From 2004 to 2009, the Tea Research Foundation of Central Africa implemented 11 out of 12 planned research projects based on its Strategic Plan for 2002 – 2007.
From 2004 to 2011, the Tea Research Foundation of Central Africa (TRFCA) implemented twelve research projects based on its Strategic Plan for the 2003 – 2008 which is now under review for another five years from Jul 2010. The 12 research projects are:
Projects 2 and 8 were funded by the European Union (EU) under the Stabex Fund up to December 2005. The Foundation continued to fund Project 2 through its own resources from 2007 but Project 8 was terminated soon after the EU funding phased out because the Foundation could not sustain it using its own resources. Project 9, which aimed at enforcing the rights of the plant breeders in developing new cultivars, did not actually take off because it was later felt that this was not a high priority area for the Foundation.
These research highlights are from results of the various project activities that were implemented from 2004 to 2009. Some of the projects have been completed and written up while others are continuing.
The overall goal of this project was to improve productivity and quality of central African teas and was implemented under two specific objectives: a) to establish rapid and reliable selection criteria for tolerance to drought, high temperature and for quality; and b) to produce better drought tolerant and high quality vegetatively propagated (VP) cultivars with a relatively long growing season.
The main activities under objective a) were evaluating made tea quality of selected cultivars by looking at leaf colour of the flush on the bush, fermentation duration using the chloroform test and tasters’ scores and valuation of made tea and, assessing various tea bush growth characteristics. The tea quality parameters were correlated to bush growth characteristics and tasters’ valuation of made tea.
Literature review was conducted on the effectiveness, methodology and practicability of using proline as selection tool for drought tolerance. Other studies for the same objective included assessment of root growth, bush characteristics and root starch content of drought tolerant and susceptible cultivars; molecular markers in relation to cultivar response to drought and the relationship between nursery growth pattern in cold and hot seasons and subsequent performance of the same bushes after planting in the field.
There was an inverse relationship between the fermentation time of leaf under miniature manufacturing conditions and tasters’ black tea quality valuation. There was a positive relationship between colour of the flush on the bush and chloroform test and tasters’ valuation. Biochemical analysis for tea quality parameters in green leaf and in black tea conducted and these were correlated to tasters’ organoleptic assessments, in order to speed up the selection process.
Studies to establish the relationship between root growth and bush growth characteristics of young and mature plants of drought tolerant and susceptible cultivars showed no significant differences between susceptible and drought tolerant cultivars in root length at 10 months after planting in pots but at 22 months. At this age, drought tolerant cultivars had longer and deeper rooted roots than the susceptible ones. This difference was not evident among plants that were semi-mature, and this validated TRFCA recommendation to prune young plants annually in the first 5 years of planting in order to protect them from water stress. Drought tolerant cultivars had more root starch content than drought susceptible ones.
There was a significant difference in the leaf: root ratio between PC 168 and PC 185. PC 168 which, readily showed sun-scorch and defoliated under severe water stress conditions had a lower leaf: root ratio than PC 185 which was generally free from sun-scorch and defoliation. This difference probably accounted for the difference in cultivar response to drought conditions whereby, those with larger leaf area like PC 168 had to defoliate to avoid loss of water from a large leaf area.
Results from molecular markers revealed that none of the screened RAPD markers showed any association to Helopeltis or low temperature resistance. RAPD8 primer showed a band at 3 000 bp which was strongly associated to drought tolerance and six of the 8 drought tolerant cultivars had this band which was absent in all drought susceptible cultivars tested in this study. RAPD7 marker, showed a band at 1 400bp in four of the 8 drought tolerant cultivars. The two primers considered together clearly distinguished all the 8 drought tolerant cultivars from the susceptible ones.
Cold season plant growth in the nursery assessed in July / August followed by field assessment of the same plants under field conditions in the hot season in November 2005 and two years later in November 2007 was not correlated to hot season growth characteristics under field conditions. The hot season growth characteristics of plants in the nursery were however correlated to growth characteristics in the hot season under field conditions.
Literature review on use of proline accumulation as possible selection criterion for drought tolerance in tea showed that the method can only be reliably applied under controlled drought conditions since proline accumulation increases under prolonged severe drought conditions and levels return to normal within few hours of rehydration.
The evaluation of cultivars under objective b) included selection for drought tolerance under rainfed conditions and off-season growth. The 2005 and 2008 drought conditions offered ideal conditions for selecting drought tolerant tea cultivars. Sixteen selections were found more promising and short-listed for further evaluation for yield and other agronomic attributes and black tea quality.
