This program builds on research and extension activities started in an AusAID ACNRS project Management of potato late blight in PNG (2004). The objectives of the current project are to introduce, multiply, evaluate and deploy late blight resistant clonal material into PNG and to develop safe, cost effective integrated late blight management strategies for existing and new potato cultivars and ultimately to rehabilitate potato production for smallholders.

Thirty-six International Potato Centre (CIP) potato clones, introduced into PNG in 2003, were resurrected from tissue culture in Kerevat and propagated to seed tubers in National Agricultural Research Institute (NARI) facilities in Aiyura and Tambul. In field trials without fungicide sprays, 12 of these clones survived late blight disease several weeks longer than more susceptible clones, which died before reaching maturity. Four of 12 cultivars from Australia that were screened in 3 field trials proved to be significantly less susceptible than the standard Sequoia and will be further evaluated in under a fungicide spray regime.

Ten 'best bet' late blight resistant CIP potato clones were propagated as minitubers by Lima, Peru and will be shipped to PNG in December/January to boost seed supplies for trials. Tissues culture plantlets of the 10 clones will be also be sent to PNG from Peru to refresh current stocks, as well as to Australia as back-up tissue culture stocks.

Lack of seed potatoes is a critical factor preventing farmers from participating in potato production. A potato production specialist, Corina Horstra from Department of Primary Industries Victoria, reviewed propagation and multiplication capability in PNG during a visit to the tissue culture and seed tuber production facilities at Aiyura and Tambul, respectively, in June 2005. It was concluded that both NARI (tissue culture production) and Fresh Produce Development Agency (seed potato production) have the technical capability to produce high quality seed potatoes for PNG. A number of technical problems at the tissue culture facility at Aiyura, which were identified as hampering the consistent supply of tissue culture plantlets to stock the FPDA screen houses in Tambul, are being rectified. FPDA has built additional screen houses at Tambul to increase their minituber production capability for the seed program.

Availability of fungicides in PNG is limited to copper and chlorothalonil based products. Preliminary fungicide evaluation trials had demonstrated that weekly sprays with copper based products provided sufficient control of late blight to allow the susceptible cultivar Sequoia to be grown to maturity. In further trials, weekly sprays of chlorothalonil proved to be superior to copper sprays in protecting plants from late blight. However, chlorothalonil is significantly more expensive than copper and the challenge is to determine whether the integration of the two fungicides can provide sufficient protection of Sequoia crop but at a reduced cost.

FPDA, with input from NARI, have been successful in laying the foundation for rebuilding PNG potato industry through the delivery of supplies of quality seed and through village extension worker training activities which have involved 2500 smallholders. However, at present potato production in PNG is generally limited to a relatively small number of 'commercial' growers who have access to land, backpack sprayers, chemicals, seed potatoes and labour and based on the highly susceptible cultivar Sequoia.

There is renewed confidence in potato production in PNG following the epidemic of potato late blight that wiped out potato production in 2003. Quantities of locally grown potatoes of the favoured variety Sequoia can be found in the market places of major centres in PNG. For the moment it seems that potatoes are grown mostly by a small number of 'commercial' farmers who can afford the seed, chemicals and labour. They have learnt from the results of field trials conducted through this project, and from their own experience, how to manage late blight in the highly susceptible Sequoia. In order to keep the plants alive until maturity, the crop must be sprayed every 3 to 5 days with fungicides. The average crop receives 12 to 20 fungicide sprays throughout its lifetime, an intensive regime that may be too much for 'subsistence' farmers who once relied on potatoes as a valuable cash crop. This situation will not change unless late blight resistant varieties are made available.

One of the objectives of the project is to establish late blight resistant cultivars in PNG. It should be possible to grow resistant cultivars with significantly less chemical treatments than the current variety. Several potato varieties developed by the International Potato Centre in Peru (CIP) were tested in the field by National Agricultural Research Institute (NARI) scientists and proved to be very resistant to potato late blight. In these trials, a number of varieties showed no sign of disease throughout the life of the crop, whereas the susceptible Sequoia died within weeks of planting. A selection of these varieties is now being multiplied in tissue culture by NARI and will be grown on as seed potatoes by the Fresh Produce Development Agency for distribution to selected growers for further testing. In the meantime, several additional CIP varieties will be screened for disease resistance so that further selections can be made. This will ensure the availability of several varieties in the market place over the next few years.

