Breeding of sugar beet genotypes with improved production traits
1-Improvement of sugar yield and processing quality
The aim of the sugar beet breeding is the selection of stable varieties producing
the highest amount of extractable sugar per unit area. The expression of sugar
yield and quality traits is mainly influenced by the environment, but the selection
of improved varieties is still possible:
i) using particular methods of recurrent selection;
ii) with the enhancement of combining ability between the parents of the monogerm
hybrid varieties;
iii) reducing the damages caused by diseases and stresses through genetic resistances.
2-Improvement of cercospora leaf spot resistance
Cercospora l.s. is the most damaging disease in the Italian sugar beet cultivation
areas. The first source of genetic resistance was identified by Munerati in this
Institute. This resistance trait is the only used today in the commercial varieties.
Owing to the additive action of the resistance, the improvement through mass
selection in diseased natural conditions is scarcely effective. In fact, the
resistance expression is strongly conditioned by environmental effects. To minimize
environmental interactions in the breeding program it is necessary to produce
inbred 2n lines of the less diseased plants carrying self-fertility or pseudo
self-fertility traits.
3-Improvement of bolting resistance
Bolting resistance is a determinant trait for sugar beet, both for autumnal and
spring sowing conditions. In order to reduce the percentage of flowering plants
in the crop, it is necessary to selection in both multigerm (pollinators) and
monogerm (male sterile and O-Type lines) genotypes in greenhouse or in early
sowing, as well as to test the hybrids in field conditions. Increasing degrees
of inbreeding in the genotypes under selection improve the identification and
the elimination of the bolting susceptible individuals. Several genotypes (2n
and 4n pollinators, CMS, O-Types) are available both for autumnal and spring
sowing.
4-Improvement of rhizomania resistance
Rhizomania is the most damaging sugar beet virus worldwide. The resistant varieties
allow the cultivation of the crop in light and medium diseased soils without
significant yield losses. It was speculated that at least one source of rhizomania
resistance was derived from the germplasm released by this Institute. Mass selection
in severely infected fields lead to the isolation of the first resistant genotypes.
The rhizomania resistant traits "Rizor" and "Holly" are controlled by a single
dominant major gene, whose expression varies in relation with an unknown number
of modifying genes. Several commercial varieties are 2n hybrids composed by a
multigerm pollinator crossed with a monogerm CMS line, where usually only one
parent carries the Rz resistant gene.
Improvements were obtained with the inbreeding of resistant lines used either
to produce hybrids or to introgress the Rz gene into susceptible diploid
genotypes. Significant results were achieved using plantlets selected on the
basis of low concentration of BNYVV (beet necrotic yellow vein virus), the causal
agent of rhizomania.
A number of viruses infect the sugar beet crop and could be an additional reason
for yield reductions in addition to that caused by BNYVV.
More recently, the BSBV (beet soil borne virus) appeared to be a potential damaging
root virus. Environmental conditions increasing the aggressiveness of BNYVV display
similar effect toward BSBV. Immunological tests (ELISA) were carried out for
detecting the presence in the soil of transmitted sugar beet viruses. The study
of BSBV is done in collaboration with Dr. Imma Rubies (University of Bologna).
Release of varieties and breeding lines
ARCO: genetic monogerm
3n hybrid variety. It has been produced with a tetraploid pollinator Arco4x and
the cytoplasmic male sterile (CMS) inbred coded MS2 and maintained by its own
equivalent maintainer (O-Type). The canopy development is reduced in comparison
with similar varieties. The root shape is relatively short with small crown size.
The root grooves are scarcely pronounced; low presence of fanginess. The bolting
resistance of Arco is good; it has a low level of resistance to cercospora l.
s., but higher than similar varieties. The yielding ability is intermediate (type
N). Good sugar yield in healthy soils and normal level of extractable sugar.
It is advised for middle harvesting periods in healthy soils on northern Italy.
The variety was registered in 1986.
Distributor:
Agra Società del Seme s.r.l. Massa Lombarda.
DURO: genetic monogerm
3n hybrid variety obtained crossing the pollinator Arco5 on the CMS named MS2
and maintained by its own equivalent O-Type. The canopy is reduced in comparison
with similar varieties. The root shape is short with reduced crown development.
