Spelling suggestions: "subject:"farms, small."" "subject:"farms, tmall.""
131 |
Drought coping mechanisms : a case study of small scale farmers in Motheo district of the Free State provinceOlaleye, Olubunmi Leke 09 1900 (has links)
A case study on drought coping mechanisms was conducted among small-scale farmers in the
Motheo District of the Free State Province in Republic of South Africa, to determine how farmers
cope with drought effects with or without external influence in terms of drought relief packages
from the government and non-governmental organizations. Data was collected by administering a
semi-structured questionnaire to 200 farmers. The data were captured and analysed using SPSS to
obtain frequency, cross-tab, univariate ANOVA as well as logistic regression analysis.
Findings of the study revealed that only 12.5 percent of the respondents were aware of drought,
while a larger percentage of 87.5 of the respondents were not aware of a drought incidence before
its onset, which made them more vulnerable to the drought disaster; 8.5 percent of them protected
water sources for livestock while 91.5 percent of the farmers did not protect water sources for their
livestock because they farm on a communal land; 42.5 percent provided supplementary feeds to
livestock during the drought, but 57.5 percent did not provide supplementary feed for their animals
for lack of funds.
Ninety-nine (99.0) percent of the respondents shared grazing lands while only 1 per cent did not
because most farmers operates on a communal system of farming; 35.5 percent changed cropping
systems; 50.5 percent had alternative water sources for crops which included mini and hand
irrigation systems while 49.5 percent of the respondents depended solely on streams and rivers
available in the villages; 19.3 percent sold or pledged assets in order to be able to cope with
drought effects while most farmers did not pledge or sell assets not because they did not want to,
but because they did not have assets to sell. / Envornmental Science / Thesis (M.Sc. (Environmental Management))
|
132 |
An evaluation of the performance of the Department of Agriculture in Limpopo Province in improving the livelihood of smallholder farmers during the period 1994-2004, with special reference to the Vhembe DistrictSitholimela, Silas Ndwakhulu 03 1900 (has links)
Thesis (MPA)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: This research work focuses on the role that the Department of Agriculture has played in
the improvement of the livelihood of smallholder farmers in the Vhembe District,
Limpopo Province, for the period 1994 to 2004. The research endeavours to determine
what was done to improve the livelihood of smallholder farmers, and the extent to which
smallholder farmers were developed. It determines the stage of development smallholder
farmers are in after a decade of democracy. The study considers various variables that
could be responsible for the good or bad performance of the Department of Agriculture in
the Vhembe District.
The Vhembe District was chosen because it consists of varied ecological and climatic
regions, making it possible for various farming enterprises to flourish in one area. The
research links the role played by the Department of Agriculture with the level of
development of smallholder farmers in the District. It investigates the support that the
Department of Agriculture provided through various strategic programmes, such as the
Comprehensive Agricultural Support Programme, the Revitalisation of Smallholder
Irrigation Schemes, training and development, and poverty-alleviation programmes,
aimed at kick-starting micro-enterprises.
The research identifies areas where the Department did not meet the expectations of the
smallholder farmers regarding support. It outlines possible reasons for good and poor
performance of the Department of Agriculture and its extension officers in the four local
municipalities of the Vhembe District, namely Makhado, Musina, Mutale and Thulamela.
This is based on data gathered through focus group discussions with various groups of
farmers and extension officers.
The research reveals that the budget allocation for agricultural development has never
been enough to address the pressing and varied needs of smallholder farmers in the
Vhembe District. The conclusion is reached that the support provided by the Department
of Agriculture to improve the livelihood of smallholder farmers was inadequate. Another conclusion is that smallholder farmers are heavily reliant on the Department for almost
all their farming needs. This dependency has led to many smallholder farmers not being
able to creatively initiate any action that would ultimately empower them to become selfreliant.
However, the research shows that a small percentage of farmers have realised the
need to become independent in order to avoid lifelong dependency on the Department of
Agriculture.
The researcher concludes that, after a decade of democracy, there is still a great need for
the Department’s support in order to improve the livelihood of smallholder farmers.
