Abstract
The identification of traits associated with drought tolerance in popcorn is a contribution to support selection of superior plants under soil water deficit. The objective of this study was to choose morphological traits and the leaf greenness index, measured on different dates, to estimate grain yield (GY) and popping expansion (PE), evaluated in a set of 20 popcorn lines with different genealogies, estimated by multiple regression models. The variables were divided into three groups: morpho-agronomic traits—100-grain weight (GW), prolificacy (PR), tassel length (TL), number of tassel branches, anthesis-silking interval, leaf angle (FA) and leaf rolling (FB); variables related to the intensity of leaf greenness during the grain-filling period, at the leaf level, measured by a portable chlorophyll meter (SPAD) and at the canopy level, calculated as the normalized difference vegetation index (NDVI). The inbred lines were cultivated under two water conditions: well-watered (WW), maintained at field capacity, and water stress (WS), for which irrigation was stopped before male flowering. The traits GY (55%) and PE (28%) were most affected by water restriction. Among the morpho-agronomic traits, GW and PR were markedly reduced (>10%). Under dry conditions, the FA in relation to the plant stalk tended to be wider, the FB curvature greater and leaf senescence accelerated (>15% at 22 days after male flowering). The use of multiple regression for the selection of predictive traits proved to be a useful tool for the identification of groups of adequate traits to efficiently predict the economically most important features of popcorn (GY and PE). The SPAD index measured 17 days after male flowering proved useful to select indirectly for GY, while, among the morphological traits, TL stood out for the same purpose. Of all traits, PR was most strongly related with PE under WS, indicating its use in breeding programs. The exploitation of these traits by indirect selection is expected to induce increments in GY and PE.
Highlights
The following scientific question arise: (i) Which of the trait(s) associated with drought stress is most appropriate for the indirect selection of drought-tolerant popcorn germplasm? The objective of this study was to select spectral vegetation indices, such as the greenness index (SPAD) and the Normalized Difference Vegetation Index (NDVI) of the canopy in popcorn lines from different geographic origins in the Americas, to predict the grain yield and popping expansion using model selection based on multiple regression
Under WW conditions, the mean grain yield was 2548.07 kg ha−1 compared to 1139.11 kg ha−1 under water stress (WS)
On the other hand, considering another set of variables, FB was selected in Model 4 (PE under WW); with a low coefficient, low relative importance and low R2 in simple regression, indicating an ineffectiveness in indirect selection, FB is recommended to be used separately
Summary
Soil water restriction, caused by the irregular distribution of rainfall during the growth and development of agricultural crops, has a strong impact on yield [1,2,3,4]. Yield losses caused by drought events have become recurrent [5,6,7] and to find measures to minimize them is a challenge nowadays for global agribusiness and, in particular, for Brazil, where agriculture is a key component of the economy [8]. The impact of water restriction depends on the intensity and duration of a dry spell, as well as on the phenological stage of the plant when it occurs [1]. The grain yield was strongly reduced when the water stress coincided with the phenological stages flowering and grain filling [1,9]
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