Sorghum (Sorghum bicolor [L] Moench) was first introduced to the United States
in the 1800s. These introductions consisted of tropical varieties with a short day
photoperiod response that limited their use in temperate hybrid breeding programs.
Commercial exploitation of F1 hybrids in grain sorghum started by the mid 1950s with
the use of cytoplasmic male sterility system CMS (A1). Even though other CMS are
available, most sorghum hybrid seed production still relies on the A1 system. Genetic
gain in most agronomic crop species is limited by several factors. In the specific case of
sorghum, the uniform use of the CMS (A1) system and the recent introduction of
sorghum to the United States have resulted in a reduction of its genetic base. In order to
create enough genetic variability, plant breeders might utilize exotic non adapted
material, exotic adapted material or existing elite material as a source of new alleles that
will protect and improve genetic gain through selection. This study provides an estimate
of the genetic diversity existing in a set of sorghum conversion lines. The objectives of
this study were: (1) to estimate the genetic diversity present among a set of 16 sorghum
conversion linesþ (2) to classify this set of lines based on genetic similarities estimated using AFLP markers and (3) to estimate heterosis, general and specific combining ability
for grain yield among the set of conversion lines.
Genetic diversity was present in the set of conversion lines evaluated. For the
lines included only in this study, Caudatum was the most homogenous race (average GS
= 0.69), and this race was closely related to the Durra race (Average GS = 0.66). Two
other homogenous races were Bicolor and Kafir with average GS of 0.67. Highest GCA
effects were obtained from the Kafir and Caudatum races. Good heterotic responses
were obtained from DurraKafir
races and CaudatumKafir
races. Estimation of SCA,
MPH and BPH identified specific crosses that were numerically superior than those of
the checks.
The use of AFLP markers allowed the identification of five strong clusters
through estimates of genetic similarities. This classification did not group the lines by
either their genetic background or their fertility reaction. This study provides
information to identify specific combinations that would help to understand heterotic
relationships in sorghum, and support the suggestions made by Menz and Gabriel that
races in sorghum are not well defined.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/4874 |
| Date | 25 April 2007 |
| Creators | Mateo Moncada, Rafael Arturo |
| Contributors | Rooney, William L |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | 869808 bytes, electronic, application/pdf, born digital |
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