GLOMUS RHIZOBIUM LEUCAENA LEUCOCEPHALA …biology-web.nmsu.edu/~bailey/Volume11/Guzman-PIazoIa, R....
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Guzman-Piazola R. A., R. Ferrera-Cerrato, and J. D. Etchevers Barra. Centro de Edafologfa, Colegio de Postgraduados, Montecillo 56230, Mdxico. EFFECT OF THE DOUBLE INOCULATION GLOMUS + RHIZOBIUM IN EARLY ADAPTATION OF LEUCAENA LEUCOCEPHALA ON ACID SOILS One of the principal factors that determine the capacity of survival or dominance of legumes in several plant communities is their capability to associate with fungi of the family Endogonaceae and with bacteria of the genus Rhizobium (Guzman-Piazola and Ferrera-Cerrato 1990). Leucaena leucocephala growth was stunted when transplanted to acid soils in the absence of vesicular-arbuscular mycorrhizal (VAM) fungi. Inoculation reversed this effect and caused significant increases in phosphorus absorption, nitrogen fixation and dry matter production (Guzman-Piazola et al. 1988). A similar effect was reported for Acacia saligna by Gardezi et al. (1988). In this work we present information about the effect of Glomus intraradices and Rhizobium loti inoculation on the adaptability of young plants of L. leucocephala when transplanted to acid soils. Materials and methods. An experiment was carried out under greenhouse conditions, using plastic pots with 4 kg soil fumigated with methylbromide. The soil (8.7 ppm P Bray-1, 0.05% N and pH 5.3) was collected in Chiautla, state of Puebla, Mexico, in an area undergoing active soil erosion. The experiment was a randomized complete block design with three replicates. Seeds of the Peruana variety were scarified by immersion in concentrated sulfuric acid for 17 minutes followed by immediate washing with abundant sterilized water. After scarification, seeds were sown in sterilized tezontle (inert material). Twenty days after sowing four seedlings were transplanted to each experimental unit to evaluate the effect of Glomus intraradices with different levels of phosphorus application (0, 50, 100 and 150 ppm P2Os), and with and without Rhizobium loti inoculation or 20 ppm N. One gram of corn roots (with 80% VAM colonization) plus 50 g of soil containing spores of Glomus inlraradices were applied to each plant as mycorrhizal inoculant. Thirty days after transplanting, fallen leaflets were collected, dryed and weighed. Fallen leaflets were collected over the next 100 days to determine their accumulated total dry weight at the harvest time. Fallen leaflet dry wight was used as an indicator of the adaptive capacity of leucaena to acid soils. Results and discussion. Thirty days after transplanting, the VAM-plants inoculated with Glomus intraradices, as well as plants treated with the highest phosphorus rate, showed the best growth and less defoliation than remaining non VAM-plants. The latter had almost twice the defoliation exhibited by mycorrhizal plants (Table 1). This indicates the positive effect of mycorrhizae on the adaptability of Leucaena leucocephala to growth on acid soils. The plants inoculated with Rhizobium loti but not inoculated with mycorrhizal fungi had a higher proportion of fallen leaflet. In contrast, initial defoliation of VAM-plants was not influenced by Rhizobium loti inoculation. The application of 20 ppm N to the VAM and non VAM-plants had no visible effects on the initial defoliation. Dry weight of the fallen leaflets of the non VAM-plants at 30 days was least with higher rates of applied phosphorus (Table 1). The defoliation level of VAM-plants was as low as the defoliation of non VAM-plants treated with 150 P2Os. The application of 50 ppm P20 5 to mycorrhizal plants produced a small increase in early defoliation; higher rates of phosphorus did not have any effect on this variable. The previous results indicate that the effect of the mycorrhizae on reducing the amount of early defoliation was mainly due to an increased ability of plants to absorb phosphorus, as shown by Guzman-Piazola et al. (1988), and confirmed in the present work by the mycorrhizal hyphae in the early stages of the symbiosis. Between day 30 and day 130 defoliation also occurred. This phenomenon was more evident at the end of the assay. At the harvest time (130 days after transplanting), the accumulated dry weight of
Transcript of GLOMUS RHIZOBIUM LEUCAENA LEUCOCEPHALA …biology-web.nmsu.edu/~bailey/Volume11/Guzman-PIazoIa, R....
G uzm an-Piazola R. A., R. F erre ra -C erra to , and J . D. Etchevers B arra . C entro de Edafologfa, Colegio de Postgraduados, M ontecillo 56230, Mdxico.
