Document Type

Dissertation - Open Access

Award Date

1978

Degree Name

Doctor of Philosophy (PhD)

Department

Plant Science

First Advisor

Darrell G. Wells

Abstract

A virus disease, wheat streak mosaic, has been an important, unsolved problem of winter wheat which is a major crop in South Dakota. F1BC3 monosomic alien addition seeds having three doses of Centurk were irradiated with fast neutrons to translocate a segment of the alien chromosome accounting for immunity from wheat streak mosaic virus to a Centurk chromosome. Immune plants from the irradiated seeds were used as male parents onto Centurk and about 2,000 F1BC4 seeds obtained. Cytological examination of pollen mother cells of 151 resistant F1BC4 plants indicated that the majority of the plants continued to have an apparent alien univalent present in addition to the wheat complement. Fourteen suspected translocations were identified in F2BC4 on the basis of genetic segregation. The breeding behavior of nine of these 14 was studied in F3BC4, F4BC4, F6BC4 and F2 generations. Most of these lines became more stable with advancing generations. Pollen mother cells of 37 plants in F3BC4 and F4BC4 were examined cytologically and 21 bivalents counted. The frequency of transmission of the translocations through male and female gametes of translocation heterozygotes was found to be about 50 percent since the F2 generation involving translocation lines A, B, C, D and G, 81, 75, 75, 78 and 78 percent of the progeny were resistant. In line F, however, immunity was transmitted with a reduced frequency of 68 percent. A test to evaluate the effects of the suspected translocations on agronomic qualities and yield components of the plants indicated that all the translocation lines except D1 had less tillers per plant than the recurrent parent, Centurk. Fertility in the main tiller was higher in translocation lines C1 and D1 than Centurk. All the resistant lines tested in the field were shorter and headed earlier than Centurk except line E2, which headed three days after Centurk. Seeds were larger in all the lines than Centurk except lines B and C. Number of seeds in the main spike was lower in all the lines except C1. Yield per plant was also lower in all the lines. Variation in the frequency of transmission of resistance through male and female gametes, plant height, tillers per plant, percent fertility in the main spike, number of seeds in the main tiller, seed size, yield and heading date of the six suspected translocation lines indicate that the substitution of the A. intermedium chromatin for the different segments of a Centurk chromosome had varying effects. The genetic data show that resistance is controlled by a single dominant gene. Translocation of the gene from A. intermedium to a Centurk chromosome did not affect the expression of resistance. The study provided a least six translocation lines, some of which may possibly be used as direct releases or certainly as parents to incorporation resistance to wheat streak mosaic virus into commercial varieties.

Library of Congress Subject Headings

Wheat -- Diseases and pests
Wheat streak mosaic virus
Irradiation
Wheatgrasses

Format

application/pdf

Publisher

South Dakota State University

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