There is also a need to conduct a skills audit, which will help the Department to place
officials according to their areas of expertise, and to capacitate officials who may be
lacking some skills through various capacity-building programmes. The research revealed
that there may be officials who are morally corrupt in their behaviour and conduct. This
has resulted in inefficiency and poor service delivery to farmers. On the other hand there
are officials who perform exceptionally well and whose behaviour is beyond reproach.
The researcher concludes that these exceptional performers should be recognised and
rewarded for their good performance, while those with unsatisfactory performance should
be dealt with according to the disciplinary code and procedures of the public service.
The need is identified to channel resources to smallholder farmers who will utilise them
effectively. This would promote self-sufficiency in the long term. In channelling these
resources, the Department should also consider the promises made, with the view to fulfil
them as far as possible.
The researcher concludes that in order for smallholder farmers to realise their potential
they have to change their lives through agriculture. They need to become more organised
in order to speak with one voice. They also need to participate in secondary agriculture,
where they are able to access more markets, not only as producers but as agro-processors
as well. With appropriate and consistent support by the Department of Agriculture in the Vhembe
District, smallholder farmers’ livelihood could be improved, which will lead to economic
development of the local municipality, the district, the province and ultimately South
Africa as a whole. / AFRIKAANSE OPSOMMING: Hierdie navorsingstudie fokus op die rol wat die Departement Landbou gespeel het in die
verbetering van die lewensbestaan van kleinboere in die Vhembe-distrik, Limpopo, vir
die tydperk 1994 tot 2004. Die navorsing poog om te bepaal wat gedoen is om die
lewensbestaan van kleinboere te verbeter, en in watter mate daar tot die ontwikkeling van
kleinboere bygedra is. Daar word ook bepaal in watter ontwikkelingsfase kleinboere hulle
ná ’n dekade van demokrasie bevind. Die studie ondersoek verskeie veranderlikes wat vir
die goeie of swak prestasie van die Departement Landbou in die Vhembe-distrik
verantwoordelik kan wees.
Die Vhembe-distrik is gekies omdat dit uit verskillende ekologiese en klimaatstreke
bestaan, wat verskeie boerdery-ondernemings in staat stel om in een gebied te gedy. Die
navorsing veronderstel ’n verband tussen die rol van die Departement Landbou en die
ontwikkelingsvlak van kleinboere in die distrik. Dit ondersoek die steun wat die
Departement Landbou deur middel van verskeie strategiese programme gebied het, soos
die Program vir Omvattende Landbou-ondersteuning, die Opknapping van Kleinboerbesproeiingskemas,
opleiding en ontwikkeling, en programme vir die verligting van
armoede, wat daarop gemik is om stukrag aan mikro-ondernemings te verleen.
Die navorsing identifiseer gebiede waarop die Departement Landbou nie aan kleinboere
se verwagtinge ten opsigte van steun voldoen het nie. Dit verskaf moontlike redes vir die
goeie of swak prestasie van die Departement en sy voorligtingsbeamptes in die Vhembedistrik
se vier plaaslike munisipaliteite, naamlik Makhado, Musina, Mutale en Thulamela.
Dit is gegrond op data wat deur middel van fokusgroep-besprekings met verskeie groepe
boere en voorligtingsbeamptes verkry is.
Die navorsing toon dat die begrotingstoewysing vir landbou-ontwikkeling nog nooit
genoeg was om aan die dringende en verskillende behoeftes van kleinboere in die
Vhembe-distrik te voldoen nie. Die navorser maak die gevolgtrekking dat die steun van
die Departement Landbou nie voldoende was om die lewensbestaan van kleinboere te verbeter nie. ’n Verdere gevolgtrekking is dat kleinboere vir byna al hulle boerderybehoeftes
van die departement afhanklik is. Hierdie afhanklikheid lei daartoe dat menige
kleinboere nie in staat is om enige kreatiewe optrede te inisieer wat hulle eindelik sal
bemagtig om selfstandig te word nie. Die navorsing toon egter dat ’n klein persentasie
boere besef het dat hulle onafhanklik moet word om lewenslange afhanklikheid van die
Departement Landbou te vermy.
