United States 

Department of Relative Fusiform Rust 

Agriculture Resistance of Loblolly and Slash Pine 

Forest Service Sources and Families in 

Georgia and South Carolina 

Southern 

Research Stat ion E. George Kuhlman, Harry R. Powers, 

Research Paper and William D. Pepper 

SE-291 
Relative Fusiform Rust 

Resistance of Loblolly and Slash Pine 

Sources and Families in 

Georgia and South Carolina 

E. George Kuhlman, Harry R. Powers, 

and William D. Pepper 

Abstract 

Loblolly and slash pine seedlings from the fusiform rust 

resistant orchards developed cooperatively by the USDA 

Forest Service and the Georgia Forestry Commission had 

significantly less rust 7 to 8 years after planting on four of 

five sites in the Southeastern United States than seedlings of 

the same species from orchard sources developed primarily 

for silvicultural improvement. Loblolly and slash pine family 

plantings varied in rust susceptibility on eight sites after 

5 to 7 years. Although rust incidence was relatively low, 

many families contributed to a significant interaction effect of 

family by location in the 7-year-old planting. This significant 

interaction indicates that relative performance of families is 

affected by the variation in virulence of the rust pathogen at 

different locations. This finding supports the hypothesis that 

mixes of resistant families will limit fusiform rust infections 

more effectively than single family plantings. 

Keywords: Concentrated basidiospore spray, disease resistance, 

rust fungus, rust susceptibility. 

Introduction 

The study of relative fusiform rust resistance in pine 

families and sources in field plots is the final indicator 

that the trait is valuable. Greenhouse inoculations 

with the concentrated basidiospore spray (CBS) 

system (Matthews and Rowan 1972) or the forced air 

system (Snow and Kais 1972) are useful techniques in 

rust resistance screening. These provide information 

about the relative rust resistance of families or sources 

compared to other families or sources exposed to a 

limited inoculum source of the fungus under uniform 

conditions. However, the greenhouse results should be 

compared to field tests because the pathogenicity of 

the rust fungus can vary considerably from location 

to location. Furthermore, very young seedlings 

inoculated in the greenhouse may not respond to the 

rust fungus in the same manner as trees growing in 

the field. 

Previously, Miller and Powers (1983) demonstrated 

that rust incidence in field plantings in central 

Georgia and in CBS inoculations correlated well 

for several loblolly pine families. Similarly, Powers 

and Kuhlman (1987) reported that results from 

the CBS inoculations generally correlated well with 

field progeny tests in Greene County, Georgia (GA). 

Recently, Hodge and others (1993) reported that 

each mix of six resistant slash or resistant loblolly 

pine families always had less rust than mixes of 

six susceptible slash or susceptible loblolly pine 

families in six plantings in Georgia, Florida, and 

Mississippi. Sluder (1988) has shown that some 

loblolly pines selected for resistance in field plantings 

can dramatically reduce rust incidence in high hazard 

areas. 

The virulence of the rust fungus can vary with 

location. Virulence is the genetic capacity of some 

isolates of the fungus to overcome resistance in some 

pine families. Powers and others (1977) and Snow 

and others (1975) reported how various loblolly and 

slash pine families responded differently to rust 

inocula from different geographic locations. Both 

reported that some rust isolates caused more disease 

on some families than on other families. Griggs 

and Walkinshaw (1982) reported that a single-gall 

aeciospore isolate was virulent on two slash pine 

families and caused galls on nearly 100 percent of 

the seedlings, while another single-gall isolate was 

completely avirulent on these families and produced 

no galls. Kuhlman (1990) showed that single-gall 

aeciospore isolates with virulence toward specific 

resistant families were present in some populations, 

but the frequency of occurrence was often low. 

