# Genetic Control of Photosynthesis in Sugarcane During Successive Ratoon Cycles

## TL;DR

This study shows that sugarcane's photosynthetic efficiency is strongly influenced by genetics and can be used to breed better varieties for higher yield and quality.

## Contribution

The study identifies key photosynthetic traits and their heritability, offering a framework for breeding high-efficiency sugarcane cultivars.

## Key findings

- Photosynthetic traits showed high heritability (0.70–0.86), indicating strong genetic control.
- Three key photosynthetic aspects explained 99.9% of the variance in performance.
- High-efficiency genotypes correlated with increased stalk weight and sucrose content.

## Abstract

Sugarcane (Saccharum spp.) is a globally significant crop for both sugar production and bioenergy generation. Investigations into its photosynthetic characteristics and underlying genetic mechanisms are of paramount importance for yield enhancement and quality improvement. This study demonstrates that genotype constitutes a critical determinant in modulating sugarcane’s photosynthetic traits. The canal point series cultivars introduced from the United States demonstrate superior photosynthetic efficiency, thereby presenting substantial value for breeding programs aimed at developing sugarcane varieties with enhanced photosynthetic performance. By systematically dissecting these photosynthetic determinants, this work establishes a robust theoretical foundation for developing next-generation high-photosynthesis cultivars, thereby paving the way for optimized sugarcane cultivation systems worldwide.

This study analyzed the photosynthetic traits of 74 sugarcane genotypes using PAM-2500 and SPAD instruments over three years. Our findings revealed significant variations in photosynthetic characteristics among different genotypes and ratoon years, highlighting the complex interplay between genotype and ratoon age. Notably, the heritability of these traits ranged from 0.70 to 0.86, indicating a strong genetic influence. Through principal component analysis, we identified three critical aspects of photosynthesis: efficiency and light utilization, electron transfer and reaction center status, and chlorophyll content, which collectively accounted for 99.9% of the observed variance. The germplasms were categorized into three efficiency groups—high, moderate, and low—based on their photosynthetic performance. Among these, 45 genotypes were classified as High Photosynthetic Efficiency (HPE), 19 as Moderate Photosynthetic Efficiency (MPE), and 10 as Low Photosynthetic Efficiency (LPE). Importantly, germplasms with high photosynthetic efficiency correlated with increased stalk weight and sucrose content, suggesting potential targets for breeding programs. These findings establish a quantitative framework linking photosynthetic performance with agronomic outputs, providing breeders with measurable selection criteria for developing next-generation sugarcane cultivars optimized for both biomass and sucrose production.