Meiotic Behavior of a Hodo Sorgo ✕ Johnsongrass Hybrid¹

Abstract

Meiosis Of ‘Hodo’ sorgo was slightly more irregular than that reported for other varieties of Sorghum bicolor, notably by having a higher frequency of quadrivalent associations. Meiosis of the fertile interspecific S. bicolor × S. halepense hybrid was almost as regular as that of S. halepense, johnsongrass, and suggests close genomic relationship of the parental species. The 2n chromosome number was 20 for Hodo sorgo, 40 for johnsongrass, and 40 for the interspecific hybrid. The mean chromosome association was: Hodo sorgo, 8.2 II, and .91 IV; jonhsongrass, .19 I, 11.81 II, .09 III, 3.31 IV, .09 V, .28 VI, and .06 VIII; F1 hybrid, .04 I, 7.2 II, .17 III, 4.6 IV, .02 V, .7I VI, .02 VII, and .27 VIII. The frequent occurrence of quadrivalents in the hybrid suggests that part of the parental chromosomes are quite similar if not identical. Although the origin of octoploid (2n=40) johnsongrass is uncertain, experimental evidence substantiates the hypothesis that the species is an autopolyploid derived from S. bicolor.

Crop‐to‐weed introgression has impacted allelic composition of johnsongrass populations with and without recent exposure to cultivated sorghum

“…Based on reports of S. halepense × S. bicolor hybrids in experimental crossing and cytological studies (e.g. Hadley 1958; Bennett & Merwine 1966) and in test plots (Arriola & Ellstrand 1996), some introgression was expected, particularly in S. halepense populations NE and TX1, growing adjacent to fields were S. bicolor is cultivated. Not anticipated was the finding that the majority of S. halepense plants in these populations carry cultivar‐specific alleles, and thus appear to be S. halepense × S. bicolor hybrids.…”

Molecular Characterization of Non-flowering Perennial Sorghum spp. Hybrids

“…Despite these concerns, Columbusgrass hybrids offer a potential germplasm base from which improved perennial sorghum biomass feedstocks can be developed. Controlled hybridization between S. bicolor and S. halepense has been successful in previous studies with varying results (Bennett and Merwine, 1966;Bennett, 1966, Sengupta andWeibel, 1971;Dweikat, 2005). Hybrid fertility varies across ploidy levels, with diploid (2n=2x=20), triploid (2n=3x=30) and tetraploid (2n=4x=40) F 1 hybrids having 90%, 1.1%, and 66% average seed set, respectively (Endrizzi, 1957;Dweikat, 2005).…”

Possible repetitive DNA markers for Eusorghum and Parasorghum and their potential use in examining phylogenetic hypotheses on the origin of Sorghum species

“…Other views hold that S. bicolor is a diploid or a secondary polyploid with a basic number of n = 7 or 8 (De Wet 1978;Duara and Stebbins 1952;Sangduen and Hanna 1984;Huskins and Smith 1932;Pritchard 1965). Correspondingly, S. halepense was considered to be an autotetraploid (Casady and Anderson 1952;Duara and Stebbins 1952), an autooctoploid (Bennett and Merwine 1966), or an autoallooctoploid (Hadley 1953). In terms of physiology and morphology, S. halepense can be distinguished from all 20-chromosome species, with the exception of Sorghum propinquum, in the section Eusorghum by the presence of its rhizomes and a true perennial growth habit (Bhatti et al 1960;De Wet 1978).…”