ARC Institute for Tropical and Subtropical Crops

Hluhluwe, South Africa

ARC Institute for Tropical and Subtropical Crops

Hluhluwe, South Africa

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De Beer Z.C.,ARC Institute for Tropical and Subtropical Crops | Sigawa A.,Mabhovo EBP
Acta Horticulturae | Year: 2010

The banana (Musa spp.) cultivars grown in the rural areas of South Africa are 'Pisang Awak' (ABB genome) (70%) and 'Cavendish' (AAA genome) (30%) in contrast to only 'Cavendish' in the commercial banana growing areas. 'Pisang Awak' is a hardy banana cultivar that is currently not grown for commercial purposes but as a domestic fruit for home use on small plots and as a fencing shrub. It does not seem to require expert commercial farming skills to cultivate and requires very little in terms of care as compared to established banana cultivars currently on the market. This makes it ideal for exploitation as a commercial crop by rural communities in these areas. However, until recently, this potential was overlooked and fruit was mostly wasted. Since the establishment of a banana-juice factory by the University of Johannesburg in 2005 in White River, South Africa, this cultivar is generating an income. Although 'Pisang Awak' is a low-yielding cultivar, it is a very good juice banana and up to 50% juice concentrate is extracted from the fruit in comparison to the 15% juice from 'Cavendish'. This project is aiming to evaluate several high-yielding juice bananas including hybrids from Honduras and to supply farmers with plants in two rural banana growing areas. Technology transfer on banana production is being done to cooperatives in selected areas and transport of fruit to ripening rooms and factories is being established. In a later stage, a packhouse will be built. This industry can be expanded significantly as the market for banana juice exists and is hardly exploited by the present juice production. Because of the organization of cooperatives in different areas, farmers do not require 30 ha or more to create an income-producing business.


Cronje R.B.,ARC Institute for Tropical and Subtropical Crops | Mostert P.G.,Mostert Consulting Services
Acta Horticulturae | Year: 2010

Fruit size plays an important role as a quality parameter and is as important as yield in the determination of profitability in litchi production. There is a limited increase in fruit size through optimization of standard cultural practices like fertilization, irrigation and pruning. Auxins play an important role in fruit size as they stimulate cell division and enhance cell enlargement. Therefore, the application of auxins increases fruit growth rate and influences size, ripening time, colour and storage quality. Many attempts have been made to increase litchi fruit size. Maxim® (3, 5, 6-TPA), a synthetic auxin, has shown good results on litchis in many countries including Israel, China and South Africa. Maxim® is already registered for citrus in South Africa and registration on litchis is planned. The aim of this research, therefore, was to evaluate Maxim® for the increase in fruit size and fruit retention in litchi (Litchi chinensis Sonn.), cv. HLH Mauritius, for the registration of Maxim® in South Africa. In the first year (2005/06) Maxim® was applied at the 1-, 2- and 3-g fruit let stage at 20 and 40 ppm, and the effect on yield and fruit size was determined. All treatments increased yield and fruit size, with the 40 ppm treatment at the 3-g stage performing best. In the second year (2006/07) the Maxim® applications were extended due to the first year's results. Maxim® was applied at the 2-, 3- and 4-g fruitlet stage at 20, 40 and 80 ppm. The effect on yield, fruit drop and fruit size was determined. All treatments increased yield and fruit size. The applications at the 3- and 4-g fruitlet stage, after the second natural fruit drop, proved to be most beneficial in increasing litchi fruit size. Considering the data obtained in both years, Maxim® application at 40 ppm after the second natural fruit drop (3- to 4-g stage) can be recommended. Furthermore, economic calculations revealed that the application of Maxim® can benefit producers financially.


Cronje R.B.,ARC Institute for Tropical and Subtropical Crops | Mostert P.G.,Mostert Consulting Services
Acta Horticulturae | Year: 2010

Like in all woody plants, carbohydrates are also important in the growth of litchi trees. There are strong seasonal influences in carbohydrate reserves which reflect the growth stages of a tree such as vegetative shooting, flowering and fruit growth. The starch reserves of HLH Mauritius litchi trees were determined as part of an orchard management program. Wood samples from the main branches of trees of various treatments were taken up to six times a year according to certain phenological stages of the trees. The starch content was analyzed using a modified AOAC method. Starch content varied from year to year, reflecting alternate bearing, as well as within a year, reflecting tree phenology. Vegetative growth, flowering and fruit growth reduced starch reserves while rest periods, such as the end of fruit growth until new vegetative flushing and the winter rest period, increased starch reserves again.