Die navorser kom tot die gevolgtrekking dat, ná ’n dekade van demokrasie, daar steeds ’n
groot behoefte aan steun van die departement ten opsigte van die verbetering van
kleinboere se lewensbestaan is. Daar is ook ’n behoefte aan ’n vaardighede-oudit wat die
departement sal help om amptenare na gelang van hulle kundigheidsgebied te plaas, en
om deur verskeie kapasiteitsbou-programme daardie amptenare wat sekere vaardighede
kortkom, op te bou. Die navorsing het onthul dat daar moontlik amptenare is wat moreel
korrup in gedrag en optrede is. Dit het ondoeltreffendheid en swak dienslewering aan
boere tot gevolg. Tog is daar amptenare wat besonder goed presteer en wie se gedrag bo
verdenking is. Die navorser is van mening dat hierdie goeie presteerders erkenning moet
ontvang en vir hulle goeie prestasie beloon moet word, en dat diegene wat ontoereikend
presteer ingevolge die staatsdiens se dissiplinêre kode en prosedures hanteer moet word.
Daar is ’n behoefte om hulpbronne te kanaliseer na kleinboere wat doeltreffend daarvan
gebruik sal maak. Dit sal op die lang termyn selfvoorsiening bevorder. In hierdie opsig
moet die departement poog om die beloftes wat hulle gemaak het, so ver moontlik na te
kom.
Die navorser kom tot die gevolgtrekking dat, vir kleinboere om hulle potensiaal te
verwesenlik, hulle hul lewens deur landbou moet verander. Hulle moet beter georganiseer
wees sodat hulle uit een mond kan praat. Hulle moet ook by sekondêre landbou betrokke
raak waar hulle toegang tot Met die gepaste en konsekwente steun van die Departement Landbou in die Vhembedistrik
kan die lewensbestaan van kleinboere verbeter word, wat ekonomiese
ontwikkeling van die plaaslike munisipaliteit, die distrik, die provinsie en eindelik Suid-
Afrika as geheel tot gevolg sal hê.
|
133 |
An analysis of the impact of contract farming on smallholding farming as a mechanism for value chain efficiency enhancement : the case of Mashonaland central province (Zimbabwe) smallholder tobacco farmersSibindi, Angels 12 1900 (has links)
Thesis (MDF)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: This research study has examined the impact of contract farming on enhancing efficiencies with the agricultural value chain for smallholder tobacco farmers in Mashonaland Central Province in Zimbabwe. The major challenges facing smallholder farmers in Africa in general and Zimbabwe in particular relate to financial constraints, technical expertise and market access. Contract farming as a transactions-cost-focussed-model is considered more effectively responsive to those challenges than the pure market approach which insufficiently addresses the impact of information asymmetries, bounded rationality, uncertainty, governance challenges and infrastructure challenges, among others. It allows for closely monitored smallholder financing by agribusiness entities which reduces or eliminates the probability of loan default. Contract farming is seen as an important mechanism in transforming the fragmented, subsistence agriculture in rural Africa into high commercialised and viable business undertakings.
In this study, extensive reference is made to literature on agriculture financing; empirical research data on smallholder productivity and loan recoverability is drawn and analysed using the quantitative research methodology. The analysis sought to test for relationships among a set of variables and in the process examined the impact of contract farming. A comparative analysis of national data on the contract and auction system of tobacco marketing was done with emphasis on production and sales volumes, crop quality, price stability and market access.
The results from the quantitative analysis of farmer-level and country-level data indicated a strong correlation between smallholder farmer production, productivity and loan recoverability and contract farming value chain intervention mechanisms.
