Drought is a major problem for rainfed lowland rice in Laos as well as for other countries in the Mekong region, and different drought screening methods under managed environments have been used to develop varieties adapted to drought prone environments. This paper evaluates the appropriateness of on-research station screening methods conducted under intermittent and terminal drought conditions, using the yield results of 12 on-farm multi-location trials with 25 genotypes some of which had been selected for drought tolerance. In these multi-location trials drought stress was rather mild, even in the intermittent or terminal drought trials which tended to develop in the higher fields of the rainfed lowlands. The high position generally produced low yielding crops but no significant interaction between position and genotypes were found for grain yield of 25 genotypes grown at 4 pairs of high and low field positions.
Genotypes that performed well under higher yielding conditions in the on-(research) station experiments also performed well in on-farm multi-location trials. Genotypes that were identified as drought tolerant using drought response index as a criterion in the on-station experiments generally performed well in the on-farm multi-location trials (r = 0.49**), particularly in high yielding environments, but not under low yielding environments where low soil fertility appeared to be a major limitation for high yield. Similarly, genotypes that were identified to have high potential yield in flooded conditions in the on-station experiments also performed well in on-farm multi-location trials (r = 0.43*). Drought tolerance determined on-station either intermittent or terminal drought was similarly effective and was at least as effective as potential yield determined on-station in predicting on-farm yield. On-farm multi-location trials in combination with on-station experiments identified several promising lines that were well adapted to rainfed lowland conditions. It is concluded that genotypes selected for high yield potential under favorable conditions and for high drought tolerance determined in the on-station experiments would result in the development of well adapted cultivars suitable for drought-prone rainfed lowlands, and that either intermittent or terminal drought conditions developed at a research station is suitable for this purpose. The intermittent drought condition had the added advantage that genotypes selected directly for high yield, performed well in farmer's fields in the rainfed lowlands.
Xangsayasane, P.; Fukai, S.; Mitchell, J.H.; Jongdee, B.; Jothityangkoon, D.; Pantuwan, G.; Inthapanya, P. Genotypic performance in multi-location on-farm trials for evaluation of different on-station screening methods for drought-prone rainfed lowland rice in Lao PDR. Field Crops Research (2014) 160: 1-11. [DOI: 10.1016/j.fcr.2014.02.009]