The Fertile Families - and Beyond

 

The concept of a Fertile Family, members of which produce more members of the same family when intercrossed, has been used by hybridizers for decades to describe the more intricate workings of wide crosses.  In its most precise form, a separate symbol is used for each aril species.  The more general version, however, recognizes only aril and bearded chromosome sets and makes no distinctions among the many different types in each group.  This simplifies to only 12 types involved in producing arils and arilbreds. 

Type Description Functional Gametes

AA

Diploid Aril A
AAA Triploid Aril A & AA
AAAA Tetraploid Aril AA
AB Diploid Arilbred A & B
AAB Triploid Arilbred A & AB
ABB Triploid Arilbred AB & B
AAAB Tetraploid Arilbred AA and AB
AABB Amphidiploid Arilbred AB
ABBB Tetraploid Arilbred AB & BB
BB Diploid Bearded B
BBB Triploid Bearded B & BB
BBBB Tetraploid Bearded BB

 

That may still seem like a lot, but when these crosses are charted they sort themselves out quite neatly into manageable categories. 

In the chart below, the parental types are shown as both row and column labels.  If you pick a column corresponding to one type and a row corresponding to the other, the cell where they intersect gives the results of that cross – the possibilities, not the expected ratios.  Fertile families are shown in light green and the relatively infertile intermediate types in yellow.  Other color codes are explained in the categorical descriptions below the chart.  Clickable links lead to the corresponding Photo Gallery.

AA

AAA

AAAA

AB

AAB

ABB

AAAB

AABB

ABBB

BB

BBB

BBBB

AA

AA

AA AAA

AAA

AA AB

AA AAB

AB AAB

AAA AAB

AAB

AAB ABB

AB

AB ABB

ABB

AAA

AA AAA

AA AAA AAAA

AAA AAAA

AA AB AAA AAB

AA AAA AAB AAAB

AB AAB AAAB  

AAA AAB AAAA AAAB

 AAB AAAB

 AAB ABB AAAB AABB

 AB AAB

AB AAB ABB AABB

ABB AABB

AAAA

AAA

AAA AAAA

AAAA

AAA AAB

AAA AAAB

AAB AAAB

AAAA AAAB

AAAB

AAAB AABB

AAB

AAB AABB

AABB

AB

AA AB

AA AB AAA AAB

AAA AAB

AA AB BB

AA AAB AB ABB

AB AAB BB ABB

AAA AAB ABB

AAB ABB

AAB ABB BBB

AB BB

AB ABB

ABB BBB

AAB

AA AAB

AA AAA AAB AAAB

AAA AAAB

AA AAB AB ABB

AA AAB AABB

AB AAB ABB AABB

AAA AAB AABB AAAB

AAB AABB

AAB ABB ABBB AABB

AB BBB

AB ABB ABBB

ABB ABBB

ABB

AB AAB

AB AAB AAAB 

AAB AAAB

AB AAB BB ABB

AB AAB ABB AABB 

BB ABB AABB

AAB ABB AABB AAAB

ABB AABB

ABB AABB ABBB BBB

ABB BB

BB BBB ABB ABBB

 BBB ABB

AAAB

AAA AAB

AAA AAB AAAA AAAB

AAAA AAAB

AAA AAB ABB  

AAA AAB AABB AAAB

AAB ABB AABB AAAB

AAAA AAAB AABB

AAAB AABB

AAAB AABB ABBB 

AAB ABB

ABB ABBB ABB ABBB

AABB ABBB

AABB

AAB

AAB AAAB

AAAB

AAB ABB

AAB AABB

ABB AABB

AAAB AABB

AABB

ABBB AABB

ABB

ABB ABBB

ABBB

ABBB

AAB ABB

AAB ABB AAAB AABB

AAAB AABB

AAB ABB BBB

AAB ABB ABBB AABB

ABB AABB ABBB BBB

AAAB AABB ABBB

ABBB AABB

BBBB ABBB AABB

ABB BBB

ABB ABBB BBB BBBB

ABBB BBBB

BB

AB

 AB AAB

AAB

AB BB

AB BBB

ABB BB

AAB ABB

ABB

ABB BBB

BB

BB

BBB

BBB

BBB

AB ABB

AB AAB ABB AABB

AAB AABB

AB ABB

AB ABB ABBB

BB BBB ABB ABBB

ABB ABBB ABB ABBB

ABB ABBB

ABB ABBB BBB BBBB

BB BBB

BB BBB BBBB

BBB BBBB

BBBB

ABB

ABB AABB

AABB

ABB BBB

ABB ABBB

BBB ABB

AABB ABBB

ABBB

ABBB BBBB

BBB

BBB BBBB

BBBB

 

The symmetry of the chart may not be immediately obvious because the cells aren't square, but if we also ignore the direction of the cross we need to deal with only 78 different types of crosses that fall into five categories.  The simplest cases, crosses within type, appear along the diagonal.

  

Crosses Within the Fertile Families

Five of these are crosses within one of the familiar fertile families:  the diploid arils, tetraploid arils, amphidiploidlike arilbreds, diploid beardeds, and tetraploid beardeds.  All offspring from such a cross have the same type of chromosome complement as their parents, which makes them by far the easiest to work with. Like their parental types, these are shown in light green. They yield a high percentage of takes and produce full pods.  Their seeds exhibit relatively good germination and their seedlings have highly predictable results. Entire programs can be conducted working within one of these cells.

Crosses Within a Relatively Infertile Type

The other seven along the diagonal are crosses between two members of the same relatively infertile group.  Because neither parent is fully fertile, the chances of getting any offspring at all are slim.  In fact, it was this contrast that led many to label the intermediate types as “sterile” when the concept of Fertile Families became widely used.  Intermediate types like this, however, are capable of producing two different types of gametes – so such a cross can produce three types of offspring: the parental type or either of the ancestral types. These crosses are shown in brown.

 

Crosses Between the Fertile Families

Ten more are crosses between two of these fertile families.  They also have predictable results because all of the offspring from a cross between two such families have the same type of chromosome complement.  Of these, one produces offspring that are members of a fertile family other than that of either parent while the other nine produce relatively infertile intermediate types.  These are shown in green and yellow, respectively.  Some of these have also been quite popular because they reliably produce valued garden subjects like 1/4-breds and 3/4-breds. A great deal can be accomplished without venturing beyond this category into the world of more complex crosses.

   

Crosses Between a Fertile Family and a Relatively Infertile Type

Thirty-five are crosses between a member of one fertile family and a relatively infertile type.  These are somewhat more complicated than working within or between fertile families because the relatively infertile partner produces two types of gametes and the seedlings thus fall into two types. The real challenge comes in evaluating the seedlings for possible registration because sibs may have different chromosome complements and thus belong to different registration classes. Although this group is more difficult to work with, there is enough fertility to make it worthwhile for the adventuresome.  These cells are shown in dark green. 

 

Crosses Between Two Different Relatively Infertile Types

The final 21 are the widest type of cross.  The odds are greatly against getting any offspring at all, but because each parent produces two types of gametes.  Because the two parents do not necessarily produce any gametes of the same type, however, some very interesting recombinations can occur.  For example, crossing a triploid aril with a triploid bearded could produce four types of arilbreds: an AB-type diploid, ABB- and AAB-type triploids, or an AABB-type amphidiploid.  These crosses are shown in gray.

 

 

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