The grain outcross off-type is caused when pollen from another grain sorghum source pollinates the sterile female parent within the seed field. The sorghum contaminant may be an off-type within the parent seed itself, or a commercial hybrid grown near the production area. The grain outcross will have a different head shape and/or color than the hybrid.
The grain forage off-type is the result of pollen from a forage sorghum (silage type) plant crossing with the female seed parent within the seed field. This off-type can be the same height as a mutation, but is generally 2 to 4 feet taller than the typical grain sorghum hybrid. The grain forage will typically have a compact head similar to grain sorghum, but the stalk is usually more robust. This off-type will produce very few tillers, but the plant height poses a problem during harvest of the grain sorghum. The heads of the grain forage are often unharvestable by the combine and could create a volunteer concern the following year. Volunteer plants will segregate as either grain sorghum plants or tall grain forage plants.
Open Head Forage
The open head forage off-type is the result of pollen from an open-headed forage plant cross-pollinating with the seed field. The pollen source is usually sudangrass, but can also include shattercane or broomcorn. This non-rhizomatous grassy type plant is usually taller than grain sorghum. It produces many slender tillers with open heads that bear large amounts of viable seed, which can remain dormant for a long period of time. The open head forage off-type is objectionable, due to a grassy appearance and volunteer concerns.
The johnsongrass outcross occurs when pollen from johnsongrass pollinates the male sterile plant in the seed production field. This cross-pollination does not readily take place due to the genetic differences between grain sorghum and johnsongrass. The johnsongrass outcross is rhizomatous, taller than grain sorghum, and has slender stalks, which produce many tillers. Johnsongrass outcrosses are almost always sterile and thus do not usually produce viable seed. However, these outcrosses produce rhizomes, which can potentially survive mild winters and allow infestation to reoccur in subsequent growing seasons.
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The foregoing is provided for informational use only. Please contact your Pioneer sales professional for information and suggestions specific to your operation. Product performance is variable and depends on many factors such as moisture and heat stress, soil type, management practices and environmental stress as well as disease and pest pressures. Individual results may vary.