E FFE C T O F TH E DOUBLE INOCULATION G L O M U S + R H IZ O B IU M IN EARLY ADAPTATION O F L E U C A E N A L E U C O C E P H A L A ON ACID SOILS
O ne of the principal factors that determ ine the capacity of survival or dom inance of legumes in several plant com m unities is their capability to associate with fungi of the family E ndogonaceae and with bacteria of the genus R hizobium (G uzm an-Piazola and F errera-C errato1990). Leucaena leucocephala growth was stunted when transplanted to acid soils in the absence of vesicular-arbuscular mycorrhizal (VAM ) fungi. Inoculation reversed this effect and caused significant increases in phosphorus absorption, nitrogen fixation and dry m atter production (G uzm an-Piazola et al. 1988). A sim ilar effect was repo rted for A cacia saligna by G ardezi et al. (1988). In this work we present inform ation about the effect of G lom us intraradices and R hizobium lo ti inoculation on the adaptability of young plants of L . leucocephala w hen transplanted to acid soils.
M ateria ls an d m ethods. A n experim ent was carried out under greenhouse conditions, using plastic pots with 4 kg soil fum igated with m ethylbrom ide. The soil (8.7 ppm P Bray-1, 0.05% N and pH 5.3) was collected in Chiautla, state of Puebla, Mexico, in an area undergoing active soil erosion. T he experim ent was a random ized com plete block design with three replicates. Seeds of the P eruana variety w ere scarified by im m ersion in concentrated sulfuric acid for 17 m inutes followed by im m ediate washing with abundant sterilized water. A fter scarification, seeds w ere sown in sterilized tezontle (inert m aterial). Twenty days after sowing four seedlings w ere transplanted to each experim ental unit to evaluate the effect of G lom us intraradices with different levels of phosphorus application (0, 50, 100 and 150 ppm P 2O s), and with and without R hizobium loti inoculation or 20 ppm N. O ne gram of corn roots (with 80% VAM colonization) plus 50 g of soil containing spores of G lom us inlraradices w ere applied to each plant as mycorrhizal inoculant. Thirty days after transplanting, fallen leaflets w ere collected, dryed and weighed. Fallen leaflets w ere collected over the next 100 days to determ ine their accum ulated to tal dry weight at the harvest time. Fallen leaflet dry wight was used as an indicator of the adaptive capacity of leucaena to acid soils.
Results an d discussion. Thirty days after transplanting, the V A M -plants inoculated with G lom us intraradices, as well as plants treated with the highest phosphorus rate, showed the best growth and less defoliation than rem aining non VAM -plants. T he la tter had alm ost twice the defoliation exhibited by m ycorrhizal plants (Table 1). This indicates the positive effect of m ycorrhizae on the adaptability of Leucaena leucocephala to growth on acid soils. T he plants inoculated with R hizobium lo ti but not inoculated with mycorrhizal fungi had a higher proportion of fallen leaflet. In contrast, initial defoliation of VA M -plants was not influenced by R hizobium loti inoculation. The application of 20 ppm N to the VAM and non V A M -plants had no visible effects on the initial defoliation.
D ry weight of the fallen leaflets of the non VAM -plants at 30 days was least with higher rates of applied phosphorus (Table 1). T he defoliation level of VA M -plants was as low as the defoliation of non V A M -plants trea ted with 150 P2Os. The application of 50 ppm P20 5 to m ycorrhizal plants produced a small increase in early defoliation; higher rates of phosphorus did not have any effect on this variable. T he previous results indicate that the effect o f the m ycorrhizae on reducing the am ount of early defoliation was mainly due to an increased ability of plants to absorb phosphorus, as shown by Guzm an-Piazola et al. (1988), and confirm ed in the presen t work by the m ycorrhizal hyphae in the early stages of the symbiosis. Between day 30 and day 130 defoliation also occurred. This phenom enon was m ore evident at the end of the assay. A t the harvest tim e (130 days after transplanting), the accum ulated dry weight of
fallen leaves from non V A M -plants increased as new increm ents of phosphorus fertilizer w ere added (T able 2). V A M -plants defoliated similarly to non V A M -plants trea ted w ith 150 ppm P 20 5. M ycorrhizal p lants trea ted w ith phosphorus fertilizer showed no significant increase in defoliation. T he trea tm en t w ithout phosphorus and m ycorrhizae showed in general the greatest percen t defoliation. P ercentage defoliation dim inished drastically with phosphorus application. T h e V A M -plants had the sam e percentage of fallen leaves in all cases, independent of applied phosphorus rate.