However, a resistant slash pine family was more 

susceptible to rust isolates from infected family 

members than to isolates from a wild population 

(Snow and others 1976). 
Many studies report that host genotype x 

environment (location) interaction for fusiform rust 

infection is of little importance in either slash or 

loblolly pine. This suggests that any variations in 

the virulence of the rust fungus have not affected 

the incidence of infection. Kinloch and Stonecypher 

(1969) found no significant environmental effect on 

relative ranking of rust susceptibility among controland open-pollinated loblolly pine families planted 

on sites with various cultural histories within a 

4-kilometer area in south Georgia. Wells and others 

(1982) reported that six loblolly sources from west of 

the Mississippi River had stable resistance, whereas 

resistant sources from east of the river were generally 

less stable at three sites in Louisiana, Mississippi, and 

Alabama. Hodge and others (1993) reported the 

ratios of infection in mixes of resistant and susceptible 

seedlots of slash and loblolly pines were stable on six 

sites in Georgia, Florida, and Mississippi. However, in 

a geographic seed source study, Wells and Wakeley 

(1966) report the seed source x location interaction 

effect on rust resistance was highly significant in their 

series that included sources and planting sites from 

Maryland to Texas. This interaction was distributed 

randomly over the study area and was not due to 

a few seed sources or a single site. No interaction 

occurred in the less widely distributed series that did 

not include seed sources or planting sites in Maryland 

or Texas. 

The primary objective of the studies reported in this 

paper was to determine if orchard and family sources 

resistant to fusiform rust in greenhouse tests would 

be resistant in field plantings in Georgia and South 

Carolina. A secondary objective was to determine 

if rust infection varied on different sites in the 

Southeastern United States because virulent isolates 

of the rust fungus were present. Fourteen different 

studies were established between 1986 and 1989. Six 

orchard source plantings compared rust resistant 

seedlings from the Georgia Forestry Commission 

(GFC)/USDA Forest Service (USFS) rust resistant 

orchards of slash and loblolly pines with commercially 

available pines of these two species selected primarily 

for silvicultural improvement by the GFC. Eight 

family plantings compared individual families of 

loblolly and slash pines. All plantings occurred in 

areas rated as high hazard in region-wide surveys 

(Phelps 1974, Bechtold and others 1992). 

Methods 

Source Studies 

Fusiform rust resistant slash and loblolly pine seeds 

were collected in the GFCIUSFS rust resistant 

orchards and improved slash and loblolly pine seeds 

were collected in the GFC silviculturally improved 

orchards. Seedlings were approximately 9 months old 

when lifted from the nursery beds. 

In the 1986 study, seedlings were machine-planted on 

the Savannah River Site (forests managed by the 

USFS for the Department of Energy) in Barnwell 

County, South Carolina (SC). The three replications 

of each seed source had eight rows of seedlings. 

Within replications, seed sources were randomly 

assigned to each location. The length of the rows 

varied from 160 to 275 meters (m). Seedlings were 

spaced at 2.5-m intervals within the rows, and 

rows were 3 m apart. In 1994, within each source 

replication, the presence of branch or stem galls for 

all trees in two rows and the diameter at breast 

height (d.b.h.) of every second tree in one row were 

recorded. Total trees examined for each source varied 

from 469 to 511 trees. 

In 1987, seedlings were hand-planted on the Savannah 

River Site in Aiken County, SC; on private lands in 

Mitchell and Sumter Counties, GA; and on GFC land 

in Baldwin County, GA. The two sites on private land 

had been previously used for agricultural crops. The 

other two sites had been previously forested. The 

four replications of each seed source had eight rows 

of seedlings with 15 seedlings per row (120 seedlings 

per replication). Sources were randomly assigned to 

locations within replications. Seedlings were spaced at 

2.5-m intervals within rows, and rows were spaced at 

3 m. 

In 1989, a planting was made in Barnwell County, SC. 