Potatoes cannot be grown in PNG without fungicide treatments. An objective of the project is to identify cost effective and safe chemical treatments for control late blight. Fungicide products containing copper or chlorothalonil are being currently by farmers. In recent trials, spray treatments with chlorothalonil were superior to treatments with copper and significantly delayed the onset of late blight in the crop. In trials that tested how often a crop needed to treated for effective disease control, chlorothalonil treatments applied no less than every 7 days resulted in the best yields. In contrast, crops sprayed with copper every 7 days did not reach maturity.

Reliance on one fungicide for potato late blight control is not sustainable. The systemic fungicide potassium phosphonate, which has shown promise in controlling late blight in a number of countries around the world. It is available in PNG (Agri Phos 600) and has registration for potato late blight control. This fungicide is relatively cost effective and safe to use. It will be trialled in the field and integrated with the protectant fungicide chlorothalonil.

An important project objective is the consistent and assured supply of seed potatoes of current and new varieties into the market place. The tissue culture laboratory at Aiyura is critical to this process. Several changes to operational protocols over the past year resulted in significant improvements in the quality and throughput of potato plantlets from this laboratory. These plantlets are used by FPDA to produce minituber and the subsequent field grown generations of Certified Seed Potatoes in PNG.

At a meeting late in 2006, the project team selected four CIP clones that had looked promising in field trials for fast track multiplication for farmer trials. The clones were selected on the basis of their resistance to potato late blight and favourable agronomic, cooking and flavour traits. Twelve hundred tissue culture plantlets of each clone were multiplied at the tissue culture facility in Aiyura (Coffee Industry Council) and planted in screenhouses at Tambul in early June to be grown-on to produce minitubers. This material will be multiplied in the field to Generation 2 and distributed to selected commercial and smallholder farmers for evaluation by the end of 2008. In the meantime, the performance of other CIP clones is being evaluated in a series of field trials at Tambul and Mt Hagen. Although many of these clones are resistant or moderately resistant to potato late blight, some have proved to be highly susceptible to the intractable disease bacterial wilt, which is more difficult to manage than blight.

The effectiveness of the systemic fungicide potassium phosphonate in controlling potato late blight was evaluated in field trials at two different locations. Different rates and intervals of application of the fungicides were compared with an untreated control and a standard chlorothalonil treatment (applied every 7 days). The phosphonate treatments provided some measure of protection against potato late blight on the susceptible variety Sequoia but were not as effective as the standard chlorothalonil treatment. Experience in South America indicates that this fungicide is likely to be more effective when used on potato cultivars that have some resistance to potato late blight. Further trials will test whether there are any benefits in integrating the phosphonate and chlorothalonil treatments, since the optimum spray interval for phosphonate was 14 days compared with 7 days for the standard treatment.

There is currently a serious shortage of seed potatoes in PNG due to a shortage of supply of tissue culture plantlets of the cultivar Sequoia over the past few years. Production of plantlets has been scaled in the past 12 months and the tissue culture laboratory has been producing nearly 6000 plantlets per month. However, it will take two years to produce stocks of Certified Seed (generation 4) from each batch of plantlets.

Whilst this project is focused on potato late blight, a number of other diseases are posing significant challenges for potato seed and ware production. These include the potato leaf-roll virus, Rhizoctonia stem canker, bacterial wilt and target spot (Alternaria solani), which appear to have become more prevalent in commercial scale production of potatoes.

