From WIEGAND@lufa-sp.vdlufa.de Mon Oct 18 14:56:22 1999 Date: Mon, 18 Oct 1999 16:54:57 +0200 From: Klaus Wiegand To: WILSONDO@phibred.com, sanet-mg@ces.ncsu.edu Subject: RE: harnessing endophytic and epiphytic relationships hello dale, >I'll bet that under breeding and selection, some of the changes that occur >in crop varieties result from changes in the endophyte. Since most >endophytes are passed through the seed, genetic changes or selection among >strains could masquerade as genetic change in the plant. i just came back from a congress, where they showed a tissue-print immunoplot method for endophytes in festuca. the lecturer made clear, that plants infested with endophytes never show any phenological symptoms.... might only be valid for the small grasses he worked with... >F.moniliforme, for example, is practically an endophyte in corn. >The relationship is highly evolved, and from an evolutionary >perspective, F. moniliforme and related species might be on the >road to becoming full-fledged endophytes. we have a monoculture trial in the 32nd year, corn after corn after corn... and we can only confirm your observations. there never was any REAL strong infestation of fusarium ON the plants. that was amazing, as we know of several larger regions, where corn is grown very intensively. the real problem is not corn after corn, but small grains after corn. 6 or 7 years of corn and then a wheat on this field will result in a DESASTER. in several years though we had problems with the corn cob mixtures from these plots. it wasn't analysed, but my predecessor highly suspected it to be F. oxysporum. problem: BOTH are known to produce mycotoxins (mostly DON) >the Fusaria. My impression from cutting up a lot of corn stalks is that >good corn varieties are able to keep the fungus under control and mostly >confined to the lower few internodes until late in the life cycle of the >plant. how do you understand "good" varieties ? infection resistant ? or might most of the "good" properties even be the major result of resistance ? our experience clearly show, that the grade of fusarium infection is a (highly significant) function of the length of the stalk. the shorter the stalk, the faster the infection and the more intense. so the tendancy to shorter varieties due to better stand and larger (or treatment with ccc) cobs results in higher infection rates. >Maybe seed-transmitted hypovirulent strains exclude more harmful >strains from the cornstalk niche? might very well be. there are significant negative correlations between seed infection level and field emergence, but in our experience the infection level of the cob depended much more on environmental factors (mostly humidity resp. the lack of soil water) and even more on the tillage system (no-till with mulch- seeding had the worst effect on infection in small grains, which followed after corn) than on seed infection rates. would you confirm our observations, that breeders are more and more breeding for industrial usage properties and less and less for agronomical advantages ? and even more: at the expense of agronomical properties ? klaus To Unsubscribe: Email majordomo@ces.ncsu.edu with the command "unsubscribe sanet-mg". If you receive the digest format, use the command "unsubscribe sanet-mg-digest". To Subscribe to Digest: Email majordomo@ces.ncsu.edu with the command "subscribe sanet-mg-digest". All messages to sanet-mg are archived at: http://www.sare.org/san/htdocs/hypermail From WILSONDO@phibred.com Mon Oct 18 14:57:35 1999 Date: Mon, 18 Oct 1999 11:31:56 -0500 From: "Wilson, Dale" To: sanet-mg@ces.ncsu.edu Cc: "'Wiegand@lufa-sp.vdlufa.de'" Subject: RE: harnessing endophytic and epiphytic relationships [ The following text is in the "iso-8859-1" character set. ] [ Your display is set for the "US-ASCII" character set. ] [ Some characters may be displayed incorrectly. ] Klaus, > the lecturer made clear, that plants infested with endophytes > never show any phenological symptoms.... might only be valid > for the small grasses he worked with... You mean "phenological" or "phenotypical." The Festuca sp. may not look different, but they sure are more toxic to animals when infected with the typical endophytes. > there never was any REAL strong infestation of fusarium ON the > plants. that was amazing, as we know of several larger regions, > where corn is grown very intensively. the real problem is not > corn after corn, but small grains after corn. 6 or 7 years of > corn and then a wheat on this field will result in a DESASTER. > in several years though we had problems with the corn cob > mixtures from these plots. it wasn't analysed, but my > predecessor highly suspected it to be F. oxysporum. In moist northern climates corn ears and stalks are often rotted by Fusarium graminearum (Gibberella zea). This fungus also causes scab in small grains. The Fusarium moniliforme complex (moniliforme, subglutinans, proliferatum) is more subtle. If you split a normal, healthy corn plant when knee-high you will see a faint darkening in the center of the stem at the base of the plant. This is more pronounced in sweet corn. Whenever I have tried, I have been able to isolate F. moniliforme from aseptic cubes of this tissue. What is more, I have isolated ergosterol (a uniquely fungal lipid) from this part of the stem. > how do you understand "good" varieties ? infection resistant ? or > might most of the "good" properties even be the major result of > resistance ? I am thinking that in selection for yield and late-season stalk strength, inadvertent selection for a favorable association has occurred. Modern breeders do inoculate with these things, but in my hands, F. moniliforme seems strangely non-virulent when inoculated. > our experience clearly show, that the grade of fusarium > infection is a (highly significant) function of the length of the > stalk. the shorter the stalk, the faster the infection and the > more intense. It may be that southern (US) dent germplasm develops a more favorable association with F. moniliforme than do the northern flints, from which short, early corn varieties are largely derived. In my garden, ultra-early sweet corns (northern flint background) seem to have more stalk Fusarium than later sweet corns (also flinty, but probably with more S. dent introgression). My model is that F. moniliforme and it's ilk, infect the seedling as the radicle wounds and penetrates the coleorhiza. The fungus grows up the mesocotyl and forms a latent infection in the crown, and only becomes "pathological" under certain kinds of stress. After flowering, the fungus begins to ramify in the stalk. In favorable associations, nothing bad happens to the corn plant, but F. moniliforme gets to eat it all at senesecence. Ears become infected largely via silk infection and the fungus is transmitted in the pedicel remnant at the base of the kernel. > in our > experience the infection level of the cob depended much more on > environmental factors (mostly humidity resp. the lack of soil > water) and even more on the tillage system (no-till with mulch- > seeding had the worst effect on infection in small grains, which > followed after corn) than on seed infection rates. Again, are you sure we are talking about the same species of Fusarium? > would you confirm our observations, that breeders are more and more > breeding for industrial usage properties and less and less for > agronomical advantages ? and even more: at the expense of > agronomical properties ? Pioneer has always been, and still is very, very focused on agronomic traits. The big things have been yield and standability. Special grain traits get more press intentionally, but yield and stalk are still our bread and butter. The grain traits I hear the most about include: - improved milling properties (better product recovery) - reduced mycotoxin (better food-grade corn) - high oil (high energy corn) - exotic starches and polymers for special uses - low phytate (reduced P in manure) - high sucrose soybeans (not so fartatious in soymilk and tofu and in feed) Some of these will be challenging in the seed quality area, since dinking around with the grain is also messing with the seed. (seed quality is my thing). Dale To Unsubscribe: Email majordomo@ces.ncsu.edu with the command "unsubscribe sanet-mg". If you receive the digest format, use the command "unsubscribe sanet-mg-digest". To Subscribe to Digest: Email majordomo@ces.ncsu.edu with the command "subscribe sanet-mg-digest". All messages to sanet-mg are archived at: http://www.sare.org/san/htdocs/hypermail