Each source was spaced in four rows with 25 seedlings 

per row. Between January and March 1994, rust 

incidence (stem galls, branch galls, or rust-associated 

mortality (RAM)), survival, and growth measurements 

were made in all plots. Growth was determined as 

total tree height to 0.1 m or d.b.h. to the nearest 0.1 

centimeters. 
Family Pfantings Results 

In 1987, loblolly and slash pine families were planted 

in areas adjacent to the source studies in Barnwell 

County, SC; Mitchell County, GA; Sumter County, 

GA; and Baldwin County, GA. At each site, 7 to 10 

half-sib loblolly pine families and 6 to 7 half-sib slash 

pine families were hand-planted in 1 to 9 replications 

with 20 seedlings per replication per family. All 

except 1 of 9 slash families and all 11 loblolly 

families were planted at 2 to 4 locations to determine 

variations in rust incidence among locations. 

In 1988, half-sib slash and loblolly pine families were 

hand-planted on industry lands in Colleton County, 

SC; Effingham County, GA; and on the Savannah 

River Site in Barnwell County, SC. Previously, the 

three sites had been forested. At each site, 10 to 

13 loblolly families and 4 to 8 slash families were 

planted. Twelve of 15 loblolly families and 5 of 9 

slash families were planted at more than 1 location. 

Twenty seedlings per replication per family and P to 9 

replications per family were installed. 

In 1989, 19 half-sib loblolly pine families were 

hand-planted on the Savannah River Site in Barnwell 

County, SC, on previously forested land. There were 

2 to 9 replications per family with 20 seedlings per 

family per replication. 

In 1994, survival, growth, and rust-incidence data 

were collected. Growth was determined by height to 

the nearest 0.1 m for the 1989 planting and for the 

1988 plantings in Barnwell and Effingham Counties. 

Growth was determined by d.b.h. for trees in the 

remaining plantings. The presence or absence of rust 

galls on all trees were recorded. 

Stat istical Analysis 

The percentage of trees with galls within a replication 

was calculated for each family, source, or treatment. 

Both the raw percentages and the arc sines of their 

square roots were used in the analyses of variance 

(ANOVA) (SAS Institute 1988). Mean separation was 

performed with Tukey's Studentized Range (HSD) 

Test at the 10-percent level of significance. 

Source Study 

In the 7- and 8-year-old plantations, the rust resistant 

sources showed significantly better disease resistance 

than sources selected primarily for silvicultural 

improvement in four of the five loblolly and three of 

five slash pine plots (table 1). Interaction among 

sites for the 7-year-old orchard source plantings was 

not significant, suggesting these mixes of resistant and 

improved trees responded similarly on these four sites. 

Although the largest variation in frequency of trees 

with galls occurred in the 5-year-old planting, this 

planting was not replicated and a statistical analysis 

could not be made. In that planting, rust resistant 

loblolly and slash pine trees had only 10 percent with 

galls compared to 44 and 28 percent trees with galls 

in the improved loblolly and slash sources. 

Family Plant ings 

At best, rust infection levels in these tests were 

generally moderate, even in the susceptible controls 

(loblolly 4666-4 and slash MassSus). However, 

loblolly family 151-491 had 60-percent infection 

in the 7-year-old study in Barnwell County, SC 

(table 2), and families 11-10 and 29R had 57 

percent and 56 percent infection, respectively, in the 

6-year-old planting in Colleton County, SC (table 

3). The highest rate of infection (52 percent) of 

mass susceptible slash pine (MassSus) occurred in 

the 7-year-old Barnwell County planting. MassSus 

slash had the highest infection rate among the slash 

families in five of seven plantings. Family 4666-4 was 

included in all of the plantings because it has often 

served as the susceptible standard in CBS greenhouse 

tests at our lab. In these field studies, this family had 

an infection rate close to the average for all families 

at a site. With an average infection of 29 percent in 

the eight locations, it appears to have field resistance. 

Notwithstanding, the relatively low average, progeny 

of 4666-4 had the highest rates of infection in two of 

eight plantings-the 7-year-old Baldwin County and 

the 5-year-old Barnwell County (table 4). 

