🧬 Sugarcane — Genetics and Breeding

Sugarcane breeding is genetically complex due to high polyploidy and interspecific genome mixtures. This lesson explains nobilization, trait priorities, and long-cycle clonal selection in Indian sugarcane programmes.

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Origin and Importance

Sugarcane belongs to the genus Saccharum in the family Poaceae. India is both the centre of origin for Saccharum barberi (thin canes) and the world's largest sugarcane producer. The crop is propagated vegetatively through setts and is harvested for sucrose-rich juice used to produce sugar, jaggery, and ethanol. Uttar Pradesh, Maharashtra, and Karnataka are the major producing states.

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Species of Saccharum

The genus Saccharum includes six species, collectively known as the Saccharum complex:

Species	Chromosome No. (2n)	Key Features
S. officinarum	80	Noble canes, thick, juicy, high sugar
S. spontaneum	40-128	Wild, thin, vigorous, hardy, disease resistant
S. barberi	81-124	North Indian thin canes
S. sinense	111-120	Chinese thin canes
S. robustum	60-80	Wild, tall, low sugar
S. edule	60-80	Edible pith, low sugar

Modern sugarcane cultivars are complex polyploid interspecific hybrids with chromosome numbers ranging from 100 to 130. This extreme polyploidy creates challenges for genetic analysis and Mendelian genetics.

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Nobilization

Nobilization is the process of crossing the wild species S. spontaneum (which contributes vigour, tillering, hardiness, and disease resistance) with S. officinarum (which provides high sugar content and thick canes), followed by repeated backcrossing to S. officinarum to recover high sugar while retaining the hardiness of the wild parent.

The concept was pioneered at Coimbatore (Sugarcane Breeding Institute, SBI) in the early 1900s. The landmark variety Co 205 (1918) demonstrated that nobilized canes could vastly outperform the thin, low-yielding indigenous varieties of North India. This achievement, often called the Coimbatore Miracle, transformed Indian sugar production.

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Breeding Objectives

1. High cane yield — through thick stalks, high tiller number, and vigorous growth.
2. High commercial cane sugar (CCS) — sucrose percentage of juice, purity, and extraction efficiency. Brix (total dissolved solids) and pol (sucrose) are key measurements.
3. Early maturity — varieties that attain peak sugar by October-November (e.g., CoJ 64, Co 0238) for early crushing.
4. Red rot resistance — caused by Colletotrichum falcatum, the most destructive disease. Resistance is polygenic and non-durable, requiring continuous varietal replacement.
5. Smut resistance — caused by Sporisorium scitamineum; a whip-like structure emerges from the growing point.
6. Drought and waterlogging tolerance — for sub-tropical and tropical zones respectively.
7. Ratoon ability — good regrowth after harvest to reduce planting costs over 2-3 crop cycles.

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Breeding Methods

Sugarcane flowering (arrowing) occurs under specific photoperiod and temperature conditions, often requiring photoperiod facilities to induce flowering in non-flowering genotypes. Seedling selection begins from thousands of fuzz (true seed) progeny, with rigorous clonal selection over 10-12 years before variety release. Important varieties include Co 0238, CoLk 94184, Co 86032, and CoC 671.

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Summary Cheat Sheet

Quick Recall Points\n- Modern cultivars are complex polyploid interspecific hybrids.\n- Nobilization: spontaneum hardiness + officinarum sugar recovery.\n- Breeding priorities include CCS, disease resistance, maturity, and ratooning ability.\n\n### Exam Traps\n- High cane yield does not automatically mean high sugar recovery.\n- Variety development is long-term clonal screening, not quick line release.

References

2 sources • [1] [2]

[1]

ICAR eCourse: GPBR 213 Crop Improvement-I (Kharif Crops)

Book

[2]

ICAR Crop-specific research bulletins (IIRR, IIMR, IIMR Sorghum, ICRISAT, CICR, SBI, CRIJAF)

Website