Germination and grain vigour of naked oat in response to grain moisture atharvest

Naked oat grain, which is free from lemma and palea, has high nutritional q uality, but the unprotected grain is prone to mechanical damages caused by combine harvesting. Naked oats were grown for 3 years in southern Finland, at Viikki Experimental Farm, University of Helsinki (60 degrees 13'N) to pr oduce seed material for laboratory tests that evaluated: (1) genotypic diff erences of naked oat in sensitivity to damage during harvesting at grain mo isture varying from c. 10 % up to 50 % (2) the effect of mechanical damage on germination and grain vigour, and (3) grain characteristics contributing to susceptibility to reduced grain viability. In 1997, one naked (Rhiannon ) and husked oat cultivar (Salo) were harvested, and in 1998-1999 additiona l four naked cultivars (Bullion, Lisbeth, Neon, SW 95926) were included. On e large plot (14 m x 10 m) was sown per cultivar. Two sowing times were use d. Fully ripened grains were combine harvested on several occasions for eac h plot to obtain differences in grain moisture at harvest. Simultaneously, panicle samples were collected, dried and threshed by hand (controls). Grai n moisture at each sampling and harvesting was monitored. About 3 months af ter harvesting, germination tests on blotting paper were carried out. Propo rtions of normally developed seedlings, seedlings lacking either radicle or hypocotyl, damaged coleoptiles, dead grains and lethally fungus-infected g rains were recorded from combine harvested and hand threshed samples on dif ferent cultivars and harvest moistures. Tests on seedling elongation, seedl ing emergence through sand (2 cm and 5 cm. depth), and ion leakage were app lied to evaluate grain vigour. Groat weight, diameter, length, roundness, h ardness and protrusion of embryo were determined. Our results indicated that naked cultivars were far more prone to mechanica l damages than husked Salo, but differences among naked cultivars in suscep tibility occurred. When targeting germination of greater than or equal to 7 5 %, grain moisture at harvest should not exceed 19-26 % depending on culti var. Abnormal seedlings appeared irrespective of grain moisture at harvest, but the higher the grain moisture, more dead grains were found in harveste d grains after storage. Seed vigour did not alter parallel to germination a bility. High proportion of small grains in harvested yield and softer groat s contributed to decreased sensitivity to mechanical damages.