Document Type

Dissertation - University Access Only

Award Date

1990

Degree Name

Doctor of Philosophy (PhD)

Department / School

Plant Science

Abstract

Thirty three wheat cultivars {CV's) and 26 single gene leaf rust {Lr) lines were inoculated with 26 isolates of Puccinia recondita tritici {PRT) and the resulting infection types (IT's) were compared in order to hypothesize resistance genes present in the cultivars. Cultivars were then crossed to lines containing single hypothesized genes and the F 2 populations were inoculated with appropriate PRT isolates to verify the presence or absence of the hypothesized gene in the cultivars. Genes verified in the cultivars were: 'A99AR', 'Apex 83', and 'Challenger': Lr 1; 'Butte', 'Norak', 'Norseman', 'Olaf', 'Oslo', and 'Wheaton': Lr 10; 'Alex' 'Erik', 'Len', 'Marshall' and 'Olaf': Lr 2a + Lr 10; 'Butte 86': Lr 10 + Lr 24; 'Guard' and 'Shield': Lr 2a; 'Bennet', 'Brule', 'Lancer', 'Rita' and 'Rose': Lr 3; 'Dawn' and 'Nell':Lr 3 + Lr 10; 'Sarhad 83' and 'Pakistan 81': Lr 26 +; 'Punjab 83' : Lr 1 +; 'Pavon 76': Lr 1; 'Centura' and 'Sage': Lr 3 + Lr 24; and finally 'Siouxland': Lr 3 + Lr 24 + Lr 26. The second objective was to study the inheritance of resistance to leaf rust and its response to chloride {Cl-) in segregating wheat populations. Resistance of progeny from crosses of susceptible Thatcher with Sharp, Shield, Prospect, Pakistan 81, Pavon 76, Sarhad 83 and Punjab 83 was studied by inoculating F 2 Bc and F 2 populations with two races of�- recondita. Based on the Chi-square tests and segregation ratios in the F 2 Bc and F 2 generations, a dominant gene Lr 2a and probably a modifier was identified in Shield, two dominant genes and a recessive gene in Prospect, a dominant gene Lr 1 in Pavon 76, a dominant Lr 26 plus an unknown recessive gene in Pak 81 and two dominant genes each were identified in Sarhad 83 and Punjab 83. Two or three dominant genes were indicated in Sharp. Cultivar Shield showed reversal of dominance when segregating progenies were inoculated with PRT isolate 27 in a second chloride study. Chloride did not significantly alter segregation ratio in any test. F 2 plants were used to i) study the linkage of genes in coupling or repulsion and ii) calculate recombination values based on Product-Ratio method. Two field experiments were conducted to determine if chloride reduced infection type (s) and rust severity regardless of host resistance genes or pathogen virulence combinations. In the first, coefficient of infection and reaction was affected on 16 wheat cultivars by chloride concentration and by cultivar but there was not a chloride by cultivar interaction. In the second, chloride did not reduce rust. Significant chloride dose by cultivar interactions occurred in growth chamber experiments. Stoa was particularly responsive to low Cl concentrations. The amount of chloride required to reduce urediospore germination in vitro ranged from 1300 to 9400 mg L-1 . Reduced germination of urediospores and stunted germ tubes in the xylem sap was explained by high quantities of Cl ions in the sap. There was no relationship between chloride content in the sap and ED_50 values.

Format

application/pdf

Number of Pages

95

Publisher

South Dakota State University

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