Differential Responses to Various Stress Conditions in Upland Cotton Near Isogenic Lines Differing in Fiber Maturity

Fiber maturity representing the degree of fiber wall thickness is a key determinant of the value of cotton. The immature fiber (im) mutant with low maturity and its near isogenic line (NIL) Texas Marker-1 (TM-1) with high maturity have been extensively used for identifying genetic factors regulating fiber maturity. However, little is known how environmental factors affect their maturity. To determine which and how environments regulate fiber maturity, we compared the growth and photosynthesis of the NILs grown under different abiotic and biotic stress conditions. Under a normal temperature, the im plants managed to maintain equivalent net photosynthesis to the TM-1 by significantly increasing stomatal conductance. Under instantaneous heat stress, photosynthesis was significantly suppressed in im compared to TM-1. We did not detect significantly different responses between the NILs whose developing bolls and roots were infected by two fungal pathogens. The results provide insight into how abiotic stress conditions and genetic factors synergistically regulate fiber maturity in cotton fibers.