Family 153-353 had the lowest gall frequency (4, 5, 

and 11 percent) for loblolly in each of the three 

6-year-old plantings (table 3). Slash family 1663-1 1 

had a low infection rate of 3 to 8 percent on three 

sites: Barnwell County (6-year-old), Sumter County 
Table 1-Frequency of fusifom rust and relative growth of trees from rvst resistant 

and silviculturally improved sources of slash and loblolly pines 7 and 8 years after 

planting on five sites in Georgia (a) and South Carolina (SC) 

7 yrs 7 yrs 7 yrs 7 yrs 8 yrs 

Source 

Aiken Mitchell Sumter Baldwin Barnwell Avg. for 

Co., SC Co., GA Co., GA Co., GA Co., SC 7-yr-olds 

Loblolly 

Resistant 

Improved 

Slash 

Resistant 

Improved 

Loblolly 

Resistant 

Improved 

Slash 

Resistant 

Improved 

-------- Trees with galls (percent) - - - - - - - - - - - 

- - - - - - - - Relative growth (d.b.h., cm) - - - - - - - - - - - 

'For rust incidence and relative growth data, means followed by the same letter 

within columns are not significantly different at the 10-percent level with Tukey's 

(HSD) Studentized Range Test. 
Table 2-Incidence of fusiform rust galls on 7-year-old loblolly and slash pine 

families plmted on four locations in Georgia (GA) and South Carolina (SC) 

Family 

Barnwell Mitchell Sumter Baldwin 

MRS~ DR~ Co., SC Go., GA Co., GA Go., GA 

Loblolly 

151-144 

151-263 

151-491 

151-754 

152-61 

152-130 

152-297 

152-309 

153-32 

4666-4 

7840-16 

Average, loblolly 

Slash 

1663-11 

2882-23 

3288-22 

3297-21 

3302-21 

3365-8 

4555-4 

4913-10 

MassSus 

Dodge 36 

J18XJ6 

Dodge 2 

Mitch 10 

Em 5 

Dodge 4 

Ter 2 

Whe 11 

Mix 

Average, slash 

Average, loblolly and slash 

- - -- Trees with galls (percent) - - - - - 

-- -- 8d 3c 

24bc 14bc 13bcd 24abc 

25bc 2c -- -- 

20c 13bc llcd 4bc 

24bc 23abc l7abcd 17abc -- -- 17abcd 2labc 

16c -- -- -- 

3labc 2 Oabc 26abcd -- 

52ab-c 

MRS = maternal resistance source (assumed source of resistance), 

"R = disease ratio. It is the frequency of galls on this family compared to those 

on a susceptible family (in greenhouse test) x 100. 

3~ithin columns, means followed by the same letter are not significantly different 

at the 10-percent level with Tukeyfs (HSD) Studentized Range Test. 
Table 3-Incidence of fusiform rust galls on 6-year-old loblolly and slash pine 

families planted on three locations in Georgia (a) and South Carolina (SC) 

Family 

Colleton E ffingham Barnwell 

Co., SC Co., GA Go., SC 

Loblolly 

151-97 

151-364 

152-387 

153-238 

153-243 

153-353 

10-5 

11-10 

11-20 

2 9R 

42R 

4625-3 

4666-4 

7840-16 

Average, loblolly 

Slash 

10-226 

1663-11 

2882-23 

3302-21 

3365-8 

3384-9 

4555-4 

7703-2 

MassSus 

Average, slash 

10-226 

Dodge 36 

518 x J6 

Em. 5 

Dodge 4 

Telf. 37 

Ter. 2 

Bull. 6 

Mix 

Average, loblolly and slash 

- - Trees with galls (percent) - - - 

33abc3 

-- 

29bc 

29bc 

-- 

llc 

35abc 

57a 

46ab 

56a 

-- 

35abc 

35abc 

-- 

MRS = maternal resistance source (assumed source of resistance). 

