Faculty of Science and Agriculture
http://hdl.handle.net/10386/7
2018-05-27T19:51:35ZMechanism of resistance to Meloidogyne Incognita and Meloidogyne Javanica in Cucumis Africanus and Cucumis myriocarpus seedlings
http://hdl.handle.net/10386/1935
Mechanism of resistance to Meloidogyne Incognita and Meloidogyne Javanica in Cucumis Africanus and Cucumis myriocarpus seedlings
Ramatsitsi, Mukondeleni Ndivhuwo
Root-knot (Meloidogyne species) nematodes are economically destructive pathogens of over 3000 species, whereas others have resistance to Meloidogyne species. Wild watermelon (Cucumis africanus) and wild cucumber (Cucumis myriocarpus) are highly resistant to Meloidogyne species, particularly M. incognita and M. javanica. The two Cucumis species are used in inter-generic grafting with watermelon (Citrullus lanatus) as nematode resistant rootstocks. Also, the two Cucumis species are used in traditional medicine and in plant-parasitic nematode management as phytonematicides. The form of nematode resistance, which is essential in plant breeding, is not documented for the two Cucumis species. The objective of this study was to determine the form of nematode resistance in the two Cucumis species to M. incognita and M. javanica under greenhouse conditions. Four parallel experiments were each conducted under greenhouse conditions. Uniform six-week old Cucumis seedlings were transplanted into 250 ml polystyrene cups filled with 200 ml growing medium of steam-pasteurised fine sand. A week after transplanting, Cucumis seedlings were each infested by dispensing approximately 100 M. incognita second-stage juveniles (J2) or M. javanica J2 using a 20 ml plastic syringe by placing into 5-cm-deep furrow around the seedling stem and covered with growing medium. Treatments (periodic harvest intervals) were arranged in a randomised complete block design, replicated five times. Five seedlings from each experiment were harvested every second day, for 30 days, with stained roots being assessed for necrotic spot (suberised cells) number, giant cell number, proliferation of rootlet interference number and root gall number. Periodic harvest intervals were highly significant (P ≤ 0.01) on necrotic spot number, proliferation of rootlet interference number and root gall number in C. africanus-M. incognita relations, but were not significant for giant cell number. Treatments contributed 59, 64 and 50% in total treatment variation (TTV) of necrotic spot number, proliferation of rootlet interference number and root gall number, respectively. Harvest period had highly significant effects on necrotic spot number, giant cell number, proliferation of rootlet interference number and root gall number in C. africanus-M. javanica relations. Treatments contributed 55, 71, 63 and 59% in TTV of necrotic spot number, giant cell number, proliferation of rootlet interference number and root gall number, respectively. Periodic harvest intervals were significant (P ≤ 0.05) on giant cell number and highly significant on root gall number in C. myriocarpus-M. incognita relations. However, there were no significant treatment differences on necrotic spot number and proliferation of rootlet interference number. Treatments contributed 57 and 57% in TTV of root gall number and giant cell number, respectively. Harvest period had highly significant effects on giant cell number, proliferation of rootlet interference number and root gall number, but were not significant on necrotic spot number in C. myriocarpus-M. javanica relations. Treatments accounted for 67, 49 and 53% in TTV of giant cell number, proliferation of rootlet interference number and root gall number, respectively. In conclusion, the mechanism of resistance to M. incognita and M. javanica in both C. africanus and C. myriocarpus was post-infectional nematode resistance, which has attributes for introgression into commercial nematode-susceptible Cucumis cultivars.
Thesis (M.Sc. (Horticulture)) -- University of Limpopo, 2017.
