OKLAHOMA STATE UNIVERSITY
Plant Pathology Department, 110 Noble Research Center, Stillwater,
OK 74078-9947, USA.
R.M. Hunger and J.L. Sherwood.
Wheat leaf rust.
Seedling and adult plant reactions of wheat genotypes
to leaf rust were determined in the 1995 Southern Regional Performance
Nursery. Two races of Puccinia recondita f. sp.
tritici and a mixture of races were used to test seedlings.
Adult plant reaction to leaf rust was determined in field plots
located near Stillwater (STW) and Altus (ALT), OK. The experimental
design was a randomized complete block with three replications
per entry. Plots consisted of six, 10-ft rows. Seed was planted
1-in deep at 1 bu/acre, and recommended management practices were
followed for each location. Leaf rust severity was assessed on
18 April, 1995 (ALT), and 4 May, 1995 (STW), using a disease index
of 1-9, where 1-3, 4-6, and 7-9 indicate
increasing leaf rust severity (% leaf area with pustules) within
resistant, moderately resistant, and susceptible categories.
Nurseries were harvested on the 15 June, 1995 (STW) and 19 June,
95 (ALT).
Plant stands at STW were fair, with low yields resulting
not only from leaf rust, but also from wheat soilborne mosaic
virus, barley yellow dwarf virus, root rots, a late-spring freeze,
and excessive moisture at harvest. Stands at ALT were thin because
of autumn and winter drought, but leaf rust pressure was high.
Eighteen entries (04-06, 09, 10, 13, 17-19, 22-24,
33, 36-39, and 42) were resistant (severity ratings ²
3.0) to leaf rust in the field. Ten (04, 05, 09, 10, 17-19,
22, 39, and 42) of these 18 entries were susceptible to leaf rust
as seedlings, indicating that they may possess an adult plant
resistance gene(s).
A low incidence and mild severity of WSBMV occurred
in Oklahoma during spring 1995. This resulted partly from masking
of WSBMV symptoms by the widespread high incidence and severity
of root rots and BYDV. Screening of breeder lines for reaction
to WSBMV in the WSBMV nursery located near Stillwater was attempted,
but was unsuccessful because of the severity of root rots and
BYDV.
Results from field tests conducted during 1993-95
demonstrate an interaction between WSMV serotypes and HRWW cultivars.
These trials are being continued during 1995-96 to confirm
past results and document the `serotypes x cultivar'
interaction. In addition, variability in the sequence of the
coat protein region of a number of isolates of WSMV is being determined.
Table 1. Seedling and adult plant reaction of wheat genotypes to leaf rust determined in the 1995 Southern
Regional Performance Nursery.
___________________________________________________________________________________________
Adult plant leaf rust reaction1
Seedling leaf rust reaction1 _________________________________________
Entry and ________________________ Stillwater Altus
selection number race 1 race 2 mixed severity yield2 severity yield2
___________________________________________________________________________________________
01 CI1442 3 3 3+ 4.0 6.3 7.3 21.1
02 CI13996 3c 3 3 2.0 13.4 6.3 33.7
03 PI495594 3 3+ 3 7.7 13.2 8.0 35.2
04 HBZ374C 3+ 3 3 1.3 39.1 2.0 47.3
05 OK91P648 3 X3-0; 3 1.3 46.2 1.0 52.8
06 OK93P735 X3c0; X30; X0;3- 1.3 44.5 1.0 58.8
07 OK93P656 3c 3 3 4.0 34.3 2.3 44.6
08 OK93P727 3+ 3+ 3 6.7 38.1 2.0 49.6
09 TX91D6913 3 3 3 1.0 50.0 1.7 51.1
10 TX91D6991 3 3 3+c 3.0 35.1 2.7 43.9
11 TX90V6313 3 3+ 3+c 5.7 25.0 2.3 51.2
12 TX92V4135 3 3 3+ 7.0 31.9 1.3 46.3
13 HBE0726-1 X30; 0; X0;3- 1.3 29.6 1.0 62.3
14 TX92V3108 3- 3cn 3-c 5.3 17.8 5.0 49.1
15 HBI0531-A2 3 3 3+ 2.3 28.0 3.7 61.7
16 TX93V5919 3 3 3+ 5.0 28.0 5.7 48.5
17 TX93V5922 3 3-c 3-c 3.0 22.9 2.3 54.5
18 TX93V4927 3 3 3- 2.3 23.8 2.0 54.5
19 TX92V2519 3 3+ 3-c 1.7 18.9 2.7 47.9
20 CO890323 3+ 3 3+ 6.0 15.1 5.7 42.1
21 CO900166 3+ 3+ 3+ 6.7 20.2 7.7 39.0
22 KS92P0263-137 3 3 X0;3-c 2.0 31.2 2.0 42.9
23 KS93U206 0; 0; 0; 1.0 31.5 1.0 57.4
24 KS91H153-2 X30; 3 3-cn 1.0 31.4 1.3 55.7
25 N93L058 3 3 3 2.0 27.9 3.3 48.7
26 NE91651 3=cn X0;3-n X0;3-c 6.0 28.0 3.0 44.3
27 NE90476 3=cn 3-n X0;3-c 1.0 22.3 5.7 45.7
28 NE92458 3c 3-n 3-c 6.3 27.1 6.7 28.3
29 NE92614 3 3-nc 3+ 3.0 19.5 5.0 43.1
30 NE92646 3 3c 3c 2.7 21.8 6.7 44.2
31 XH1706 3 X0;3-n X0;3 4.7 31.6 1.7 56.4
32 XH1752 3c 3-c 3-c 3.7 33.4 2.3 55.0
33 XH1778 0; 0; 0; 1.3 30.2 1.0 66.1
34 XH1798 3c X0;3- X0;3- 4.0 45.3 2.0 57.8
35 W91-091 X0;3=n 0; 3 5.7 23.4 2.0 47.7
36 W91-287 3- X0;3= 3-c 2.3 28.7 2.0 50.5
37 AP 7501 3- X0;3=n X0;3-c 1.3 28.7 1.7 56.4
38 WX92-0408 3 X0;3-n X0;3- 2.7 35.0 2.3 43.7
39 WI89-163W 3 3 3c 1.3 23.3 1.3 50.5
40 WI90-540W 3 3-c 3+ 4.3 29.2 1.3 44.1
41 W88-2619W 3 3+ 3 7.3 23.3 5.7 43.4
42 T702 3c 3+ 3 1.7 22.6 2.3 51.9
Table 1 (continued). Seedling and adult plant reaction of wheat genotypes to leaf rust determined in the 1995 Southern Regional Performance Nursery.
