Growth, development, and yield of three oilseed Brassica species in a water-limited environment

Abstract

Representative lines of Brassica napus, B. campestris, and B. juncea were compared at East Beverley in the central wheatbelt of Western Australia on the basis of agronomic and physiological characters known to affect seed yield. Seed yield of B. juncea line 81794 was 32% higher than the locally adapted B. napus cv. Wesbrook (76 g/m2). Yields of B. napus cv. Eureka and the 2 B. campestris populations were not significantly different from Wesbrook and were lower than 81794. The higher yield of 81794 was due to higher dry matter production, particularly after first open flower. Yield superiority of 81794 was not associated with any single yield component. Under the water-stressed conditions of this experiment, seed yield had a strong positive correlation with dry matter production after first open flower. Differences in dry matter production during this period were due to variation in crop growth rates among the lines, not to variations in duration of the period. There was no relationship between flowering time and seed yield in this experiment, suggesting earlier reproductive development is not obligatory for high yield of oilseed Brassicas in low rainfall mediterranean environments. Total water use throughout the season differed little among populations, but there were differences in water use patterns over time. The greater rate of dry matter accumulation of 81794 is due to its ability to extract more water from the soil profile after anthesis; postanthesis water use of 81794 was 20% higher than that of Wesbrook. Water use efficiency of 81794 was also higher than that of Wesbrook, because soil evaporation comprised a smaller proportion of evapotranspiration. Further increases in seed yield of oilseed brassicas in this environment should be possible if higher postanthesis water use could be combined with lower soil evaporation and improved water use efficiency.