2~~ = disease ratio. It is the frequency of galls on this family compared to 

those on a susceptible family (in greenhouse test) x 100. 

3~ithin columns means followed by the same letter are not significantly different 

at the 10-percent level with Tukey's (HSD) Studentized Range Test. 
Table 4-Frequency (percent) of survival and of trees with fusifom rust galls 

and relative growth (height in meters) of nineteen loblolly pine families in a 

5-year-old planting in Barnwell County, South Carolina 

Family MRsl DR~ Galls Height Survival 

Average 

3333 

TFS 

HH 

11-9 

-- 

1495-35 

SML- 9 

7-56 

29Rx10-5 

11-ZOMR 

2 9RxA 

T601 

-- 

2318 

3 c3 

5bc 

5bc 

10abc 

llabc 

12abc 

l2abc 

12abc 

16abc 

17abc 

2labc 

22abc 

24abc 

25abc 

25abc 

26abc 

26abc 

30ab 

32a 

'MRS = maternal resistance source (assumed source of resistance). 

DR = disease ratio. It is the frequency of galls on this family compared to 

those on a susceptible family (in greenhouse test) x 100. 

Within columns means followed by the same letter are not significantly 

different at the 10-percent level with Tukey's (HSD) Studentized Range Test. 
(7-year-old) , and Baldwin County (7-year-old) (tables 

2 and 3). Slash family 3365-8 had less than half the 

rate of infection of the mass susceptible control in two 

of these three plantings. In the 5-year-old loblolly 

planting, families 154-60, 152-60, and 151-791 had 5 5 

percent infection, compared to 32 percent infection in 

family 4666-4 (table 4). 

Some families had significant interaction in the 

ANOVA between rust incidence and location for the 

7-year-old, but not for the 6-year-old family plantings. 

For example, family 151-144 was very resistant in 

Sumter County (13 percent) but relatively susceptible 

in Barnwell and Baldwin Counties (table 2). Slash 

family 2882-23 was quite resistant in Mitchell and 

Sumter Counties but more susceptible in Barnwell and 

Baldwin Counties. Slash family 3297-21 was most 

resistant in Baldwin County. 

Survival 

Survival in the source and family plantings was 

generally good with up to 93 percent of the trees still 

alive and very little rust-associated mortality 6 and 

7 years after planting. Loblolly families in Colleton 

and Mitchell Counties averaged 86 and 85 percent 

survival, respectively. Slash families also had the best 

survival in these two locations. The 6-year-old slash 

family plantings in Effingham County had the poorest 

survival averaging 41 percent, probably due to a poor 

site and drought conditions soon after planting. 

Growth 

In the source plantings, no significant differences in 

growth occurred between the rust resistant sources 

and the improved sources (table 1). In the Mitchell 

County and the &year-old Barnwell County plantings, 

the two loblolly sources had larger diameters than the 

two slash sources. 

In the family plantings , significant differences in 

growth occurred among families at all locations 

(tables 4, 5, 6). The stringent Tukey7s Studentized 

Range Test at the 10-percent level used for statistical 

comparisons indicated a lot of overlap in growth 

among the families. Slash families generally grew 

less well than loblolly families. The MassSus slash 

family had the poorest growth at most locations. 

Regressions of family growth versus family resistance 

(gall frequency) were computed, but no significant 

relationship between rust incidence and growth was 

present. Similar comparisons across all locations for 

the 7-year-old plantings indicated that selecting for 

rust resistance does not significantly affect growth. 

Discussion 

On most sites in Georgia and South Carolina, 

fusiform rust resistant orchard sources of loblolly 

and slash pines had less rust after 7 to 8 years than 

orchard sources selected primarily for silvicultural 

improvement. Because rust resistant orchards are 

continuously rogued of the most rust-susceptible 

individuals, seedlings from these orchards should 

continue to improve in relative fusiform rust 

resistance. 

