Heterosis in CMS hybrids of cotton for photosynthetic and chlorophyll fluorescence parameters

The characterization of photosynthetic, chlorophyll fluorescence parameters and yield and yield components was compared between two newly developed CMS cotton hybrids (H1, H2) and their parents, as well as currently planted hybrid and conventional cultivars (C1, artificially produced hybrid CCRI 29 and C2, conventional cultivar CCRI 12) under the field condition. The results showed that P _n, F _v/F _m, Φ_PSII and qP of hybrids was significantly higher than that of C1 and C2. Furthermore, heterosis was found on photosynthetic parameters in hybrids over their parents at the first four growth stages, while only heterosis over mean of parents (HOMP) was detected in chlorophyll fluorescence parameters. It was clearly shown that one male-sterile line M2 was higher than the hybrids in F _v/F _m, Φ_PSII and qP over all growth stages. Significantly positive correlations (P < 0.01) were found between LAI or Yield and P _n, C _s, T _r, F _v/F _m, Φ_PSII, or qP, while significantly negative correlations between C _i and LAI or Yield, and no significance between qN and Chl a, C _s and qP were found. It was concluded that CMS hybrid cottons showed better potential to maintain relatively higher photosynthetic ability during the growth, which contributes to the increased lint yield.