Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: In order to test the effect of different plant growth-promoting strategies on Triticum
aestivum L. (wheat), we investigated the ability of biochar and a grain-associated soil
yeast, to improve the growth of this crop. Our first goal was to study the effect of biochar
amendments to sandy soil on the growth and nutrition of wheat in the presence of
mycorrhizal fungi. This was accomplished by amending soil with 0%, 1%, 2.5%, 5% and
10% (w/w) biochar and cultivating wheat plants in these soil-biochar mixtures. After
harvesting, plant growth and mycorrhizal colonization of roots were measured. In addition,
we studied the nutritional physiology of these plants with regards to nitrogen (N),
phosphorous (P) and potassium (K) concentrations, as well as the growth efficiencies and
uptake rates of these nutrients. We found that wheat growth was improved by biochar
amendments to soil, probably as a result of elevated K levels in the plant tissues supplied
by the biochar amendments.
The second goal of this study was to obtain a soil yeast from the rhizosphere of another
monocot in the family Poaceae, i.e. Themeda triandra Forssk. (red grass), and then
evaluate this isolate for its ability to improve wheat performance. Three different
Cryptococcus species were isolated from the rhizosphere of wild grass, i.e. Cryptococcus
zeae, Cryptococcus luteolus and Cryptococcus rajasthanensis. Since C. zeae was
previously isolated from maize, an isolate representing this species was selected to be
used in further experimentation. With the ultimate goal of testing the ability of this yeast to
improve wheat growth, its effect on wheat germination was investigated and compared to
that of two other soil yeasts, i.e. Cryptococcus podzolicus CAB 978 and Rhodotorula
mucilaginosa CAB 826. These three yeasts were subsequently tested for their ability to
improve wheat growth in pot cultures in a greenhouse. After one and two months of
growth, the culturable yeasts present in the rhizosphere and bulk soil were enumerated.
The effects of these yeasts were elucidated by measuring wheat growth in terms of dry
weight, as well as root and shoot relative growth rates (RGR). Changes in wheat nutrition
were evaluated by determining the concentrations, growth efficiencies and uptake rates for
P, K, zinc (Zn) and iron (Fe). During this study, it was found that only C. zeae CAB 1119
and C. podzolicus CAB 978 were able to enhance seed germination. Similarly, it was
shown that C. zeae CAB 1119 was able to improve wheat growth during the first and
second month of cultivation, whereas C. podzolicus CAB 978 only improved growth during
the first month, and R. mucilaginosa CAB 826 had no effect on growth. This improved growth could be attributed to C. zeae CAB 1119 improving the P, K, Zn and Fe growth
efficiency of wheat, which positively influenced the root and shoot RGR, and subsequently
wheat growth.
Our final goal was to test whether C. zeae CAB 1119 could affect wheat growth and
nutrition when cultivated in sandy soil, which contained natural microbial consortia and
10% (w/w) biochar. Plants treated with viable or autoclaved cells of C. zeae CAB 1119,
were subsequently cultivated in soil only or soil amended with biochar. After one month,
plants were harvested and growth was measured with regards to dry weight, root RGR
and shoot RGR. In addition, the concentrations of P, K, Zn and Fe were analyzed for these
plants, where after the growth efficiencies and uptake rates were calculated for these four
nutrients. Results indicated that plants growing in soil amended with biochar, and treated
with viable C. zeae CAB 1119, showed the best growth. The increased root and shoot
RGR witnessed in these plants was probably due to increased concentrations of P and K
in the plants. This study opens new avenues of research with regards to the bio-fertilizers
of wheat. / AFRIKAANSE OPSOMMING: Die uiteindelike doel van die studie was om die effek van verskillende plantgroei
bevorderende metodes op die groei van Triticum aestivum L. (koring) te ondersoek. Dus
het ons die vermoë van houtskool en ‘n graan-geassosieerde grondgis getoets om die
groei van dié plant te bevorder. Die eerste doel van die studie was om die effek van
houtskool toedienings tot sanderige grond te evalueer. Dit is bewerkstellig deur 0%, 1%,
2.5%, 5% en 10% (w/w) van die houtskool by die sand toe te voeg en koring in die
houtskool-sand mengsels te kweek. Na die verlangde groei tydperk is die koring geoes en
die mikorrizale kolonisasie op en in die koring wortels bepaal. Gedurende hierdie studie is
die effek van bogenoemde toedienings op die fisiologie van die plante ondersoek deur die
konsentrasies, opname tempo’s, en groei ekonomie van die plante vir stikstof (N), fosfaat
(P) en kalium (K) te bepaal. Ons het gevind dat die groei van koring deur die toediening
van houtskool bevorder is en dit blyk dat dié effek weens die teenwoordigheid van hoë K
vlakke in die plantweefsel is.
