Comparative effectiveness of commercial tomato rootstocks to control bacterial wilt

Bacterial wilt, caused by Ralstonia solanacearum, is one of the main diseases of solanaceous crops in Tropical regions, being the major limiting factor for tomato production in the North Region of Brazil. The disease has also been a constraint to tomato production under protected cultivation, which had solid expansion in the South and Southeast regions in the last decades. Although sources of resistance to bacterial wilt have been identified in S. lycopersicum germplasm, no resistant cultivars are available to growers. However, commercial rootstocks are available to protect scions against the disease, thus reducing the incompatibility associated to the use of different Solanaceae species/genera. The main objective of the present work was to evaluate the levels of resistance of a group of commercial hybrid/inbred tomato rootstocks to a diverse array of five R. solanacearum isolates (all obtained from infected tomato plants). A clear discrimination was observed among the evaluated rootstocks in relation to disease incidence. The phenotypic reaction of the tomato rootstocks was isolate-specific. The tomato hybrids 'Muralha' and 'Guardião' and the inbred line 'Hawaii 7996' (international resistance standard) were the rootstocks with best performance against the majority of the five R. solanacearum isolates, displaying significantly better resistance when compared with the hybrids 'Magnet' and 'Protetor'. However, all rootstocks were highly susceptible (100% mortality) to the R. solanacearum CNPH 488 isolate (classified as race 1 / Biovar 2, collected in Paraná State, Brazil). The same set of rootstocks was also evaluated under artificially infested soil (with less intense inoculum pressure). The hybrids 'Guardião' and 'Muralha' repeated their good performance when compared with 'Magnet' and 'Protetor'. Our results reinforce the notion that under favorable environmental conditions and/or in the presence of highly virulent strains, the system based upon tomato scion grafted onto tomato rootstock might provide unsatisfactory levels of bacterial wilt control. Therefore, complementary and preemptive control measures will be necessary in order to reduce the initial inoculum pressure in the soil.</p

Spring planting favors yield of new Brazilian potato cultivar BRS F63 Camila

ABSTRACT The objective of this work was to evaluate the effect of different planting dates on the morphological variables and yield of new potato cultivars. The treatments were three cultivars (Agata, BRS Clara and BRS F63 Camila) and three planting date (October, December and February), carried out in two crop years (2014/15 and 2015/16). Total and marketable yields, average mass of total and marketable tubers, growth period, leaf area index, number and dry weight of the tubers were evaluated. The first planting date resulted in higher yield than the third date. Cultivar BRS F63 Camila was the one with highest yield in this first planting date (47.4 t ha-1), due to greater number of tubers produced in relation to the other cultivars and to higher average tuber weight (166 g tuber-1) in relation to Agata (113 g tuber-1). In the second planting date, no difference in yield was observed among cultivars. In the third planting date, BRS Clara was the cultivar with highest yield (21.3 t ha-1), due mainly to higher average weight of tubers (105 g tuber-1) in relation to Agata (49 g tuber-1), a fact favored by the higher leaf area index and longer growth period of BRS Clara. Depending on the planting date, one should choose the cultivar that results in maximum yield potential, since it is a plant management with low cost and high yield impact. For the second planting date, any of the studied cultivars can be used.</div

Does planting time affect the nutritional demand and yield of potato cultivars?

ABSTRACT: Determining the level of absorption of nutrients in the potato crop at different stages of development is important because it allows identification of the time when the elements are most required by plants. The objective of this research was to evaluate the level of nutrient absorption in cultivars after different planting times. Field experiment was conducted in Guarapuava-PR. Treatments consisted of three cultivars (Agata, BRS Clara, and BRS F63 Camila) and two planting times (October and February), in randomized blocks, with three replications in the crop season 2015/16. The total macro and micronutrient content (leaves, stems, and tubers) was quantified at 15 and 45 days after plant emergence. The total dry weight of plants was verified at 45 days after emergence. At harvest, dry weight of tubers, and total and commercial yield was recorded. It was observed that BRS F63 Camila produced a higher total dry weight of plants at 45 days after emergence, and higher dry weight of tubers at harvest because of the higher accumulation of Fe, Mn, and Zn following the October planting. The BRS Clara produced higher total dry weight and higher dry weight of tubers following February planting with higher Ca and S accumulation. Depending on the developmental period and planting time, cultivars differed in nutrient accumulation and tuber dry weight production. Greater nutritional demand and higher yield occurred following the October planting.</div

New national potato genotypes: yield response to different doses of 4-14-8 NPK fertilizer

<div><p>ABSTRACT The fertilization of potato crops generally does not take into account the genotype, although genotypes may respond differently to fertilization. This study aimed to determine the yield of new potato genotypes (cultivar BRS Camila and clone CL 02-05), as well as the cultivar Ágata, submitted to four NPK 4-14-8 fertilizer doses (0, 2, 4 and 6 t ha-1) in the crop seasons of 2013/14 and 2014/15. We evaluated the total and marketable tuber yield, total and marketable tuber number, percentage of marketable tuber dry weight, average marketable tuber weight and plant growth period. The experimental design was randomized blocks in split plot scheme, with fertilizer doses allocated as main plots and genotypes as subplots, with three replications. We did not observe significant interaction for any analyzed variable. The clone CL 02-05 showed higher total and marketable tuber yield compared to the other cultivars, mainly due to its higher production of tuber number. However, we observed a high amount of tubers not suited for commercialization from the clone CL 02-05. Cultivar BRS Camila produced fewer marketable tubers than cultivar Ágata in crop season 2014/15, but without difference in marketable yield. On the other hand, plants of cultivar BRS Camila had a longer growth period of 7 days and the tubers of this cultivar accumulated higher percentage of dry weight compared to cultivar Ágata. The new tested genotypes had yield response similar to cultivar Ágata when submitted to doses of 4-14-8 NPK fertilizer. Therefore, the fertilization management of these new genotypes may be similar to that used with cultivar Ágata.</p></div

Growth, yield and dormancy of aeroponically produced potato minitubers as a function of planting density and harvesting date

ABSTRACT Potato seed is one of the largest costs of a crop. This is mostly due to the incidence and spread of viruses that occurs when the crop is grown in the open field. Thus, it is necessary to obtain virus-free potato plantlets through meristem isolation, with subsequent cultivation in a protected environment, where it is easier to control virus-spreading insects. One way to increase greenhouse viability is by multiplicating potato seed using high technology systems, among them, aeroponics. The objective of this work was to determine the effect of planting density on the growth and yield of potato plants cv. Agata in aeroponic cultivation, and the effect of harvesting dates and planting densities on the dormancy of harvested minitubers. The number of stems, leaves, and the number and fresh weight of minitubers/plant reduced when planting density was increased from 60 to 180 plants/m2. However, the number of stems, leaves, initiated minitubers, and the number and fresh weight of minitubers/m2 increased when planting density was increased from 60 to 180 plants/m2. The maximum number of type III minitubers (>30 mm) was 613/m2, obtained at the density of 180 plants/m2. Plant density did not affect the dormancy of harvested minitubers, but harvesting date did. Minitubers obtained from latter harvesting dates had a shorter dormancy period. Minitubers harvested at 78 and 64 days after transplanting sprouted 21 and seven days earlier than those picked at 50 days after transplanting.</div