Seed yield and biomass allocation in Sorghum bicolor and F₁ and backcross generations of S. bicolor × S. halepense hybrids

Abstract

The Land Institute is developing perennial grains to be grown in prairie-like mixtures. One approach involves the development of a perennial grain sorghum by crossing tetraploid Sorghum bicolor with wild S. halepense to combine high seed yield with overwintering ability via rhizome production. We grew tetraploid S. bicolor, F1 hybrid (BC0), and two backcross generations (BC1 and BC2) in a randomized block design to examine total biomass, seed yield, and allocation to plant parts within and across generations. Root, rhizome, stem and leaf, and total biomass decreased from the BC0 to BC2 to S. bicolor generations, whereas panicle mass, seed mass, and reproductive allocation were lowest in the BC0 generation (p < 0.05, ANOVA). Mean seed mass (g ∙ plant−1) was 39.1 in the BC0, 107.3 in the BC1, 84.1 in the BC2, and 92.7 for the S. bicolor parent, which translated into yields of 171.9, 471.6, 396.7, and 407.5 g ∙ m−2, respectively. Reproductive allocation varied from 14.7% in BC0 to 28.9% in BC2 compared with 33.5% in S. bicolor. Mean allocation to rhizomes was 2.71% in BC0 but negligible in BC1 and BC2. There was no relationship between rhizome mass and seed mass within any generation, but there was a positive correlation between total plant mass and rhizome mass in BC0. We divided the BC0 population into four groups with respect to rhizome production and found no significant differences among the groups in plant size or seed yield. Within each generation, reproductive allocation was inversely related to culm mass. The lack of an apparent trade-off between allocation to rhizome versus allocation to seed within any generation supports the possibility of combining within a population high seed yield and production of perennating belowground organs. Key words: backcross, hybrid, perennial grains, reproductive allocation, rhizome, seed mass, Sorghum bicolor, Sorghum halepense.

Development of dual purpose sorghum: correlation and path-coefficient analysis of grain yield and stem sugar traits

“…Therefore, although leafy plants might have positive or no relationship between stem sugar and grain yield, the less leafy ones (at the same photosynthetic rates) tend to have a negative relationship between the two traits due to competition for the limited photo-assimilates. Piper and Kulakow (1994) reported that 42 to 74% of grain yield was attributed to plant biomass, results that are consistent with the positive and significant correlation coefficient between the two traits observed in the current study, although this is true only within a certain range after which the biomass start competing with the grain for photo-assimilates. The observed positive correlation coefficient between stem biomass and (i) head length, (ii) number of leaves per plant; (iii) plant height, and (iv) stem diameter (Table 3) could be attributed to the fact that plant height and stem diameter are major components contributing to the overall plant stem biomass.…”

Breeding Perennial Grain Crops

“…The increased seed yield did not come at the expense of plant vigor or longevity. Piper and Kulakow (1994) found no correlation between seed and rhizome production in a population of unreplicated, winterhardy F3 plants from an interspecific cross between tetraploid Sorghum bicolor and S. halapense; however, rhizome production was all but lost in backcrosses to S. bicolor, the cultivated species.…”

“…Hybrids between S. halapense and induced tetraploid lines of S. bicolor are easily made (Casaday and Anderson, 1952;Sanguden and Hanna, 1984;Piper and Kulakow, 1994). In an effort to produce a perennial grain sorghum at The Land Institute, Piper and Kulakow (1994) crossed S. halapense with tetraploid grain sorghum lines.…”

“…In an effort to produce a perennial grain sorghum at The Land Institute, Piper and Kulakow (1994) crossed S. halapense with tetraploid grain sorghum lines. In an interspecific F3 population, approximately 40% of plants were rhizomatous.…”

“…Of course, this implies increased biomass. Piper and Kulakow (1994) concluded that development of a winterhardy sorghum (i.e., one that produces 80g of rhizomes per plant) with a grain yield of over 4000 kg/ha is feasible, through selection for greater biomass and reallocation of photosynthate to seed production. The foundation germplasm for breeding a perennial sorghum may necessarily consist of highbiomass plants that produce more tillers than annual sorghum.…”