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CIMMYT stands for Centro Internacional de Mejoramiento de Maíz y Trigo, which translates to English, International Maize and Wheat Improvement Center (of Mexico). They have created standard notation for documenting different maize pedigrees. Labeling your pedigrees of maize breeds can offer an easy way to keep track for you breeds of maize by years, location and parents. Another method for describing your breeds is to use the Purdy pedigree notation system. Both notations are described in this howto.

How do I write a maize pedigree?

University textbooks in Biology, Plant Breeding, and Genetics don't mention much more than placing one parent on one side of a small 'x' and the other parent on the other side.But there's much more to it than that.

I have been unable to find material in textbooks regarding Plant Breeding and Genetics stating how plant breeders create pedigrees for a maize cross.Outside of textbooks, the most often quoted reference is a paper by Purdy et al. from 1968 in Crop Science Vol. 8,pp. 405–406.This pedigree format was used for small grains such as Wheat and Barley.Since these are self-pollinating crops there is no need for small grains breeders to create pedigrees for inbreds.

It's clear from documentation of ICIS (International Crop Information System) that CIMMYT was not using the Purdy pedigree notation system and furthermore, needed a modified version to incorporate it's Maize pedigrees into the ICIS Purdy format(GMSinput.pdf).

Basic Method - Maize Inbred

  1. Harvest a number of ears (E.g. 4) from one row of an ear-to-row Inbreeding Nursery.
  2. Record the number of ears collected from the row.
  3. For each ear collected, assign a number from 1 to the number of ears collected (E.g. 1,2,3,4)
  4. Get the pedigree of the plant whose seed was planted in the row. (E.g. Year: 2000,Row: 1, Pedigree: CML159)
  5. For each ear, assign a pedigree that consists of the plant pedigree, a dash, and the ear number (E.g. CML159-1)
  6. Put the seed from each ear in a separate storage container with its unique pedigree label on the front.
  7. Each time seed is grown and harvested, repeat the procedure.
  • Year: 2000,
Row 1, Pedigree: CML159, Number of ears collected: 4
CML159-1 (Ear #1)
CML159-2 (Ear #2)
CML159-3 (Ear #3)
CML159-4 (Ear #4)
  • Year:2001
Row:1,Pedigree:CML159-1,Number of Ears collected:2
Row:2,Pedigree:CML159-2,Number of Ears:3
Row:3,Pedigree:CML159-3,Number of Ears:1
Row:4,Pedigree:CML159-4,Number of Ears:4

2001 Pedigrees

Row 1 (2 ears)


Row 2 (3 ears)


Row 3 (1 ear)


Row 4 (4 ears)


Basic Method - Maize Cross

Old Notation System

  1. Write the female name (mother)on the left side of the cross designator
  2. Write the Cross Designator (students use 'x' but in Purdy notation one uses '/')
  3. Write the male name(father)
  4. Use brackets to denote pedigrees of one parent in a cross

Mother: CML159, Father: CML144

CML159 x CML144

Mother: CML159 x CML144, Father: CML182

([CML159 x CML144] x CML182)

Mother: CML159 x CML144, Father: CML159

([CML159 x CML144] x CML159)

Purdy Notation System

In the Purdy system, a cross is denoted with a forward slash '/' rather than with an 'x'. So (A x B) old notation = (A/B) Purdy.A second cross is shown with two forward slashes (//) and each additional cross is shown by placing the cross number between the slashes (/n/).

A x B = A/B
(A x B) x C = (A/B//C)
(A x B) x (C x D) = A/B//C/D
[(A x B) x C] x D = A/B//C/3/D

A backcross is shown using an asterisk '*' and the number of times the specified parent was backcrossed.

((A x B) x B) = (A/2*B)
[(A x B) x B] x B = A/3*B



Deciphering Wheat Pedigrees

CIMMYT Modified Purdy Notation for Maize

There is a very good explanation of how to write a maize pedigree in a CIMMYT Field Book .pdf but I don't know about the legality or availability of that document online. Here is a CIMMYT maize pedigee from page 7 of "A Batch processing download tool for historical crosses and pedigree selection data" by William H. Eusebio (GMSInput.pdf).


Much more to come!

Looking forward to merciless edits!

Is the last Purdy pedigree correct?

What is -#b?{1}?W?Sn?(BC4)?

University of Iowa pedigree notation variations (thinking cycle 4 etc.)

See Also

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