III.1. Identification of zebra (zb) stripe character at early seedling stage.
T. Tsuchiya and R. J. Singh, Department of Agronomy, Colorado State University, Fort Collins, Colorado 80521, U.S.A.
A mutant for zebra stripe character (zb) was obtained by Burnham (1958) and used in linkage studies by Kasha and Walker (1960). According to Robertson (1964) the leaves at early seedling stage are banded with lighter colored stripes across the leaves. The later leaves do not show the banding. At temperatures of 21°C or higher the banding may fail to show. Also, the zebra stripe character failed to show even at 5°C when we attempted to use it in linkage studies. This directed us to develop easy approach to observe the zebra stripe character.
Three sets of experiments were conducted:
Set - 1
(i) About 25 seeds of zebra stripe mutant and SE16 (control)
were put in germination boxes.
(ii) Seeds were kept immediately in the dark cold room (0 - 1°C)
for 15 and 21 days.
(iii) Seeds were taken out after cold treatment when they started
germinating in the cold room (15 days), and kept at room temperature for
further growth.
(iv) The expression of zebra stripe character was observed. The
leaf tip was yellow while control showed normal green leaf tip.
(v) The expression of the character was good enough to distinguish
the mutant character after this treatment (Table 1).
Set - 2
(i) The second set was divided into four groups which consisted
of seeds of zebra stripe mutant and SE16 (control) as was in Set 1.
(ii) Seeds of all groups were left at room temperature for one
day (24 hours).
(iii) Seeds of groups I, II, III, and IV were taken out from
cold room after 3, 7, 10, and 15 days, respectively, and left at room temperature
(Table 1).
(iv) The expression of the zebra stripe character was not observed
in group I and II which were given cold treatments of 3 and 7 days, respectively.
The expression of the mutant character was very good in group III and IV
which were given cold treatment of 10 and 15 days, respectively.
(v) This indicates that 3- and 7-day cold treatment period was
not enough for the expression of the character.
Set - 3
(i) Seeds of all groups were left at room temperature for 2 days
(48 hours). Seeds started germinating at room temperature after the period
of 2 days.
(ii) The period of cold treatment was the same to all groups
as it was in Set 2.
(iii) Seeds were taken out from the cold room and kept at room
temperature for further growth.
(iv) The expression of the mutant character was not observed
in any groups (Table 1).
(v) This indicates that cold treatment is effective in the expression
of the mutant character only at a very early stage of germination.
Table 1. The expression of zebra mutant character at various lengths of cold treatment.
Attempts were also made to observe zebra stripe character when it was very cold outside. Seeds of mutant and SE16 (control) were sown in pots and were kept outside to germinate. The seeds of zebra stripe mutant showed yellow banding across the first and second leaves. Later leaves were green. F3 test of monotelotrisomics obtained in F2 populations of telo-3L x zb was conducted outside at very cold temperature to observe any zb homo in monotelotrisomics. The results were similar to the laboratory tests:
1. For laboratory test - it is necessary to give cold treatment (0 - 1°C) at very early stage of germination. The length of cold treatment should be 10-15 days.
2. When zebra mutant is used in linkage studies outside, the temperature should also be about 0 - 1°C.
References
Burnham, C. R. 1958. Barley Newsletter 1:44-47.
Kash, K. J. and G. W. R. Walker. 1960. Canad. J. Genet. Cytol. 2:397-415.
Robertson, D.W. 1964. Barley Genetics I:159-180.
Supported by NSF Grant GB 30493 and CSU Experiment Station Project (Hatch 8).
