Cutting propagation of ‘Cambona 4’ yerba mate clones

The ‘Cambona 4’ yerba mate (Ilex paraguariensis A. St. Hil. - Aquifoliaceae) stands out for the high productivity and soft taste of the raw material obtained. The seedlings come from the controlled crosses of a female and a male plant. In order to guarantee the planting of even more uniform and productive herbs, the cutting is an alternative of propagation. The objective of this research was to evaluate the rooting capacity of apical and subapical cuttings of six ‘Cambona 4’ clones (C7, C8, C9, C10, C11 and C13) in two seasons, in january (summer/autumn) and april (autumn/winter) treated with 2.000 mg/kg of IBA in the form of talc. The cuttings were standardized with 10 cm, keeping a pair of leaves cut in half. The cutting was done in an agricultural greenhouse, with irrigation by intermittent nebulization, the cuttings were placed to rooting in plastic tubes containing carbonized rice husk. After 120 days, it was verified that the cutting season influenced the response of each clone, but for most clones rooting was higher when performed in summer/autumn, with better rates varying between 78.2% to 90.6% (C8, C9, C11 and C13), while in autumn/winter it was from 59.4% to 75.0% (C7, C10, C11 and C13). In the summer/autumn cutting period, subapical cuttings showed greater survival and rooting than the apical ones, but they didn’t differ when performed in autumn/winter. Leaf retention positively influenced the survival.

Efficiency of the Polycross and Controlled Hybridization Methods in Sweetpotato Breeding in Uganda

Sweetpotato is an important crop in many parts of the world especially in developing countries. It is used for both human consumption as well as livestock feed. It is an important source of carbohydrates, vitamin C, fibre, iron, potassium, protein and β-carotene. Its production is, however, constrained by several biotic and abiotic factors, including pests and diseases, low soil fertility, drought, cold and salinity. Breeding is one of the ways to overcome some of these constraints and in sweetpotato the polycross or controlled cross methods can be used. To determine which of the two methods was more efficient, genotypes generated by both methods were evaluated over two seasons at Namulonge and Kachwekano. The type of cross (polycross or controlled) was significantly (P ≤ 0.05) different for storage root yield, response to sweetpotato virus disease, Alternaria blight, and harvest index (HI). The controlled cross families had a significantly higher mean HI of 43.2% than the polycross families with a mean HI of 31.8%. Therefore, controlled crosses could be deployed to systematically increase the HI in sweetpotato breeding populations. Significant (P ≤ 0.05) differences were observed among families for all traits. This stresses that the parents used in a cross are very important in generating genotypes with desired attributes. It was apparent that both the polycross and controlled crosses are good methods for generating new sweetpotato genotypes in a sweetpotato breeding program. Where aggregate performance was considered (selection index) the controlled crosses method produced more (75% of the top 20 desirable genotypes) than the polycross method across the two sites. However, the best three genotypes over the two sites were from the polycross family of Ejumula. Therefore, sweetpotato controlled crosses could be very useful for population improvement using recurrent selection while polycrosses could be suitable for variety development. Both hybridization methods require cautious selection of parents to match the breeding objectives.

Obtaining Triploid Hybrids by Means of Open Pollinations and Controlled Crosses Involving Diploids Parental

The creation of triploid hybrids is an important genetic improvement strategy for the development of new commercial citrus scion varieties. The objective of this work was to quantify the frequency of triploids obtained from natural and controlled crosses of different mandarin varieties under varying environmental conditions in the state of Bahia. The experiments were conducted in the municipalities of Cruz das Almas (Recôncavo Baiano region) and Mucugê (Chapada Diamantina region). The first experiment was based on fruits from open pollinations of the varieties ‘Page’, ‘Ortanique’, ‘Ellendale’, ‘Clemenules’, ‘Swatow’, ‘Piemonte’, ‘Fortune’, ‘South Africa’, ‘Montenegrina’, ‘Kincy’, ‘Span Americana’, ‘Fremont, ‘Nova’, ‘Dancy’ and ‘Murcott’, and the second involved fruits from controlled crosses of female parents ‘Nova’, ‘Fortune’ and ‘Ortanique’ and male parents ‘Page’, ‘Montenegrina’, ‘Swatow’, ‘Fremont’ and ‘Kincy’. The seeds selected were inoculated in test tubes containing approximately 10 mL of Woody Plant Medium (WPM). When the plants reached circa 60 days of age, leaf samples were removed for quantification of the DNA by the flow cytometry technique. In Mucugê, three triploids were identified from open pollinations, ‘Clemenules’ (1) and ‘Ortanique’ (2), while in Cruz das Almas, no triploids were obtained. In the controlled crosses, triploids were only obtained in Mucugê: ‘Ortanique’ × ‘Montenegrina’ (4), ‘Ortanique’ × ‘Kincy’ (1) and ‘Ortanique’ × ‘Swatow’ (2). Based on the data, it is suggested that the environmental conditions of Mucugê favored the formation of triploids.

Obtaining hybrids of cultivars and wild subspecies of cassava

The objective of this work was to evaluate the crossability between cassava (Manihot esculenta subsp. esculenta) cultivars and the subspecies M. esculenta subsp. flabellifolia and M. esculenta subsp. peruviana. Plants from the BRS Jari, BRS Formosa, BRS Verdinha, and BGM 2050 (Equador 72) cultivars were crossed with the two subspecies. During flowering, at pre-anthesis, pistillate flowers were covered with a nylon bag and staminate flowers on the same inflorescence were emasculated. The staminate flowers were collected and placed in flasks previously labeled and sterilized with alcohol; some fresh flowers were stored at room temperature due to asynchronous flowering. The crosses were made between 10 a.m. and 2 p.m. After pollination, the flowers were covered again. Evaluations were made from the moment of pollination to the dehiscence of the fruit. Of the total flowers pollinated, 38% were fertilized, and 504 developed fruits and 816 produced seeds were observed. As a male parent, M. esculenta subsp. flabellifolia is more efficient in crosses with M. esculenta subsp. esculenta and may be recommend for controlled crosses. The crosses between the cassava cultivars and M. esculenta subsp. flabellifolia and M. esculenta subsp. peruviana produce viable seeds.