Proceedings of the XLVII Italian Society of Agricultural Genetics - SIGA Annual Congress

Verona, Italy - 24/27 September, 2003

ISBN 88-900622-4-X

 

Poster Abstract - 2.10

 

FOUR AND EIGHT-CONSTITUENTS FREE-HYBRIDS IN ALFALFA. DRY MATTER YIELD FROM DIALLEL CROSSES: SOWING YEAR RESULTS

 

P. ROTILI*, C. SCOTTI*, S. GNOCCHI*, D. KERTIKOVA**, G. GNOCCHI*

 

*) 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 (S2) constituents originating each from different sources (groups A and B). Diallel crossing among 6S2Syn3 parents to obtain Double Hybrids (DH).

 

8-constituents program: partly inbred (S2) constituents originating each from different sources (group C), each from two different sources (group E) and each from a single cultivar (group D). Diallel crossing among 8 S2DHF2 to obtain Octuple Hybrids (OH).

 

The trial was planted in a cold greenhouse, in concrete boxes 25x80x65 cm containing two rows of plants (final density of 250 plants/m2), in a randomized block design with 5 blocks. Data were collected on the 15 central plants of each row, each population being then represented by  150 plants; irrigation was not limiting. Five cuttings were made during the sowing year; dry matter yield, earliness and mortality were recorded at plot basis.

 

At the 4-constituents level, only one hybrid significantly outyielded for the total year production the corresponding synthetic 4S2Syn4 (+ 29%), although 8 and 2 hybrids respectively in the two diallelic groups showed dry matter production 10-23% higher than the corresponding synthetic. At the 8-constituents level, the hybrids were not different or significantly less yielding than the corresponding 8S2Syn4.

 

As for the free-hybrids, 4-constituents model resulted significantly more performing than 8-constituents one; the synthetics at 4 and 8 constituents did not differ significantly in Syn4 generation while in Syn3 the 4-constituents model showed higher DMY than 8-constituents one.

 

Both G.C.A. and S.C.A. variances were highly significant in all the diallelic groups. However, S.C.A. resulted more important than G.C.A. in the 4-constituents crosses while the opposite was true for the 8-constituents crossings.