Bernardo Chaves

GROWTH OF LULO (Solanum quitoense Lam.) PLANTS AFFECTED BY SALINITY AND SUBSTRATE 1

The effects of 0, 30 and 60 mM NaCl and substrates (red peat, sand or 3:1:1 (w/w) mixture of peat, sand, or soil) on vegetative growth of lulo, an Andean fruit species, during 12 weeks were studied. The experiment was carried out by using 2000 cm 3 of polypropylene plastic pots under greenhouse conditions. Plant height, number of leaves and nodes, leaf area, total plant dry matter (DM), and shoot/root ratio were evaluated. With the increase of salt concentration, the plant height, the number of leaves and nodes, the leaf areas and plant dry mass DM decreased, whereas shoot/root ratio increased. Sand grown lulo plants were most affected by salinity and presented total mortality at 60 mM NaCl. On the other hand, plants held either in peat or in substrate mixture developed larger height, greater leaf and node numbers, higher leaf area and dry matter content. Shoot/root ratio in control (soil) and sand-grown plants (30 mM NaCl) was lower. Index Terms: Lulo, naranjilla, salinity, NaCl, plant height, leaf area, dry matter, peat, sand.

Base temperature and simulation model for nodes appearance in cape gooseberry (Physalis peruviana L.)

Data was analyzed on development of the solanaceen fruit crop Cape gooseberry to evaluate how well a classical thermal time model could describe node appearance in different environments. The data used in the analysis were obtained from experiments conducted in Colombia in open fields and greenhouse condition at two locations with different climate. An empirical, non linear segmented model was used to estimate the base temperature and to parameterize the model for simulation of node appearance vs. time. The base temperature (Tb) used to calculate the thermal time (TT, oCd) for node appearance was estimated to be 6.29 oC. The slope of the first linear segment was 0.023 nodes per TT and 0.008 for the second linear segment. The time at which the slope of node apperance changed was 1039.5 oCd after transplanting, determined from a statistical analysis of model for the first segment. When these coefficients were used to predict node appearance at all locations, the model successfully fit the observed data (RSME=2.1), especially for the first segment where node appearance was more homogeneous than the second segment. More nodes were produced by plants grown under greenhouse conditions and minimum and maximum rates of node appearance rates were also higher.

Predicting Key Phenological Stages for 17 Grapevine Cultivars (Vitis vinifera L.)

Weather conditions have a significant impact on crops, and temperature is one of the main factors that controls plant development. Thermal time models based on temperature have been applied to predict the development of many species. To implement these models, determination of an appropriate base temperature (Tb) is required to characterize the differences among developmental stages and cultivars. The goal of this study was to determine the unique Tb and degree-days (DD) to predict budbreak, bloom, and veraison for 17 cultivars. Tb’s were estimated with the minimum variance method using phenological data collected over 23 years in Prosser, WA. Tb increased throughout grapevine development and ranged from 6.1 to 8.4°C for budbreak, from 7.2 to 10.5°C for bloom, and from 9.4 to 12.8°C for veraison. Starting DD accumulation on 1 Jan and using the Tb’s estimated for each cultivar, the duration to budbreak ranged from 78 to 180 DD, from budbreak to bloom ranged from 240 to 372 DD, and from bloom to veraison ranged from 556 to 800 DD. Errors in prediction varied between 4.8 and 7.8 days to budbreak, between 1.9 and 5.5 days to bloom, and between 7.1 and 12.4 days to veraison. Based on the errors in prediction, models that used an estimated Tb specific for a phenological stage performed better than models that had a fixed Tb of 0 and 10°C. The estimated thermal time parameters provide a simple approach for characterizing differences among cultivars and assist growers and industry in implementing management practices through simple decision support tools based on thermal time models.

Use of Cordon Wire Tension for Static and Dynamic Prediction of Grapevine Yield

An automated system was used during three growing seasons to monitor the change in tension (ΔT) in the load-bearing wire of a trellis to estimate yield in vineyards. Actual yield varied nearly four-fold among the three study years, but in each year the fruit was uniformly distributed along the length of the wire. The automated sensor detected sequential harvests up to ~12 m to either side of the sensor, or 24 m total wire length, in a nonlinear fashion. Yield was predicted statically from ΔT at the lag phase (L) of berry growth (ΔTL) and dynamically from continuous output of ΔT. Relationships between ΔTL and yield were linear. Estimated yield was not sensitive to the date of ΔTL, within 10 days. In using the ratio between the current year ΔT and that of a specific previous year, the differences between estimated and observed yields depended upon the choice of predictor year(s), where years with similar ΔT were the most accurate. Across an estimation interval of L to harvest, the precision of dynamic estimates was determined by the similarity in the day-to-day shapes of the double-logistic curves of ΔT over time. Due to a catastrophic frost in the second year of the study, an extremely small crop and an uncharacteristic growth curve made it difficult to predict yield either statically or dynamically. In practice, the method requires a grower to collect multiple years of growth curves from which to build a robust linear relationship between ΔTL and yield (static estimates), or to apply an average of multiple years’ ΔT values dynamically.