|
134 |
Analysis of the challenges and opportunities for smallholder farmer value chain integration in the Western Cape : a public and private sector organisation perspectiveShange, Nikiwe 12 1900 (has links)
Thesis (MBA)--Stellenbosch University, 2014. / Access to markets is an essential requirement for smallholder farmer development. The limited access to formal value chains for smallholder farmers in South Africa is a key challenge that is facing both public and private value chain actors. Despite the substantial investments by government, the performance of smallholder farmers in South Africa remains poor. Several studies have been done to understand the key challenges facing smallholder farmer value chain integration. This study takes a unique view by understanding the challenges and opportunities facing farmer integration from a public and private stakeholder perspective, specifically analysing the Western Cape. The study showed that the most influential constraints for smallholder farmer value chain integration are access to informal and formal markets, resources and infrastructure, and the functioning of local institutions. The study also showed that the key opportunities to improve value chain integrations are in improving the non-financial and financial support provided to smallholder farmers. The results of the study are in line with the value chain theory around integration of smaller producers.
|
135 |
Evaluation of nutritional, chemotherapeutic and educational approaches to manage gastrointestinal nematodes and improve small-scale goat farming.Vatta, Adriano Francis. January 2007 (has links)
Small-scale goat farmers from south-western KwaZulu-Natal Province, South Africa, identified gastrointestinal helminths, dry-season feed scarcity and poor reproductive performance as major production constraints and highlighted the paucity of information on goat health and management. The research and extension processes adopted to address these problems comprised on-station experimentation, followed by on-farm validation combined with the participatory dissemination of both study findings and relevant information on goat health care. The approach included the use of the FAMACHA© system to assess anaemia, a characteristic symptom of infection with the gastrointestinal nematode, Haemonchus contortus (Rudolphi, 1803). On-station experimentation indicated that urea-molasses block supplementation during the dry, winter season was a cost-effective option. Unfortunately, when tested on-farm, the value of such supplementation proved inconclusive, possibly due to low block consumption and further research into alternative and palatable protein supplements for goats is suggested. However, tactical anthelmintic treatment with ivermectin effectively reduced faecal egg counts and is recommended, as is concurrent symptomatic anthelmintic treatment, as determined by the FAMACHA© system, since this practice appeared to improve reproductive capacity. Investigations to better adapt the FAMACHA© system to goats is, however, recommended. A flexible training framework was developed with the collaboration of the farmers, providing them with advice on goat health and management. This ‘hands-on’ approach encompassed regular meetings geared to the farmers’ current expertise and exploited the on-farm experimentation as a training vehicle. The process nurtured local farmer ‘champions’, strengthened the extension skills of researchers and technicians and incorporated the development of a Goatkeepers’ animal health care manual. Indications are that the use of such an approach has considerable potential for the development of goat farming. Moreover this process, which is relatively novel for South Africa, is equally applicable to other similar agro-ecological zones. Access to veterinary and agricultural inputs in areas where communal grazing is practised could be vastly improved and a case is made for universities, researchers, extensionists and farmers to collaborate to encourage the long-term sustainable development of these communities. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2007.
|
136 |
Appropriate institutional and contractual arrangements for the marketing of organic crops produced by members of the Ezemvelo Farmers' Organisation in KwaZulu-Natal.Gadzikwa, Lawrence. January 2010 (has links)
The Ezemvelo Farmers’ Organisation (EFO) is a certified organic smallholder group in KwaZulu-Natal province (South Africa) that exists as an institution to improve smallholder access to niche markets by reducing unit production and transaction costs. The study is motivated by the need to understand drivers of collective action, prevalence of internal group free-riding, and the impact of contract terms on contract performance. These three theoretical concepts are pertinent in understanding organisational and institutional issues affecting the performance of smallholder organic farming groups and in formulating policies to promote the performance of such groups. The study relies on the theoretical
