Obtaining and selection of maize inbreds with high protein quality and hard endosperm from a native population from Puna (Jujuy, Argentina) was previously reported (MNL 57:73, 1982; MNL 59:67, 1985). The aim of this report is to communicate the progress obtained after three generations of selection. The selection was based on protein quality, evaluated by means of tryptophan content of endosperm protein. Other traits were also evaluated in order to get information that allowed selection of lines which combine high protein quality with hard endosperm. Kernel weight, endosperm hardness (measured on an arbitrary scale: 0 = floury to 4 = flinty) and kernel apparent density were measured. Forty-three S3 lines were studied, 22 of them from the best S2 (MNL 59:67, 1985). Results obtained on S3 are shown in Table 1. S3 lines have, on average, 75% more tryptophan than normal maize, 50% more than S1 and 25% more than S2 (Table 2).
During selection and inbreeding, some changes occurred such as kernel weight and protein content reduction. However, other traits do not change (endosperm hardness and kernel apparent density). Protein quality (tryptophan content) was not increased, due to the decrease of hard endosperm ratio. The best S3 lines have a good combination of protein quality and endosperm hardness (Table 3).
High protein quality of selected Puna lines may be attributed to a modification of normal endosperm protein pattern. From lines selected with high tryptophan content (H8) the endosperm proteins were fractioned according to Landry-Moureaux and compared with normal inbreds (DY). Results obtained are given in Table 4. H8 line with high tryptophan content has less zein and more saline soluble and glutelin-3 than normal DY. Results obtained indicated that: 1) protein quality selection has been rapid and positive and 2) Puna maize may be employed to improve protein quality of maize endosperm without affecting its normal corneous phenotype.
Table 1: Characteristics of Puna S3 lines.
Table 2: Differences between S1, S2, S3 lines.
Table 3: Characteristics of the best Puna S3 lines.
Table 4: Endospem protein pattern of normal (DY) and hard endosperm-high quality protein Puna S3 line (H8).
A.M. Broccoli, M.E. Streitenberger, A.A. Nivio and
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