Photosynthesis and Growth of Cotton (Gossypium hirsutumL.) Lines Deficient in Chlorophyll Accumulation

Abstract

Three virescent mutants and two wild-type lines of upland cotton were evaluated for chlorophyll (Chl), carotenoids (Car), carbon exchange ratio (CER), water use efficiency (WUE), chlorophyll fluorescence, and growth. Lines 30 and 174 were allelic for the virescent locus and had reduced ratios of Chl Tot , Chl a , Chl b , CER, and WUE compared to DP90ne (in both 1995 and 1996). Line 174 had a higher CER than line 30 in both 1995 and 1996. The CER values of line 174 were similar to those of line 31. The only differences in fluorescent measurements were found in initial fluorescence (F 0 ) values, reflecting the concentrations of Chl. Of the three plant growth indicators, only plant height showed consistent statistical differences during growth. Reduced plant height was associated with lower chlorophyll concentrations. The number of main-stem nodes was slightly affected, with statistical differences occurring on only two dates-41 and 82 days after planting. The data indicate that these virescence alleles negatively influence most measurements of photosynthesis and cotton growth, but not all. Also, as previously reported in other crops, cotton leaf CER is not totally dependent on Chl Tot levels.

Comparison of Growth, Yield, and Fiber Quality of the Obsolete SA30 Yellow Leaf with Four Sets of Modern Yellow and Green Leaf Near Isogenic Cotton (Gossypium hirsutum L.) Lines

“…This removal of leaves and or cotyledons would reduce the total photosynthesis. This is theoretically comparable to what is occurring in reduced photosynthesis in the virescent (Turley and Pettigrew, 2011) leaf cotton lines used in this work. However, neither in the Turley and Pettigrew (2011) paper nor in the research presented in this paper did we ever see a reduction in the number of nodes.…”

“…This study measured the photosynthesis strength of these obsolete cotton lines and compared various growth parameters with two modern wild-type lines. The virescent lines SA30 and SA174 were of the deep yellow phenotype reported by (Zhang et al, 1997) and during this study also were found to be allelic (Turley and Pettigrew, 2011). The virescent plant SA31 also expressed a virescent and red leaf phenotype that gave its leaves a bronze color.…”

“…Plant height-to-node ratios were calculated from these measurements. Turley and Pettigrew (2011) made similar comparisons between SA30 and two other virescent lines -SA174 and SA31 (bronze leaf) along with two wildtype lines. Kerby and Keeley (1987) reported that plant height was more sensitive to environmental stress than the number of mainstem nodes.…”

“…One avenue for improvement could be to identify components of cotton photosynthesis that could be manipulated to improve cotton yields (Cornish et al, 1991). The problem with this approach is the complexity of the photosynthesis apparatus, which uses sunlight, water, CO 2 , and various nutrients to manufacture the basic building blocks for plant growth and, therefore, is essential in increasing yields and fiber quality of cotton (Turley and Pettigrew, 2011). The use of genetics to target and improve photosynthesis in cotton has not been emphasized by breeders/ geneticists.…”

“…Using a variant allele from an obsolete cotton (Gossypium hirsutum L.) line and comparing the expression of this same allele in modern lines will facilitate the identification of physiological changes associated within the modern selections that result in increased yields. The expression of this detrimental virescent allele was reported to double the Chl a /Chl b ratios of the SA30 line over two wild-type cotton lines due to a reduction of Chl b most likely from a reduction in the light harvesting complex (Turley and Pettigrew, 2011). This scenario reflects on the difficulty of not only identifying the virescent allele but identifying the mechanism that increases reproductive development.…”