foundations of collective action, free-riding and contracts found within the realm of New Institutional Economics (NIE). These theories, though separate, are in fact related in certain respects. Collective action in smallholder groups, apart from being a function of a plethora of socio-economic factors, including transaction costs, could be constrained by free-riding within the group, which in turn could be influenced by flawed contractual arrangements. This study of collective action focuses on 200 farmers drawn from a sample survey of 49
non-EFO members, and a census survey of 103 partially certified and 48 fully certified EFO members. A ‘collective action’ model investigates the impact of perceived benefits and savings on production and transaction costs attributed to collective action by drawing comparisons between EFO members and non-members using a multinomial logit model. The study of free-riding uses data from 151 members of the EFO to construct an index of free-riding within the group using principal components analysis (PCA). A ‘contract model’, which also focuses on EFO members only, attempts to measure the impact of
verbal contract provisions on contract performance in addition to evaluating the determinants of preferred contract terms using a combination of PCA, Ordinary Least Squares (OLS) regression, and logit models. Results indicate that continued participation in EFO is not influenced by the age or gender of the farmer, but positively influenced by growth in the net benefits of participation, and negatively by an increase in the size of the household’s cropland or on-farm earnings. With respect to production and transaction costs, the results suggest that EFO has reduced fully certified members’ concerns that crops would be damaged by livestock or constrained by inadequate technical information. However, this is not the case for other problems such as price uncertainty in conventional markets, a lack of affordable operating inputs, a lack
of affordable transport, and a lack of communications infrastructure. The index of free-riding behaviour constructed using principal components analysis
suggests that free-riding poses a serious threat to EFO’s collective marketing efforts. Ordinary Least Squares regression analysis of the index scores shows that members who are male, poorly educated, partially certified, aware of loopholes in the grading system, and who do not trust the buyer are more likely to free-ride. Benefits accruing to EFO members are limited and there is substantial confusion among members about the terms of EFO’s verbal contract with the pack house that purchases their organic produce. Ordinary Least Squares regression analysis of the impact that perceived contractual terms have on quantities delivered to the pack house yielded interesting
findings. Perceptions that delivery calls are made by the buyer, that grading procedures are flawed and that prices are not jointly established were found to reduce quantities delivered to the pack house, after controlling for differences in farm and farmer characteristics. Logit models estimated to identify the determinants of preferred contract clauses indicate that farmers with higher levels of formal education and farm income, and lower levels of experience, favour a written contract over a verbal contract. Similarly, farmers with higher
levels of formal education and lower levels of family farm labour favour a contract
denominated by area rather than weight. It is concluded that EFO should recruit households that rely on farming for income and which are land constrained. EFO is more likely to survive if it continues to secure fully
subsidised information, transport, fencing, and certification services for its members, and if it improves the benefits of participating by synchronising harvest and delivery dates, negotiating price discounts for organic inputs, and by maintaining an office with telephone, fax and postal services. In the longer-term, EFO should address institutionalised free-riding by issuing tradable ownership rights. In the short-term, EFO must engage with the pack
house (buyer) to remove flaws in the grading process that conceal the origin of low quality produce. Transparent and mediated negotiations leading to an incentive compliant contract with the buyer may also help to build trust and reduce free-riding within EFO. It is also recommended that the terms of EFO’s contract with the pack house should be revised so that; (a) delivery calls can be made by either the pack house or by EFO during specified periods and with reasonable notice, and (b) grading procedures are fully transparent and ensure traceability so that losses caused by poor quality can be internalised to members who deliver inferior produce. In addition, it is important that prices be
negotiated at the beginning of each season and that the contractual parties have recourse to pre-agreed facilitators and an arbitrator to resolve disputes on price and quality. A written contract is recommended to support these more complex terms, with the proviso that the contract is explained to current and prospective members, and that growers are fully informed of their rights and obligations. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.