Cronje R.B.,Mostert Consulting Services | Mostert P.G.,ARC Institute for Tropical and Subtropical Crops
Acta Horticulturae | Year: 2010

The South African litchi industry is predominantly export orientated and great effort is put into gaining high yields and marketable fruit size. In spite of profuse flowering, litchi yield is usually inadequate, mainly because of massive fruitlet drop during the early period of fruit development. Fruit size is often hampered by insufficient irrigation and fertilization during the critical periods of fruit development. Although good research has been done on various aspects of litchi production this research often does not find its way into farm management. This background in litchi production was the reason for initiating a project which combines 'good agricultural practice' with research results in the area of irrigation, fertilization, use of plant growth regulators as well as other horticultural practices in order to reduce alternate bearing and increase yield and fruit size. Five management programs were developed and are compared with one another according to their effects on yield and fruit size. Three years of data have been collected and give a clear indication on how to manipulate litchi cropping. Furthermore, a software program to provide guideline for the management of litchi orchards is being developed and is currently being tested on various litchi farms. This program will include phenological charts for each production area, fertilizer and irrigation scheduling according to tree requirement as well as other practices that need to be done during the year. The data is interlinked and guidelines for orchard practices are given according to tree phenology and fruit development.


Rabie E.C.,ARC Institute for Tropical and Subtropical Crops | Mbatha B.W.,ARC Institute for Tropical and Subtropical Crops
Acta Horticulturae | Year: 2016

Sunburn on 'Queen' pineapples in South Africa can occur any time of the year but is more prominent during the summer months, peaking often during January and February. Temperatures >32°C and no breeze to cool the fruit are often experienced in cases of severe sunburn damage while other factors such as growing conditions (plants/fruit are "soft"), plant characteristics (ex. long peduncle and translucent fruit), nutritional status of the plant (ex. too much nitrogen) and the surrounding area where fields are planted (surrounding bush prevents air flow), also play a role. Crop losses can be as high as 25%, while in extreme cases damages can reach 70%. Eclipse®, a calcium carbonate and boron colloidal liquid sun shield film, was applied to a number of fields in trials during January/February 2013 and 2014 to prevent sunburn. Application took place at 4 and 2 weeks before harvest at 18 and 9 L ha-1 respectively during the first season (2013), while 5 different treatments were applied from 6 weeks to 1 week before harvest during the second season (2014). External sunburn damage was rated according to the degree of severity, namely 1 (slightly damaged - fruitlets show browning; fruit is still marketable), 2 (moderately damaged - fruitlets show more severe browning, sunken skin and often cracking between fruitlets; fruit will be rejected) and 3 (severely damaged - fruitlets show severe browning and cracking between fruitlets, flesh underneath the skin is whitish in colour and often extends to the core of fruit; fruit will be rejected). Severe symptoms provide easy access for diseases. Sunburn in these trials varied between 2 and 27% and the application of Eclipse reduced sunburn to between 0 and 14.4%. Eclipse® especially reduced moderate and severe sunburn damage.


Rabie E.C.,ARC Institute for Tropical and Subtropical Crops | Mbatha B.W.,ARC Institute for Tropical and Subtropical Crops | Tustin H.A.,ARC Institute for Tropical and Subtropical Crops
Acta Horticulturae | Year: 2013

Ninety percent of South Africa's fresh market pineapples are produced in Hluhluwe and consists of the 'Queen' cultivar. Managing the crop to produce pineapples all year round is achieved by planting the correct size of planting material at a certain planting time and manipulating the harvesting date by the artificial induction of flowering while applying standard cultivation practices for nutrition and crop protection. Natural induction of flowering is a severe problem for the pineapple grower and can result in serious losses. In Northern Kwazulu Natal, natural flowering occurs during the winter months (May-August), yielding an overproduction of fruit in December/January with consequently lower market prices. It affects crop management, increases harvesting cost due to multiple harvesting actions and can affect fruit quality. The main environmental factors responsible for natural flower induction are photoperiod (short days) and low temperatures but radiation and water supply can also play a role. The susceptibility of the pineapple plant to natural flowering is related to the age and the size of the plant. Aviglycine, an ethylene biosynthesis inhibitor, proved to control natural flowering to less than 2% at 100 mg L-1 applied in a spray volume of 1500 L/ha every fortnight. These application rates are costly and a series of trials were conducted to evaluate more cost effective application rates. The effect of plant size and planting time on the efficacy of treatments were also evaluated. It was found that by increasing the spray volume from 1500 to 3000 L/ha, and not increasing the amount of Aviglycine to apply a specific concentration of product (mg L-1), the dosage per hectare could be reduced. Plant size is also critical and therefore plantings made between November and January should be planted with smaller plants for Aviglycine treatments to be effective.


