Growth and yield of sorghum lines extracted from a population for differences in osmotic adjustment

Abstract

From 47 S2 lines which had been extracted from a random mated population of sorghum, eight lines for a glasshouse experiment and four lines for a field experiment were divergently selected for variation in osmotic adjustment, and were grouped into two, High and Low osmotic adjustment (OA). Both the glasshouse and field experiments examined whether osmotic adjustment modified the plants' response to soil water deficit and also whether grain sink demand for assimilates, varied by removal of 50% spikelets, affected osmotic adjustment. In each experiment, there were well-watered control and water stress treatments. In both experiments, the dawn osmotic potential in the High OA group was always lower than in the Low OA group under water limiting conditions, and the difference was significant after anthesis. The difference in osmotic potential was about 0.1 MPa in the field and up to 0.25 MPa in the glasshouse. In the glasshouse experiment, removal of 50% spikelets at anthesis significantly decreased osmotic potential during grain filling, suggesting that osmotic adjustment is influenced by the availability of assimilates in the leaves. Under well-watered conditions, the two groups behaved very similarly in terms of maximum leaf area, green leaf area retention during grain filling, total dry matter production, grain yield and grain number in both experiments. Under water-limiting conditions, the High OA group produced larger maximum leaf area and had better leaf retention during grain filling. Despite similar water use, total dry matter was also significantly higher in the High OA group though the difference was small. Grain number was also greater in this group in both experiments, whereas grain yield was significantly higher in the High OA group in the field, but not in the glasshouse where severe water stress developed more rapidly. It is concluded that the adverse effect of water stress can be reduced by adopting sorghum genotypes with high osmotic adjustment. However, selection for high osmotic adjustment needs to ensure that osmotic adjustment is not solely due to small head size.

Role of Osmotic Adjustment in Plant Productivity

“…Although the level of OA and the difference in wIL between the two poplar clones in our study were small, the fact that the TD clone had lower midday ww is consistent with other species that have the capacity for OA. Tangpremsri et al (1995) had reported that midday ww of sorghum decreased more in the high OA plants than the low OA plants, consistent with an earlier finding that genotypes with high OA or with low wx used more water than other genotypes (Tangpremsri et al 1991b). Morgan and Condon (1986) had also reported that water use of wheat genotypes with higher turgor maintenance was approximately 50% higher than genotypes with low turgor maintenance.…”

“…For example, high OA lines of sorghum produced higher maximum leaf area at anthesis and maintained higher leaf area during grain filling under dry conditions (Tangpremsri et al 1995). Sorghum cultivars with high OA capability had slightly higher turgor than the low OA lines.…”

“…Tree species growing in xeric sites generally have low leaf wX even under well-watered conditions (Abrams 1988). Although it has been suggested that OA competes with productivity (Munns 1988), several studies with agricultural crops have shown a relationship between OA and grain yield , Fukai and Cooper 1995, Tangpremsri et al 1995.…”

Response of some upland rice varieties to drought stress

“…The increase of leaf proline at the intensity of drought stress in 25% field capacity of all varieties turned out to have a positive impact on the decreased weight of 1,000 grain of pithy rice at moisture content of 25% field capacity, especially in varieties that have high proline content such as Situ Patenggang and Towuti. Tangpremsi et al (1987) stated that there is no difference in seed yield between high and low osmoregulatory sorghum genotypes, but under conditions of high osmoregrative density, the genotype produced higher yields. The effect of osmoregulation on seed yield does occur because there is an improvement in the supply of assimilates from the leaf to the seed due to decreased leaf aging rate and improvement of photosynthetic activity of the leaves during drought.…”

Improving Drought-Avoidance Root Traits in Chickpea (Cicer arietinumL.) -Current Status of Research at ICRISAT

“…Although OA has been reported to be an important trait for drought tolerance in some cereal crops, e.g. wheat (Morgan et al, 1986) and sorghum (Tangpremsri et al, 1995), there are variable reports on the association of OA with grain yield in chickpea. Some studies have shown an association between OA and seed yield under water stress conditions (Morgan et al, 1991;Moinuddin and Khanna-Chopra, 2004), while some studies found inconsistent or no relationship (Singh et al, 1990;Leport et al, 1999).…”