Differentiating pollen from four species of Gossypium

Authors: JONES, GRETCHEN; MCCURRY, HALI - TEXAS A&M UNIVERSITY

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/20/2010
Publication Date: N/A
Citation: N/A

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 separating the pollen grains of the four economically important species of cotton. Determination of which cotton species has 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 grown within or between zones or states. However, because of cotton hybridization and cultivation, cultivated cotton varieties need to be examined.

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). Some research has been conducted examining the pollen grains of the Malvaceae; however, little research has differentiated the four economically important species of Gossypium by their pollen grains. The objective of this research was to determine if the pollen grains of these four species could be differentiated. Flowers of the four taxa were collected from USDA greenhouses and fields. The stamen were removed, placed into individual packets, and dried for at least three days. Both unacetolyzed and acetolyzed pollen grains were examined with light 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). Using micro-morphometrics, it is possible to differentiate between these four species of cotton based on pollen grain morphology. Differentiation of these taxa can be useful in the determination of the origin of boll weevils that attack cotton. However, additional research is needed examining the varieties and cultivars of cotton.