Die tweede doel van ons studie was om ‘n gis vanuit die risosfeer van ‘n monokotiel wat
aan die familie Poacea behoort, naamlik Themeda triandra Forssk. (rooigras) te isoleer.
Die vermoë van die isolaat om die groei van koring te bevorder was daarna getoets. Drie
verskillende Cryptococcus spesies was vanuit die risosfeer van rooigras geïsoleer, nl.
Cryptococcus zeae, Cryptococcus luteolus en Cryptococcus rajasthanensis. Omdat C.
zeae in ‘n vorige studie vanaf mielies geisoleer was, is ‘n isolaat van hierdie spesie gebruik
in verdere eksperimente. Met die doel om te bepaal of dié gisspesie koringgroei kan
bevorder, was die effek van C. zeae op die ontkieming van koring bestudeer en vergelyk
met dié van twee ander grond giste, nl. Cryptococcus podzolicus CAB 978 en Rhodotorula
mucilaginosa CAB 826. Hierdie drie giste is ook ondersoek om die groei van koring in ‘n
glashuis te bevorder. Na een en twee maande se groei was die getalle van giste
teenwoordig in die risosfeer en grond verder weg van die wortels bepaal. Die effek van dié
giste op die groei van koring is bepaal in terme van droë gewig asook die relatiewe wortel
en halm groei tempos. Veranderinge in die nutrient status van koring is ondersoek deur die
konsentrasies, groei-ekonomie en tempo van opname vir P, K, sink (Zn) en yster (Fe) te
bepaal. Ons het gedurende dié studie gevind dat C. zeae CAB 1119 en C. podzolicus CAB
978 die ontkieming van koring kon verbeter. Ons het ook gevind dat C. zeae CAB 1119 die
groei van koring gedurende die eerste en tweede maand van groei kon bevorder, terwyl C.
podzolicus CAB 978 dit net gedurende die eerste maand kon vermag en R. mucilaginosa CAB 826 geen effek gehad het nie. Die verbeterde groei kon aan C. zeae CAB 1119, wat
die P, K, Zn en Fe groei effektiwiteit van die plante verbeter het, toegeskryf word. Die
verbetering van groei effektiwiteit het ‘n positiewe invloed op die relatiewe groeisnelheid
van die wortels en halms gehad, en dus op koringgroei.
Die laaste doel van die studie was om te bepaal of C. zeae CAB 1119 die groei van koring
kon bevorder wanneer die koring in sand wat natuurlike mikrobiese populasies bevat en
met houtskool aangevul is, gekweek word. Plante is met lewensvatbare of nielewensvatbare
selle van C. zeae CAB 1119 behandel en gekweek in sanderige grond,
en/of grond waarby 10% (w/w) houtskool toegevoeg is. Die plante is na een maand geoes
en die groei bepaal in terme van droë massa en die relatiewe wortel en halm groei
tempos. Die konsentrasies van P, K, Zn en Fe in die plante, asook die fisiologie van die
plante, nl. groei ekonomie en tempo van opname, met betrekking tot P, K, Zn en Fe is
bepaal, Ons het gevind dat plante wat in die houtskool-grond mengsel gekweek is en met
lewensvatbare selle van C. zeae CAB 1119 behandel is die beste groei getoon het. Die
verbeterde relatiewe groei tempos van die wortels en halms was mees waarskynlik die
gevolg van verhoogde P en K konsentrasies in die plante. Hierdie studie toon nuwe
resultate in verband met die gebruik van biologiese alternatiewes tot kunsmis.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/20417 |
| Date | 03 1900 |
| Creators | Moller, Leandra |
| Contributors | Botha, Alfred, Valentine, Alexander J., Stellenbosch University. Faculty of Science. Dept. of Microbiology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 118 pages : illustrations |
| Rights | Stellenbosch University |
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