Puna maize: selection for high protein quality and hard endosperm

In previous reports (MNL 57:73, 1983) it was communicated that a Puna maize germplasm has been the starting point of selection for high protein quality not associated to soft endosperm. The aim of this report is to communicate the results through two generations of selection for high protein quality and hard endosperm. The objective of this selection is to obtain maize inbred lines in which these characters are combined.

Characteristics of 31 S2 lines were studied.The results obtained are shown in Table 1. The selection was based on the tryptophan content of endosperm protein. Hardness (measured on an arbitrary scale: 0 = floury to 4 = flint) and kernel apparent density were measured in S2 lines. Protein content and protein quality are inversely associated, whereas kernel hardness and kernel density show a negative correlation with tryptophan content (Table 2). There are lines that combine a good ratio of hard endosperm with high protein quality (Table 3). S2 lines have, on average, 50% more tryptophan than normal maizes, and 20% more than S, lines (Table 4).

Protein quality selection has been positive, and the quick progress obtained in tryptophan content improvement may foretell the obtaining, in a few generations of selection, of lines whose protein quality is similar to that conditioned by known mutants. The best S2 lines obtained have 75% more tryptophan than normal maizes, and present good endosperm hardness. According to the results obtained, it can be inferred that Puna maizes constitute a germplasm source which may be used to improve endosperm protein quality without modifying its normal phenotype (hard).

Table 1: Characteristics of Puna S2 lines.

Table 2: Correlation coefficients between kernel weight (KW) , hardness (H) density (D), endosperm protein content (EP) and endosperm tryptophan content (ET) in Puna S2 lines. *-- significant at 5% level; **-- significant at 1% level.

Table 3: Characteristics of the best Puna S2 lines

Table 4: Differences between S1 and S2 lines.

Ana Maria Broccoli, Mirta E. Streitenberger and Jorge Luis Magoja

Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors.

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