Año 2020

Vol. 67

No. 2

Amaranth in southernmost latitudes: plant density under irrigation in Patagonia, Argentina

crop geometry; biomass; economic yield; phenology; protein.

In Argentina there have been few evaluations of Andean pseudocereal plantings. This study explored the response

of Amaranthus cruentus cv Mexicano to different plant densities under furrow irrigation in the lower valley of the river

Negro, Patagonia, Argentina. The experimental design consisted of 3 blocks with randomized treatments (subplots),

each one corresponding to different plant density. The treatments were sown in rows with spacing of 0.70 m (one row per

ridge) and others with a spacing of 0.35 m (two rows per ridge). The plant densities evaluated were: 70,800 – 84,200 –

97,700 – 116,000 – 114,000 – 225,300 and 394,000 plants ha-1. Different biometric variables and their components were

measured: plant height, number of leaves, biomass and economic yield. The results suggest that the optimum plant

density was 116,000 plants ha-1 with a row spacing of 0.70 m. This density produces an adequate plant stand from which

to harvest optimal biological and economical yields. The contributions of this study demonstrated the potential of the

A. cruentus crop in the lower valley of the river Negro, representing the southernmost study of plant density made for

this pseudocereal in the world.

93 - 99

Detection of foliar diseases using image processing techniques

affected area; black Sigatoka; Phytophthora infestans; yellow Sigatoka.

This paper presents the development of a methodology to detect the percentage of affected area of Phytophthora

infestans disease in tomato plants, using digital image processing techniques to extract the regions of interest with

color analysis, where the YIQ and TSL models for the detection of the disease. The method consists of solving one of

the most common problems in images that is segmentation, in this case the background and the disease with the Plant

Village database, which was captured under uncontrolled lighting conditions. In the experiments conducted, it is

observed that our method achieved a performance of 98.60% for the detection of healthy pixels and 98.17% in detection

of sick pixels. This process was subjected to comparison against other alternatives of the state of the art like K-means

with HSV and LAB, showing a referred error regarding the leaf size of 4.32 ± 5.44% in the detection of the disease and

a computational time of 0.03 ± 0.01 [s] in comparison with the other procedures, in addition, this methodology was

implemented to detect the foliar diseases black Sigatoka and yellow Sigatoka in banana leaves obtaining satisfactory

results.

100 - 110

The production of ornamental pineapple in pots under different drip-irrigation depths

Ananas comosus var. erectifolius; ornamental plants; potted plants.

The objective of this work was to evaluate the effects of irrigation depth on the commercial production of ornamental

pineapple in pots. The experiment was carried out in a greenhouse located in Fortaleza, in the state of Ceará, Brazil. The

experimental design was completely randomised, with five treatments and four replications. The treatments were

irrigation depths estimated at 50, 75, 100, 125, and 150% of the evapotranspiration of a crop of edible pineapple. The

plants were grown in one litre pots, with supplementary irrigation every two days. The variables evaluated were:

number of leaves; length and width of the ‘D’ leaf; diameter of the rosette; plant height; rate of flowering; length and

diameter of the peduncle, syncarp and crown; crown to syncarp ratio; commercial productivity and water-use efficiency.

An increase in irrigation depth produced a linear increase in the number of leaves, width of the ‘D’ leaf and rosette

diameter, but had no effect on the other variables. Water-use efficiency decreased linearly with the increases in

irrigation depth. Despite influencing leaf growth, each irrigation depth results in plants suitable for commercialisation

in pots. The smallest irrigation depth gives the greatest economy and water-use efficiency.

111 - 118

Evaluation of the injuries caused by Pachycoris torridus (Scopoli, 1772) (Hemiptera: Scutelleridae) in Jatropha curcas (Linnaeus) (Euphorbiaceae)

bug of the Jatropha; plant growth; photochemical efficiency; accumulation of biomass.