___________________________________________________________________________________________
Adult plant leaf rust reaction1
Seedling leaf rust reaction1 _________________________________________
Entry and _______________________ Stillwater Altus
selection number race 1 race 2 mixed severity yield2 severity yield2
___________________________________________________________________________________________
43 T834 3c 3 3 3.3 27.5 4.3 46.0
44 T812 3 X3-0; 3-c 6.0 20.4 2.7 47.7
45 T861 3 3 3 4.0 21.1 4.3 31.8
LSD (P=0.05) 1.5 5.5 1.0 9.3
CV (%) 25.9 12.3 18.7 11.9
___________________________________________________________________________________________
1Avirulence/virulence formulas: Race 1 = 2a 3ka 9 16 19 / 1 2c 3 11 17 24 26 30;
Race 2 = 2a 3ka 9 16 19 26 30 / 1 2c 3 11 17 24; Mixed = 9 16 19 26 / 1 2a 2c 3 3ka 11 17 24 30.
2Yield is in bu/acre.
Breeding for disease resistance.
Emmer wheats (T. dicoccoides) from Israel
and Turkey resistant to leaf rust, wheat soilborne mosaic virus,
tan spot, and powdery mildew have been identified and crossed
with adapted hard red winter wheats. F1 progeny from these crosses
resistant to leaf rust, WSBMV, and powdery mildew have been identified
and are being increased and/or backcrossed to the adapted HRWW.
Reaction of the F1 progeny to tan spot showed no adavantage compared
to the resistant check (Red Chief) and were dropped from the program.
Testing of 26 germplasm lines that were developed
from crosses between a WSBMV-resistant HRWW and a leaf rust-resistant
European wheat revealed an unacceptable number of plants susceptible
to leaf rust. Many individual heads were selected from resistant
plants and are being grown and tested in the greenhouse and in
the field as head rows during 1995-96. Over the next 2-3
years, lines resistant to leaf rust and WSBMV will be identified,
tested for homogeneity, bulked, and tested for release as germplasm.
Personnel changes.
Dr. C.K. (Kent) Evans received his Ph.D. in March,
1995, under the direction of Robert M. Hunger. The title of Kent's
dissertation was, `Infection efficiency of propagules of
Pyrenophora tritici-repentis isolates and evaluation of
wheat for reaction to tan spot'. Kent accepted a postdoctoral
position at the University of Minnesota working with Drs. Ruth
Dill-Macky and Don Rassmussen on developing barley resistant to
Fusarium head blight.
Dr. Joe R. Montana received his Ph.D. in December,
1995, under the direction of Robert M. Hunger and John L. Sherwood.
The title of Joe's dissertation was `Characterization
of wheat streak mosaic virus serotypes and their effect on wheat'.
Dr. Montana has returned to his home state of New Mexico.
Publications.
Chenault K, Hunger RM, and Sherwood JL. 1995. Sequence
analysis of the coat protein region of wheat streak mosaic virus
(WSMV) isolates. Phytopath 85:1185 (Abstract).
Hunger RM, Sherwood JL, Siegerist WC, and Myers LD.
1995. Reaction of the Southern Regional Performance Nursery
to wheat soilborne mosaic, 1994. Biol & Cul Tests for Control
of Plant Dis 10:126.
Hunger RM, Siegerist WC, Evans CK, Smith EL, and
Morgan G. 1995. Reaction of the Southern Regional Performance
Nursery to wheat leaf rust and tan spot, 1994. Biol & Cul
Tests for Control of Plant Dis 10:120.
Hunger RM, Siegerist WC, Myers LD, Sherwood JL, and
Evans CK. 1995. Reaction of the Northern Regional Performance
Nursery to wheat soilborne mosaic and tan spot. Biol & Cul
Tests for Control of Plant Dis 10:127.