Euphytica 56: 133-135, 1991. © 1991 Kluwer Academic Publishers. Printed in the Netherlands.

Backcross breeding to increase seed retention in cocksfoot (Dactylis glomerata L.)

M. Falcinelli Istituto Miglioramento Genetico Vegetale Universith degli Studi di Perugia, 06100 Perugia, Italy

Received 10 June 1991; accepted 15 August 1991

Key words: Dactylis glomerata, cocksfoot, orchardgrass, seed production, seed shattering, selection criteria

Summary

The objective was to evaluate the effectiveness of the backcross breeding method to improve an existing variety(Hallmark) for higher seed retention.

The recurrent parent was cv. 'Hallmark' (H) and the donor parent was cv. 'Marta' (M). Marta is an Italian cultivar with a high degree of seed retention. Two cycles of backcrossing with selection for higher seed retention were conducted. In each cycle, 1200 plants were grown. In both BCa F1 and BC2 F1, 20 plants were selected for general features of H and for a high degree of seed retention. The 20 plants of BC2 F1 were intercrossed in 1989. The bulked population thus obtained (HS) was evaluated in 1989-90 together with H and M as spaced plants in a randomized complete block design with 4 replicates. Regarding seed retention, H had a score of 7.9, M of 1.7 and HS of 2.8, LSD (0.05) = 0.8, on a scale from 1 to 9. Consequently HS had similar seed retention to M but similar ear emergence date, plant height and panicle morphology to H. The results confirm that seed shattering is under control of a single partially or completely dominant gene.

Introduction

Cocksfoot or orchardgrass, Dactylis glomerata L., is a cool season, perennial grass, normally propaga- ted by seed. The improvement of seed retention in commercial cocksfoot varieties, by transferring high strength genes from other natural populations has been a practical breeding objective (Falcinelli, 1987; Falcinelli et al., 1989). Increased seed reten- tion, which does not influence forage quality, is one of the most desirable characters in grass seed crops (Griffiths, 1965). Selection for seed retention in grass breeding is therefore strongly recommended (Elgersma et al., 1988).

The mechanism of seed retention in cocksfoot was histologically determined by Picciriili & Falci- nelli (1989) in two cultivars, Hallmark and Marta. Hallmark is one of the most popular cocksfoot

cultivars in the USA and is characterized by a high level of seed shattering, which may occur from the soft dough stage onward; Marta, an Italian cultivar with a high degree of seed retention at the full maturity stage, was selected from a nonshattering Italian ecotype. Since seed retention is under ge- netic control (Falcinelli, 1987; Falcinelli et al., 1989), the backcross method was employed for this simply inherited character.

The main objective of this study was to evaluate the effectiveness of the backcross breeding method for producing a Hallmark population with a high degree of seed retention.

Materials and methods

Two cycles of backcrossing with selection for gen-

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2

1

LiI

Fig. 1. Inflorescence of D. glomerata L. 1 = total length; 2- 3-4 = 1st, 2nd, and 3rd internode length; 5-6-7 = 1st, 2nd, and 3rd branch length.

eral features of (H) and for higher seed retention of (M) were conducted at Perugia Italia (43 ° 08' N lat, 12 ° 23' E long). The recurrent parent was (H) and the donor parent was (M).

One-hundred pairs of plants were obtained from 100 random plants of H and 100 plants of M crossed in both directions in 1983. The 100 plants of M were obtained from 20 different genotypes, vegetatively propagated to obtain 5 plants per clone, character- ized by high seed retention and by a similar heading date as H. In August 1983, 2000 F~ seeds (H x M) and 200 H seeds were germinated in Petri dishes. 1200 randomly selected F1 seedlings and 120 H seedlings were transferred to Jiffy-pots, and grown in a greenhouse. In November 1983, the pots were transplanted in the experimental field in Perugia as spaced plants (60 x 40 cm) in 12 rows. In each row there were 50 Fa plants, 10 H plants and 50 Fa plants. Hallmark plants were used as a check. In

1984 20 F1 plants were selected for general features of H and for high seed retention.

The selection was based on the following charac- ters scored from i to 9: - general features: 1 (similar to H), 9 (similar to

M); - seed retention: 1 (less than 5 seeds shattered), 9

(all seeds shattered). Seed retention was evaluated at the full maturity stage when the panicle was struck on a white card- board and scored.

In September 1984 each of 20 selected plants were cloned into 5 plants and transferred to pots together with 100 plants of H. In 1985, these plants were backcrossed with H. The same steps de- scribed from F1 to BC1 F1 were repeated and 20 plants of BC2 F1 w e r e intercrossed in 1989 (Table 1). The bulked population so obtained, hereafter named HS, was evaluated in 1989-90 together with H and M.