P lan ts inoculated w ith R h izobium lo ti had an accum ulated dry weight of fallen leaves smaller th an th a t of the contro l which received no N. The dry weight of fallen leaves in the experim ental unit trea ted with 20 ppm N was statistically equal to the no N treatm en t (Table 3). In th e absence of G lom u s intraradices, plants trea ted with 20 ppm N had a lower percentage o f fallen leaves than those inoculated with R hizobium loti, but the sm allest value was obtained in the p lants inoculated w ith bo th symbionts.
P lan ts producing the greatest dry weight of leaves also had the greatest accum ulated dry weight o f fallen leaves (r = 0.85). H ow ever, it was evident tha t the plants inoculated with G lom us + R h izob iu m had the lowest defoliation with respect to the total dry weight of leaves produced by plants. This was attribu ted to an im provem ent in plant phosphorus and nitrogen nutrition len t by the symbiotic m icroorganism s. Defoliation observed at the end of the experim ent was m ainly a ttribu ted to environm ental factors.
T ab le 1. Effects of d ifferent nitrogen sources an d ra tes of phosphorus on dry weight (mg) of fallen leallets of m ycorrhizal and nonm ycorrhizal p lan ts of L eucaena leucocephala 30 days a fte r tran sp lan tin g .
Source o f N -VAM + VAM R ate of P2Os -VAM + VAM1 1 1 5
0 110 a A 35 a BW ithou t N 68 b A 25 a B
50 91 a A 24 a B20 ppm N 66 b A 27 a B
100 6 0 b A 23 a BR hizobium loti 90 a A 25 a B
150 36 c a 20 a B
VAM = Glomus intraradices. For each variable, two means from a same column or line are statistically equal (MSD, a = 0.05) if followed by the same lower-case letter or capital letter, respectively. Percentages were calculated with respect to the total dry weight of leaves.
T ab le 2. Effect of d ifferent ra te s of P2Os on the accum ulated dry weight (g) of fallen leaves an d on the percen t defoliation on m ycorrhizal an d nonm ycorrhizal p lan ts of
__________Leucaena leucocephala evaluated 130 days after of the tran sp lan t.________________
R a te of P2O s Fallen leaf dry weight Percent defoliationppm -VAM + VAM -VAM + VAM
________________________ g ------- --------------------% ...............
0 0.30 c B 1.74 b A 64.0 a A 32.0 a B50 0.38 c B 1.85 b A 21.2 b B 33.6 a A
100 0.96 b B 2.04 a A 24.0 b B 34.4 a A150 1.39 a A 1.97 a B 26.7 b B 32.5 a A
Use the same legend in the Table 1.
T he plants with initial defoliation was lower had the greatest nodule biom ass (r = -0.73) and nitrogen (r = -0.62) and phosphorus (r = -0.74) foliar contents. W e consider that Leucaena leucocepliala used for reforestation program s on eroded acid soils m ust be inoculated with VAM and also with R liizob iw n in the nursery before outplanting to the field. D ouble inoculation could reduce the nursery tim e required before transplanting L . leucocephala and would assure high survival rates under these conditions.
Table 3. Effect o f th ree nitrogen sources on the accum ulated dry weight o f fallen leaves and on the percentage of defoliation of m ycorrhizal an d nonm ycorrhizal p lan ts of
_________Leucaena leucocephala evaluated 130 days a fte r transp lan ting .
Source of A ccum ulated dry weight Percentnitrogen of the fallen leaves defoliation
-VAM + VAM-........... g -----------
X -VAM.......-....... % -
+ VAM
W ithout N 20 ppm NR hizobium loti
0.86 a A 0.75 a A 0.68 a A
1.93 a A 2.01 a A 1.77 a A
1.40 a 1.38 ab 1.22 b
35.8 a A 32.0 b A 35.5 ab A
35.1 a A 34.8 a A 29.3 b B
Use the same legend in the Table 1.
References: I
G ardezi, A.K., R . Ferrera-C errati, and V. Lara-Fernandez. 1988. Effect of the double inoculation of R hizobium sp and VA endom ycorrhizae on A cacia cyanophylla in an A ndosol in Mexico. N itrogen Fixing T ree Res. R eports 6:31-33.
Guzm an-Plazola, R . y R. F crrcra-C crrato . 1990. La endom icorriza vesiculo-arbuscular en las leguminosas. Colegio dc Postgraduados. M ontccillo, Mdxico, (in press). 107 p.
Guzm an-Plazola, R A ., R . Ferrera-C errato , and J.D . Etchevers. 1988. Leucaena leucocephala, a plant o f high m ycorrhizal dependence in acid soils. Leucaena R es. R eports 9:69-73.