The interaction of rust incidence among families 

on different sites indicates that the rust varies in 

virulence on different sites. Virulence in the pathogen 

is genetically controlled, just Pike resistance in the 

pine host. The presence of interaction indicates that 

different genes for virulence in the rust population 

are present on different sites in Georgia and South 

Carolina. Because predicting the virulence of local 

rust populations to different rust resistant families is 

not presently possible, planting a mix of families to 

ensure a heterogenous rust resistant pine population 

appears to be the safest means of limiting rust-related 

losses. 

Concern about selecting for rust resistance has been 

expressed. Some believe growth would suffer, while 

others feel susceptible trees grow faster and make 

up any loss to rust. Our data does not support 

these ideas because no relationship between rust 

susceptibility and growth was observed. Moreover, 

in developing these rust resistant families for the 

USFS/GFC Rust Resistance Orchards, Powers and 

Kraus (1983) selected in progeny test blocks first for 

growth and then within the fastest growers selected 

for rust resistance. The fusiform rust resistant sources 

grew as well as the silviculturally improved sources, 

indicating that selecting for rust resistance did not 

result in growth loss. 
Table S-Growth of loblolly and slash pine families in 7-year-old plantings 

on four locations in Georgia (a) and South Carolina (SC) 

Family 

Barnwell Mitchell Sumter Baldwin 

Co. , SC Co. , SC Co., GA Go., GA 

Average, loblolly 

Slash 

1663-11 

2882-23 

3288-22 

3297-21 

3302-21 

3365-8 

4555-4 

4913-10 

MassSus 

10. Obci 

9.8bc 

12.3a 

11. lab 

10.5ab 

9.6bc 

10. labc 

-- 

10.0bc 

9.9bc 

10.5ab 

13.8bcde 

14. Obcd 

14.5abc 

14.8ab 

13.3bcdef 

15.7a 

14. lbcd -- 

12.9def g 

12.5defg 

14. Obcd 

13.8bcd 

13.9abcd 

-- 

14.8ab 

14. labc 

15.5a 

13.4bcdef 

13.4bcde 

13.4bcde 

12.9cdef 

13.2bcdef 

-- -- 12.5cdef 9.0cd 

8.9bc 12. lgh 12.0ef 10.4abc 

9.7bc 10.9h -- -- 

9.3bc 12.9defg 12.7def 7.8d 

9.7bc 13. Ocdefg 12.4def 9. lbcd -- -- 12.6def 9.4abcd 

9.2bc -- -- -- 

9.3bc 12.3efgh 12. lei -- 

9.0bc 11.6ah 11.8f 9.5abcd 

Average, slash 9.3 12.1 12.3 9.2 

Average, loblolly 

and slash 10.0 

'within columns means followed by the same letter are not significantly different 

at the 10-percent level with Tukey's (HSD) Studentized Range Test. 
Table 6-Relative growth of loblolly and slash pine families 

in 6-year-old plantings in three locations in Georgia (GA) and 

South Carolina (SC) 

Family 

Colleton 

Co., SC 

Ef f ingham 

Co., GA 

Barnwell 

Co., GA 

Loblolly 

151-97 

151-364 

152-387 

153-238 

153-243 

153-353 

10-5 

11-10 

11-20 

2 9R 

42R 

4625-3 

4666-4 

7840-16 

Average, loblolly 

Slash 

10-226 

1663-11 

2882-23 

3302-21 

3365-8 

3384-9 

4555-4 

7703-2 

MassSus 

dbh fcm) - - - - - Height (m) - - - - - 

9. 5de1 2.55de 4.77abcd -- 2.7 6abcde -- 

10.6cd 2.89abcde 4.95abc 

12.0ab 2.99abcde -- -- 3.07abcde -- 9.0e 2.62cde 4.16cdef 

12.5a 3.35a 5.71a 

11.7abc 3.39a 5.45ab 

12.3ab 3.41a 5.63a 

9 6de 2.653bcde 4.62bcdef -- 3.lOabcde 4.47cdef 

12.0ab -- 4.95abc 

10. Ode 2.6lcde 4.42cdef -- 2.73abcde -- 

Average, slash 10.4 3.75 4.32 

Average, loblolly 

and slash 10.7 

'within columns means followed by the same letter are not significantly 

different at the 10-percent level with Tukeyts (HSD) Studentized Range 

Test. 
Acknowledgment 

T;Ve thank the Georgia Forestry Commission (GFC) 