It presents a good bolting resistance level, small presence of fangy beets. The
cercospora l. s. resistance is higher than similar varieties. Duro shows a tendency
to produce roots with good sugar content (N-NZ type). The variety is adapted
to middle-late harvesting periods in healthy soils of northern Italy. The variety
was registered in 1986.
Distributor:
Agra Società del Seme s.r.l. Massa Lombarda.
SCUDO: genetic monogerm
3n hybrid variety obtained crossing the pollinator T12 on the CMS named MS2 maintained
by its own equivalent O-Type. The leaves development is reduced in comparison
with similar varieties typology. The root shape is moderately shorten. The root
grooves are rather deep; some presence of fangy beets. The variety has a good
bolting resistance; the cercospora leaf spot resistance is better than similar
varieties. Fairly good sugar yield in healthy soils and high degrees of technological
quality. The variety is adapted to middle-late harvesting times in healthy soils
of northern Italy. The variety was registered in 1986.
Distributor:
Agra Società del Seme s.r.l. Massa lombarda.
FALCO: genetic monogerm 2n hybrid variety obtained crossing the pollinator 412 on the CMS coded MS2 and maintained by its own equivalent O-Type. The foliar apparatus development is reduced and with erected leaves. Root shape is fairly elongated. The root grooves are normally deep with normal fangy beets. The cercospora leaf spot resistance is good; quite good rhizomania resistance. Good yielding ability (type N). The variety is adapted to middle-late harvesting periods in healthy soils of center-northern Italy. The variety was registered in 1990.
SAURO: genetic monogerm 2n hybrid variety obtained crossing the pollinator 410 on the F1-CMS between MS2R and the OT2. The pollinator is endowed with rhizomania resistance similar to "Rizor type". The foliar apparatus is normal with erected leaves. Root shape fairly elongated. The root grooves are normally deep with reduced fangy beets. Yielding ability is on average (type N). In rhizomania diseased soils the variety shows high sugar content (type NZ) and good extractible sugar yield. The variety is adapted to middle-late harvesting periods in healthy and rhizomania diseased soils of center-northern Italy. The variety was registered in 1990.
LAMPO: genetic monogerm 3n hybrid variety obtained crossing the pollinator T21 on the CMS coded MS2 maintained by its own equivalent O-Type (OT2). The foliar apparatus development is reduced in comparison with similar varieties. The root shape is relatively short. The root grooves are only a little deep; low presence of fangy beets. The bolting resistance is fairly good. It has a good level of resistance to cercospora l. s. higher than similar varieties. The yielding aptitude is intermediate (type Good sugar yield in healthy soils and very good level of extractible sugar. It is advised for middle-late harvesting periods in healthy soils on northern Italy. The variety was registered in 1990.
ROMBO: genetic monogerm 3n hybrid variety obtained crossing the pollinator T10 on the CMS coded MS2 maintained by its own equivalent O-Type (OT2). The foliar apparatus development is reduced in comparison with similar varieties typology. The root shape is relatively short. The root grooves are a little deep; very low presence of fangy beets. The bolting resistance of ROMBO is good. It shows a good level of resistance to cercospora leaf spot higher than similar varieties. The yielding attitude is fairly high sugar content (type NZ). Fairly good sugar yield in healthy soils and very good level of extractible sugar. It is recommended for middle-late harvesting in healthy soils on northern Italy. The variety was registered in 1990.
STILO: genetic monogerm 3n hybrid variety obtained by crossing the pollinator BA0401 (cercospora resistant) on the F1-CMS between the CMS MS17 with OTXR. The last component is endowed with the "Holly" rhizomania resistance gene Rz. The leaf canopy is well developed. The root shape is relatively shorten, with grooves just a little deep with lack of fangy beets. The variety is highly resistant to cercospora l. s. and endowed with a good level of rhizomania resistance. The yielding ability is fairly good addressed to show high sugar content (type NZ). It is well adapted to northern Italy cultivation areas either healthy or rhizomania diseased, particularly in middle-late harvesting periods. The variety is under registration.
