In an effort to identify the efficacy of this mutation, several stocks containing ig in different genetic backgrounds were grown and crossed as female parents by an unrelated glossy (gl) tester with normal cytoplasm (Table 1). Progeny were planted in the sandbench and individual gl plants were identified to determine the frequency of androgenic plants produced by each genotype. To verify that the gl plants were indeed haploids, root tips were harvested and the ploidy level of each plant determined cytologically by counting the metaphase chromosomes of at least 3-5 cells. Several androgenic diploids (10.8%) were also recovered in this study, a result consistent with Kermicle�s observations (1974, p. 137 in Proc. First Intnl. Symp. on Haploids in Higher Plants, ed. K. Kasha, Guelph, Canada).

The materials from the Stock Center that were originally provided by B. Kindiger which should have possessed two normal chromosome 3's with ig and a B3-Ld with Ig did not produce the expected plant types in our hands. Every one of these stocks produced large numbers of small plants that had a distinctive abnormal phenotype that was different from the phenotype of haploids. This abnormal phenotype was the same as plants that had lost much of the long arm of chromosome 3 or all of this chromosome (hypoploid for 3L or monosomic for chromosome 3). Furthermore, these exceptional plants were examined cytologically and were found to contain 20 chromosomes. From these and other observations, it appears that the complete B-A translocation was present in these stocks and that the chromosome constitution was not as described by Kindiger and Hamann (1993, Crop Sci. 33:342-344). Also, the frequency of haploids produced by these stocks was much lower than reported by Kindiger and Hamann (1993). The materials provided by J. Laughnan (Stock Center) were also difficult to discern. The fact that the plants were not definitely male sterile and did not produce haploids in the expected frequency suggested that ig was segregating, or a restorer gene was segregating. Certain plants of the two stocks originally provided by R. Brawn and D. Alvey that had been maintained for over 25 years in our culture collection did produce higher frequencies of paternal haploids than the other stocks, 1.67% and 1.18% respectively. The reason for this is unknown. The materials provided by Jerry Kermicle produced paternal haploids but at a lower frequency than expected. This survey has allowed us to determine which ig containing materials produce paternal haploids with the highest frequency and also suggests that genetic background is important.

Table 1.
 

Source/Stock	Total # grown	Total gl identified	Total # AndrogenicHaploids	Total # Paternal Diploids	% Androgenic Haploids/ Diploids produced
B. Kindiger (several cytoplasms) provided by the Stock center	5331	24	20	4	0.45%
J. Laughnan (various lines & cytoplasms), provided by the Stock center	6503	6	6	0	0.09%
Originally from Bob Brawn (Funks) N cytoplasm; D. Weber�s collection	3482	13	12	1	0.09%
Originally from Bob Brawn (Funks) C cytoplasm; D. Weber�s collection	2234	8	6	1	0.37%
Originally from David Alvey (Indiana); D. Weber�s collection	1553	26	26	0	1.67%
Originally from Jerry Kermicle, U of Wis.;D. Weber�s collection	936	5	3	2	0.53%
Originally from Bob Brawn (Funks) C cytoplasm; D. Weber�s collection	2120	25	24	1	1.18%
Jerry Kermicle; U of Wisconsin	1739	8	8	0	0.46%
Jerry Kermicle; U of Wisconsin	1456	1	1	0	0.06%
Originally from Bob Brawn (Funks) N cytoplasm; D. Weber�s collection	1013	4	2	2	0.39%

 

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