SELECTION CRITERIA FOR BREEDING WRINKLED PEAS SPECIALLY SUITED FOR FREEZE-DRYING

74 RESEARCH REPORTS PNL Volume 12 1980

SELECTION CRITERIA FOR BREEDING WRINKLED PEAS SPECIALLY SUITED FOR FREEZE-

DRYING

Wende, E.

Federal Research Centre for Hort. Plant Breeding, Ahrensburg, West Germany

A breeding program is underway to develop varieties of peas which are

specially suited to freeze-drying. Parental lines for crosses were chosen

from among 55 wrinkled varieties surveyed. Some of the special criteria

considered in the selection were: color of the fresh, immature pea; absence

of seedcoat splitting; quality of peas after freeze-drying; and the rehydration

properties (i.e. maintenance of shape of the green peas). Examination of

these quality characteristics was begun in F3 families derived from 3900 single

F2~single plants, originating, in turn, from 78 crosses.

R.H.S. color charts were used to evaluate the color intensity and vari-

ation in samples of fresh, deep-frozen, freeze-dried, and rehydrated green

peas. Progenies with light green color were rejected (group yellow-green

145 A-D). Samples from advanced generations were also studied to determine

the influence of the seedcoat and cotyledons on the color of green peas.

From this the following conclusions were drawn: 1) Color of the seedcoat,

which can vary from white to dark green, is of importance because the cotyledons

themselves are always green (with the exception of the off-color "blonds").

2) The thickness of the seedcoat increases the color of cotyledons when the

seedcoats are green and diminishes it when the seedcoats are white and thick.

3) Seedcoat and cotyledon color affect the maintenance of color, which normally

brightens during the freeze-drying process, and also influence the recovery

of shape of freeze-dried peas after rehydration.

Rehydration in boiling water was strongly influenced by the shrinking

of either the cotyledons and/or the seedcoat. The term "quality of green

peas" after freeze-drying reflects a capacity to rehydrate and this is based

on two essential charactistics: 1) rapid swelling of the cotyledons and 2)

good permeability of the seedcoat. Selection against seedcoat splitting

ordinarily is a desirable goal when breeding garden peas for canning or freezing,

but non-split seedcoats do not rehydrate rapidly and thus are undesirable from

the standpoint of breeding for adaptability to freeze-drying. Because of the

highly significant correlation between seedcoat splitting after freeze-drying

and rehydration capacity, it may be necessary to select lines which show seed-

coat splitting to some extent (i.e. clefts from 3 to 1 mm); if not, the seedcoat

must be perforated mechanically.

The structure of the seedcoat of fresh, frozen, and freeze-dried peas

was examined microscopically. The thickness of palisade tissue (macro- and

osteosclereids) was not affected even after preservation and only the parenchyma,

which also determines the thickness of the seedcoat, was influenced by deep-

freezing and freeze-drying. The greater destruction of parenchyma may result

in less seedcoat splitting.

The selection criteria described appear to be heritable characters in

view of the selection results achieved. Genetical analyses have just begun.