Browsing by Author "Van den Heever, Christiaan Frederick"
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- ItemThe interactions between the soil yeast Papiliotrema laurentii and two Western Cape crops, wheat (Triticum aestivum L.) and rooibos (Aspalathus linearis (Burm. F.) R. Dahlgren)(Stellenbosch : Stellenbosch University, 2020-04) Van den Heever, Christiaan Frederick; Botha, Alfred; Stellenbosch University. Faculty of Science. Dept. of Microbiology.ENGLISH SUMMARY: Wheat (Triticum aestivum L.) is one of the most widely cultivated cereal crops and serves as a staple food for nearly one third of the world’s population. Rooibos (Aspalathus linearis (Burm. F.) R. Dahlgren) is a leguminous shrub endemic to the Cape Floristic Region of South Africa, the leaves of which is used to produce a health promoting beverage, namely rooibos tea. Both these plants are cultivated on a large-scale in the Western Cape province. However, climate change and extreme environmental conditions in this region threatens the production of these crops, and subsequently declines in both wheat and rooibos yields have recently been recorded. Globally, declines in wheat yields threaten food security and, together with the need to mitigate the environmental consequences of nitrogen fertiliser, novel agricultural methods to improve crop production in a sustainable manner are increasingly being explored. One such method is the use of plant growth promoting yeasts (PGPYs) as bio-fertiliser, as it is known that PGPYs possess plant growth promoting (PGP) traits that can affect the germination and growth of plants. However, the effect of a yeast seed coating to increase the germination and growth of wheat is unknown. It is also unclear whether yeasts are present in the rhizosphere of rooibos and if these yeasts could benefit rooibos. Since the yeast Papiliotrema laurentii CAB 91 has previously been demonstrated to improve the growth of a variety of plants, we hypothesised that this yeast could be used as a seed coating of wheat and that potential PGPYs are present in the rhizosphere of rooibos that could affect the growth of this plant. To test these hypotheses, we first evaluated the PGP properties of P.laurentii CAB 91, before determining the effect of this yeast on the germination and vigourof three wheat cultivars, namely cv. Ratel, cv. SST027 and cv. SST047. It was found that P.laurentii CAB 91 produced a number of PGP traits and could increase the germination ofcv.Ratel and cv. SST027, while improving the vigour of all three wheat cultivars. Since thegreatest effect was observed for Ratel and SST027 seeds, these two cultivars were chosen to determine the effect of a P. laurentii CAB 91 seed coating on the growth of wheat plants under field conditions. We subsequently found that both Ratel and SST027 plants treated with the yeast produced grain with greater protein content than control plants and that P. laurentii CAB 91 also affected the grain morphology of SST027 plants. Furthermore, yeasts were isolated from the rhizosphere of rooibos plants and found to possess PGP traits. Subsequently, the effect of selected isolates and P. laurentii CAB 91 on the germination and vigour of rooibos was evaluated. Three yeasts, namely P. laurentii CAB 91, P. laurentii CAB 2913 and Papiliotrema terrestris CAB 2921 were found to improve the germination of rooibos seeds, while P. laurentii CAB 91 and P. laurentii CAB 2913 could also increase rooibos vigour. These findings indicate that P. laurentii CAB 91 could be used as a seed coating to improve the growth of a variety of plants, including wheat and rooibos, while yeasts originating from the rhizosphere of rooibos plants should be investigated further for their ability to improve plant growth under field conditions.