Presence of active Ubiquitous in a 'high haploidy' ACR line
-- B.M. Prasanna and K.R. Sarkar

A 'high haploidy' ACR line was screened for the presence of three mobile element systems--Uq, Mrh and Cy. This ACR line is characterized by its high haploid induction frequencies when used as a female parent in crosses with the 'Stock 6' C-I male lines. For instance, in Hyderabad winter 1993-94, the haploid frequencies ranged from 0.07 to 20.43% (2397/56640 haploids; av. 4.23%) out of a total of 115 plants tested. In Delhi monsoon 1994, the same line yielded 155 haploids out of 3759 total colorless kernels (av. 4.12%) (unpublished results from our laboratory).

About 6-8 plants each of the ACR line were crossed as female parent with the MERL (Mobile Element Receptor Line) series: a-ruq, a-mrh and bz-rcy. The resultant F2 (colored/mottled) plants were selfed and the F2 progeny were evaluated for the presence/absence of mutability of the alleles of the MERL series (Table 1).

Table 1. Classification of progeny kernels following self-pollination of ACR/MERL plants.
Origin No. Ears Cl Spotted* cl Total K.
ACR/a-ruq 27 4174 1275 726 6175
ACR/a-mrh 8 954 2** 352 1308
ACR/bz-rcy 14 3364 0 1026 4390
*'Spotted' refers to the characteristic mutability pattern of the element system
**One-spot Mrh kernels

Uq mutability pattern was observed in each of the 27 ears scored, clearly indicating that at least one active copy of the element is present in the ACR line. On the other hand, one-spot kernels for Mrh could be observed in only two of the eight ears scored. The limited sample size does not allow us to conclude about the frequency and nature of Mrh element activity, whereas absence of Cycler mutability in the 14 plants tested suggests the lack of Cy in the material tested. It shall be interesting to analyze the role of the active Uq element, if any, in the haploid occurrence of this high haploidy ACR line in crosses with the C-I inducer males in subsequent seasons. 

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