Abstract
The Brazilian sugarcane industry plays an important role in the worldwide supply of sugar and ethanol. Investigation into the genetic structure of current commercial cultivars and comparisons to the main ancestor species allow sugarcane breeding programs to better manage crosses and germplasm banks as well as to promote its rational use. In the present study, the genetic structure of a group of Brazilian cultivars currently grown by commercial producers was assessed through microsatellite markers and contrasted with a group of basic germplasm mainly composed of Saccharum officinarum and S. spontaneum accessions. A total of 285 alleles was obtained by a set of 12 SSRs primer pairs that taken together were able to efficiently distinguish and capture the genetic variability of sugarcane commercial cultivars and basic germplasm accessions allowing its application in a fast and cost-effective way for routine cultivar identification and management of sugarcane germplasm banks. Allelic distribution revealed that 97.6% of the cultivar alleles were found in the basic germplasm while 42% of the basic germplasm alleles were absent in cultivars. Of the absent alleles, 3% was exclusive to S. officinarum, 33% to S. spontaneum and 19% to other species/exotic hybrids. We found strong genetic differentiation between the Brazilian commercial cultivars and the two main species (S. officinarum: = 0.211 and S. spontaneum: = 0.216, P<0.001), and significant contribution of the latter in the genetic variability of commercial cultivars. Average dissimilarity within cultivars was 1.2 and 1.4 times lower than that within S. officinarum and S. spontaneum. Genetic divergence found between cultivars and S. spontaneum accessions has practical applications for energy cane breeding programs as the choice of more divergent parents will maximize the frequency of transgressive individuals in the progeny.
Highlights
Sugarcane has a worldwide economic importance, with Brazil being the largest producer, harvesting over 657.2 million tons of sugarcane in 2016/17 [1]
A total of 137 genotypes encompassing 81 Brazilian commercial sugarcane cultivars and 56 basic germplasm accessions (19 S. officinarum, 26 S. spontaneum and 11 genotypes comprising five Saccharum spp. exotic hybrids and six accessions representing other species—S. barberi, S. robustum and Miscanthus spp.) were collected from the IAC Sugarcane Germplasm Collection maintained at the Sugarcane Center, in Ribeirão Preto, SP, Brazil
The availability of an efficient and adequate size set of Single Sequence Repeats (SSRs) primer pairs has a great impact for routine management of sugarcane germplasm and cultivar identification in a Cultivars Saccharum officinarum Saccharum spontaneum Other species/exotic hybrids
Summary
Sugarcane has a worldwide economic importance, with Brazil being the largest producer, harvesting over 657.2 million tons of sugarcane in 2016/17 [1]. In addition to its importance as a food, sugarcane is increasingly more important for ethanol production, and electricity cogeneration currently accounts for 4% of Brazilian electric energy demand [2]. Brazil’s position as a world leader in sugarcane production is attributed to climate conditions and adequate agronomical management practices, and to the high performance of Brazilian commercial sugarcane cultivars, which have been developed by the country’s three main sugarcane breeding programs (RIDESA: Interuniversity Network for the Development of the Sugarcane Sector; CTC: Sugarcane Technology Center; IAC: Agronomic Institute of Campinas). Sugarcane belongs to the genus Saccharum, related to other genera as Erianthus sect. Camus, which grouped together, constitute the Saccharum Complex [3]
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