Hybrid reconstruction in maize

Summary The production of seed of the maize single cross hybrid F68^*NE2 is uneconomic because of the low grain yield of the maternal line. Therefore the aim was to produce it from newly developed inbred lines obtained by reshuffling the genes in the hybrid, accompanied by selection. Thus in open pollinating generations derived from this hybrid, i.e. in C0, C1, C2, C3 and C4, honeycomb selection for grain yield improvement was applied. Selfing of one ear and open pollination of another ear of selected prolific C4 plants yielded 20 pairs of S1/half sib progenies. Plants grown from remnant S1 seed corresponding to superior progeny pairs were selfed. In each S2-line a single plant was selected and selfed. The S3-lines were evaluated for yield. Two S3-lines, i.e. 6D and 2B, attracted attention because they yielded two and a half times as much as the best commercial inbred line B73.The S1-and S2-lines were tested for combining ability with the related inbred lines NE2 and F68 by means of honeycomb design experiments and for combining ability with unrelated, freely available inbred lines by means of randomized complete block designs. Two S2-lines, i.e. 5C and 6E, were selected for their good combining ability. The six single cross hybrids produced by crossing the four S3-lines 6D, 2B, 5C, and 6E were compared with the original hybrid F68^*NE2 in a honeycomb design at two sites. The grain yields of the single cross hybrids 6D^*6E and 5C^*6E were similar to that of F68^*NE2. However, these two reconstructed hybrids can be produced in a cheaper way because the new maternal inbred lines yield as good as B73 (line 5C) or much better (line 6D).