The Tea Research Foundation established a field gene bank of 267 accessions collected from the tea estates in Malawi and a duplicate one in Zimbabwe. A conservatory of released cultivars has also been established. The objective of establishing the field gene bank is to conserve the tea germplasm which could be lost through the replacement programme of the Indian and China seedling tea with vegetatively propagated cultivars. Once conserved, the germplasm will facilitate future breeding programmes and enhance further genetic improvement of the crop.
In order to broaden the tea genetic base which is essential for plant breeding, cultivars and plant materials from other parts of the world will be introduced and included in the gene-banks in Malawi and Zimbabwe.
To fully utilise the collection, there is need to characterize them using morphological, biochemical and molecular markers. The characterisation of accessions is on-going and should be completed when they are mature.
Tea breeding programmes generate new cultivars for adoption by growers. In order to promote adoption, superior rooted planting materials must be propagated and used by growers and this requires use of suitable propagation facilities. These facilities were old at Mimosa Research Station and needed upgrading. This was the aim of the project through funding by the European Union.
Old nurseries were rehabilitated and one new nursery erected. A field of vetiver grass was established for a reliable source of grass for weaving the nurseries. The facilities are used at the Foundation.
Successful field crop establishment depends on several factors, one of which is the quality of planting materials. A good nursery plant growth will produce vigorous plants easy to establish in the field and the growth can be enhanced through several ways. Several experiments were conducted from 2004 to 2008 in order to determine how nursery plant growth can be enhanced and how seedling plants planted at young age can easily establish in the field.
Results showed that plant survival and field establishment after planting 4-6 months old seedlings was good provided the soil moisture conditions were adequate soon after planting and field management practices were optimal. This underscored the need to monitor the local meteorological forecast in order to decide the best time of planting out young plants in the field.
When young seedlings were planted in trenches and bigger planting holes, trenching or digging big single holes had no advantage in plant survival and crop establishment over planting in holes equivalent to the size of planting pots.
The use of Rootstim rooting hormone promoted early callus - development and rooting of cuttings and plucking shoots. Foliar feeds Calmag + B and magnesium sulphate enhanced post-rooting growth of nursery plants. These products could therefore be used in the nursery to enhance early rooting and nursery plant growth.
Results from the experiments on establishing the best method of bringing into bearing of plants raised from plucking shoots and transplanted at an early age demonstrated that annual prunes are unnecessary for good field establishment and development. A maximum of 2 – 3 prunes over the first six years would be adequate and pruning may be delayed up to the third year, provided the bushes are tipped in and kept under plucking in the first and second year.
Top-working experiments revealed that in Malawi, the period between April and August were optimum time for grafting in the field. Top working was found not a feasible technique for the multi-stemmed china seedling tea because of problems of sucker growth from the un-grafted stems.
Among the factors that affect made tea yield and quality is the length of the plucking round which can either be cultivar or season or location dependent. Some cultivars require a longer plucking round length while others a short cycle. The cycle can also be long or short depending on the season. In the cool dry season in Malawi, rate of plant growth is slow and the cycle is longer than 10/11 days. This is optimal round in the wet season which is universally used on all cultivars.
The objective of this project was to establish optimum shoot age and optimum plucking round for the different commercial cultivars so that plucking is done at the right time when majority of the shoots have reached the required plucking standard and when the proportion of 2 + bud and 3 + bud shoots is highest.
Results from the experiments showed that most of the cultivars have a shoot replacement cycle of 42 days while others have a replacement cycle of 38 / 39 or up to 49 days depending on the growing conditions. The 42 days replacement cycle length validates the current plucking rounds of 10/11 days or 14 days. Optimum plucking round experiments showed that 16/17 days was the optimum plucking round length for SFS 150 at Mimosa during the rainy season. Yields from the 10/11 days round, the current commonly used plucking round, were not significantly different from those of other tested rounds for SFS 204 at Mimosa and Satemwa, suggesting that growers could plan to put some fields under longer rounds to cope with labour shortages during the main season.
The experiments for two other cultivars, PC 117 and PC 168 are still ongoing to determine the effect of the plucking round lengths on yield and made tea quality, before concluding this project.
Availability of labour to pluck tea at most estates, especially in Zimbabwe, is a critical constraint to production of tea, and successful machine plucking could address this problem. The objective of this project was to generate information and procedures on how plucking of tea could be successfully mechanised by reducing the negative effects of machine plucking on yield and quality.