2017-01-01T00:00:00ZUsing plant growth regulators and Vesicular Arbuscular Mycorrhiza to improve growth of the slow growing indigenous Mimusops zeyheri seedlings and accumulation of essential nutrient elements
http://hdl.handle.net/10386/1934
Using plant growth regulators and Vesicular Arbuscular Mycorrhiza to improve growth of the slow growing indigenous Mimusops zeyheri seedlings and accumulation of essential nutrient elements
Radzuma, Mosibudi Glad
Refer to document
Thesis (M.Sc. (Horticulture)) -- University of Limpopo, 2017
2017-01-01T00:00:00ZNon-phytotoxic concentration of nemarioc-AL and nemafric-BL phytonematides on green bean cultivar "Tahoe"
http://hdl.handle.net/10386/1931
Non-phytotoxic concentration of nemarioc-AL and nemafric-BL phytonematides on green bean cultivar "Tahoe"
Chokoe, Francinah Mologadi
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Thesis ( M.Sc.(Horticulture)) -- University of Limpopo, 2017.
2017-01-01T00:00:00ZModification, development, application and computational experiments of some selected network, distribution and resource allocation models in operations research
http://hdl.handle.net/10386/1930
Modification, development, application and computational experiments of some selected network, distribution and resource allocation models in operations research
Nyamugure, Philimon
Operations Research (OR) is a scientific method for developing quantitatively
well-grounded recommendations for decision making. While it is true that it
uses a variety of mathematical techniques, OR has a much broader scope. It is
in fact a systematic approach to solving problems, which uses one or more analytical
tools in the process of analysis. Over the years, OR has evolved through
different stages. This study is motivated by new real-world challenges needed
for efficiency and innovation in line with the aims and objectives of OR – the
science of better, as classified by the OR Society of the United Kingdom. New
real-world challenges are encountered on a daily basis from problems arising
in the fields of water, energy, agriculture, mining, tourism, IT development,
natural phenomena, transport, climate change, economic and other societal requirements.
To counter all these challenges, new techniques ought to be developed.
The growth of global markets and the resulting increase in competition
have highlighted the need for OR techniques to be improved. These developments,
among other reasons, are an indication that new techniques are needed
to improve the day-to-day running of organisations, regardless of size, type and
location.
The principal aim of this study is to modify and develop new OR techniques
that can be used to solve emerging problems encountered in the areas of linear
programming, integer programming, mixed integer programming, network
routing and travelling salesman problems. Distribution models, resource allocation
models, travelling salesman problem, general linear mixed integer
ii
programming and other network problems that occur in real life, have been
modelled mathematically in this thesis. Most of these models belong to the
NP-hard (non-deterministic polynomial) class of difficult problems. In other
words, these types of problems cannot be solved in polynomial time (P). No general
purpose algorithm for these problems is known. The thesis is divided into
two major areas namely: (1) network models and (2) resource allocation and
distribution models. Under network models, five new techniques have been developed:
the minimum weight algorithm for a non-directed network, maximum
reliability route in both non-directed and directed acyclic network, minimum
spanning tree with index less than two, routing through 0k0 specified nodes,
and a new heuristic to the travelling salesman problem. Under the resource
allocation and distribution models section, four new models have been developed,
and these are: a unified approach to solve transportation and assignment
problems, a transportation branch and bound algorithm for the generalised assignment
problem, a new hybrid search method over the extreme points for
solving a large-scale LP model with non-negative coefficients, and a heuristic
for a mixed integer program using the characteristic equation approach. In
most of the nine approaches developed in the thesis, efforts were done to compare
the effectiveness of the new approaches to existing techniques. Improvements
in the new techniques in solving problems were noted. However, it was
difficult to compare some of the new techniques to the existing ones because
computational packages of the new techniques need to be developed first. This
aspect will be subject matter of future research on developing these techniques
further. It was concluded with strong evidence, that development of new OR
techniques is a must if we are to encounter the emerging problems faced by the
world today.
Key words: NP-hard problem, Network models, Reliability, Heuristic, Largescale
LP, Characteristic equation, Algorithm.
Thesis (Ph.D. (Statistics)) -- University of Limpopo, 2017
2017-01-01T00:00:00Z