Potential Physiological Frameworks for Mid-Season Field Phenotyping of Final Plant Nitrogen Uptake, Nitrogen Use Effi ciency, and Grain Yield in Maize

Improved phenotyping tools for simultaneously characterizing maize (Zea mays L.) genotypes with superior grain yield (GY) and N use effi ciency (NUE) would be benefi cial for breeding progress. Possible phenotypic predictors of the crowding intensity and N availability effects on maize plant N uptake, GY, and NUE were evaluated for different genotypes in two environments. Our objectives were to develop phenotyping framework tools to predict plant N uptake, GY, and NUE via (i) identifi cation of important mid-season morpho-physiological traits (from a total of 80 parameters), (ii) assessment of correlations between predictive traits (principal component analyses identifi ed 21 traits), and (iii) arrangement of key traits into sequential pathways of mechanistic functions (3 traits). Plant phenotyping measurements taken during vegetative stages were poor predictors of GY and NUE. Plant N status at silk emergence was strongly associated with grain components. At silking, the chlorophyll contents (Soil Plant Analysis Development [SPAD] readings) were highly correlated to leaf N concentration, and the latter with the N nutrition index (NNI). As expected, NNI fairly refl ected plant N uptake at silking and correlated well to relative GY. Maize plant biomass and N uptake at maturity were predicted via stem volume estimation at silking. The latter predictive model accurately simulated both GY and NUE in other fi eld experiments. Physiologically based frameworks for midseason prediction of maize GY and NUE require further testing but hold promise. I.A. Ciampitti and T.J. Vyn, Agronomy Dep., Purdue Univ., 915 W State Street, West Lafayette, IN 47907-2054; H. Zhang, Dep. of Forestry and Natural Resources and Dep. of Statistics, Purdue Univ., 536 Mathematical Science Building, West Lafayette, IN 47907-2054; P. Friedemann, Dow Agrosciences, Mycogen Seeds, 2310 County Road 1050N, Homer, IL 61849. Received 17 Mar. 2012. *Corresponding authors ([email protected]; [email protected]). Abbreviations: %N, N concentration; %Nc, critical N concentration; 0N, 0 kg N ha−1; 90N, 90 kg N ha−1; 112N, 112 kg N ha−1; 146N, 146 kg N ha−1; 165N, 165 kg N ha−1; 202N, 202 kg N ha−1; 224N, 224 kg N ha−1; 330N, 330 kg N ha−1; ACRE, Purdue University Agronomy Center for Research and Education; BE, ear biomass; BM, biomass; CRM, comparative relative maturity; E, environment; G, genotype; Gl, number of green leaves; GY, grain yield; GYA, grain yield per unit area; HI, grain harvest index; Kn, kernel number; Kw, kernel weight; LAI, leaf area index; LAId, reduction in leaf area index expressed as a proportion of the maximum attained at silking time; NE, ear N uptake; NIE, N internal effi ciency; NLAI, N content per unit of leaf area index; NNI, N nutrition index; NRE, N recovery effi ciency; NUE, N use effi ciency; PCA, principal component analysis; PH, plant height; RGY, relative grain yield; RSDR, robust standard deviation of the residuals; STD, stem diameter; Sink:Source; relationship between the fi nal kernel number (sink) achieved at R6 stage relative to the leaf area index (source) at R1 stage; SPAD, Soil Plant Analysis Development. Published in Crop Sci. 52:2728–2742 (2012). doi: 10.2135/cropsci2012.05.0305 © Crop Science Society of America | 5585 Guilford Rd., Madison, WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.