Carlos Francisco Ragassi

Diversidade genética em germoplasma tropical de cebola estimada via marcadores RAPD

ABSTRACT Genetic diversity of tropical-adapted onion germplasm assessed by RAPD markers Onion is a crop of significant socioeconomic importance to Brazil. Onion germplasm with adaptation to tropical and sub-tropical conditions has played an important role in the development of this crop in the country. In this context, we studied the genetic diversity in a germplasm collection potentially useful for the development of cultivars for tropical and subtropical regions. The genetic variability of 21 accessions/cultivars that have been used as germplasm and/or were developed by onion breeding programs in Brazil was evaluated via RAPD markers. The following accessions were included in the study :‘Red Creole’, ‘Roxa IPA-3’, ‘Valenciana 14’, ‘Beta Cristal’, ‘Diamante’, ‘Composto IPA-6’, ‘Aurora’, ‘Bojuda Rio Grande’, ‘Alfa Tropical’, ‘Pera IPA-4’, ‘Primavera’, ‘Belem IPA-9’, ‘Crioula Alto Vale’, ‘Conquista’, ‘Pira-Ouro’, ‘Vale-Ouro IPA-11’, ‘Franciscana IPA-10’, ‘Serrana’, ‘CNPH 6400’, ‘Petroline’, and ‘Baia Periforme’. From the 520 primers used in the initial screening only 38 displayed stable polymorphisms. They produced 624 amplicons, of which 522 (83.7%) were monomorphic and 102 (16.3%) were polymorphic. An average similarity coefficient of 0.72 was calculated among accessions based upon this subgroup of polymorphic amplicons. This allowed the discrimination of this germplasm collection into six groups with only one of them comprising more than one accession. The main group was formed by 16 accessions (‘Diamante’, ‘Composto IPA-6’, ‘Aurora’, ‘Bojuda Rio Grande’, ‘Conquista’, ‘Pira-Ouro’, ‘Serrana’, ‘Vale-Ouro IPA-11’, ‘Baia Periforme’, ‘Primavera’, ‘Franciscana IPA-10’, ‘Belem IPA-9’, ‘Crioula Alto Vale’, ‘Petroline’, ‘Pera IPA-4’ and ‘Alfa Tropical’), for which the genetic origin (with few exceptions) can be traced back to the variety ‘Baia Periforme’. The populations ‘Red Creole’, ‘Roxa IPA-3’, ‘Beta Cristal’, ‘CNPH 6400’, and ‘Valenciana 14’ comprised a set of five isolated groups, showing genetic divergence among them and in relation to main ‘Baia Periforme’ group. This germplasm displayed a relatively low genetic diversity, with the predominance of materials originated from the base population ‘Baia Periforme’. There are, however, some accessions, which can add genetic diversity to this germplasm and they can be exploited by onion breeding programs aiming to develop cultivars for tropical regions of the world.

Crescimento da batateira em sistema de preparo profundo de solo e sucessão de poáceas

Potato in Brazil is often cultivated after corn (Zea mays) using the conventional tillage system, which achieve about 20 cm depth, not deep enough to remove physical impairments below the prepared layer. Thus, a deep tillage system associated to succession with grass types is postulated as an alternative to promote the adequate development of the potato crop. This study, with the cultivar Atlantic, aimed to compare the conventional tillage (PC) used in potato, in succession to corn, to a deep tillage system (PP), in succession with three different grass types (corn, Brachiaria brizantha cv. Marandu and Panicum maximum cv. Tanzânia) on the growth dynamics of potato. The dry matter production (MS, t/ha) of the aboveground part of the grasses was different in descending order: Tanzânia PP (26.56) > Marandu PP (19.94) > Corn PP (5.57) = Corn PC (5.72). With respect to potato development, Corn PP (5.56 and 85.51) was higher than Corn PC (4.34 and 64.83 g/plant MS) for the production of roots and leaves respectively, no statistical difference being found among the other treatments. For the production of stalks, Corn PC (5.53 g/plant MS) was the lowest and for the production of tubers, Marandu PP and Corn PP (152.16 and 149.01 g/plant MS) were higher than Corn PC (115.73 g/plant MS). In summary, the deep tillage system provided better development of potato and the effects varied depending on the grass type used for succession.

Genotipagem de polimorfismos associados com sistemas de macho-esterilidade em acessos de cebola adaptados ao Brasil

The synthesis of onion (Allium cepa) hybrids relies upon the use of two genetic-cytoplasmic male-sterility systems, CMS-S and CMS-T, in association to the normal male-fertile (N) cytoplasm. However, the molecular phenotyping of male-sterility-inducing and normal cytoplasms of many onion accessions adapted for cultivation under tropical conditions is not available. Some of these accessions were reported as presenting tolerance to diseases and adaptation to tropical and subtropical regions. Therefore, these accessions are potential sources of parental lines for the Brazilian onion hybrid breeding programs. In the present work, polymerase chain reaction (PCR) assays were conducted using mitochondria-derived markers in order to characterize the cytoplasm type present in different morpho-agronomic onion types cultivated in Brazil. The S cytoplasm appeared to be the most frequent one among the 66 evaluated accessions with a frequency of 56%. The T male-sterility-inducing cytoplasm was observed in 25.8% of the accessions. Of the samples, 18.2% displayed exclusively the cytoplasm N. This information could be useful to guide the onion breeding programs in the selection of parental lines aiming to develop hybrid cultivars adapted to tropical and subtropical areas of the world.

Effect of Soil Compaction Alleviation on Quality and Yield of Potato

Soils of tropical environments are exposed to the process of degradation when the natural ecosystems are converted to unsustainable agro-ecosystems. Soil compaction, which is part of that degradation process, is widely found in Brazilian cultivated areas, especially in the potato fields in which the intensive soil revolving operations promote the disruption of aggregates. Furthermore, potato is very sensitive to the problems associated to the soil compaction, such as the low development of roots and the diseases that are favored by high humidity in the tuber. In this way, a tillage system based on deep alleviation of soil compaction for the potato crop is presented in this chapter. This system, named “deep soil loosening” was evaluated in two Brazilian producing regions in Bahia and Sao Paulo States and provided higher yields, which were associated to the improvement of soil physical attributes. Thus, the “deep soil loosening” system is suggested as an alternative to improve potato production in compacted areas and, also, as a tool for promote the recuperation of soils damaged by compaction.