Differentiating pollen from four species of Gossypium

Authors: Jones, Gretchen; MCCURRY, HALI - Texas A&M University

Submitted to: Palynology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/10/2011
Publication Date: 6/1/2012
Citation: Jones, G.D., McCurry, H. 2012. Differentiating pollen from species of Gossypium. Palynology. 36:80-85.

Interpretive Summary: The boll weevil, Anthonomus grandis Boheman, remains one of the most devastating insect pests of cotton, Gossypium spp., in the southern United States. Although immature and adult stages of weevils forage on cotton pollen, little research has been conducted distinguishing the pollen grains of the four economically important species of cotton. Determination of which cotton species have been utilized by weevils before capture in traps may be useful in identifying the origin of weevil re-infestation. The length and width of 300 pollen grains and 100 processes (spines) of tree cotton (Gossypium arboreum L.), American pima cotton (G. barbadense L.), levant cotton (G. herbaceum L.), and American upland cotton (G. hirsutum L.) were measured. American pima and American upland cotton had the largest pollen grains (105.48 and 94.59 µm, respectively) and the longest processes (18 and 15 µm, respectively). There are sufficient differences in the length, width, and processes of pollen grains to differentiate these four cottons, which may help identify likely sources of weevil re-infestations when different species of cotton are planted within zones or states.

Technical Abstract: Cotton, Gossypium (Malvaceae), has been spun, woven, and dyed since prehistoric times. Four cotton species are economically important, Gossypium arboreum (tree cotton), G. barbadense (American pima cotton), G. herbaceum (levant cotton), and G. hirsutum (American upland cotton). Previous research has been conducted examining the pollen grains of the Malvaceae and there is a key that differentiates the four economically important species of Gossypium by their pollen grains. However, the cotton pollen found in boll weevils, Anthonomus grandis Boheman, and other insect pests cannot be keyed to the species using the published key. The objective of this research was to determine if the pollen grains of these four species could be differentiated and develop a key that works for cotton pollen found in insect pests. Flowers of the four taxa were collected from USDA greenhouses and fields and dried. Both unacetolyzed and acetolyzed pollen grains were examined with light microscopy and scanning electron microscopy. The length and width of 300 pollen grains and 100 processes (spines) of each taxon were measured. There were no size differences between the acetolyzed and the unacetolyzed grains. Gossypium barbadense and G. hirsutum had the largest grains (105.48 and 94.59 µm, respectively) and the longest processes (18 and 15 µm, respectively). Differentiation of these taxa can be useful in the determination of the origin of insect pests that attack cotton when different cotton species are grown within a region. However, additional research is needed examining the varieties and cultivars of cotton.