable markets by IPTAs in three DONATA project countries. While some IPTAs have segmented the market and differentiated the producer groups along product lines, others have supported various chain actors to strengthen their businesses thus increasing throughput to the markets. Hence in the former case, groups are classified along major OFSP products marketed (vines, roots and processed products), while in the latter, specialized actors take on these functions. Successes include firm contracts for supply of OFSP flour to supermarkets in Kenya, supply of roots to urban markets in Uganda, and sale of vines to individuals and organizations in Tanzania. The major challenges include aligning production to demand for consistent supply, poor market infrastructure and low consumer awareness of the benefits of OFSP. Future prospects lie with newly established relations with big buyers and also working closely with other initiatives to consolidate gains achieved to date

Screening of selected brazilian and tanzanian cotton (Gossypium spp.) cultivars for Fusarium wilt resistance.

Fusarium wilt of cotton caused by Fusarium oxysporum f.sp. vasinfectum Atk. Sny & Hans is one of the major diseases of cotton in Tanzania. Resistant varieties provide useful tools for management of this disease. Varieties developed at Lake Zone Agricultural Research and Development Institute with previous records of resistance are currently susceptible in areas with high level of inoculums warranting the need to search for additional sources of resistance. Further, cotton varieties of Brazil indicate some level of resistance against F. oxysporum f. sp. vasinfectum that can be exploited in breeding programmes. In present study, four varieties from Brazil and three from Tanzanian were screened under greenhouse conditions for resistance to Fusarium wilt. A population of 40 plants per variety was inoculated with a crude inoculum of F. oxysporum f. sp. vasinfectum by root - dip method. Randomized complete block design was used with four replications. Resistance was evaluated on basis of foliar symptoms (disease severity index) and plant survival percentage. Further, all plants showing wilting symptoms were examined for vascular discoloration. Among various tested varieties, two cultivars from Brazil (Ipê and Aroeira) had relatively lower disease severity index and higher plant survival, these results suggesting their potential candidature for use in br eeding programmes for Fusarium wilt resistance. On the other hand, two local cultivars (UK91 and UK08) presented the highest disease severity index and lowest plant survival

Marker-assited screening of cotton cultivars for bacterial blight resistance gene.

Bacterial blight or leaf blight is a common disease of cotton in almost all cotton growing countries, including Tanzania. Bacterial blight is caused by infection of plants with the bacteria (Xanthomonas axonopodis pv. malvacearum) and the use of resistant cultivars is the most effective long-term strategy to manage the disease. The strategy starts with identification of resistant individuals, which can be identified either phenotypically by inoculation or by use of molecular markers linked to genes that confer resistance. The B12 gene is known to confer a high level of resistance to all Xanthomonas axonopodis pv. malvacearum races found in USA and Africa. Four Brazilian and three local cultivars were screened for the presence of SSR (CIR246) and SNP NG0207155 markers linked to B12. The SNP marker showed the greatest frequency of resistance-linked alleles in the cultivar UK08 (85.71%) followed by UK91 (75%),UKM08 and Ipê (25%), Araça(8.33%),Aroeira (7.1%) and the least in Cedro (0%). Comparable results were recorded for SSR marker where the cultivar UK08 presented relatively higher frequency of resistance alleles (85.71%) of samples tested followed by UK91 (68.75%), UKM08 (25%), Ipê, Aroeira and Araça (8%) and the last was Cedro (0%). The results suggest the potential utility of Tanzanian germplasm in breeding for resistance to Xanthomonas axonopodis pv. malvacearum race 18 and the need to purify the same germplasm by marker assisted selection

Diallel analysis and inbreeding depression in agronomic and technological traits of cotton genotypes

ABSTRACT Cotton provides about 90% of the world textile fiber, and is one of the crops of greater industrial relevance. The objectives of this study were to estimate the inbreeding depressionand the genetic effects involved in the control of the agronomic andfiber quality traits in F1 and F2 generations and to identify promising hybrids for obtaining superior cotton genotypes. Two cultivars of upland cotton and two moco (Brazilian endemic) cotton were crossed using a half-diallel scheme. The following traits were evaluated: percentage of fibers and weight of one boll, fiber length, fiber uniformity, short fiber index, fiber strength, and micronaire index. The additive genetic effects are predominant in the evaluated agronomic and fiber quality traits. Cultivar FM 966 is the most suitable parent to compose crossing blocks for the improvement of cotton agronomic and fiber quality traits. The hybrids FM 966 × CNPA 7MH and FM 966 × BRS 286 are the most promising for obtaining segregating populations aiming to select superior genotypes. Inbreeding depression is more pronounced in the agronomic traits than in the fiber quality traits