|
137 |
Determining the potential for smallholder organic production among three farming groups through the development of an empirical and participatory decision support tool.Thamaga-Chitja, Joyce Magoshi. January 2008 (has links)
Organic farming is increasingly viewed as a plausible production system for sustainable agriculture for smallholder farmers. However, there is not enough scientific evidence and knowledge to advocate certified organic farming for African smallholder farmers who face several constraints related to production, storage and marketing. The potential for organic farming for smallholder farmers, faced by these constraints, is not clearly defined. As a result, this study set out to evaluate the production potential of organic agriculture among three smallholder farmer groups. Production questions were used to investigate and evaluate the potential for organic agriculture among three smallholder farmer groups and constituted the following subproblems: · What crops can be grown in the three study areas, based on climatic data ? · Do farmers concur that these are the most suitable potential organic crops? · How useful do the farmers find the decision making tool? · What constraints threaten commercial production of the identified crops for these farmers? Participatory methodologies that included the use of Force Field Analysis, discussions and workshops were used to identify organic production constraints related to production decisions. Farmers faced constraints related to finance, capacity enhancement, technical knowledge, fencing, irrigation, and a lack of, or inappropriately trained extension officers. As a response to identified production constraints, a decision support tool was developed. Natural resource data, including climatic and agronomic data, was used to create a specially calibrated Microsoft Excel spreadsheet interface that functions as an empirical organic production decision support tool for organic and aspirant organic smallholder farmers, by providing answers for farmer-prioritised production constraints. A list of potential crops for each of the three study areas was subjected to a series of checks against suitability for climate and disease conditions and nutrient requirements. A limited supply of manure, to meet the enormously high requirements for organic production in the poor soils of these areas, is the major constraint to exclusive organic production and renders certified organic production difficult and unsustainable. Farmers disagreed with some of the crops on the list, arguing that familiar crops were rejected by the model, but they were excited by the prospects for production of “new” crops suggested as suitable by the decision support tool, but not yet grown in the study areas. End users welcomed the model and expressed the opinion that it would be useful in decision making related to organic crop production. The study concludes that, although a number of agronomically-suitable crops can grow in the study areas, organic production is restricted by rather high manure requirements, lack of compost making skills, lack of knowledge on natural pest and disease control and poorly nourished soils, leading to poor yields. The rainy season creates a disease-supporting environment, rendering organic farming risky for rain-fed smallholder farming. Risk in certified organic farming for smallholders was further exacerbated by a hardly inconducive policy environment that low literacy levels exist amongst farmers. This study is innovative for three reasons. First, farmers were true participants and drivers of the research. Second, trans-disciplinary expert seminars were attended by experts from different disciplines who critiqued the conceptualisation, design, and implementation of the study. Third, the development of a practical decision-support tool shows innovation towards solving complex smallholder farmers decisions. If organic farming is to be promoted, commitment by government is needed in order to establish policy and legislation on organic farming to direct and govern training, information provision and marketing. Intensive training and knowledge building of organic production for smallholder farmers and extension officers is critical. There are also agroecological risks associated with organic farming for smallholder farmers. Recommendations for future research include comparison between organic agriculture and conventional agriculture, where sustainability of certified organic farming and economic viability can be conducted in the South African context. Improvement of the decision making tool will require involving information technology specialists so that the tool can be installed in community centres, extension offices and other accessible places for farmers and others. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.
|
138 |
Breeding investigations for resistance to Phaeosphaeria Leaf Spot (PLS) and other important foliar diseases and a study of yield stability in African maize germplasm.Sibiya, Julia. January 2009 (has links)
Abstract not available. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.
|
139 |
Genetic effects and associations between grain yield potential, stress tolerance and yield stability in southern African maize (Zea mays L.) base germplasm.Derera, John. January 2005 (has links)
