1Adaptation of new species of Leucaena in Costa Rica, Central America.
Preliminary results
P. J. Argel and G. Pérez1
There are 17 species of Leucaena identified that are all native to the New World; however,
the more researched and utilized species worldwide continues to be L. leucocephala (Lam)
de Wit, that is known by its high forage quality, but deficient cold and drought tolerance,
poor growth on acid soils, heavy pod production, low wood durability and susceptibility to
a defoliating psyllid (Hughes 1993). Other species of Leucaena are little known despite that
indigenous people, particularly of Mexico and Central America, have utilized them for
centuries as sources of food, firewood, timber for construction and feed for domestic
animals.
In 1996 CIAT agree to collaborate with the Oxford Forestry Institute (OFI) of England to
evaluate the adaptation and potential use of new species of Leucaena along the tropics of
Latin America. OFI provided experimental seed of 18 new lines of Leucaena, supplied the
inoculum and the experimental methodology for evaluation. During the last year, seed has
been distributed to collaborators in Costa Rica, Mexico, Honduras, Nicaragua, Belize,
Panamá, Colombia, Venezuela and Brazil. The trials are coordinated from a regional CIAT
office located at the headquarters of the Instituto Interamericano de Cooperación para la
Agricultura (IICA) in San José, Costa Rica.
Preliminary results of the first trial established in Costa Rica are presented.
Materials and methods
The experimental site is located at the Escuela Centro Americana de Ganadería (ECAG) in
Atenas, Costa Rica. This locality is placed at 9º 58' lat N and 84º 23' long W at 200 m.a.s.l.;
it is classified as subhumid tropical forest with 23.7 ºC mean temperature and 1600 mm of
annual rainfall distributed from May to November. The soils are inceptisols of medium
fertility that have the following characteristics:  pH 5.9 (H2O); 7.6 % OM; 3.6 ppm of P;
9.5, 6.0 and 0.24 meq/100 g respectively of Ca, Mg and K; the Al content is negligible.
Seed of 18 species of Leucaena were scarified with sand paper, inoculated and  planted
directly in the field placing two seeds per site. Plants were thinned lately to one per site for
a total of 10 plants per plot spaced at 0.50 m between plants. Checks were made of one line
selected by CIAT of L. leucocephala (CIAT 17263), one introduction of Calliandra
callothyrsus from Australia (CPI 115690) and the shrub Cratylia argentea (CIAT 18668).
Each species was replicated  four times.
Measurements of plant height and diameter, foliar retention and plant mortality  were taken
3.5 months after planting at the end of the dry season. Plant height was measured again 9.8
months after planting, before the uniformity cut made at 0.50 m height. At this age the form
and growth habit of the different accessions was ranked using a scale suggested by OFI.
                                                          
1 Centro Internacional de Agricultura Tropical (CIAT). Regional Office at IICA, Apdo 55-2200, San José,
Costa Rica.
2Evaluation cuts at 0.5 m height have been carried out at 8 weeks of regrowth during the
period of the rains; the material harvested is separated in edible component (leaves
and thin stems) and woody parts. Dry weight is taken after drying the samples for 48 hours
in a forced air oven. Psyllid damage has been monitored at monthly intervals.
Results and discussion
Considerable variation has been observed in growth vigour between Leucaena species as
indicated by plant height, stem diameter, foliar retention and plant mortality at the end of
the 6 months dry period (Argel and Pérez 1997). Most Leucaena species showed strong
apical dominance, with the exception of L. pallida 79/92, L. leucocephala CIAT 17263 and
L. hybrid 1/95.
Table 1 indicates that plant height increments varied from 0.49 m to more than 1.5 m 9.8
months after planting, with ten lines reaching more than 1 m height. The best growth was
recorded in L. collinsii 52/88, which outyielded 3 times the poorest species (L.
multicapitulata 81/87). Other outstanding lines up to this date were L. salvadorensis 17/86,
L. diversifolia subspp. stenocarpa 53/88 and diversifolia 83/92, L. leucocephala subsp.
glabrata 34/92 (K 636) and L. macrophylla subsp. nelsonii 47/85. These observations are
in agreement with those reported by Karachi and Lefofe (1997) in a different environment
at Morale, Botswana; however, none of them has showed adaptation to acidic ultisols (pH =
4.7) with Al saturation of 49 % ( Castillo et al. 1997).