In August 1989, 200 seeds of each population (H, M and HS) were germinated in Petri dishes. For each population, 100 random seedlings were trans- ferred to Jiffy-pots and grown in a greenhouse. In November 1989 the 100 random plants of M, H, and HS were transplanted in the field as spaced plants in a randomized complete block design with 4 replicates, each of 25 plants. In 1990 the following characters were evaluated: - heading time (number of days from May 1st,

1990); - seed retention, evaluated 50 days after anthesis.

The panicle was chosen at anthesis when one

Table 1. Crossing and selection history used to develop seed retention in Hallmark (HS)

Year Pedigree Seed produced

1983 H x M F1 1983-84 1200 F~ plants (20 selected) 1984-85 20 F1 x H BC1 F1 1985-86 1200 BC1 F~ plants (20 selected) 1986-87 20 BC1 F1 x H BC~ F1 1987-88 1200 BC2 F~ plants (20 selected) 1988-89 20 plants intercrossed Hallmark-Select-

ed (HS)

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Table 2. Heading time (days after May 1), seed retention (1 = max; 9 = min), panicle traits (cm) and plant height (cm) in Hallmark, Marta and Hallmark Selected

Populations Heading time Seed retention Panicle length Internode length

1st 2nd 3rd

Branch length Plant height

1st 2nd 3rd

Hallmark 8.1 7.9 26.4 7.9 5.1 3.1 13.8 9.0 6.0 135.1 Marta 12.9 1.7 20.8 6.7 4.1 2.4 10.3 7.0 4.4 121.8 Hallmark Selected 9.3 2.8 25.4 7.5 5.4 2.7 11.2 7.8 5.1 131.3 L.S.D. (0.05) 2.3 0.8 2.1 0.6 0.5 0.4 1.7 1.0 0.8 6.5

inflorescence per plant was selected for unifor- mity of size and labelled; panicle length, internode and branch length (cm) as shown in Figure 1; plant height (cm).

Results and discussion

Heading time, seed retention, morphological char- acteristics of the panicle and plant height of H, M and HS are reported in Table 2. H was earlier than M (8.1 v s 12.9 days) but similar to HS (9.3 days). Large differences were observed for seed retention between H and M (7.9 v s 1.7, respectively). HS was more similar to M (2.8 v s 1.7) than to H. Panicle traits (total length, lenght of internode, length of branches) and plant height were higher in H than in M. HS showed generally intermediate characteristics but closer to H. No statistical differ- ences were observed between H and HS for panicle and internode length and for plant height. As far as panicle characteristics are concerned, HS was more similar to M for branch length. In fact, the length of the 1st, 2nd and 3rd branches in H were significant- ly higher than in HS (P < = 0.05).

Two cycles of the backcross procedure were, therefore, effective: in improving seed retention in an American variety. HS showed close similarities to H in terms of general features (heading time, panicle length, internode length and plant height) and a close resemblance in seed retention to M. According to previous results (Falcinelli 1987; Fal- cinelli et al., 1989) and to the results achieved, the character seed shattering seems to be controlled by a single partially or completely dominant gene,

although modifying genes may also be present in M. A third cycle of backcross and selection is ex- pected to further improve HS for all general fea- tures of H. Due to variability originating by grow- ing a variety outside of its region (Ceccarelli & Lorenzetti, 1977) faster progress is expected to be achieved by conducting the third and following backcross cycles in the zone where H is normally cultivated by farmers.

Acknowledgements

The research was supported by grants from CNR, Italy.

References

Ceccarelli, S. & F. Lorenzetti, 1977. Within varieties variability in differently adapted types of Lolium perenne. XIII Interna- tional Grassland Congress, Leipzig, GDR, 1: 292-299.

Elgersma, A., J.E. Leeuwangh & H.J. Wilms, 1988. Abscission and seed shattering in perennial ryegrass (Lolium perenne L.). Euphytica S: 51-57.

Falcinelli, M., 1987. Breeding for seed retention in orchardgrass (Dactylis glomerata L.). J. Appl. Seed Prod. 5: 25-31.

Falcinelli, M., Negri, V. & F. Veronesi, 1989. Breeding in progress for seed retention in orchardgrass (Dactylis glomer- ata L.). XVI International Grassland Congress, Nice, France, 1: 665~566.

Griffiths, D.J., 1965. Breeding for higher seed yields from herb- age varieties. J. Nat. Inst. Agric. Bot. 10: 320-331.

Piccirilli, M. & M. Falcinelli, 1989. Anatomy of seed dispersal mechanisms in high and low seed shattering cultivars of or- chardgrass. Crop Sci. 29: 972-976.