GLADIO: genetic monogerm 2n hybrid variety obtained crossing the pollinator 450 (endowed with the type Rizor gene of rhizomania resistance Rz) on the F1-CMS between the CMS-MSXR (with "Holly" Rz gene) and the high yielding maintainer OT3. The leaf development is on average of similar varieties. The root shape is rounded and conical, the crown size is quite small. The roots do not show any fanginess. Gladio is highly resistant to rhizomania. The reduced level of cercospora l. s. resistance is enough to benefit the chemical treatment against the disease. The yielding ability is high particularly in sugar production. It is adapted to center-northern Italy growing areas either healthy or rhizomania diseased in early harvesting period. The variety is under registration.
Pollinator 412: multigerm 2n, partially self-fertile pollinator derived to the first source of cercospora resistance. It was extracted from composite cross used to develop the family 401. Family 412 was produced with multiple cycle of recurrent selection. In related genotypes was detected the first multigenic source of rhizomania resistance "Alba". The roots are well shaped with grooves scarcely pronounced. The foliar apparatus is characterizes by large petiols and leaf blades. The general combining ability in crosses with CMS is very satisfactory. The pollinator is useful as source of both cercospora l. s. resistance and quantitative resistance to rhizomania. The pollinator was released to Alba Sementi, Dieckmann-Haimburg, Produttori Sementi.
Lines CMS-MSXR and OTXR:
respectively monogerm CMS and his maintainer. The CMS line was back-crossed 7
times with the maintainer. O-Type is characterized by self-fertility, red hypocotyl
and very uniform shape of roots and leaves. It carries the gene Rz of rhizomania
resistance similar to that classified as "Holly type".
In segregating population, the presence of recessive and therefore susceptible
individuals is lower than similar lines. The resistance against cercospora l.
s. was improved in comparison with the original lines. The CMS line is employed
mainly as source of rhizomania resistance. It was released to Dieckmann-Haimburg,
Produttori Sementi, and Lion Seed.
Study of sugar beet root system under field condition
Sugar beet root system is
studied under field conditions for evaluating the correlations with the production
ability of the crop.
An improved minirhizotron system was developed for the observation of root development
and dynamic. The method allows the study of the whole root system up to 3 meters
deep.
Effect of cercospora l.s. attack on sugar beet leaf apparatus
Cercospora leaf spot strongly
influences the leaf apparatus in sugar beet, thus reducing the active surface
and the life span of the leaves.
This study intends to clarify the effects of disease on the leaf dynamics at
different levels of genetic resistance and fungicide protection.
Pre-breeding for stress related traits
Water-nutritional stress is one of the main limits to crop yield. Greater knowledge of the morpho-physiological traits fundamental in adapting to such stress, is necessary in order to improve yield stability. The aim of this research is the identification of the sugar beet traits that are involved in plant response to water-nutritional stress. These traits are potentially useful in breeding programs aimed at increasing sugar yield. This research is carried out in collaboration with Prof. Massimo Saccomani (University of Padova).
Collection and conservation of sugar beet germplasm
Wild beets of the genus Beta are studied as source of useful traits for sugar beet. The localization and the mapping of sea beet (Beta vulgaris ssp. maritima) populations along the Adriatic coasts are in progress. A representative sample of seed has been taken from each population and stored in controlled conditions. Limited amount of seed is available for the research institutes.
Some transgenic sugar beet
varieties endowed with resistance to herbicides, rhizomania and nematodes are
currently in advanced stage of field experimentation. Several researchers pointed
out the risk of gene flow caused by the possible transfer of modified genes from
the transgenic seed production areas both to the wild or weed beets and to the
normal seed crops. In the first case, the hybrids could acquire a selective advantage
and therefore alter the genetic structure of wild populations.
The aim is the study of the genetic and phenotypic variability of each population
and the detection of possible crosses with the commercial crop.
The presence in Italian
soils of deep layers with high nitrogen content is under observation as potential
factor of sugar yield, sugar content and processing quality shortages. The research
also involves the determination of 15N absorbed by plant up to the depth of 3
m.
This activity is carried out in collaboration with Dr. Rosa Marchetti (Istituto
Sperimentale Agronomico-Modena) and Dr. Anna Benedetti (Istituto Sperimentale
per la Nutrizione delle Piante-Rome).