The Beginning of Hybrid Maize

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RyanChandler

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That's a great read. Crossbred Purebred bulls are the cattle equivalent to the open- pollinated varieties in the corn world.  It's safe to say these plant geneticist's level of understanding was easily a hundred years ahead of the modern day cattle multipliers who're utilizing mongrels as seedstock. 
 

DaveK

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-XBAR- said:
That's a great read.  Crossbred bulls are the cattle equivalent to the open- pollinated varieties in the corn world.  It's safe to say these plant geneticist's level of understanding was easily a hundred years ahead of the modern day cattle multipliers who're utilizing mongrels as seedstock.


Crossbred bulls are not the equivalent of open pollinated corn. 
 

RyanChandler

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I meant to say purebred bulls there. I'll change it. Thanks for pointing that out.  Would it be reasonable to say un-stable composite cattle have the same/similiar parent stock value as double cross hybrids in the corn world?

 

librarian

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I came across the maize paper when reading some blog about evolutionary ecology.
Mentioned was that some animal breeding students were influenced the 5 week seminar on Heterosis held during the summer of 1950 at Iowa State. I can't remember who, but it was one of those moments in academic history where a lot of energy was excited.
http://www.cabdirect.org/abstracts/19531603824.html;jsessionid=E46C0020ADE564C59F608BB5DB12B5F4?freeview=true
And from a longer abstract and summary of the collected papers from the 1950 conference. (I also wondered why the plant breeders took these ideas so far and the animal breeders didn't do the same- but I feel certain Leonhardt got to thinking on it. What interests me is "combining ability".)
http://www.cabdirect.org/abstracts/19530101524.html;jsessionid=196F9577E63EC119300FC65A41265A08

Following this shift of emphasis towards explaining hybrid vigour in terms of over-dominance, we have the statisticians developing methods for studying specific and general combining ability and techniques for estimating the average dominance of genes. These methods are now under test and they, and further improved versions of them, should lead to better methods for selecting strains for crossing to get hybrids showing good combining ability, and to the evolution of new breeding techniques which will take advantage of developments in this field. One such method, namely, recurrent selection, is dealt with in detail by its protagonist, F. H. Hull. G. F. Dickerson discusses the advantages of using inbred and partially inbred lines for heterosis tests, on the basis of his experience with pigs. The relative ineffectiveness of selection within inbred lines strongly suggests that heterozygous animals have a real advantage in such characters as suckling ability, viability and growth rate, and that, as with corn, further progress will depend on taking advantage of the hybrid vigour of crossbreds for the improvement of these important economic characters. In the case of poultry, for example, the use of a partially inbred line could be exploited with advantage as one of the two populations in a reciprocal selection programme (i. e. when guiding the development of the lines by breeding from the animals, or their close relatives, which produce the best cross).

The only example of animal improvement summarised here is that of Winters' well-known rotational crossbreeding of pigs at Minnesota. Winters gives the history of this series of experiments in some detail. He also states that in farm trials the crossbreds have a survival of 92% (248 litters) compared with 75% survival (230 litters) in purified lines, and the crossbreds appear to have approximately this advantage in other characters. However, rotational crossbreeding is merely a technique for keeping breeding females and offspring in a relatively permanent hybrid state. It makes no pretence at taking advantage of particularly good crossing strains or of exploiting combining ability. It is here that we may expect the next developments in breeding practice to come. Unfortunately, no information is given on crossing sheep and there is only a passing reference to cattle and poultry, although reciprocal selection of the last is reputed now to be part of current commercial practice. Nor is there any mention of species crosses.

 
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