The Jatropha curcas species is a perennial plant and easy to manage, being cultivated in many countries because

of its high content in oil and the lowest cost of production. This study had as objective to evaluate the injuries caused

by the Pachycoris torridus in J. curcas seedlings. Thirty-four days after the planting, 30 J. curcas seedlings were

covered with screens and submitted to herbivory of five bugs of the same sex. Morphological and physiological

evaluations were conducted 65 days after planting. Seventy-three days after planting, 24 seedlings were submitted to

herbivory, using the same methodology as the previous experiment with a quantitative differential of 10 bugs and a

batch of 6 plants without insects (control). Evaluations were done 104 days after planting. Male adults (n = 5) of the P.

torridus species caused a reduction in the growth and biomass increase in J. curcas seedlings 34 days after planting.

After 30 days of herbivores, however the same injuries were not observed in seedlings with 73 days after planting. The

injuries (34 days after planting) were considered mild and there was a decrease in the growth and in the biomass

accumulation. Upon reaching 73 days after planting, the seedlings became more resistant to the attack of this pest, in

such a way that as submitting them to twice the number of insects (n = 10), they did not negatively responded to the

herbivory. Finally, the young seedlings were more susceptible to attack, even with low levels of infestation. The pest

control should be done when there are signs of infestation at this stage.

119 - 125

Quantitative and qualitative damages of Oebalus poecilus on irrigated rice in southern Brazil

RGA 424 RI; Oryza sativa Linnaeus; rice stink bug; IPM; insect plant interaction.

Oebalus poecilus is one of the most important pests of irrigated rice in Brazil. However, the impact of this species

on the cultivar IRGA 424 RI, which is the most used, is unknown. Hence, the objective of this work is to evaluate the

damage caused by O. poecilus on cv IRGA 424 RI. Panicles of this cultivar were infested for seven days at the R5 stage,

using a randomized block design, considering the following factors sex, insect reproductive stage and insect density

(number/panicle). In order to analyze the effect of these factors, the qualitative and quantitative damage caused by

stink bugs to panicles were evaluated. An interaction was found between the sex and developmental stage for quantitative

variables, in which reproductive females were responsible for increasing the damage in comparison to pre-reproductive

females and the males, while the greatest qualitative damage was caused by reproductive insects regardless of sex and

by females, despite the reproductive stage. Density of only one infesting insect has already increased the qualitative

damage, while significant losses on the weight of the grain were verified with the infestation of two insects, demonstrating

that IRGA 424 RI is susceptible to the attack of these stink bugs.

126 - 132

Performance of ‘William’s’ pear grafted onto three rootstocks

Pyrus communis Pyrus calleryana quince vigor production

Pears are the most imported fruit from Brazil and thus, being an important opportunity to Brazilian growers. However,

there are still some problems that restrict pear production, such as the lack of suitable rootstocks. The aim of this study

was to assess growth, yield efficiency and fruit quality of ‘William’s’ pear grafted on quinces ‘Champion’ and ‘Melliforme’

and P. calleryana. The experiment was performed during 2009/2010 growing season at the Centro Agropecuário da

Palma, FAEM/UFPel. The experimental design was a completely randomized block with three replications per treatment.

The assessed parameters were trunk cross sectional area, shoot length, yield efficiency, number of fruit per tree, soluble

solids, flesh firmness, fruit weight and fruit size. It was found that ‘William’s’ pear is more efficient and less vigorous

when grafted on ‘Champion’ quince, thus being a potential scion x rootstock combination for commercial pear planting

at medium densities. Moreover, fruit of trees grafted on quince rootstocks accumulated higher amount of soluble solids.

133 - 136

Fruit quality and occurrence of mildew in Niagara Rosada grown under plastic cover and defoliation rates

Vitis labrusca L.; plasticulture; leaf pruning; Plasmopara viticola.