Late blight disease prevents smallholder farmers in Papua New Guinea (PNG) from growing the popular but highly susceptible potato variety Sequoia, which needs weekly fungicide sprays to be productive. The aim of the project is to introduce late blight resistant varieties, backed up with integrated disease management strategies, and the capacity to produce consistent quantities of quality seed potatoes of the new varieties for smallholder farmers.
The first field generation of four late blight resistant clones, bred by the International Potato Centre (CIP) and selected for farmer evaluation trials, has been harvested and will be grown on for a second generation before distribution. Selection of these clones was based on late blight resistance and favourable agronomic, cooking and flavour traits in field trials. A smaller quantity of seed of these clones is currently being multiplied for preliminary release to farmers for evaluation. Of the 59 CIP clones available, 29 have been screened so far and a further 21 as yet untested clones will undergo preliminary screening in field trials over the next 6 months. Further selections for farmer evaluation will be made when analysis of this year's trial data is completed.
Trials to date have demonstrated the effectiveness of the contact fungicide chlorothalonil in controlling late blight in Sequoia potato crops. However, additional fungicides, which have systemic and curative properties, are needed to improve late blight control, particularly in the young, rapidly growing crop. Protecting the young crop for as long as possible is critical in minimising disease spread and yield loss. Advice on the most appropriate chemicals for PNG is being sought from European experts and chemical companies.
Seed potatoes of the variety Sequoia are currently in short supply in PNG because of limited supplies of tissue culture plants in the past. The output of plantlets has increased significantly over the past 12 months resulting in a steady supply of tubers being multiplied at Tambul. As a result, new supplies of commercial seed stocks will steadily increase from June this year.
Abstracts and posters of the results of fungicide and CIP clone evaluation trials in PNG were presented at the Third International Late Blight Conference in Beijing in April 2008. Dolf de Boer and Andr Drenth attended the conference, along with 152 other delegates from 34 countries. The CIP clone trial data from PNG will prove to be very relevant to potato production in tropical highland environments in other countries, such as Indonesia and East Timor. The pre conference workshop provided valuable information on standardised international procedures for research into late blight including fungicide and variety evaluation. A CIP training manual for Training of Trainers in the management of late blight presented at the workshop and can be adapted for training Village Extension Workers in PNG. Access to world experts on late blight management was invaluable in helping to focus project activities in PNG.
The Fresh Produce Development Agency has recently employed a full-time extension officer who will facilitate a farmer survey to identify constraints to growing potatoes, conduct farmer field school activities on late blight management using the CIP training modules, and assist with farmer evaluation trials of the selected CIP clones.

The devastating late blight disease caused by Phytophthora infestans has prevented smallholder farmers in Papua New Guinea from growing the popular potato variety Sequoia. Seed potatoes, fertiliser and chemicals are expensive and weekly fungicide sprays are now needed to make this variety productive.
A major milestone for the project was achieved with the release of late blight resistant varieties for farmer trials. In December 2008, small quantities of seed potatoes of four late blight resistant clones were given to nine potato farmers in the Eastern and Western Highlands Provinces for evaluation alongside Sequoia. The farmers were Village Extension Workers and seed potato growers for the Fresh Produce Development Agency (FPDA).
The clones are part of a collection that was bred by the International Potato Centre (CIP) for tropical highland environments. The four clones selected had a high level of resistance to late blight and favourable agronomic, cooking and flavour traits in trials conducted by the National Agriculture Research Institute (NARI).
Unsprayed Sequoia plants were destroyed by late blight within nine weeks of planting in the farmers fields. A low level of late blight developed in two of the four clones as the crops began to mature. The yields of the unsprayed CIP clones were comparable to the yields of the sprayed Sequoia. However, all CIP clones were affected by low levels of early blight disease (Alternaria solani) after crop flowering. The CIP clones, in general, are susceptible to this disease, particularly under conditions of poor nutrition.
The growers rated the four clones favourably against the Sequoia on the basis of growth, tuber characteristics, cooking (frying and boiling) and taste. Field days were held at two sites at the crop flowering stage and at harvest time. Additional field days were held in the Eastern and Western Highlands Provinces where the clones were on display in field plots. More seed lots of the four clones will be released to farmers for evaluation in the coming months.
An additional four clones with good disease resistance and agronomic traits are currently being multiplied for farmer trials. In the meantime, clones from later CIP breeding populations, which have multiple, rather than single gene resistance to late blight, are being screened for resistance.
Further testing of potato late blight disease samples by the Scottish Crop Research Institute (SCRI) has confirmed that the PNG population of Phytophthora infestans is made up of only one strain, designated 2_A1. So far, a total of 130 isolates have been tested for strain type in samples taken throughout the Highland Provinces.
A restructure of work processes in the tissue culture laboratory at Aiyura resulted in significant improvements in the numbers and quality of Sequoia plantlets being delivered to the FPDA for further multiplication. Monthly targets of 12,000 plantlets have recently been achieved. However, the flow-on supply of certified seed potato stocks to farmers was slowed by crop health problems (disease and/or nutritional disorders). DNA from potato leaf samples will be sent to Australia for virus testing to help seed potato certification officers distinguish symptoms of virus infection from nutritional disorders.
The adoption of new potato cultivars by farmers depends on the availability of a consistent supply of quality seed potatoes. Eight staff from FPDA, six of whom were sponsored by the Crawford Foundation, attended the Victorian Certified Seed Potato Authority Seed Potato Certification Officers Biennial Workshop in Victoria, Australia in December 2008. The skills and knowledge acquired at the workshop will help delegate's improve their competencies in seed potato certification and improve seed potato quality in PNG.

