Senescence and yield responses to plant density in stay-green and earlier-senescing maize hybrids from Argentina

ANTONIETTA M; FANELLO D.D; ACCIARESI HA; GUIAMET J.J

FIELD CROPS RESEARCH

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2013 vol. 155 p. 111 - 119

0378-4290

Increases in maize (Zea mays L.) yield over the past few decades have been associated with breedingfor tolerance to progressively higher plant densities. Since high plant density exacerbates interplantcompetition, it has been suggested that improved resource capture through delayed senescence might beadvantageous in such situations. The main objectives of this work were to determine (1) the time-courseof canopy senescence, (2) post-silking C and N accumulation and (3) yield responses of contemporarymaize hybrids with different expression of the stay green (SG) character grown in a range of plant densitiesfrom moderate to intense crowding stress. Three experiments consisting of a combination of differentplant densities (from 6 to 10 pl m−2) and commercial hybrids with different timing of senescence werecarried out. High density accelerated leaf senescence at the lower canopy layer. The SG hybrids delayedsenescence and retained green leaves at physiological maturity at all tested densities. One of these hybrids(NK880), with a strong SG character, retained green leaves at all canopy layers, even at the lower layerexposed to limiting irradiance. Lower canopy leaves maintained high respiratory rates in NK880, whileleaves of the NSG hybrid (DK682) senesced and their respiration became not detectable. At the highesttested density, the NSG DK682 achieved greater grain yields than the SG NK880. Increased density reducedkernel weight (KW), and this decrease was more pronounced for the SG NK880 (6?18% comparing 10vs. 8 pl m−2). In spite of delayed senescence in NK880, no hybrid differences were found for post-silkingdry matter accumulation and plant dry matter at physiological maturity. Unexpectedly, plant nitrogencontent (Nc) at harvest was similar (Exp. I) or even lower (P < 0.05, Exp. II) in the SG NK880. This was theresult of lower net N accumulation during the post-silking period (Exp. I) or lower Nc achieved at silking(Exp. II) in the SG NK880. A strong positive relation was found between KW and N concentration in kernels,with %N in kernels being below the critical N concentration to achieve potential KW (around 1.4%) in theSG hybrid. This suggests that yield in NK880 was limited by N. In the SG genotype, N remobilization fromvegetative organs did not seem to compensate for the N deficit for optimum grain growth. In summary,at high densities the NK880 hybrid displayed a strong, constitutive SG character, even if it accumulatedless N, and senescence delay was not reflected in higher grain yield.