Environmental Engineering Reference
In-Depth Information
21.6 suGarcane BreedInG
There are basically six species within the Saccharum genus: S. officinarum L. (2 n = 80), S. robus-
tum Brandes and Jeswiet ex Grassl (2 n = 60-205), S. barberi Jeswiet (2 n = 81-124), S. sinense
Roxb. (2 n = 111-120), S. spontaneum L. (2 n = 40-128), and S. edule Hassk. (2 n = 60-80). Because
genomes of all of these species may be involved in some form of modern cultivars, sugarcane is
considered to have one of the highest genetic complexities among cultivated species.
The genetic breeding of sugarcane in Brazil and worldwide has been explained in great detail in
several articles and topics (Stevenson 1965; Blackburn 1983; Berding and Roach 1987; Berding and
Skinner 1987; Breaux 1987; Heinz and Tew 1987; Hogarth 1987; Tew 1987; Machado Jr et al. 1987;
Matsuoka and Arizono 1987; Matsuoka et al. 1999a, 1999b; Landell and Alvarez 1993; Landell
and Bressiani 2008). The present text will concentrate on the work of Matsuoka et al. (1999a, b).
Matsuoka et al. (1999a) showed in detail how sugarcane breeding began in Brazil in the nineteenth
century. The first reports that sugarcane seeds (not the stem) could result in offspring occurred in
Barbados in 1858 (Deerr 1921; Stevenson 1965). However, it is presumed that the breeding actu-
ally started in 1885 in Java, from the germination of S. spontaneum. But a few years earlier in
Brazil, Peixoto Lima (1842) had stated in thesis defense that sugarcane would reproduce from seeds
obtained by crossing (i.e., by sexual reproduction). This fact, combined with several others, seems
to indicate that Brazil was among the pioneers in getting new commercial varieties from seeds.
From the beginning of the twentieth century, there was an increasing concern about the poor
sugarcane productivity as well as the increase of pests (Deerr 1921; Aguirre Jr 1936; Edgerton
1955; Dantas 1960; Stevenson 1965; Andrade 1985). As a result, there was an intense exchange of
germplasm between different countries, the farmers being primarily responsible for this (Matsuoka
et al. 1999a). However, at times when the producers felt pressured by crises in the sector, there were
initiatives toward the setting up of experimental stations (Geran 1971).
At present, Brazil has four main sugarcane breeding programs: (1) the sugarcane program from
the Agronomic Institute of Campinas (IAC), which started in 1933; (2) the RIDESA Interuniversity
Network Sugarcane Genetic Breeding Program, made up of federal universities that started in 1971
as PLANALSUCAR; (3) the Sugarcane Technology Center (CTC), which began work in 1968 as
COPERSUCAR; and (4) Canavialis, which began in March 2003 and was recently acquired by
Monsanto. Syngenta also started a sugarcane breeding program in Brazil.
Despite there being large differences in the details about how the breeding programs in Brazil
(and the world) carried out their activities, there are some points in common which will be high-
lighted here. In essence, the breeding is based on the selection and cloning of superior genotypes in
segregating populations, which are obtained from the sexual crossing between different individuals.
The success rate of these processes depends on several factors including the adequate choice of the
parents to maximize the chance of response to selection; use of adequate experimental designs; and
the correct choice of the traits to be evaluated. Most of the traits considered in the selection process
have a quantitative nature and are controlled by quantitative trait loci (QTL), such as soluble solid
rate; sucrose content; diameter and number of stalks; fiber content; flowering; precociousness; resis-
tance to pests and diseases, etc.
Each year, breeding programs generate segregating populations formed by thousands of seed-
lings. The number of seedlings varies according to the program and depends on economic and tech-
nical factors. These segregating populations are then submitted to selection in different schemes,
which are presented below.
21.6.1 g EnEration of v ariaBility
The genetic variability available for selection comes from sexual crossing and can be done in dif-
ferent ways (Matsuoka et al. 1999a, 1999b): (1) biparental crossing, in which crossings are made
using two known parents, some of which may be used exclusively as a female; (2) polycrossings,
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