Proceedings
of the XLVI Italian Society of Agricultural Genetics - SIGA Annual Congress
Giardini Naxos, Italy - 18/21
September, 2002
ISBN 88-900622-3-1
Poster Abstract -
4.40
TOWARDS ALFALFA
FREE-HYBRIDS. DIALLEL CROSSES AMONG THE FREE-HYBRID PARENTAL CONSTITUENTS: POD
FERTILITY
ROTILI P.*,
SCOTTI C.*, GNOCCHI S.*, KERTIKOVA D.**, GNOCCHI G.*
*) Istituto
Sperimentale Colture Foraggere, Lodi, Italy
**) Institute of
Forage Crops, Pleven, Bulgaria
alfalfa,
diallel cross, free-hybrid, pod fertility
General
objectives: a)Construction of free-hybrids in alfalfa(Medicago sativa
L.),using partially inbred (S2) parental plants (Rotili et al.,
1999). b)Experimental evaluation of free-hybrids and synthetics derived from
the same parental plants (Table 1).
Table 1. Free-hybrid program
|
4 -
constituents |
8 -
constituents |
||
|
A B C D
|
E F G H I L M N
|
||
1997 |
Diallel cross
|
Diallel cross
|
||
1998 |
6 2S2Syn1
(SH) |
4S2Syn1
|
16 2S2Syn1
(SH) |
8S2Syn1 |
1999 |
6 2S2Syn2
|
4S2Syn2 |
8 S2DHF1 |
8S2Syn2 |
2000 |
6 2S2Syn3
|
4S2Syn3 |
8 S2DHF2 |
8S2Syn3 |
2001 |
Diallel
cross
|
|
Diallel
cross
|
|
|
15 S2DH |
4S2Syn4 |
28 S2OH |
8S2Syn4 |
2002-03 |
Agronomic Test
|
SH:
Simple Hybrid; DH: Double Hybrid; OH: Octuple Hybrid
4-constituents program:
Partly inbred constituents originating each from different sources (groups A
and B). Diallel crossing among 6 2S2Syn3 parents to obtain Double
Hybrids (DH).
8-constituents program:
Partly inbred constituents originating each from different sources (group C),
each from two different sources (group E) and each from a single variety (group
D). Diallel crossing among 8 S2DHF2 parents to obtain
Octuple Hybrids (OH).
The individual plants crossed at
each generation derived from selection for vigor (DMY/plant) within the
respective families. All the crossings were made by hand without emasculation.
The variance analysis was made by Method III Model I of Griffing ; since data
on pod fertility concern the mother plant and not their progenies, general and
specific abilities to give seeds are dealt with in the analysis.
I. For both the variety models
(free-hybrids and synthetics) pod fertility significantly increased going from
4 to 8 constituents. Irrespective of the number of constituents, pod fertility
was significantly higher in the synthetics than in free-hybrids. In
8-constituents program, diallelic crossings in group D, with the minimum
genetic diversity, showed pod fertility values significantly lower than in
group E (50% of genetic diversity); group C (100% of genetic diversity) was
intermediate between E and D. Comparing the diallel crossings at the beginning
and at the end of the program (Table 1), pod fertility of the 2S2Syn3
parents (4-constituents program) was not significantly different from that of S2
parental plants used at the beginning; the S2DHF2 parents
(8-costituents program) showed a significant increase in pod fertility compared
to the initial S2 parents.
II. The analysis of variance
showed that the general ability (GA) to give seeds was always highly
significant in the 5 diallel groups; the same was true for the specific ability
(SA) except for group B. The GA/SA ratio was positive, ranging from 2.25 to
9.09, in groups A, B and E ; it
nearly equaled the unity in groups C and D. Comparing the GA/SA ratio in
diallel crossings at the beginning and at the end of the program, an increase
of the ratio was observed for both the groups A and B (4-constituents program)
and a decrease for the groups C, D and E (8-constituents program).