and the Savannah River Forest Station (Region 8, 

USDA Forest Service) for financially supporting 

portions of these studies. We also thank the following 

individuals for allowing us to plant seedlings on 

their land: Ruby McIlwraith, Americus, GA; Ed 

Williamson, Camilla, GA; Dave Gerwig, Westvaco 

Co., Summerville, SC; John Godbee, Union Camp 

Corp., Savannah, GA.; the Georgia Forestry 

Commission, Macon, Georgia; and the Savannah River 

Forest Station, Aiken, SC. We gratefully acknowledge 

the technical assistance of Tony Blalock, Brad 

Howard, Roy Walker, Sherry Trickel, and Ed Dixon. 

Literature Cited 

Bechtold, William A.; Hoffard, William H.; Anderson, 

Robert L. 1992. Smary report: forest health monitoring 

in the South, 1991. Gen. Tech. Rep. SE-81. Asheville, 

NC: U.S. Department of Agriculture, Forest Service, 

Southeast ern Forest Experiment St ation. 40 p. 

Griggs, Margene M.; Wdkinshaw, Charles H. 1982. 

Diallel analysis of genetic resistance to Cronartium 

quercuum f. sp. fusiforme in slash pine. Phytopathology. 72: 

816-818. 

Hodge, G.R.; White, T.L.; Schmidt, R.A.; Allen, J.E. 

1993. Stability of rust infection ratios for resistant and 

susceptible slash and loblolly pine across rust hazard levels. 

Southern Journal of Applied Forestry. 17: 188-192. 

Kinloch, Bohun B.; Stonecypher, Roy W. 1969. Genetic 

variation in susceptibility to fusiform rust in seedlings from 

a wild population of loblolly pine. Phytopathology. 59: 

1246-1255. 

Ku hlman, E.G. 1990. Interaction of virulent single-gall 

rust isolates of Cronartium quercuum f. sp. fusiforme 

and resistant families of loblolly pine. Forest Science. 38: 

641-651. 

Matthews, Fred R.; Rowan, S.J. 1972. An improved 

method for large-scale inoculations of pine and oak with 

Cronartium fusiforme. Plant Disease Reporter. 56: 931-934. 

Miller, Thomas; Powers, H.R., Jr. 1983. Fusiform rust 

resistance in loblolly pine: artificial inoculation vs. field 

e. Plant Disease. 67: 33-34. 

Phelps, William R. 1974. Evaluation of fusiform rust 

incidence on loblolly and slash pine in the South. Plant 

Disease Reporter. 58: 1137-1141. 

Powers, W.R., Jr.; Kraus, J.F. 1983. Developing fusifom 

rust-resistant loblolly and slash pines. Plant Disease. 67: 

187-189. 

Powers, H.R., Jr.; Kulhman, E.G. 1987. Resistance 

of loblolly pine sources to fusiform rust in field progeny 

tests. Res. Pap. SE-268. Asheville, NC: U.S. Department of 

Agriculture, Forest Service, Southeastern Forest Experiment 

Station. 8 p. 

Powers, H.R., Jr.; Matthews, F.R.; Dwinell, L.D. 

1977. Evaluation of pathogenic variability of Cronartium 

fusifomne on loblolly pine. Phytopathology. 67: 1403-1407. 

SAS Institute Inc. 1988. SAS/stat user's guide: statistics. 

