Chickpea and lentil show little genetic variation in emergence ability and rate from deep sowing, but small-sized seed produces less vigorous seedlings

Abstract

Context Germination and emergence are key to successful annual crop establishment. Emergence rate depends on germination rate, sowing depth, and rate of pre-emergent shoot elongation. The rate at which a shoot grows prior to emerging from the soil becomes significant when crops such as chickpea (Cicer arietinum L.) and lentil (Lens culinaris Medik.) are deep sown to utilise moisture below the conventional sowing zone. Aims In seeds of contrasting size, we aimed to compare the ability of chickpera and lentil varieties to emerge from deep sowing. Here we describe genetic variation for epicotyl growth rate, and phenotypic variation for epicotyl and root growth rates and biomass partitioning, of chickpea and lentil, as they relate to seed size. We further assess the impact of deep sowing and soil type on emergence, establishment and yield of the two species. Methods Epicotyl elongation rates, root growth and seedling biomass partitioning were determined in controlled environment studies, using soil tubes. Field trials were conducted on two different soil types at two sowing depths. Key results Most of the variance in epicotyl growth rate could be attributed to species rather than variety. Although epicotyl emergence was faster in lentil, chickpea epicotyl growth rates were higher than those in lentils and unrelated to seed size, whereas growth rates in lentils were weakly correlated to seed size (r = 0.31). Root development and epicotyl diameter appeared to be traded for maintenance of growth in smaller seeds of both species. In the field, sowing depth did not affect emergence, establishment or yield of chickpeas at either site. Deeper sowing resulted in minor reductions in emergence of lentil at one site, although biomass and yield were not affected. Conclusions Emergence of both crops was unaffected by deep sowing (to at least 200 mm) under controlled environment and sandy field conditions. There was minimal genetic variation for the measured parameters within a species. Seed size was of little importance for emergence rate; however, shoot growth rate from small seeds was maintained by reducing seedling vigour. Implications Seed size should be considered when deep sowing lentils in order to maintain high seedling vigour. Further work is needed to understand how environmental factors influence seedling emergence from depth.