Development of an assay to evaluate differences in germination rate among chickpea genotypes under limited water content

An assay system that provides rapid and reproducible germination under low soil water content (<10% water holding capacity (WHC)) was developed and used to compare how chickpea (Cicer arietinum L.) genotypes complete germination, without the technical difficulties of accurately controlling water levels. The system consisted of small plastic containers (50mm×50mm×60mm) filled with river sand and tightly closed (but not sealed) to minimise water loss and maintain constant soil water content during germination. Seed size influenced germination performance at low WHC. Small seeds within a single genotype germinated successfully and entered into the early stages of seedling growth, but germination of large seeds was inhibited, failing to germinate at 5% WHC. Small seeds were more efficient in remobilising seed reserves to seedling tissues than larger seeds. Under optimal WHC, the germination rate and subsequent radicle growth was similar among genotypes but at low WHC, there was variation despite seeds being of comparable size and imbibing equally. This suggests that the physiological threshold of threshold water potential for initiation of germination reflects genotypic differences. The assay system provides a suitable experimental tool to examine gene expression in contrasting genotypes during germination and early stages of seedling growth with a view to identifying the genes involved in superior performance under water limited field conditions.