Research experience on potato late blight disease management in Bangladesh.

Potato is an important commercial crop in Bangladesh. Unfortunately, potato suffers from many destructive diseases, of which late blight, caused by Phytophthora infestans is the most important one. In Bangladesh, late blight causes serious yield loss in potato every year. Late blight was first reported in Bangladesh in 1922. In recent years more than 300 varieties, 2050 germplasm lines and 250 true potato seed (TPS) progenies were evaluated for resistance to major diseases under field conditions. Screening for late blight resistance was carried out under both natural and artificial conditions. So far more than 300 germplasm (exotic and local) and TPS progenies were screened through artificial inoculation. Of these only three lines (CIP-607, CIP-272 and CIP-616) were found to be tolerant to late blight. Some of the field resistant TPS progenies are: TS-6 × TS-9, HPS-7/67, HPS-II/13, TS-5 × TS, LM × 501, 501 × 9, 801000 and 300999. A set of 15 late blight resistant germplasm lines received from CIP, Peru in 2005 was evaluated under natural conditions of which 6-7 were found to be resistant to the disease. Attempts were made to develop late blight resistant transgenic potato varieties by transforming the RB resistance gene into two commercial varieties. Twenty races of P. infestans have so far been identified in Bangladesh. The frequency of races differed greatly with maximum occurrence of race 2. Existence of metalaxyl resistant strains of P. infestans have been identified which might be due to indiscriminate spraying of metalaxyl (Ridomil) fungicide. Both fungicide management and farmer training with farmer field schools are discussed.