Maize (Zea mays L.) is the principal crop of Southern Africa but production is threatened by gray leaf spot (Cercospora zea-maydis L.) and phaeosphaeria leaf spot (Phaeosphaeria maydis L.) diseases, drought and the use of unadapted cultivars, among other constraints. There are few studies of gray leaf spot (GLS) and Phaeosphaeria leaf spot (PLS) resistance, drought tolerance, yield stability and maize cultivar preferences in Southern Africa. The objective of this study was to: a) determine farmers’ preferences for cultivars; b) investigate the gene action and heritability for resistance to GLS and PLS, and drought tolerance; and c) evaluate yield stability and its relationship with high yield potential in Southern African maize germplasm. The study was conducted in South Africa and Zimbabwe during 2003 to 2004. A participatory rural appraisal (PRA) established that farmers preferred old hybrids of the 1970s because they had better tolerance to drought stress. Farmers also preferred their local landrace because of its flintier grain and better taste than the hybrids. The major prevailing constraints that influenced farmers’ preferences were lack of appropriate cultivars that fit into the ultra short seasons, drought and low soil fertility. Thus they preferred cultivars that combine high yield potential, early maturity, and drought tolerance in all areas. However, those in relatively wet areas preferred cultivars with tolerance to low soil fertility, and weevil resistance, among other traits. A genetic analysis of 72 hybrids from a North Carolina Design II mating revealed significant differences for GLS and PLS resistance, and drought tolerance. General combining ability (GCA) effects accounted for 86% of genetic variation for GLS and 90% for PLS resistance indicating that additive effects were more important than non-additive gene action in controlling these traits. Some crosses between susceptible and resistant inbreds had high resistance to GLS suggesting the importance of dominance gene action in controlling GLS resistance. Resistance to GLS and PLS was highly heritable (62 to 73%) indicating that resistance could be improved by selection. Also large GCA effects for yield (72%), number of ears per plant (77%), and anthesis-silking interval (ASI) (77%) under drought stress indicated that predominantly additive effects controlled hybrid performance under drought conditions. Although heritability for yield declined from 60% under optimum to 19% under drought conditions, heritability for ASI ranged from 32 to 49% under moisture stress. High heritability for ASI suggested that yield could be improved through selection for short ASI, which is positively correlated with high yield potential under drought stress. The stability analyses of the hybrids over 10 environments indicated that 86% had average stability; 8% had below average stability and were adapted to favourable environments; and 6% displayed above average stability and were specifically adapted to drought stress environments. Grain yield potential and yield stability were positively correlated. In sum, the study indicated that farmers’ preferences would be greatly influenced by the major prevailing constraints. It also identified adequate genetic variation for stress tolerance, yield potential and yield stability in Southern African maize base germplasm, without negative associations among them, suggesting that cultivars combining high yield potential, high stress tolerance and yield stability would be obtainable. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.
|
140 |
Breeding investigations for resistance to Phaeosphaeria Leaf Spot (PLS) and other important foliar diseases and a study of yield stability in African maize germplasm.Sibiya, Julia. January 2009 (has links)
Maize (Zea mays L.) yields in the smallholder (SH) farming sector in Southern Africa have remained low. despite the availability of many improved varieties. Among the major constraints contributing to tow yields and threatening food security in the region are diseases which include grey leaf spot (GLS). common rust, northern corn leaf blight (NLB) and Phaeosphaeria leaf spot (PLS). These diseases are highly unpredictable in their occurrence every season, making them difficult to control. In addition, the majority of SH farmers cannot afford to control the diseases due to limited access to chemicals. Therefore, maize cultivars with high levels of disease resistance and tolerance to abiotic stresses would provide a long-term solution to addressing the problem of low yields, especially in the smallholder-farming sector. The objectives of this study were therefore to: i) establish farmers' perceptions on diseases, key limiting production constraints and preferred traits of maize cultivars. ii) screen germplasm adapted to tropical environments for resistance to PLS, iii) determine gene action for resistance to PLS and GLS, iv) estimate combining ability effects for resistance to PLS, GLS, NLB and common rust diseases, and v) determine grain yield stability of F, hybrids derived from crosses among selected tropical advanced maize inbred lines. These studies were conducted from 2006/7 to 2008/9 seasons at various sites in South Africa, Zimbabwe, Zambia and Uganda. Structured surveys and participatory rural appraisal (PRA) conducted in Obonjaneni. Busingatha and Okhombe villages of Amazizi district in the Northern Drakensberg established maize as the principal crop grown in the area. All the farmers who participated grew the local variety (landrace) they called Natal-8- row or Is/Zulu. The adoption of hybrids and improved open pollinated varieties (OPVs) was tow. Farmers