Re: [compost_tea] Brassicas and vam fungi

From: Thomas Giannou <thomas_at_tandjenterprises.com>
Date: Fri, 29 Oct 2004 22:23:22 -0700

Brassicas and vam fungiClay,

If what your soil consultant said was true... and I don't believe a word of=
 it! How would your soil consultant explain the following research abstrac=
t? The following research findings don't support your "soil consultants" c=
laims. In this first abstract, Brassica is colonized by VAM fungi.

BTW, there's a statement in a book titled "Mycorrhizal Symbiosis" that unde=
r the right biological conditions AMF will colonize all plants.

"Nelson R; Achar PN. 2001. Stimulation of growth and nutrient uptake by VAM=
 fungi in Brassica oleracea var. capitata. BIOLOGIA PLANTARUM. 44(2):277-28=
1.
Address:

Univ Durban Westville, Dept Microbiol, ZA-4000 Durban, South Africa.


Cabbage (Brassica oleracea, var. capitata, cv. Hercules) seedlings were ino=
culated with vesicular-arbuscular mycorrhizal (VAM) fungi Glomus fasciculat=
um, G. aggregatum,, and C;. mosseae. Differential efficiency in mycorrhizal=
 colonization and the specificity of fungal symbiont to stimulate the growt=
h and nutrient uptake of the host were observed. In addition, there was an =
increase in phenol, protein, reducing sugar contents, and peroxidase activi=
ty in the VAM inoculated seedlings. Since these compounds are known to conf=
er resistance against fungal pathogens, the use of VAM as a biological cont=
rol agent to protect cabbage against several root diseases is suggested."

There are other research findings concerning brassica actually picking up g=
rowth when in the presence of Arbuscular Mycorrhiza fungi. The following a=
bstract speaks to that end. No mention of VAM fungi being killed or even r=
emotely considered in this research finding below. In fact, Brassica plant=
ed around mycorrhiza colonized plants actually improved its performance ove=
r Brassica being around non-colonized plants.

"Hodge, A. 2003. N capture by Plantago lanceolata and Brassica napus from o=
rganic material: the influence of spatial dispersion, plant competition and=
 an arbuscular mycorrhizal fungus. JOURNAL OF EXPERIMENTAL BOTANY. 54(391):=
2331-2342.

Address:

Hodge, A, Univ York, Dept Biol, Area 2,POB 373, York YO10 5YW, N Yorkshire,=
 England


This study investigated N capture by Plantago lanceolata L. and Brassica na=
pus L. from complex organic material (dual-labelled with N-15/C-13) added e=
ither as a thin concentrated layer (discrete patch treatment) or dispersed =
uniformly with the background sand:soil mix in a 10 cm band (dispersed trea=
tment) when grown in monoculture or in interspecific competition and in the=
 presence or absence of a mycorrhizal inoculum (Glomus mosseae). No C-13 en=
richments from the organic material were detected in the plant tissues, but=
 N-15 enrichments were present. Total plant uptake of N from the organic ma=
terial on a microcosm basis was not affected by the spatial placement of th=
e organic material, but Plantago monocultures captured less N than the spec=
ies in interspecific competition (i.e. 23% versus 38% of the N originally a=
dded). N capture from Brassica monocultures was no different to either Plan=
tago monocultures or both species in mixture. However, N capture from the o=
rganic material by both individual Plantago and Brassica plants was reduced=
 when grown with Brassica plants (by 10-fold and by more than half, respect=
ively). N capture from the organic material was directly related to the est=
imated root length produced in the sections containing the organic material=
: the individual that produced the greatest root length captured most N. St=
rikingly, when the organic material was added as a discrete patch the N cap=
tured by Brassica, a non-mycorrhizal species, actually increased when the G=
. mosseae inoculum was present compared to when G. mosseae was absent (i.e.=
 35% versus 19% of the N originally added)."

Here's another abstract of a brassica weed intercroped with a mycorrhiza co=
lonized plant.

Mujica, MT; Fracchia, S; Ocampo, JA; Godeas, A. 1999. Influence of the herb=
icides chlorsulfuron and glyphosate on mycorrhizal soybean inter cropped wi=
th the weeds Brassica campestris or Sorghum halepensis. Symbiosis. 27, 1:73=
-81.

Address:

JA Ocampo; CSIC, Dept Microbiol, Estac Expt Zaidin, Prof Albareda 1, E-1800=
8 Granada, ; Spain; CSIC; Prof Albareda 1; Granada; Spain; E-18008 BC.


