PASCANI, REPUBLIC OF MOLDOVA
Maize and Sorghum Research Institute

The revealing and selection of high-protein sources of maize
--V.E. Micu, Eugenia Partas and A.I. Rotari

This research began in 1974. In the first stage (1974-80) the protein content of 1,572 populations and samples was determined by the Kjeldahl semi-micromethod. In the investigated collection, including large diversity in geographical and genetic origin, morphology, growing period and other traits, samples with high protein content (12-15%) were revealed, the majority of them among local flint populations from Moldova.

In the second stage, the individual selection of high-protein plants in the best population was conducted and the results for four of them (K-44, K-466, K-553, K-1081) are presented in Table 1. Annually, 10-20 plants were self-pollinated and analyzed for protein content. Though the volume is limited, nevertheless each of the four populations reveals large genetic diversity among plants in protein content. Using long-term selection, progenies with protein content of more than 23-24% have resulted, significantly exceeding the initial level. It is necessary to note that the best progenies, with 23-24% protein, were obtained in population K-466, which had the highest initial protein content (Table 1) and highest variation. After 12 years of selection, genetic variability of protein content is not settled, as shown by the 1992 data.

Table 1. The protein content in self-pollinated progenies of the last 10 cycles of selection (% in dry matter).
 
Cycles of Selection & Year K-44 lim K-466 lim K-553 lim K1081 lim
Initial Level 12.12-12.75 13.25-15.69 12.25-13.75 14.44-14.91
3 - 1983 17.08-20.09 15.88-20.69 13.72-18.41 15.64-19.25
4 - 1984 17.06-19.00 14.68-23.35 16.37-19.25 15.88-21.66
5 - 1985 15.52-19.37 15.16-19.85 17.44-19.61 12.51-15.88
6 - 1986 13.96-19.12 12.27-21.30 15.88-16.60 12.27-16.00
7 - 1987 15.06-19.61 14.19-22.65 17.69-18.08 15.64-17.69
8 - 1988 16.97-21.17 14.80-20.21 17.08-19.13 13.83-18.53
9 - 1989 17.20-21.39 15.61-24.27 17.31-20.45 16.36-18.78
10- 1990 18.24-20.02 17.88-23.86 18.81-19.27 17.05-19.50
11- 1991 18.79-21.02 18.03-23.71 17.15-20.18 15.40-18.26
12- 1992 16.03-17.71 17.37-21.53 15.67-17.88 16.60-17.05
Populations limit 12.12-21.39 12.27-24.27 12.25-20.45 12.27-21.66
No. of Analyzed Progenies 159 626 60 68

The third stage of work began in 1987 and includes the cross of the four families highest in protein, self-pollination of hybrids, and selection in segregating progenies. Protein content in 1989-93 was determined by Near-Infrared method mod. 4500. In the F1 in all cases the protein content decreased considerably (Table 2), but the best progenies of the F2-F5 generation exceeded the best of the parental component by a considerable extent, except the hybrids with K-466. In these, the protein content of cross progenies was 21.05%, and the best selections from the F2-F5 had lower protein contents.

Nevertheless, even with these exceptions, the results testify to: (1) the presence of various genetic factors in different high protein sources; (2) the possibility of concentration of genetic factors favorably affecting the protein content from different sources into one. This allows us to expand the genetic base for further selection of a high-protein source. The work will be continued in this direction in order to obtain a source of high protein unrelated to IHP.

Table 2. The protein content of crossed families (1987), their best progenies (1988-92) and their F1-F5 (% in dry matter).
 
Sources & Hybrids 1987 1988 1989 1990 1991 1992
K-44 female 17.93 19.45 19.05 19.10 19.95 17.75
K-1081 male 16.40 16.26 17.60 18.40 17.35 17.48
K-44 x K-1081 15.83 21.30 23.31 23.40 21.95
K-1081 female 16.10 16.40 16.21 17.60 18.40 17.3 
K-553 male 16.00 17.93  18.30 18.20 18.55 18.90
K-1081 x K-553 14.49 16.60 19.55 20.40 21.10
K-1081 female 15.04 16.38 16.10 17.58 18.35 17.35
K-466 male 21.05 18.03 18.14 20.40 20.87 20.48
K-1081 x K-466 15.52 19.85 18.90 21.45 20.58


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