Integrated strategies for the management of bacterial wilt and other wilting diseases in Solanaceous crops in the Southern Philippines and Australia

Three hundred eighty two isolates were taken from extensive collection of bacterial wilt-infected soils, plant and water samples throughout the potato growing areas of Northern and Southern Philippines. Molecular characterization of the isolates revealed the predominance of tropical strain, Phyllotype 1-Race 1 Biovar 3 and cooler climate Phyllotype 2 Race 3 Biovar 2. Aggressiveness test on yellow plum tomato varies among isolates. Genetic variability among the isolates was observed from the PCR assays conducted. PCR analysis showed to be a more reliable method of detection than the ELISA technique used in the planting materials. Eighteen commercial varieties and four NOMIARC [Northern Mindanao Integrated Agricultural Research Center, Dalwagan, Malaybalay City, Bukidnon, Philippines] lines were evaluated in the greenhouse, Bacterial Wilt Nursery and at 3 farmer's field for tolerance to bacterial wilt. The most tolerant varieties and lines to bacterial wilt were Atlantic, Granola, Igorota, NOMPO B, NOMPO D, and NOMPO E. The varieties and lines moderately tolerant to bacterial wilt were Asterix, Catan, Kennebec, and NOMPO A. Plots initially inoculated with bacterial wilt were used for biofumigation study to ensure even distribution of inoculum in all the plots. Biofumigation using broccoli, radish and sunflower reduced bacterial wilt colony counts by 24.54, 39.34 and 57.43%, respectively compared to the control with 19.48% increase in bacterial wilt colony counts by 91.2, 90.6, and 95.2% in plots with broccoli, radish and sunflower amendments, respectively than in control with only 5.3% reduction. Wild sunflower amendment showed greater suppression than the brassicaceous crops which releases ITCs [isothiocyanates] that suppress bacterial wilt. Sunflower at decomposition provides high organic matter that enhances the massive growth of microorganisms that masked the harmful microbes such as bacterial wilt. These plots were used continuously and planted with other crops following a cropping scheme popular in the area such as crucifer-potato-corn-legume. When planted with corn after potato, the Ralstonia solanacearum counts were reduced in all treatments by 24.3%, 19.0%, 1.1% and 0.9% in broccoli, radish and sunflower incorporated plots and untreated plots, respectively. At harvest of cowpea planted after corn, R. solanacearum counts in the biofumigated plots all decreased but increased in untreated plots. Based on the findings from the FGD [focused group discussion] conducted, potato production can be sustainable if the following will be addressed: Insufficient supply of clean potato seeds, presence of seed investors to buy the seeds, and availability of technology on bacterial wilt management. To address the constraints in potato production, clean potato seed production were established in the farmers' field of identified collaborators. Granola seeds (GO), the preferred variety were planted at Roberto Sulatan and Erol Nabe's farm in Miarayon, at Paul Cabelada's farm in Kibangay and Gabriel Banadao's farm in Imbayao, Bukidnon. Areas selected were not previously grown to solanaceous crops to ensure none or very low incidence of bacterial wilt. The farmers were trained on biofumigation and best practice for bacterial wilt management. The areas selected were biofumigated with broccoli and sunflower. Highest yield, 18.1 tons/ha was obtained in plots with sunflower amendment at Kibangay, 11.3 tons/ha in Miarayon and 10.6 tons/ha in Imbayao compared to broccoli-incorporated plots. Seeds harvested were set aside for another planting. The next batch of seeds produced, G2 were agreed to be distributed to other interested farmers who will grow potatoes. These seeds are guaranteed clean. Papers for oral and poster presentation, flyers, leaflets, comics, exhibits, techno demo plots were developed as extension materials to promote best practices in b acterial wilt management in potato and other solanaceous crops. Presentations were done in international and local conferences, meetings and symposium, flyers, leaflets and comics were distributed during field days and farmer's meetings. Techno demos and exhibits were presented during NOMIARC annual field days attended by more or less 3000 farmers all over Mindanao and some from Luzon and the Visayas.