AB: The effect of the herbicides chlorsulfuron and glyphosate on arbuscular=
 mycorrhizal (AM) colonization and plant dry matter was examined in soybean=
 cultivated either alone or as an intercrop with the weeds Brassica campest=
ris (chlorsulfuron) or Sorghum halepensis (glyphosate). There were 48 treat=
ments, altogether, 24 with chlorsulfuron and 24 with glyphosate. Each set o=
f 24 was designed as 2 x 3 x 4 factorial with 1) plus or minus Glomus mosse=
ae, 2) soybean alone, weed alone or soybean plus weed combination, 3) herbi=
cide applied at the rates 0, 0.1, 0.5 and 1 x the field recommendation dose=
. The shoot dry mass of AM soybean treated with low doses of herbicides, wh=
en grown together with B. campestris or S. halepensis, but not when grown a=
lone, was increased. This fact together with the absence of an increase in =
plant dry mass in intercropped non-AM soybean plants, suggest that the AM f=
ungus mediates nutrient transfer from weeds to soybean. Neither herbicide a=
ffected AM colonization of plants except when glyphosate was applied at fie=
ld recommendation dose to the weed S. halepensis grown as an intercrop. The=
 most beneficial effect of G. mosseae on soybean was found when chlorsulfur=
on and glyphosate were applied at low doses, but this beneficial effect dis=
appeared when the herbicides were applied at high doses.

Here's another abstract showing Brassica interplanted with a mycorrhizal pl=
ant. Non-mycorrhizal plants decreased the colonization potential of VAM fu=
ngi when the Non-mycorrhizal plants were planted 30 days prior to the mycor=
rhizal plants. Colonization just occurred at a lower level. When the myco=
rrhizal and non-mycorrhizal plants were planted at the same time, there was=
 no decrease in the effectiveness of the mycorrhiza fungi that colonized th=
e mycorrhizal plants.

Fontenla, S; Garcia-Romera, I; Ocampo, JA. 1999. Negative influence of non-=
host plants on the colonization of Pisum sativum by the arbuscular mycorrhi=
zal fungus Glomus mosseae. Soil Biol. Biochem., 31: 1591-1597.

Address:

JA Ocampo; CSIC, Dept Microbiol, Estac Expt Zaidin, Prof Albareda 1, E-1800=
8 Granada, ; Spain; CSIC; Prof Albareda 1; Granada; Spain; E-18008.


We studied the influence of the arbuscular mycorrhizal (AM) non-host plants=
 Stellalria media (Caryophyllaceae), Chenopodium album and Spinaceae olerac=
ea (Chenopodiaceae), Brassica campestris, B. nigra, Capsella bursa-patoris =
and Sisymbrium altissimum (Brassicaceae), Juncus balticus (Juncaceae), Urti=
ca campestris (Urticaceae) and of the AM host plant Taraxacum officinale (A=
steraceae) on the colonization of Pisum sativum by the AM fungus Glomus mos=
seae. None of the non-host plants tested were colonized by Glomus mosseae. =
Older non-host plants competed with P. sativum. No inhibition of AM coloniz=
ation was observed in host plants that were grown in the same pot and at th=
e same time as non-host plants. However, when non-host plants were grown f=
or 30 d before P. sativum, they inhibited mycorrhizal colonization of the l=
atter. In a split pot system the presence of U. dioica on the left-side de=
creased AM colonization of P. sativum roots on the left-side, but not on th=
e right-side. Non-host plants decreased the inoculum potential of G. mossea=
e and in some cases the percentage AM colonization of host plants cultivate=
d after non-host plants. These results indicate that roots of non-host spec=
ies have factors that seem to affect the AM fungus before it establishes in=
 the root of host plants. (C) 1999 Elsevier Science Ltd. All rights reserve=
d.

Clay, I would say that you can inoculate your mycorrhizal plants with AM Fu=
ngi and interplant Brassica without being concerned that Brassica exudates =
will kill off the AM Fungi. Plant them at the same time and based upon the=
 above findings, you may even find that the Brassica will grow better if th=
ey are in the presence of AM Fungi even though the Brassica may not be colo=
nized by the fungi.

Best Regards,
Thomas Giannou
http://www.tandjenterprises.com


  ----- Original Message -----
  From: clay
  To: compost_tea_at_yahoogroups.com
  Sent: Friday, October 29, 2004 8:50 PM
  Subject: [compost_tea] Brassicas and vam fungi


  A soil consultant came to look at our community garden and said that we s=
houldn’t be growing anything from the brassicaceae family as intercrops b=
ecause its root exudates kill VAM fungi, and crops that rely on VAM fungi w=
ill suffer. We were growing broadbeans, and wild radish was growing with th=
em...it was a weed that I hadnt got around to removing yet.

  I know that some farmers are using brocolli to reduce nematode problems i=
n tomatoes, but if they are also killing VAM then maybe they are not so use=
full.

  Can anyone comment on this being true or not?

  Thanks

  Clay.






Received on Sat Oct 30 2004 - 01:52:08 EDT

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