The devastating late blight disease caused by Phytophthora infestans, which first occurred in Papua New Guinea in 2003, has made it difficult for all but the farmers who can afford seed potatoes, fertiliser, fungicides and labour to grow the popular but highly susceptible variety Sequoia.
The main strategy of this project has been to find late blight resistant varieties to replace Sequoia. Field evaluation of all of 55 potato clones imported from Peru is now complete. These clones are part of a collection that was breed by the International Potato Centre (CIP) for short day, tropical highland environments. Twelve clones, which consistently exhibited resistance to late blight and favourable agronomic, flavour and cooking traits in a series of field trials conducted by the National Agriculture Research Institute (NARI), have been selected for evaluation in farmer and market chain participatory trials.
A second series of farmer trials of four CIP clones first tested in December 2008, were established in December 09 in eight different locations representing four micro environments across four highlands provinces. The clones were planted in plots alongside the Sequoia variety, which were either sprayed with fungicide or not treated at all. Unfortunately, the two trials in one province were terminated due to tribal fights and logistical problems. The NARI and Fresh Produce Develop Agency (FPDA) team collected data on disease severity, yield and cost of production. Two of the clones (unsprayed) produced marketable yields comparable to that of the sprayed Sequoia, averaging 12 to 26 tonnes per hectare. The yields of unsprayed Sequoia averaged less than 5 tonnes per hectare because of severe late blight infection.
One or two field days were held at each site with attendances of between 25 to 100 farmers being recorded. Based on farmer and visitor preferences and overall performance in trials, further testing of two of the four clones will cease. Seed potato stocks for farmer trials of the remaining 10 clones are at various stages of multiplication. Potatoes will also be distributed to chicken and chip shops for an assessment of retailer and consumer responses. Most clones are much better suited to frying than Sequoia.
The adoption of new potato cultivars by farmers depends on the availability of a consistent supply of quality seed potatoes. The Aiyura tissue culture lab output averages 12,000 plantlets per month (mostly Sequoia at this stage), which fills 6 of 24 the FPDA screenhouses at Tambul each month for minituber production. FPDA now faces the inevitable challenge of finding enough suitable land and qualified and competent seed growers for multiplication of the field generations.
Late blight has now been found on tomato plants in Eastern Highlands Province of PNG. The disease symptoms were severe enough to defoliate the plants and cause serious fruit rots. Farmers are faced with prospect of regular applications of fungicides to prevent foliage and fruit blight. Tomatoes are the second most important host of the Phytophthora infestans pathogen world wide next to potatoes. Samples of diseased plants have been sent to the Scottish Crop Research Institute for identification of the pathogen strain.
DNA extracts taken from seed potato plants in PNG, which were suspected of being affected by the potato leaf roll virus, have returned positive in tests conducted in Australia. A NARI scientist based at Aiyura, and currently engaged in a virus testing of sweet potatoes, recently undertook intensive training in Australia (sponsored by the Crawford Fund) to develop competency in the virus detection so that potato and sweet potato viruses can be tested in PNG and thereby providing an important service for certified seed potato program.