Abstract
Chlorophyll is the most important pigment for plant photosynthesis that plays an important role in crop growth and production. In this study, the chlorophyll content trait was explored to improve sugarcane yield. Two hundred and eighty-five F1 progenies from the cross YT93-159 × ROC22 with significantly different chlorophyll contents were included as test materials. The chlorophyll content of the +1 leaves during elongation phase was measured using a SPAD-502 meter through a three-crop cycle (plant cane, first ratoon, and second ratoon). Linkage analysis was conducted on a high-density genetic map constructed based on the sugarcane 100K SNP chip. In addition, Fv/Fm, plant height, stalk diameter, brix data were collected on plant cane during the elongation and maturation phases. The results showed that the +1 leaf SPAD values, which can be used as an important reference to evaluate the growth potential of sugarcane, were significantly and positively correlated with the Fv/Fm during elongation phase, as well as with plant height, stalk diameter, and brix during maturity phase (P < 0.01). The broad sense heritability (H2) of the chlorophyll content trait was 0.66 for plant cane crop, 0.67 for first ratoon crop, and 0.73 for second ratoon crop, respectively, indicating that this trait was mainly controlled by genetic factors. Thirty-one quantitative trait loci (QTL) were detected by QTL mapping. Among them, a major QTL, qCC-R1, could account for 12.95% of phenotypic variation explained (PVE), and the other 30 minor QTLs explained 2.37–7.99% PVE. Twenty candidate genes related to chlorophyll content were identified in the QTLs plus a 200-Kb extension region within either sides, of which four were homologous genes involved in the chlorophyll synthesis process and the remaining 16 played a certain role in chlorophyll catabolic pathway, chloroplast organization, or photosynthesis. These results provide a theoretical reference for analyzing the genetic mechanism of chlorophyll synthesis and subsequent improvement of photosynthetic characteristics in sugarcane.
Highlights
Sugarcane (Saccharum spp. hybrids), which can ratoon for several years (Xu et al, 2021), is one of the most promising industrial crops in the world
Field experimental data were collected from three consecutive crops of a sugarcane F1 mapping population consisting of 285 progenies
A sugarcane 100K single nucleotide polymorphisms (SNP) Microarray-derived high-density genetic map was used to detect one major quantitative trait locus (QTL) and 30 minor QTLs associated with the leaf chlorophyll content
Summary
Sugarcane (Saccharum spp. hybrids), which can ratoon for several years (Xu et al, 2021), is one of the most promising industrial crops in the world. It is widely cultivated in more than 100 countries or regions in tropical and subtropical regions and provides 80% of the world’s sugar and 60% of bioethanol, and a total economic value of 75 billion US dollars (FAO, 2019). While the world’s human population is expected to exceed 9.7 billion by 2050 (United Nations [UN], 2019), the demand for energy and food will increase by at least 25% according to the current per capita consumption standard. The theoretical fresh cane yield of sugarcane can reach more than 380 t/ha (Waclawovsky et al, 2010), the current cane yields are about 77 t/ha and 73 t/ha in China and world, respectively (FAO, 2019), leaving a lot of rooms for improvement
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