The major findings from the initial work in Malawi and Zimbabwe on seedling and vegetatively propagated cultivars were that yield under mechanical plucking declined with years, particularly with PC 108; a 14-day plucking round raising the plucking blade after every 2nd or 3rd round was the best compromise for machine plucking in terms of yield and green leaf quality. The causes of yield decline were not well understood and there was need to investigate this in order to minimise crop loss under mechanical plucking of tea. This led to the second phase of the project which is determining the effect of machine plucking on bush physiology.
Low and high soil pH can be major impediments to increased made tea yields. It was suspected that low yield at some estates was caused by low soil pH and there was no information about the extent of this problem at estate in Zimbabwe and Malawi. It was further suspected that the soil pH was decreasing at some estates due to long-term use of nitrogenous fertilisers and some growers had subsequently started liming their fields in order to reduce the effect of this problem on yield. The objective of this project was to determine the magnitude of the problem at all estates in Zimbabwe and Malawi and thereafter find ways of redressing it.A soil pH survey conducted in 2006 showed that soil acidity problem was more widespread in Zimbabwe than in Malawi. There was a positive correlation between pH and yield in Malawi but negative in Zimbabwe. The results further indicated that other factors were more limiting than soil acidity at pH levels of 4. These findings shifted the focus of the project to micronutrients and bush productivity which is being pursued.
Despite the recommendations from the Tea Research Foundation of Central Africa on good agricultural practices for optimal yields, tea production practices vary between estates. When this project was initiated there was no information on the most important factors that determine the productivity of tea fields. The objective of the project was to identify the most important production factors and establish database of these factors for use by the tea industry. Growers would then intervene with appropriate practices to raise the total value (productivity and quality) of the existing seedling and vegetatively propagated (VP) cultivars.
A survey was conducted at all estates in Malawi and Zimbabwe and recorded by estate, production practices such the levels of fertiliser application, plucking methods, pruning cycles, the rainfall, temperature and other environmental conditions experienced. These data variables were correlated to tea yields at each estate. The survey further documented growers’ own practices not recommended by the Foundation and thus not found in the Tea Planters Handbook.
The results from Zimbabwe showed that there was a negative correlation between yield and altitude, plant population, area planted, machine and shear lucking, heat units and maximum temperature but positive between yield and nitrogen and years after down pruning. Similar results were found in Malawi.
Differences in plucking methods, nitrogen levels applied and plant population explained the variation in yield between estates. The type of cultivars further explained the variation in yield between estates. Those that planted large areas to clonal cultivars tended to have higher yield than those that had predominantly Indian or China seedling tea. Multiple regression analysis of the various factors of production on yield led to the development of a model for predicting yield. The model has to be pre-tested at several estates.
Growers' own field practices not found in the Planters' Hand book included pruning during the main season from November to January against the recommended practice of pruning from May to June and, lung pruning. These practices were reported in the Newsletters for the information of growers.
New information, not included in the Planters' Handbook, was also documented and this was on new rootstock cultivars, control of carpenter moth, diversification of tea product through value adding and business viability, mechanical plucking of tea, time of pruning young tea in Malawi and Zimbabwe, optimum shoot growth for some popular tea cultivars and root growth of VP cultivars and their response to drought conditions.
Tea quality is an important factor of tea production. It determines the price the tea fetches on the local and export markets. Recommended cultivars must therefore have the desired quality characteristics and all factors that influence it must be known. Further, and as marketing strategy, what distinguishes teas of this region must be known. The objective of this project was to promote the marketability of teas in the central African region and increase profit margin through production of high quality teas and tea by-products on the basis of its market requirements and the biochemical characteristics that are responsible for the buyers’ black tea quality requirements.
To achieve this goal, teas from the region had to be defined in relation to how it is influenced by the plant material, agronomic practices, manufacturing practices; seasonal variation of some quality, biochemical and physiological characteristics. Literature was searched on health benefit properties of tea and some of the desirable parameters were being quantified in TRFCA cultivars.
Literature and consultations with professional buyers of Malawi teas from the region characterised the teas from central Africa as being plain (without aroma), characterised by coppery red colour of the infused leaf, and its liquor being bright, strong, brisk and taking milk well. Its quality is governed by the fast growing conditions in the main growing season. High nitrogen rates, shade and coarse plucking all have negative effect on black tea quality. Potassium nitrate and bio-fertilizers were reported to improve quality. Withering time and temperature as well as fermentation temperature and duration all affect black tea quality and their effect is being investigated.
