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Ft. Pierce ARC Research Report RL-1977-4 Qcaber, 1977
Reaction of Macroptilium atropurpureum (D. i. LI1BRAY
accessions to a potyvirus
/ LJAN .1918
R. M. Sonoda 1 JAN 197
ABSTRACT of Florida
All plants of 13 accessions of Macroptilium atropurpureum (D.C.)
Urb. inoculated with a potyvirus were infected with the virus. The
dry matter yield of seven of eight accessions planted in the field
were reduced by 50% or more. The yield of virus-infected IRFL 1055
was the same as uninoculated IRFL 1055. Virus-infected plants of the
heavy-yielding cultivar, Siratro, however, outyielded both uninocu-
lated and virus-infected plants of IRFL 1055.
A recently discovered potyvirus on Macroptilium atropurpureum
(D.C.) Urb. reduced forage yield of the cultivar Siratro and other M.
atropurpureum accessions by 34 to 62% (6). The extent of yield re-
duction and the potential of the plant as a forage crop for south
Florida (2) makes a search for sources of resistance advisable. Pro-
widenti and Braverman (4) reported that six M. atropurpureum acces-
sions were tolerant to a strain of bean common mosaic pathogen to all
26 of their accessions of M. lathyroides, a plant related to M. atro-
purpureum. Lima et al. (37 report that the potyvirus on M. atropur-
pureum is Atmilar to bean common mosaic virus.
The purpose of this study was two-fold; 1) to determine the ef-
fect of the potyvirus on yield of several accessions of M. atropur-
pureum, 2) to inoculate available M. atropurpureum accessions with
Materials and Methods
Eight accessions of M. atropurpureum; IRFL 483 (cultivar, Siratro),
911, 912, 916, 917, 1055, and 1502, all previously found to be suscep-
tible to the virus (5) were obtained from A. E. Kretschmer, Jr. (Univer-
sity of Florida, IFAS, ARC-Ft. Pierce). Three of six accessions re-
ported to be tolerant to the strain of bean common mosaic pathogenic to
M. lathyroides by Provvidenti and Braverman (4) (P. I. 296959, 316463,
and 307599) were obtained from W. R. Langford, USDA, Southern Regional
Plant Introduction Station. Two lines, 16877 and 16879, parents of the
commercial cultivar Siratro (1) were obtained from E. M. Hutton, CSIRO,
St. Lucia, Queensland, Australia.
1/ Associate Plant Pathologist, University of Florida, Institute of
Food and Agricultural Sciences, Agricultural Research Center, Fort
Seeds of all accessions were scarified with a razor blade, germin-
ated on moistened filter paper in petri dishes and transferred to a 1:1
mix of shredded sphagnum peat moss and horticultural vermiculite. Leaves
of Siratro exhibiting virus symptoms were obtained from field plantings
at the ARC-Ft. Pierce. The leaves were triturated in distilled water
with a mortar and pestle. Inoculum was applied to leaves on sixteen
plants of each accession with a piece of cheesecloth after the leaves
had been dusted with carborundum. Inoculum was applied to the plants
in the same manner two more times at 2 week intervals to make certain
that susceptible plants did not escape infection.
The accessions IRFL 483, 911, 912, 913, 916, 917, 1055, and 1502
were inoculated initially on June 15 '76. Five infected plants and five
uninoculated plants of each accession were transplanted in the field in
a randomized complete block design. Shoots from this test were harvested
on June 21, '77 and Aug 10 '77, dried and weighed.
Results and Discussion
All individuals of all the accessions tested were susceptible to
the virus. Leaf mottling and leaf distortion occurred on all plants.
Plants of the same accession with the same treatment grew at dif-
ferent rates in the field plot due to poor drainage in some parts of
the field. However, differences in dry matter yield (Table 1) between
virus-infected plants and uninoculated plants of the same accession
were obvious except for the accession IRFL 1055. The extent of yield
reduction was similar to that obtained for accessions IRFL 483, 912,
913, and 916 in a previous test (6).
Symptoms on leaves of IRFL 1055 were similar to symptoms on in-
fected plants of the other accessions. Infected plants of IRFL 1055
grew as vigorously as uninoculated plants of the same accession. More
extensive comparisons of virus-infected and healthy IRFL 1055 are needed
to confirm the tolerance of this accession to the virus.
Virus-infected IRFL 483 (Siratro) outyielded both healthy and virus-
infected IRFL 1055 (Table 1). Thus, there is no apparent benefit in re-
placing Siratro with IRFL 1055 as planting material. If the tolerance
of IRFL 1055 to the potyvirus holds up, individuals of the accession may
serve as sources of tolerance to the virus in a breeding program.
Prowidenti and Braverman (4) reported that the strain of bean
common mosaic virus they were working with caused symptomless systemic
invasion of M. atropurpureum. The leaf mottling and leaf distortion
exhibited by P. I. 296959, 316463, and 307599 in our tests indicate
that they were working with a different virus.
Acquisition and screening of more accessions-of, M. atropurpureum
for resistance to the virus is needed.
1. Hutton, E. M. 1962. Siratro A tropical legume bred from Phaseolus
atropurpureus. Aust. J. Exp. Agr. Anim. Husb. 2: 117-125.
2. Kretschmer, A. E. Jr. 1972. Siratro (Phaseolus atropurpureus DC.),
a summer-growing perennial pasture legume for central and south
Florida. Florida Ag. Exp. Sta. Circ. S-214. 21 pp.
3. Lima, J. A., D. E. Purcifull, and R. M. Sonoda. 1977. Some proper-
ties of a potyvirus isolated from Siratro in Florida. Ann.
Proc. Amer. Phytopath. Soc. (IN PRESS).
4. Prowidenti, R. and S. W. Braverman. 1976. Seed transmission of
bean common mosaic virus in phasemy bean. Phytopathology 66:
5. Sonoda, R. M. 1976. Reaction of Macroptilium atropurpureum and
related species to three diseases in Florida. Tropical Grass-
lands 10: 61-63.
6. Sonoda, R. M. 1977. Effect of a mosaic virus on Siratro and other
Macroptilium atroppurureum (DC.) Urb. accessions. Soil and
Crop Sci. Soc. Fla. Proc. (IN PRESS).
Table 1. Dry Weight Yield per Plant in g of Healthy and Virus-infected
Macroptilium atropurpureum accessions.
Siratro (IRFL 483)
1/ Means followed by the same letters are not
level by Duncan's multiple range test.
different at the 5%