Evaluation of corn (Zea mays L.) lines promising for breeding forage hybrids by chlorophyll content and expression of PSAA and PSBA genes

Corn (Zea mays L.) is a crucial fodder crop that holds one of the leading positions among feed plants. Chlorophylls a and b, the primary photosynthetic pigments, play a vital role in determining the physiological state of plants, assessing the impact of stress factors, and predicting productivity. It is known that chlorophylls and their derivatives, phytol and phytanic acid, are extremely important in mammalian nutrition due to their positive effects on metabolic dysfunctions. The content of phytol and phytanic acid directly depends on the chlorophyll content in feed. In this regard, providing ruminants with feeds high in chlorophyll content will improve the quality of obtained animal products. In this study, samples with high chlorophyll content in leaves were identified for the first time, and a correlation between the accumulation of total chlorophylls and expression levels of photosystem genes, including transcription of psaA and psbA genes, was demonstrated in maize breeding lines from the collection of the Institute of Agriculture of the Institute of Agriculture KBRC RAS. Our aim was to evaluate the chlorophyll a and chlorophyll b contents in promising corn breeding lines from the collection of the Institute of Agriculture - a branch of the Federal Scientific Center of Kabardino-Balkarian Scientific Center RAS (Institute of Agriculture KBSC RAS) to identify fodder-oriented lines with increased chlorophyll content for further use in breeding, as well as to determine possible correlations between chlorophyll content and expression of psaA and psbA genes. For the analysis, 150 breeding lines of maize were selected from the collection of Institute of Agriculture KBSC RAS, which are used to produce varieties and hybrids for grain and universal purposes. The plants were grown in experimental plots of the Institute of Agriculture of the KBRC RAS in 2023. The determination of chlorophyll a and b content in leaves was conducted using Folch reagent. For this purpose, 5-6 days after pollination, at noon, leaves from the fifth tier of the second plant in the row were collected. Leaf discs were cut from the middle of the leaf, avoiding midribs, homogenized in liquid nitrogen, and frozen at -80 °C. The expression of psaA and psbA genes was determined in the same tissues homogenized in liquid nitrogen, for which chlorophyll content was measured, using quantitative real-time PCR (qRT-PCR). Statistical analysis was performed using Microsoft Excel 2013 and GraphPad Prism v.9 software. The results revealed significant differences in chlorophyll content among the analyzed samples. Based on total chlorophyll content, corn lines were divided into three groups, with high (> 400 mg/g, 21 samples), medium (200-400 mg/g, 91 samples), and low ( function show_eabstract() { $('#eabstract1').hide(); $('#eabstract2').show(); $('#eabstract_expand').hide(); }