preferred the local variety ahead of hybrids and improved OPVs mainly for its taste, tolerance to abiotic stresses and yield stability. Characteristics of maize varieties preferred by the farmers included: inexpensive seed, high yield, early maturity and tow input costs. Pests/d is eases and drought were not ranked highly, as farmers planted early to escape diseases and drought. Abiotic stresses were amongst the top four constraints faced by the farmers. The local varieties exhibited high yield potential and genetic variability fordisease resistance. Evaluation of maize germplasm adapted to tropical and subtropical environments of Africa for PLS resistance indicated significant (PS0.05) variation among the inbreds. populations and hybrids. In general, 63% of the inbreds/populations were resistant to PLS. Regionally important inbred lines; SC and N3 and CIMMYT's most successful lines such as CML395. CML444. CML202. CML312. and CML488 were resistant to PLS. Fifty- four percent of the single-cross experimental hybrids were also resistant to PLS. Correlation coefficients for area under disease progress curve (AUDPC) values for disease severity with PLS final disease severity scores were significant (P<0.001) and positive, implying that ranking of the genotypes for AUDPC and final PLS disease severity score was by and large similar. Forty five F, hybrids generated by crossing ten advanced maize inbred lines in a half diallel mating scheme were evaluated in two to six environments to determine combining ability, gene action and heterosis estimates for grain yield and resistance to PLS. GLS. NLB and common rust diseases. Highly significant (PS0.001) general combining ability (GCA) and specific combining ability (SCA) effects were observed for PLS. GLS. NLB. common rust, grain yield and other agronomic traits. The GCA effects were more important than SCA effects, indicating the predominance of additive over non-additive gene action for all the traits studied in these inbred lines. The inbred lines with good GCA for PLS resistance were: A12204, N3. A16. MP18 and CML488. and for GLS resistance were A1220-4. CZL00009. CZL00001. CML205 and CML443. Lines A16 and CML443 had good GCA for NLB and common rust resistance, lines A1220-4, N3, CML205, A16, and CML443 contributed towards high yield. Lines A1220-4 and A16 were late maturing, whereas CZL00009 displayed eariy maturity. High mid-parent and better-parent heterosis for high grain yield and resistance to all the diseases were observed. Generation mean analysis was used to deteimine the inheritance of PLS and GLS resistance in populations involving six tropical advanced maize inbred lines. Reciprocal crosses and backcross progenies were generated among inbreds A1220-4, A15, B17 (resistant. R), CML445 (moderately resistant. MR). CML441 and CZL00001 (susceptible. S) for PLS inheritance, and among inbreds A1220-4. A15, CML441 (resistant. R). and N3 and B17 (susceptible. S), for GLS inheritance. Results indicated highly significant additive effects (P<0.001) for PLS and GLS resistance, with dominance effects accounting forSH%of the variation in all the crosses for PLS and only A15 x B17 cross for GLS. Epistasis and cytoplasmic gene effects in favour of PLS resistance in F, crosses when the more susceptible parent was used as female were significant. For GLS resistance, epistasis was observed only in CML441 x N3 and A1220-4 x B17 crosses, while no cytoplasmic gene effects were detected. Resistance for PLS was medium to highly heritable and conditioned by less than four genes which exhibited incomplete dominance. In general resistance to GLS was controlled by two to three genes exhibiting zero to partial dominance and was moderate to highly heritable. Stability analysis of the hybrids was done over 11 environments using the additive main effects and multiplicative interaction (AMMI) and the genotype and genotype by environment (GGE) biplot analyses. Both AMMI and GGE biplot analyses selected hybrids H21 (CZL00009 x A16). H14 (A1220-4 x A16). S63 (SeedCo hybrid check). N72 (MP72/N3) and H26 (CZL00001 x A16) as stable and high yielding. Hybrids H1 (CML445 x A1220-4), H44 (CZL00009 x CML443) and H18 (CZL00009 x CZL00001) were identified by both methods as unstable but high yielding. AMMI and GGE biplot analyses identified ZAM08, C108, RAO9 and C09 as the most representative environments which were high yielding and relatively stable. In general, the study has revealed that based on the farmers ranking of the constraints in their area, breeding opportunities do exist for incorporating tolerance to both biotic and abiotic stresses in their varieties. It also identified maize lines resistant to the main foliar diseases, with good combining ability and heterosis for resistance and high grain yield. Hybrids with wide adaptation and high yields across environments were also observed. The experimental hybrids that exhibited high levels of resistance can be recommended for further testing and release. On the whole, highly significant additive effects and moderate to high heritability estimates observed for all the diseases and grain yield implied progress would be made through selection, although significant epistasis and dominance could slow progress. Dominance effects towards resistance and high yield could be exploited in developing single cross maize hybrids among these inbreds when only one parent is resistant. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.
|
Page generated in 0.062 seconds