Sweating the sweet stuff in Sulawesi
Healthy cocoa pods after grafting.
Dr McMahon and a cocoa farmer's family.
Where chocolate spells survival, not dessert
Chocolate lovers world-wide, and more than 400,000 Indonesian small-scale cocoa growers, are benefitting from successful work by two La Trobe University researchers who are helping improve cocoa crops in Sulawesi.
Their eff orts, though the Australian Centre for International Agricultural Research in collaboration with colleagues in Indonesia, the University of Sydney and the global chocolate manufacturer Mars Inc, were recently featured on ABC television.
Associate Professor in Botany Philip Keane and Post-doctoral Research Fellow Peter McMahon for the past eight years have been building on links between Australia and Sulawesi that – believe it or not – go back hundreds, if not thousands of years.
Most Sulawesi cocoa growers, Dr Keane explains, are Makassan and Bugis people, traditional seafarers whose ships visited northern Australian shores to trade for beche-de-mer and other products. As former migrant labourers on cocoa plantations in Malaysia they brought back plants and began their own cocoa farms in Sulawesi. Today their trees have made the small island the world’s third-largest cocoa exporter, aft er the Ivory Coast and Ghana. Most of this occurred over the last twenty years in a boom of spontaneous planting, leading to economic benefits that allow small holders to send their children to school and build better houses.
Chocolate is made from cocoa beans, formed in pods on small trees that originated in the Upper Amazon region of South America. Mayans and Aztecs used cocoa as currency, beverages and medicine. Cocoa production, says Dr Keane, is relatively trouble-free during its early expansion in a new area, but is oft en followed by the build-up of devastating pest and disease problems.
Pest-resistant cocoa
The same pattern has occurred in Sulawesi. The La Trobe work is helping local farmers select a new generation of pest-resistant cocoa types based on work Dr Keane had previously observed in Papua New Guinea and other places since the late 1960s.
The two researchers say there are three serious threats to the industry in Sulawesi. These are Cocoa Pod Borer, the caterpillar of the moth Conopomorpha cramerella; Pod Rot caused by Phytophthora palmivora, a very serious disease of cocoa throughout the tropics; and Vascular-Streak Dieback caused by the fungus Oncobasidium theobromae.
Luckily, cocoa grown in Sulawesi is genetically diverse, due to the range of cocoa types introduced to the region. They were generally ‘outbreeding’ – able to cross with diff erent cocoa types – and propagated by seed.
This diversity, the researchers say, is ideal when it comes to selecting plants for pest and disease resistance and improved quality. For example, during a severe epidemic of dieback in Papua New Guinea in the 1960s, resistant types were selected, while very susceptible types became extinct. This led to long-lasting control of the disease.
The main aim of the La Trobe project in Sulawesi was to show that during natural epidemics, similar ‘field-based selection’ for resistant and higher yielding types is possible from among the genetic diversity of trees grown on farms. Says Dr McMahon: ‘Farmers know their disease resistant and higher yielding trees from constant contact with them. We encourage them to identify these trees and propagate them by graft ing or budding onto inferior trees.’
During field trials, the two botanists established collections of useful genotypes and screened potentially useful clones. ‘This is not high-powered genetic engineering,’ says Dr Keane. ‘We showed that sound research and improvement in the lot of farm families can be done with minimal external resources, by using the natural advantages of the area – its genetic diversity, local epidemics, environment and the knowledge of farmers.’
Dr McMahon explains that with the help of local farmers, extension officers and other scientists, they identified potentially resistant trees, collected bud-wood from them, and graft ed this onto mature trees. This was done in a series of replicated trials.
‘The graft s were monitored for growth and dieback infection, and later for cocoa quality and the incidence and severity of Pod Borer and Pod Rot,’ he says. ‘While the old wood still produces cocoa pods, the new wood, which gradually replaces the old, produces disease-resistant pods.’
Dr Keane’s and Dr McMahon’s research found the incidence of Pod Borer ranged from 63 to 95 per cent and Pod Rot from 3 to 40 per cent. One local clone was found to have a very low amount of rot. Dieback damage was mostly low, evidence of prolonged selection for resistance in the region, although recently it has been higher in some areas, associated with a change in the symptoms of the disease that is yet to be explained.
So while botanical research and intervention has been a success, Dr Keane says social research by his Sydney colleagues reveals that lack of labour – or the return from the crop to employ enough labour – remains a major impediment to sustainable production.
Cocoa has been nominated the number one priority of West Sulawesi by the region’s Governor. The industry reportedly off ers great potential to alleviate poverty because world cocoa prices are high, about $A3,800 a tonne.
Growers, who average about one tonne per hectare, receive about eighty per cent of that amount. The Indonesian Government has begun a program to revitalise cocoa farms in the face of these problems, and the Australian projects link into this initiative.