Froneman I.J.,ARC Institute for Tropical and Subtropical Crops | Bijzet Z.,ARC Institute for Tropical and Subtropical Crops | Sippel A.D.,ARC Institute for Tropical and Subtropical Crops | Bower J.P.,University of KwaZulu - Natal
Acta Horticulturae | Year: 2012

The effect of self-and cross-pollination on fruit retention and fruit characteristics in 'Wai Chee' litchi was investigated. Enclosed flower panicles were handpollinated with male 2 (M2) pollen from 'Fay Zee Siu', 'HLH Mauritius', 'McLean's Red' and 'Wai Chee' flowers. The number of fruitlets retained per panicle was determined throughout the fruit development period from fruit set to harvest on a daily basis. At harvest, the surviving fruit was measured to determine the effect of pollen parent on different fruit characteristics. Initial fruit set in 'Wai Chee' was lower in all cross-pollinating treatments compared to the self-pollinating treatment. However, final fruit retention was higher with all cross-pollinators compared to selfpollination, with 'Fay Zee Siu' and 'McLean's Red' showing significant increases in retention of 48 and 30% respectively. Fruit size, fruit-and flesh mass in 'Wai Chee' tended to be increased with cross-pollination, but these increases were not significant. No clear effect of pollen donor could be found on seed-and rind mass of fruit, with only slight variation among the different treatments. Results indicated that the inclusion of cross-pollinators in litchi orchards may have beneficial effects on production.H.


Severn-Ellis A.,ARC Institute for Tropical and Subtropical Crops | Schoeman M.H.,ARC Institute for Tropical and Subtropical Crops | Willemse S.,ARC Institute for Tropical and Subtropical Crops | Sippel A.,ARC Institute for Tropical and Subtropical Crops | And 2 more authors.
Acta Horticulturae | Year: 2012

Soil-borne vascular wilt pathogens cause among the most devastating plant diseases worldwide. Guava wilt disease (GWD) caused by Nalanthamala psidii, resulted in the loss of more than half the guava production area in the Limpopo and Mpumalanga provinces of South Africa during the 1980s. Resistant guava selections were developed but renewed outbreaks of guava wilt disease in 2009, now also affecting the tolerant ARC-ITSC developed cultivar 'TS-G2', is placing the guava industry under threat once again. Alternative control measures are currently not available and host resistance remains the most logical choice for control. However, the lack of known sources of plant resistance and the emergence of additional pathogen races pose as major obstacles. Accurate identification and knowledge about the genetic variation within the pathogen population are therefore key aspects in the development of resistant guava cultivars. The aim of this study was firstly to determine the identity of 18 new fungal isolates obtained from infected 'TS-G2' trees. The internal transcribed spacer of the ribosomal RNA gene cluster (ITS), nuclear large ribosomal sub-unit (LSU), as well as the partial second largest subunit of the RNA polymerase II (rpb2) and the larger subunit of ATP citrate lyase (acl1) gene exons and introns of the new fungal isolates and reference isolates were sequenced and compared. Sequence analysis established the identity of the new isolates to be identical to N. psidii reference strain (CBS 439.89) previously isolated in South Africa, but differed from N. psidii stains from Malaysia and Taiwan. Although species diagnosis was possible, it was not possible to show geographic distribution- or determine pathogenicity relationships between isolates. The development of microsatellites or Simple Sequence Repeat (SSR) markers using high throughput sequencing was therefore investigated. A total of 15 645 SSRs were identified consisting mostly of tri- and tertra- nucleotide motifs. Selected SSRs will be used to facilitate further fungal population studies. © ISHS.

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