The inefficient P crop would seem to be useful and may serve to help calibrate the rest of a field (i.e., based on other field attributes like soil color, slope, soil type, etc.). What our corn breeders have found is that some corn hybrids are much more efficient than others when it comes to plant P concentrations. I don’t know why or anything about the pedigrees. The idea of using a low P efficiency test crop would be useful to guide spatial P applications. Another approach would be to put a high P efficiency gene into all crops. In the end, both approaches have merit.

Will any of your presentations or posters talk about the Octa-Sensor. There might be a band that is useful for P deficiency detection?

Jim Schepers

You will find in the attachment file a list of ten entries, five which are P inefficient in Patzcuaro and five which are P inefficient in Obregon.  I think it was last year that I sent seed of these lines and others from Obregon to Martin Rodriguez to multiply in El Batan.  This multiplication was to be able to send seed to Canada. I have been trying to contact Martin but as you know it is harvest time and they are in the field all the time.  It is likely that he kept some of the left over seed, if that is the case we can send that to Art.  If he doesn’t have any seed then hopefully there is seed of these entries in the bank.  I can’t remember if Gunther sent seed to the bank before he left.  I only have the cross but not the selection history of these lines.

Ivan Ortiz-Monasterio

A P marker?  I wouldn't count on a single marker for selection because Pi nutrition of plants is linked to a multitude of mechanisms affecting Pi acquisition that range from number, type and activity of Pi transporters, root morphology, rhizosphere secretions of phytases and organic acids, and arbuscular-mycorrhizal associations that definitely occur with wheat even when soil Pi is sufficient.  The following review article examines the complexity of plant Pi nutrition. -

Charles MacKown

If I remember correctly from our visit to Noble Foundation almost two years ago that they were claiming to have a P marker gene in the the Arabidopsis plant.  They were trying to move it into wheat.  It appears that there are a number of biotech groups trying to do the same thing.  My gut feel is that none of them are close to succeeding.

http://www2.warwick.ac.uk/fac/sci/whri/about/staff/jhammond/proj/smart/

http://www.plantphysiol.org/cgi/content/full/132/2/578?ck=nck

http://pewagbiotech.org/buzz/printfull.php3?IssueID=25

It talks about a de-greening circuit to shut down chlorophyll in the presence or absence of an element.

http://www.blackwell-synergy.com/doi/abs/10.1111/j.1467-7652.2006.00205.x

John Solie

Some people were asking if we could use a greenhouse of lab screening technique.  I think we need to be cautious with this strategy.  What I can remember is that most papers that evaluated the same germplasm for P efficiency in a greenhouse study and compared it to a field study did not find a correlation.  Therefore, my suggestion would be that before any lab or the greenhouse screening is done that these methods are shown to correlate with field studies.  

Another comment is that we found a fair amount of G X E for P use efficiency when comparing wheat genotypes under high pH vertisols (Yaqui) vs low pH (without Al toxicity) andisols (Patzcuaro).

Ivan Ortiz Monasterio

Purple coloration of shoots can be triggered by stresses that may be unrelated to P nutrition. Listed below is the content of an e-mail regarding one of Carver's trials at Lahoma that I collected samples from. I believe I have notes for appearance of purple shoots among the 220+ lines that I sampled. If you want me to retrieve these notes, let me know.

Charles Mackown

Perhaps this is a crazy idea, but we're looking at wheat germplasm developed by Ed Souza (now at Ohio State, Wooster) low in phytate, for increased micronutrient availability in the grain.  Phytate is phosphorus based, hence perhaps low phytate germplasm would be more susceptible to phosphorus deficiency???  Ed's colleagues at UIdaho/Aberdeen have published alot on this germplasm, so some of their findings may be applicable.

Tom Payne

Ivan has replied to you regarding Gunter Manzkie's reseach at CIMMYT regarding P deficiency/efficiency.  His papers may yield appropriate genotypes. Hans has extensive soil micronutrient experiences, and he may also be able to point in appropriate directions.

