Sugarcane (Saccharum spp. hybrid) is an important commercial crop which contributes 80% of total sugar production of the world. Besides sugar, it also forms source of various byproducts namely jaggery, ethanol, bagasse, press mud etc., It is a complex polyploid crop with variable chromosome number, which is propagated vegetatively through setts.

Sugarcane breeding is challenging owing to constraints like complex ploidy, absence of homozygous lines, low heritability of economic traits, non-synchronous flowering. In spite of challenges associated with sugarcane breeding, it has played a significant role in growth and sustenance of sugar industry along with farmers in the country through timely release of high yielding and sucrose rich varieties. Genetic resources have played a vital role in sugarcane varietal improvement which include cultivated species like Saccharum officinarum, Saccharum barberi, and S. sinense and wild species viz., S. spontaneum, S. robustum and S. edule besides other allied genera like Erianthus, Miscanthus etc2. Interspecific hybridization revolutionized sugarcane breeding in early 1900s and the main reason for its success is attributed to 2n+n transmission involving S. officinarum as female parent and S. spontaneum as male, through the process of nobilisation.

Essential activities in sugarcane breeding are broadly classified into two major categories; clonal selection and clonal hybridization. Hybridization between desired heterozygous parental clones generate enormous variability in the F1 generation, which can be subjected to selection. Selection can be based on individual plants (mass selection) or families (family selection). Family selection is proved to be effective for selection of elite progenies, especially for traits with low heritability. Different selection criteria were compared for traits like tonnes of brix per hectare, cane yield and estimated selection efficiencies revealed mass selection and BLUPAUS were better than other studied methods1. Index based selection can be efficient for multi-trait selection of clones in segregating generations.

PCR based molecular markers have been employed in diversity analysis, mapping and tagging traits. Single dose markers are preferable for mapping as they segregate in 1:1 ratio irrespective of ploidy3. Pseudo test cross populations synthesized through hybridizing parents contrasting for the trait and progenies derived from selfing commercial clones are used as populations for mapping. Such selfed populations from popular cultivar LCP 85-384 has served as base population for performing GWAS and GS4.

With the availability of reference sequence of cultivar R570, sugarcane genomics is expected to progress at faster pace, which would hasten the efficiency of breeding program through the development of trait specific markers. Such markers would enable diversification of breeding programmes to develop trait specific clones to harness the potentiality of this multipurpose crop.

References:

1. CURSI, D. E., COX, M. C., ANONI, D. C., HOFFMANN, H. P., GAZAFFI, R. AND GARCIA, A. A. F., 2020, Comparison of different selection methods in the seedling stage of sugarcane breeding. J. Agron., 112(6):4879-4897. 

2. HEMAPRABHA, G., MOHANRAJ, K., JACKSON, P. A., LAKSHMANAN, P., ALI, G. S., LI, A. M., HUANG, D. L. AND RAM, B., 2022, Sugarcane genetic diversity and major germplasm collections. Sugar Tech, 24(1):279-297. 

3. HENRY, R. J. AND KOLE, C., 2010, Genetics, genomics and breeding of sugarcane. CRC Press, pp: 69-96.

4. XIONG, H., CHEN, Y., PAN, Y. B. AND SHI, A., 2023, A genome-wide association study and genomic prediction for fiber and sucrose contents in a mapping population of LCP 85-384 sugarcane. Plants, 12(5):1041-1055.