Foliar retention and plant survival is very important in environments like Atenas with 6
months dry season. L. shannonii subsp. magnifica 19/84, L. leucocephala subsp. glabrata
34/92 (K 636) , L. macrophylla subsp. nelsonii 47/85 and L. hybrid 1/95, all combined
both, over 60 % foliar retention and nil or very little plant mortality under the conditions of
the trial. On the other hand, L. multicapitulata 81/87, an introduction from Los Santos
(Panamá) and the check C. calothyrsus DPI 115690  had  high plant mortality.
Considerable variation has been recorded in individual plant dry matter yield. Table 2
indicates that there is significant variation within and between species of Leucaena. L.
diversifolia subsp. stenocarpa 53/88, L. collinsii 52/88, L. hybrid 52/87 and L. pallida
14/96 are among the best yielders; meanwhile that  L. diversifolia subsp. diversifolia 83/92
and L. collinsii subsp. zacapana 56/88 have yielded significantly much less (P<0.05). Other
species of poor yields have been the check L. leucocephala CIAT 17263, L. lempirana
6/91, L. trichodes 61/88 and L. multicapitulata 81/87. However, all lines have produced a
high proportion of edible forage.
3Table 1. Plant height, diameter, foliar retention and plant mortality of Leucaena and other species planted for
evaluation in Atenas, Costa Rica. (Adapted from Argel and Pérez 1997).
                                                                                     Plant *                                 Plant **  
         Species                                                ____________________        _________________   Plant***
                       Height          Diameter       Height        Foliar        Mortality
       (ID No.)            (cm)             (mm)              (cm)        retention       (No.)
L.collinsii zacapana
L. collinsii
L.diver. diversifolia
L.diver. stenocarpa
L.esculenta esculenta
L. hybrid
L. pallida
L.hybrid
L. lanceolata
L. lempirana
L. l. glabrata
L. macrophylla nelsonii
L. multicapitulata
L. pallida
L. pulverulenta
L. salvadorensis
L. shannonii magnifica
L. trichodes
L. leucocephala CIAT
C. calothyrsus DPI
C. argentea CIAT
56/88
52/88
83/92
53/88
47/87
52/87
79/92
1/95
43/85
6/91
34/92
47/85
81/87
14/96
83/87
17/86
19/84
61/88
17263
115690
18668
51
63
35
54
52
40
57
44
45
45
45
38
25
58
28
64
47
32
38
27
38
3.6
5.6
3.2
5.0
5.6
3.2
4.7
4.0
4.7
3.4
4.3
3.4
2.8
5.0
2.9
4.7
4.0
2.8
3.6
3.8
4.2
112
151
119
121
81
110
97
94
96
111
116
115
49
111
59
140
94
67
84
94
149
3.4
3.5
2.8
3.1
1.9
1.9
2.9
4.0
3.5
3.1
4.4
4.1
2.5
3.1
3.4
3.9
4.0
2.5
3.8
2.9
4.5
    0
    0
    0
    0
    0
    1
    0
    0
    0
    0
    0
    1
    14
    1
    0
    1
    1
    6
    0
    11
    0
* Measurements taken 3.5 months after planting.
** Measurements taken 9.8 months after planting and before the uniformity cut at the end of the dry season
1997.
Foliar retention scale: 1= less than 20% foliar retention; 2=20 - 40%; 3 = 40 - 60%;   4= 60 - 80% and 5 >80%
foliar retention.
*** Plant mortality at the end of the 6 months dry season.
The shrub C. argentea CIAT 18668 is placed between the best Leucaena species in terms
of DM yields and foliar retention during the dry season (Table 1 and 2). This plant develops
a kind of 'climbing branches' that makes it difficult to determine a clear pattern of growth;
under cutting it produces multiple branches that replace the main stem. L. leucocephala
CIAT 17263 is within the intermediate group of  Leucaena species with comparable yields
to C. calothyrsus DPI 115690, although with better plant survival (Table 1).
4Table 2. Psyllid damage and dry matter (DM) yields of Leucaena and other species established in Atenas,
Costa Rica (Mean of 2 evaluations cuts after 8 weeks of regrowth during the wet season).