We have lots of P deficient soils, especially in Southern OK. If we grow different wheat in a severely P deficient soil in the greenhouse, and keep other conditions the same, would the inefficiency show up, such as purple color, low P content in the tissue, or other physiological symptoms?  We can test for P content in the leaf or whole plant in the lab.

Hailin Zhang

Do you have a quick test for P inefficiency?  Would there be a way to ID the poor materials in a lab test?  We can make the required crosses but how do we select for inefficiency?  Can we use a test similar to the aluminum toxicity test used by Eva at CIMMYT?  Let’s discuss.

Art Klatt

As Ken mentioned some years ago I worked with Gunther Manske characterizing a group of bread wheats for P use efficiency.   We screened germplasm under sufficient soil P and under deficiency.   Our definition of P efficient germplasm was when we obtained a similar yield under low and high P, while the P inefficient germplams showed a large difference in yield with and without P.  I do remember that some genotypes showed the purple leaf margins some years but we didn’t take notes of that so I can not tell you for sure if all the inefficient ones will show the purple margins or if this will happen every year.  I have a set of about 5 or 10 spring bread wheat genotypes that we characterized as P inefficient that would improve your odds of finding some type of P deficiency symptoms.  We have seed available so let me know if you would like us to send you some.  I know that the phytosanitary restrictions for sending seed from Obregon to the US are pretty strict so we may have to multiply the lines in El Batan before we can send them to you.

Ivan Ortiz-Monasterio

I have come across wheat varieties (e.g. Alondra) that are more P efficient than others, but nothing that stood out as less P efficient – it would probably have just been thrown out during the selection process for low yield. Up in the Andes th variety Antezana used to have a lot more purple leaves than other varieties, but I don’t think this was due to P deficiency, just high radiation and probably not a very good sink – others may call it cold-induced P deficiency!

Pat Wall

At the moment I can’t recall a variety which has been more deficient – one which has been more efficient was BW Alondra, and information has been published. There should be plenty of data/information re P deficiency at CIMMYT; unfortunately I don’t have data/literature at Cali. I suggest asking Tom Payne as head of wheat genetic resources for further information (field books, passport data, literature search) – he also can assist in establishing contacts e.g. with colleagues in Brazil.  

CIMMYTs crop improvement agenda expanded to acid soil environments in the late 1970s/early 1990s in a shuttle breeding approach with four institutions in Brazil. The strategy at CIMMYT entailed combining Al tolerance with P efficiency as P in Brazilian oxisols is fixed in Al and Fe phosphates (whom do I tell!)  -> seedling screening in the lab for Al tolerance followed by field screening at Patzcuaro for P efficiency and shuttling the germplasm to Brazil for field testing under low pH/high Al und relevant (high) biotic stresses. The strategy evolved from screening results from Brazil; genotypes, in particular Alondra, displayed good performance in field testing, but susceptibility to Al in lab screening. In follow-up research, the results could be traced to superior genotypic P efficiency. Patzcuaro had been selected for screening (apart from high disease prevalence - Septoria, Fusarium) for its suitability to select for P efficiency. Low pH soils are deficient in P, but as soils are of volcanic origin, there is little free Al. Hence, over time a large number of genotypes has been screened and data re efficiency should be available at CIMMYT; further several studies have been conducted and certainly genotypes characterized for P efficiency/deficiency.

Wolfgang Pfeiffer

About 15 or so years ago, there was a fellow from Germany, Gunther Manske, who did a Ph D at CIMMYT looking at differeneces in wheat root development and  P uptake differences in the high pH soils in Obregon and the low pH soils in Pascuaro.  He worked more closely with Ivan on this.  Perhaps Ivan can provide you with some leads on this.  Tom Payne, with the gene bank, may also have some information.

Ken Sayre

Are either one of you aware of a wheat variety that systematically showed up as being more P deficient than others?  Over your many combined years in the wheat program, was there one that showed up with the purple leaf margins more than others?  Durum? Breadwheat? Barley? Triticale? 

We are looking for an indicator plant for P deficiencies that could tie into the exact same work we are doing with N.

I understand this is a strange request, but you guys have looked at lots of varieties in the field.

Bill Raun, John Solie, Randy Taylor