Literature review further showed that polyphenols, flavonoids, caffeine and some amino acids such as theanine and gallated catechins offer a number of health benefits to tea drinkers These parameters are being quantified in TRFCA cultivars.
Collaborative activities with other Institutions
The Research Foundation of Central Africa has a policy to collaborate with local and international research organisations. The objectives of this policy is scientists to exchange scientific information, plant germplasm, scientific manpower and publications with fellow scientist of other institutions, share with them experiences and other services like analytical services and conduct joint experiments. Such activities can improve and increase the Foundation's capacity to conduct its research programmes.
The Foundation has been collaborating with the University of Pretoria for a long time, dating back to the early eighties. Ongoing collaborative activities are under the Technology and Human Resources Program (THRIP) project and Southern Africa Biochemistry and Informatics for Natural Products Network (SABINA)
In the THRIP project, the UP seeks, with contribution from the Foundation as an industrial partner, research grants from the Government of the Republic of South Africa. The Foundation benefits from the collaboration by accessing some of the University's facilities such as the biochemistry analytical laboratory for made tea sample and data analysis. In 2007, TRFCA contributed ZAR 1,894,030 to the project called “Matching tea cultivars with market demand". These funds contributed to the purchase of an Environmentally Controlled Miniature manufacturing unit, the Tea Craft. This unit is used to manufacture made tea samples at the Foundation and sends them to the University for Biochemical analysis of Tea Quality Parameters using facilities such as HPLC and other services. This analysis cannot be done at the Foundation because there are no analytical laboratory services.
Through the THRIPS project, one scientist from the Foundation, Mrs Chikondi Katungwe, was enrolled for Masters of Science degree training and she accesses other facilities within the project to conduct her research. A new similar THRIP project proposal has been developed in which the Foundation is classified, in order to qualify as a partner in the project, as a small enterprise. As in the first project, TRFCA will contribute to this project through biochemical analysis of made tea samples for tea quality at the University.
The Southern Africa Biochemistry and Informatics for Natural Products Network (SABINA) is a network of University of Dar Es Salaam, University of Pretoria, Witwatersrand University, University of Namibia, University of Malawi and the TRFCA as an industrial partner. Carnegie Foundation in New York will financially support the network for three years through the Regional Initiative in Science and Technology.
The objective of the Network is to train students from the network Universities and scientists from collaborating research institutes to PhD and MSc levels through research in the biochemistry and chemistry of natural products, including bioinformatics. The network coordinating office is located in Malawi at the University of Malawi, Chancellor College. Professor J. D. Saka is the head of this office.
Through this network, the Foundation has secured a fellowship to train Mr. N I K Mphangwe, a plant breeder at TFCA, to a Ph D level in the field of genetics and informatics. This is a huge benefit to TRFCA through collaboration with the UP.
The Foundation has also co-joined the University of Pretoria to prepare a proposal seeking funding from the African Caribbean and Pacific countries Science and Technology programme. The objective of this programme is to develop policies about the promotion or dissemination of technologies developed through SABINA network to intended end users.
In the proposal, the Foundation and the UP have sought funding for the erection of a rain shelter at Mimosa Tea Research Station. The rain shelter will be used to screen tea cultivars for resistance to drought and demonstrate the resistant one to the tea industry. Through the demonstrations, it is expected the adoption of drought resistant cultivars will be increased and production to increase as well, particularly under the current frequent weather conditions.
The Foundation signed collaborative agreements with the Tea Research Foundation of the United Planters Association of Southern India (UPASI TRF) in 2008, with the Tea Research Institute of Tanzania and with the Tea Research Foundation of Kenya in 2004. Through these collaborations TRFCA has agreed to exchange with the institutions annual reports, Newsletters and other publications. Exchange visits and scientific manpower interactions are part of the agreements. The Foundation attaches these collaborations significant importance because they contribute to its performance.
Through the agreements, TRFK, TRFCA and TRIT have agreed to form a joint Committee chaired by TRFK. The committee will monitor and evaluate the tripartite collaborative activities. One of the important activities is the implementation of a regional cultivar trial in order to identify cultivars that are regionally suitable and those that have specific adaptability to environmental conditions in any of the three countries. This trial will generate useful information for tea hybridisation programmes for the region.
Japan Tea research Institution