Effect of the cytoplasmic male sterility type on the chlorophyll content in the leaves of grain sorghum hybrids

New types of CMS-inducing cytoplasms cannot be applied to hybrid sorghum breeding without the knowledge of their effects on major biological and commercial plant traits. In our studies of F 1 hybrids, obtained by crossing two sets of isonuclear CMS lines (with the nuclear genomes of cv. Pishchevoe 614 (P614) and Zheltozernoe 10 (Zh10)) to two pollen parents (cv. Pishchevoe 35 (P35) and Mercury), we focused our attention on the effects of A3, A4, 9E, and M35-1A cytoplasms on the chlorophyll content at different developmental stages of sorghum plants. It was found that hybrids with different types of male-sterile cytoplasm differed in chlorophyll content, and the genotypes of the CMS line and the pollen parent influenced the manifestation of cytoplasmic differences. In the F 1 hybrids obtained with CMS lines possessing the P614 genome, the sterile M35-1A cytoplasm increased the chlorophyll a content in comparison to the 9E cytoplasm. In the F 1 hybrids obtained with CMS lines with the Zh10 genome and the P35 pollen parent, the sterile A4 cytoplasm increased the sum of chlorophyll a and b , in comparison to the A3 and 9E cytoplasms, whereas no differences were recorded in the F 1 hybrids obtained with Mercury. The F 1 hybrids obtained with CMS lines with the P614 genome showed heterosis for total chlorophyll content at the tillering stage. Overdominance of this trait was observed in hybrids with the M35-1A cytoplasm; the heterosis exceeded the analogous indices in the 9E cytoplasm by 19.0%, and the hypothetical heterosis, by 20.6%. These data demonstrate that the application of new types of CMS-inducing cytoplasms allows raising F 1 hybrids with heterosis for chlorophyll content. Thus, such types can be used to increase hybrid productivity.