Putative WSMV-induced mutants: Uq-861058A, ba*-861059B

In this experiment, the wheat stripe mosaic virus (WSMV) was used to inoculate 34 maize seedlings at the 3 to 4 leaf stage. All seedlings were grown from a-ruq/Uq sectored kernels (MNL 60:5-6, 1986). The plants were kept in a growth chamber with a set temperature of 21 C for the development of virus infection. After transplanting into the field, 3 plants showed clear symptoms of the virus infection. These plants were numbered 861058A, 861058D and 861059B, respectively. All the plants (both infected and non-infected) were crossed reciprocally with the a-ruq tester. Examination of the resulting progeny ears indicated the following:

1) Plant 861058A produced only colorless kernels in reciprocal crosses. However, in further testing these colorless kernels by crossing by a-o sh2(no Uq) tester, 5 out of 14 tested kernels from the ear of 861058A/a-ruq produced low-spotted kernels at frequencies ranging from .11 to .32. In contrast, none of the 42 tested kernels from 3 ears of a-ruq/861058A segregated for spotted kernels. The recovered Uq activity may be induced by WSMV infection. We designate this putative mutant Uq-861058A and are currently testing this new Uq element.

2) Plant 861059B, when selfed, produced 54 defective kernels in addition to 302 colorless normal kernels. It produced 97 colorless normal kernels when crossed onto an a-ruq tester plant. The defective kernels germinated very poorly. Only 3 plants were grown from 39 defective kernels. All were of dwarf and late type. On the other hand, 29 plants were grown from 30 colorless normal sibs. Seven plants, however, produced no ear at all. It seems, therefore, that a barren-type mutant gene has been induced by WSMV infection, and that this mutant gene is recessive. We designate this putative mutant ba*-861059B. It should also be mentioned here that another set of 29 plants grown from the colorless normal kernels of the ear a-ruq/861059B did not segregate for barren-type plants. No Uq activity has been seen in the progeny of this mutant.

3) Plant 861058D was male sterile and had a dwarf phenotype. Although 4 colorless kernels were set from the cross of 861058D x a-ruq tester, they all failed to germinate.

Yong-Bao Pan and Peter A. Peterson


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