U.S. Department of Agriculture

Forest Seruice Research Note S E- 285 December I979

EFFECT OF CALCIUM, MAGNESIUM, AND ALUMINUM-IRON

ON THE SUSCEPTIBILITY OF LOBLOLLY PINE

SEEDLINGS TO FUSIFORM RUST

by S. J. Rowan’

ABSTRACT.-The susceptibility (percentage of seedlings infected) of Pinus faeda seedlings to

infection by Cronarfium yuercuum f. sp. fusiforme was not affected by fertilization with calcium,

magnesium, or aluminum-iron. Fertilization with Al as AIJSO,):, and Fe as FeCI:,, however, significantly reduced seedling height growth during the first 8 weeks after seedling emergence and

increased numbers of fusiform rust galls per unit of seedling height present at time of inoculation.

Keywords: Pinus taeda, Cronartium quercuum, rust testing, disease resistance.

The susceptibility of slash (Pinus elliotrii

Engelm. var. elliottii) and loblolly pine (P. taeda

L.) seedlings to fusiform rust (caused by

Cronartium quercuum (Berk.) Miyabe ex Shirai f.

sp. fusiforme Burdsall & Snow) is apparently increased by many factors that increase seedling

growth (Rowan 1977, 1978; Rowan and Steinbeck

1977). Susceptibility of pine seedlings to the disease may be directly correlated with the size of

the infection court (Rowan 1978; Rowan and

Steinbeck 1977) and with the physiological condition of host tissues. Resistance, however, must

depend on more than the infection court size because two genetically distinct families of pine

seedlings may grow at equal rates and produce

infection courts of equal size but differ markedly

in susceptibility (Rowan 1977). The effect of fertilization with calcium (Ca), magnesium (Mg), or

aluminum-iron (Al-Fe) on growth and susceptibility of loblolly pine seedlings to infection by C.

quercuum f. sp. fusiforme has not been reported.

Significant effects of any one of these nutrients

would require control of its rate of supply to seedlings tested for susceptibility to the disease

‘Plant Pathologist, U.S. Department of Agriculture,

Forestry Sciences Laboratory, Carlton Street, Athens,

Georgia 30602.

Southeastern Forest Experiment Station - Asheville, North Carolina

(Matthews and Rowan 1972; Powers 1974). This

Note reports the effects of such fertilization on

the susceptibility of loblolly pine seedlings in

greenhouse sand culture.

METHODS

Seeds collected from open-pollinated lob1011~ pines were stratified 30 days and planted in

flats of common builder’s sand. The seeds, collected in Georgia, were supplied by the Georgia

Forestry Commission. Seedlings emerging during

a 4-day period were transplanted to plastic flats

(33. x 13 x 11 cm) at the rate of 20 per flat. Each

flat was filled with builder’s sand which had been

washed repeatedly with tapwater before washing

with pH 2.0 deionized water. The washed sand

contained 99.6 percent sand; 0.4 percent silt,

trace clay; 6.0 pg/g NO:<-N; 0.1 Fg/g PO,-P; 2.9

,xglg Mg; 14.0 pglg Ca; 0.05 pglg Mn; 0.1 pglg Cu;

1.0 pg/g Fe; and nondetectable levels of K, MO,

B, Zn, and organic matter.

Calcium, magnesium, and aluminum-iron

were applied at three levels in a randomized

complete-block design with 10 replications (flats).

The three nutrients were supplied at 0,80, and 160

pg/ml Ca as CaC12; 0, 25, and 75 Fg/ml Mg as

MgSO,; and 0, 100, and 200 pg/ml Al as Alz(S001
mixed respectively with 0, 5.5, and 55.0 pg/ml Fe

as FeCl::. All flats received 0.001 kg/ml MO as

Na?MoO ,, 0.006 pg/ml Cu as CuSO ,, 0.090 pg/ml

B as H-BOX, 0.100 pg/ml Zn as ZnSO+ 0.700

pg/ml Mn as MnC12, 100.0 Fglml N as NHrNOYr,

75.0 pug/ml P as Na?HPO,, and 100.00 pg/ml K as

KC]. All flats receiving Ca treatments also received 25.0 ,ug/ml Mg as MgSO, and 5.5 pg/ml Fe

as chelated sodium ferric diethylenetriamine

pentaacetate. All flats receiving Mg treatments

also received 80.0 pglml Ca as CaCl? and 5.5

pg/ml Fe from the source just mentioned. The

chelated iron was not used to test the effects of

iron as a nutrient because of the desire to provide

a form of iron that would quickly ionize and reach

equilibrium with aluminum. All flats receiving the

Al-Fe treatments also received 80.0 pg/ml Ca as

CaCI? and 25 Fg/ml Mg as MgSO,. All nutrient

solutions were prepared and the pH adjusted to

5.5 the day of application. For 12 consecutive

weeks, beginning the first week after emergence,

400 ml of nutrient solution were applied weekly to

each flat. Similar amounts were applied 14, 16,20,

24, 32, and 40 weeks after emergence. Seedlings

did not require additional irrigation during the

first 12 weeks, but tapwater was applied as

needed after the 12th week.

Aeciospores (source G-3) were collected from a

single loblolly pine gall in Clarke County,

Georgia. Thus, a Georgia spore source was used

to inoculate a Georgia loblolly seed source.

