Onion leaf or fused leaf in barley was reported earlier by Tsuchiya (1958, 1964, 1967) in primary trisomics for chromosome 1 (Bush), chromosome 2 (Slender), and chromosome 5 (Pseudonormal). It was also found in ditelotetrasomic for the short arm of chromosome 5 (Wang and Tsuchiya, 1988). The onion leaves usually showed up in the late plant growing stage. The whole leaf blade was rolled (fused) to show the typical onion- like leaf, which occurred more frequently in later tillers.

Observations were made on the plants of trisomics and ditelotetrasomics of chromosome 5 and related materials. Onion leaves were found in triplo 5, ditelo 5S, and monotelo 5S plants, but not in diploid siblings and triplo 5L. Also, this trait was observed more frequently in triplo 5 and ditelo 5S than in monotelo 5S. This result indicated that gene(s) for onion leaf might be located on the short arm of chromosome 5, and it is assumed that certain gene(s) in the long arm of chromosome 5 may enhance the onion leaf expression. Further investigation is needed to explore the genetic nature of this phenomenon.

References:

Tsuchiya, T. 1958. Studies on trisomics in barley I. Origin and the characteristics of primary simple trisomics in Hordeum spontaneum C. Koch. Seiken Ziho 9:69-86. (Jap. Eng. resume).

Tsuchiya, T. 1964. Chromosome aberrations and their use in genetics and breeding in barley - Trisomics and aneuploids. Proc. lst Internal. Barley Genet. Symp. (Barley Genetic 1):116-150.

Tsuchiya, T. 1967. The establishment of a trisomic series in a two-rowed cultivated variety of barley. Can. J. Genet. Cytol. 9:667-682.

Wang, S., and T. Tsuchiya. 1988. Ditelotetrasomics for the short arm of chromosome 5 (ditelo 5S) in barley. BGN 18:21-23.