         Species   DM Yields  (g/plant)
           Pysillid   __________________
(ID No.)           damage *            Total              Edible
L. diver. stenocarpa
C. argentea CIAT
L. collinsii
L. hybrid
L. pallida
L. l. glabrata
L. pallida
L. diver. diversifolia
L. hybrid
L. pulveruleuta
L. salvadorensis
L. macrophylla nelsonii
L. lanceolata
L. pulverulenta
C. calothyrsus DPI
L. leucocephala CIAT
L. shannonii magnifica
L. lempirana
L. collinsii zacapana
L. trichodes
L. multicapitulata
53/88
18668
52/88
52/87
14/96
34/92
79/92
83/92
1/95
47/87
17/86
47/85
43/85
83/87
115690
17263
19/84
6/91
56/88
61/88
81/87
1.1
          1.0
2.1
1.8
1.2
3.5
1.5
1.6
2.4
1.0
3.9
2.3
3.1
2.1
          1.0
2.6
3.1
3.7
4.0
3.6
4.1
    111   a **
106 ab
90 abc
84 bcd
83 bcd
81 bcde
73 bcdef
68 cdef
64 cdef
64 cdef
58 defg
54 efgh
49 fgh
48 fgh
47 fgh
47 fgh
33 ghi
31 ghi
28 hi
13 i
7      i
90
98
75
65
72
67
63
55
61
59
51
46
48
48
43
44
29
29
27
13
7
(81) ***
(92)
(83)
(77)
(87)
(83)
(86)
(81)
(95)
(92)
(88)
(85)
(98)
(100)
(91)
(94)
(88)
(94)
(96)
(100)
(100)
* Mean of 4 ratings at monthly intervals. Scale used: 1= no damage; 2 = young leaves moderately curled; 3 =
tips and young leaves curled and yellow; 4 = tips and young leaves severely curled, yellow and covered with
sap;  5 = loss of up to 25% of young leaves; 6 = loss of up to 50% of young leaves;  7 = loss of up to 75% of
young leaves; 8 = loss of up to 100% of young leaves and darkening of older leaves, and 9 = stained stems
and loss of total foliage.
** Means followed by similar letters are not significantly different (P < 0.05)
*** Between brackets the percent edible DM relative to total, DM yield.
The psyllid insect has been present during the period of the observations; however, plant
damage has been mild up to date.  Table 2 shows that the lower yielding species of
Leucaena have been slightly more affected by psyllid, but producing only curled young
leaves and tips; however, in any case the defoliation of young leaves has been more than 25
per cent. L. diversifolia subsp. stenocarpa 53/88, L. pallida 14/96 and L. pulverulenta 47/87
have showed less susceptibility to the psyllid insect. This insect has natural enemies in the
area that make an effective biological control; however, it has been mentioned that it could
become a problem if the area planted with leucaena continues to expand (Schultze-Kraft
1994).
Mild attacks of the fungus Camptomeris leucaenae have been recorded, particularly in old
leaves of Leucaena species. This fungus is particularly severe in species of L. leucocephala,
but it has been reported that the species L. diversifolia, L. esculenta, L. lanceolata, L.
macrophylla and L. trichodes are not affected (Moreno et al. 1988).
5This trial will continue for another growing season.
Conclusions (preliminary)
Considerable variations have been recorded between Leucaena species in terms of plant
height and vigour, foliar retention during the dry period, plant mortality and DM yields.
Most Leucaena species showed strong apical dominance as habit of growth.
L. diversifolia subsp. stenocarpa 53/88, L. collinsii 52/88, L. hybrid 52/87, L. pallida 14/96
and L. leucocephala subsp. glabrata 34/92 (K636) are among the best yielders, meanwhile
that L. lempirana 6/91, L. collinsii subsp. zacapana 56/88, L. trichodes 61/88 and L.
multicapitulata 81/87 have produced poor DM yields as an indication of poor adaptation to
the climatic and soil conditions of the trial.
Only mild attacks of the psyllid insect have been recorded.
References
Argel, P. J. and Pérez, G. 1997. LEUCNET Leucaena trials in Mexico, Central  and South
    America, and early results from Costa Rica. LEUCNET News, No 4 July 1997, 13-14.
Castillo, A. C., Acasio, R. N., Victorio, E. E., Moog, F. A. and Palis, R. 1997. Leucaena
    productivity on the highly acidic soil of Tany, Rizal, Philippines. LEUCNET News, No
    4. July 1997, 20-22.
Hughes, C. E. 1993. Leucaena Genetic Resources. The OFI Leucaena seed collection and a
    synopsis of species characteristics. Oxford Forest Institute, Department of Plant
    Sciences, University of Oxford, 117 p.
Karachi, M. and Lefofe, B. M. 1997. The performance of Leucaena spp. at Morale,
    Botswana. LEUCNET News, No 4 July 1997, 11-12.
Moreno, J., Torres, C. G. and Lenné, J. M. 1987. Reconocimiento y evaluación de
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    9(3), 30-35.
Scultze-Kraft, R. 1994. El 'psyllid' de Leucaena también puede ser un problema en América
    tropical. Pasturas Tropicales  16(2), 48-50.