Seedling Traits of Primary Trisomics

Rick, C.M.
[From TGC Volume 37 pg. 60 - 61]

A revision of my note on managing trisomics (TGC5:24-25) is long overdue. In the intervening 32 years we have become aware of errors and additional key traits. Although this note deals primarily with seedlings, the same syndromes continue throughout growth. Another motive is selfish: all too often I am asked to identify trisomics in overgrown jungles - situations that could have easily been avoided by ruthless elimination of diploids in early seedling development. By thus narrowing the populations to entirely or predominantly trisomic individuals, the investigator can save valuable greenhouse space, favor the desired trisomics with better growing conditions, and save time and, often, seeds. As indicated in the following table, nearly all the primaries can be identified in seedlings. They are generally slower and differ from diploids and each other in an array of readily identifiable traits.

			true leaves
Triplo-	growth rate	cotyledons	color	surface	serration	other
1	extremely retarded*	small, dark	dark green*	convex* deep veins	reduced	often malformed
2	moderately retarded	+	light green	+	increased*	slender, lax stems and leaves*
3	moderately retarded	narrow, elongate*	+	+	reduced	elongate, narrow segments
4	retarded	small	light green*	+	+	first and second often malformed*; downcurled tip
5	moderately retarded	+	yellow green	rugulose*	reduced	*
6	very retarded	small*	+	+	+	fewer segments*
7	extremely retarded	small, often tricot*	dull green	upcurled margins	increased	short, stocky plants*
8	retarded	small	grey green*	convex*	greatly reduced*	broad segments*
9	retarded	small	+	+	+	reduced leaves; diminutive, often blind plant*
10	very retarded	short	dark green	rugose	increased	short, stocky plants*
11	very retarded	?	light green	?	reduced	very low transmission rate limits observations
12	extremely retarded	tiny dark*	dark green	+	increased*	slow, early growth*

key
+	like diploid
*	most diagnostic features