Release 6.03 ed. Cary, NC: SAS Institute. 

Sluder, E.R. 1988. Inheritance and gain in a half-diallel cross 

among loblolly pines selected for resistance to fusiform rust. 

Silvae Genetica. 37: 22-26. 

Snow, G.A.; Kais, A.G. 1972. TeChnique for inoculating 

pine seedlings .with Cronaritum quercuum. In: Biology 

of rust resistance in forest trees. U.S. Department of 

Agriculture, Misc. Publ. 1221: 325-326. 

Snow, G.A.; Dinus, R.J.; Kais, A.G. 1975. Variation in 

pathogenicity of diverse sources of Cronartium fusif orm e on 

selected slash pine families. Phytopathology. 65: 170-175. 

Snow, G.A.; Binus, R.J.; Walkinshaw, C.H. 1976. 

Increase in virulence of Cronartium fusiform e on resistant 

slash pine. Phytopathology. 66: 511-513. 

Wells, Qsborn 0.; Switzer, George L.; Nance, Warren 

L. 1982. Genotype-environment interaction in rust 

resistance in Mississippi loblolly pine. Forest Science. 28: 

797-809. 

Wells, Qsborn 0.; Wakeley, Philip C. 1966. Geographic 

variation in survival, growth, and fusiform-rust infection of 

planted loblolly pine. Forest Science Monograph 11. 40 p. 
I Kuhlman, E. George; Powers, Harry R.; Pepper, William D. 1995. Relative I Kuhlman, E. George; Powers, Harry R.; Pepper, William D. 1995. Relative 

fusiform rust resistance of loblolly and slash pine sources and families in Georgia fusiform rust resistance of loblolly and slash pine sources and families in Georgia i 

I and South Carolina. Res. Pap. SE291. Asheville, NC: U.S. Department of 1 and South Carolina. Res. Pap. SE291. Asheville, NC: U.S. Department of I 

I Agriculture, Forest Service, Southern Research Station. 12 pp. I Agriculture, Forest Service, Southern Research Station. 12 pp. I 

1 I I 

Loblolly and slash pine seedlings from the fusiform rust resistant orchards developed 

cooperatively by the USDA Forest Service and the Georgia Forestry Commission 

had significantly less rust 7 to 8 years after planting on four of five sites in the 

Southeastern United States than seedlings of the same species from orchard sources 

developed primarily for silvicultural improvement. Loblolly and slash pine family 

plantings varied in rust susceptibility on eight sites after 5 to 7 years. Although rust 

incidence was relatively low, many families contributed to a significant interaction 

effect of family by location in the 7- year-old planting. This significant interaction 

indicates that relative performance of families is affected by the variation in virulence 

of the rust pathogen at different locations. This finding supports the hypothesis that 

mixes of resistant families will limit fusiform rust infections more effectively than 

single family plantings. 

. 

I Loblolly and slash pine seedlings from the fusiform rust resistant orchard. developed 

cooperatively by the USDA Forest Service and the Georgia Forestry Cornmission I had significantly less rust 7 to 8 years after planting on four of five sites in the I Southeastern United States than seedlings of the same species from orchard sources 

1 developed primarily for silvicultural improvement. Loblolly and slash pine family 

( plantings varied in rust susceptibility on eight sites after 5 to 7 years. Although rust 

I incidence was relatively low, many families contributed to a significant interaction 

effect of family by location in the 7-year-old planting. This significant interaction I indicates that relative performance of families is affected by the variation in virulence I of the rust pathogen at different locations. This finding supports the hypothesis that 

I mixes of resistant families will limit fusiform rust infections more effectively than 

I single family plantings. 

I 

I Key words: Concentrated basidiospore spray, disease resistance, rust fungus, rust I Keywords: Concentrated basidiospore spray, disease resistance, rust fungus, rust I 

susceptibility. I susceptibility. f 

I 

I