Osmotic adjustment, drought tolerance and yield in castor (Ricinus communis L.) hybrids

A study was conducted to analyse the association of osmotic adjustment (OA) with drought tolerance and yield in castor (Ricinus communis L.). Hybrids (GCH4, DCH32 and DCH177) and their respective parents (VP-1, 48-1, LRES17, DCS5, DPC9 and DCS9) were assessed for their osmotic adjustment, leaf water relations, accumulation of compatible solutes in relation to seed yield in response to moisture stress at primary spike development stage. OA increased with increasing stress period up to 33 days and the increase was more rapid in the high OA (HOA) genotypes. HOA genotypes also had higher leaf RWC and ELWRC and maintained higher leaf water potentials (Psi(1)) compared to LOA genotypes under water deficit. Genotypes with HOA accumulated greater levels of proline, total soluble sugars (TSS), total free amino acids (FAA) and potassium than those with LOA in response to water deficit. Contribution of TSS was the maximum (61%), compared to FAA (17%), proline (12%) and potassium (2.8%) to the Psi(s) at 33 days after imposing water deficit indicating that sugars were the major contributors towards OA in castor leaves. A positive relationship existed between OA of expanded leaf 33 days after imposing stress (r = 0.8539) and total seed yield under water-limited conditions in various castor genotypes tested and HOA genotypes had higher total seed yield than genotypes with LOA. Genotype variability exists for OA and it is a heritable trait in castor. Hybrids followed their superior parents in terms of OA. HOA genotypes of castor produced significantly higher seed yield than LOA genotypes. Accumulation of TSS contributed largely to the OA in castor. (C) 2010 Elsevier B.V. All rights reserved.