The purpose of this study was to evaluate the agronomic behavior of the Niagara Rosada variety cultivated under

plastic cover, using defoliation intensities, and its influence on the Plasmopara viticola. The experiment was conducted

in Francisco Beltrão, PR, Brazil, in a vineyard of Niagara Rosada variety in a trellised system during the 2016/2017 and

2017/2018 crop seasons. The experimental design consisted of randomized blocks, in a 5 x 2 factorial scheme being five

percentages of defoliation (0%, 10%, 20%, 30% and 40%,) and use of coverage (with and without coverage), with three

blocks of three useful plants per experimental plot. The temperature, air humidity and incidence of mildew on the

bunches and leaves were recorded. At the end of each crop station, three bunches per plant of each plot were evaluated

for the fresh biomass of the bunches, length and width of the bunches, soluble solids content, pH, number of bunches

per plant, production, and productivity. It was concluded that the plastic cover associated with the environmental

conditions, and phytosanitary management can favor the physical-chemical quality and reduce the severity of the

mildew in the Niagara Rosada variety providing greater production and productivity. The use of defoliation does not

favor the cultivation of this variety in southwestern Paraná.

137 - 146

Scolytinae species damaging Carya illinoinensis trees in southern Brazil

Forest Entomology; pest management; pecan

This study aims to report two species of Scolytinae that have been damaging Carya illinoinensis trees in southern

Brazil. In two Brazilian municipalities, Guarapuava in Paraná State and Pantano Grande in the Rio Grande do Sul State,

insects of the Scolytinae family were found damaging pecan trees. Infested tree samples were kept in the laboratory in

glass tubes sealed with a voile tissue until the emergence of adults. After the adults’ emergence, the specimens were

identified by their morphological characteristics and sent to a taxonomist specialized in Scolytinae family for

identification. The species Xyleborus retusus was identified causing damages to pecan trees from Guarapuava while

the species Xyleborus ferrugineus was identified in pecan trees from Pantano Grande. Trees injured by these insects

displayed similar symptoms in both study areas. In Guarapuava and Pantano Grande, 13 and 10 trees, respectively, died

due to stem lesions caused by Xyleborus spp. Thus, this study reports for Brazilian pecan growers the occurrence of

Scolytinae species X. retusus and X. ferrugineus damaging C. illinoinensis plants in southern Brazil. It also emphasizes

the importance of constant crop monitoring to minimize the risk of pest damage.

147 - 151

Avocado: Is it possible to produce two seedlings with one seed?

Persea americana Mill.; propagation; rootstocks; multiple stems

It was evaluated the possibility to produce two seedlings per avocado seed, through the separation of cotyledons.

Two seed lots from two different ungrafted trees were evaluated. From the first tree were obtained 60 seeds, and 50 from

the second. Half the seeds of each lot had their cotyledons separated and then whole seeds and half-seeds were sown

in river sand. At 90 days after sowing, percentage of germinated seeds, shoot height, main root length, fresh and dry

mass of shoots, roots and cotyledons were evaluated. From the first lot of seeds, there was 100% germination, both for

the whole seeds and for the half-seeds. For all traits evaluated, higher mean values were observed for seedlings formed

from whole seeds. In the second lot of seeds, 88% of germination was observed for whole seeds and 82% of germination

for half-seeds. In this second lot, there were no significant differences between the seedlings formed from whole seeds

and half-seeds for any of the characteristics evaluated, except for fresh and dry mass of cotyledons. Thus, it is possible

to produce two seedlings or rootstocks with a single avocado seed, although this may slightly delay the development

of the seedlings

152 - 155

Determination of the grapevine virome by high-throughput sequencing and grapevine viruses detection in Serra Gaúcha, Brazil

RT-qPCR; HTS; NGS; Vitis; indexing; survey

Among grapevine (Vitis spp.) pathogens, viruses stand out, considering that this fruit plant is broadly susceptible

to them and that they cause several diseases, reducing quality and yield of grape production. However, detecting and

identifying viral infections in grapevines can be challenging. The objectives of this study were to detect grapevine

viral pathogens by high-throughput sequencing (HTS) and identify grapevine viruses associated with plant propagation

material from different origins. A comprehensive picture of a vine exhibiting virus-related symptoms was generated.

The detected virome included four different pathogens and their variants. In addition, the incidence of seven viral

pathogens was determined in samples collected in three vineyards of the main grape-growing region of Brazil. It is

suggested that the observed infections could be related to the technological level of the production system adopted

by these grape growers.

156 - 163