Northern red oak (Quercus rubra L.) seedlings

were inoculated with these spores, and basidiospores were collected from the oak leaves. Suspensions containing 75,OflO basidiospores per ml

were used to inoculate the 8-week-old pine seedlings (Matthews and Rowan 1972; Powers 1974).

Basidiospore viability on 1.5 percent water agar

was 84 percent at time of inoculation.

Seedling heights to the terminal needle tips

were recorded at inoculation, and numbers of

seedlings infected were recorded 12 months after

inoculation. An index of rust susceptibility was

calculated as the ratio of number of galls in each

flat to the total height of all seedlings in each flat at

time of inoculation multiplied by 100. The index,

therefore, is a measure of the number of galls per

unit of seedling height present at the time of inoculation.

RESULTS AND DISCUSSION

Neither growth nor the percentage of loblolly

pine seedlings infected with fusiform rust was

significantly affected by fertilization with Ca, Mg,

or Al-Fe (table 1). Therefore, variations in the

quantities of these elements that were supplied

pine seedling progenies should not affect susceptibility tests for fusiform rust. Fertilization with

100 or 200 pg/ml Al and 5.5 or 55.0 pg/ml Fe

significantly reduced seedling height at inoculation, but this reduction in height was not accom-

‘panied by a reduction in percentage of seedlings

infected with fusiform rust (table 1). The number

of galls per unit of seedling height was increased

by Al-Fe fertilization, indicating that rust suscepTable l.-Effects of calcium (Ca), magnesium (Mg), and aluminum-iron (Al-Fe) supply upon susceptibility

to fusiform rust and height growth at inoculation in loblolly pine seedlings

Nutrient

Concentration

in

solution

Seedlings

infected

Seedling

height at

inoculation

Rust

susceptibility

index’

Ca

Ca

Ca

Mg

Mg

Mg

Al-Fe

Al-Fe

Al-Fe

glml Percent

0 245.5a

80 40.8a

160 54.6a

0 45.0a

25 53.5a

75 42. la

o-o 46.8a

100-5.5 49.4a

200-55.5 49.4a

mm

118.7cd

118.8cd

113.2~

I19.7cd

118.8cd

120.7cd

126. Id

97.0b

8l.Ia

7.7ab

6.9a

9.7bc

7.0a

9.0abc

7.0a

7.5a

10.2c

12.2d

‘Rust susceptibility index = (galls per flat/total height at time of inoculation of all seedlings in each flat) x 100.

‘Means followed by a common letter are not significantly different (P = 0.01) according to Duncan’s multiple range test.
tibility was increased by these treatments.

It was not surprising that Al-Fe reduced

seedling growth because these elements interact

to affect the availability of P in the soil (Hesse

1971). The lack of correlation between seedling

growth rate and susceptibility to rust was a surprise. In genetically similar seedlings, rust incidence increases with the amount of susceptible

tissue (shoot length above cotyledons in young

seedlings) exposed to infection (Rowan and Steinbeck 1977). A lack of correlation between rust

incidence and seedling growth has been reported

in field studies (Dinus and Schmidtling 197 1) and

in a greenhouse study in which several pine families were included (Rowan 1977). The highest

level of Al-Fe applied reduced seedling height 36

percent and caused a 64 percent increase in number of galls per unit of seedling height. If the

infection court size is proportional to seedling

height at inoculation, then fertilization with Al-Fe

increases susceptibility to fusiform rust without

increasing the amount of susceptible tissue.

Additional studies are planned to determine

more fully the effects of Al and Fe on growth and

susceptibility of loblolly pine seedlings to fusiform rust. At present aluminum is not supplied in

fertilizer supplements to seedlings in the Fusiform

Rust Testing Center, nor do I recommend that it

be supplied. An adequate supply of Fe should be

maintained in fertilizer supplements to seedlings

in the testing center to promote growth and prevent chlorosis.

LITERATURE CITED

Dinus, R. J.. and R. C. Schmidtling

1971. Fusiform rust in loblolly and slash pines after

cultivation and fertilization. U.S. Dep. Agric.

For. Serv., Res. Pap. SO-68, IO p. South. For.

Exp. Stn., New Orleans, La.

Hesse, P. R.

1971. A textbook of soil chemical analysis. 520 p.

Chem. Publ. Co., Inc., New York.

Matthews, F. R., and S. J. Rowan

1972. An improved method for large-scale inoculations of pine and oak with Crc~~~tiurn fitsiforme. U.S. Dep. Agric., Plant Dis. Rep. 56:

93 I-934.

Powers, H. R., Jr.

1974. Breakthrough in testing for fusiform rust resistance. For. Farmer 33(4):7-8.

Rowan, S. J.

1977.

Rowan, S.J.

1978.

Rowan, S.J.

1977.

Fertilizer-induced changes in susceptibility to

fusiform rust vary among families of slash and

loblolly pine. Phytopathology 67: 1280- 1284.

Susceptibility to fusiform rust in slash pine

seedlings depends upon fertilization and cumulative inoculum density in multiple inoculalations. U.S. Dep. Agric. For. Serv.. Res. Note

SE-254, 5 p. Southeast. For. Exp. Stn.. Asheville, N.C.

and K. Steinbeck

Seedling age and fertilization affect susceptibility of loblolly pine to fusiform rust. Phytopathology 67:242-246.
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