Senescencia foliar en maíz: diferencias genotípicas ante cambios en la relación fuente-destino postfloración.

OTEGUI, M.E.; MARTÍNEZ, E.L.; OTEGUI, M.E.

Rosario, Santa Fe, Argentina

Congreso; VIII Congreso Nacional de Maíz.; 2005

A.I.A.N.B.A.

Maize post-silking leaf senescence depends upon the source-sink ratio (SSR) during this stage, but the response is genotype dependent. The objective of this research was to analyze the pattern of leaf senescence (LS) in response to the post-silking SSR in single-cross maize hybrids a priori classified as contrasting for LS. We hypothesize that there is a quantitative rather than a qualitative response. The field experiment conducted at Pergamino (33º56’S, 60º34’W) during 2004-2005 included a factorial combination of two stand densities (8 and 12 pl m-2), six hybrids (only two reported in this paper), and five SSR treatments (1- control with natural pollination; 2- control + ear removal on 12 days after silking; 3; reduced kernel number; 4- reduced kernel number + ear removal on 12 days after silking; 5- pollination prevented). Measurements included silking date of each tagged plant, plant leaf area on silking + 12 days, post-silking LS, shoot biomass production during active grain filling, shoot biomass at physiological maturity, plant grain yield and kernel number per plant (KNP). A common two-phase pattern was determined for post-silking LS, but hybrids differed (P<0.01) in the period required for starting a more active senescence in phase II, and in the rate of senescence during this phase. The response of LS to the SSR treatments was qualitative (i.e. depending on the presence or absence of growing kernels) rather than quantitative (i.e. depending on the variation in KNP), but a strong genotypic effect was observed. The absence of growing kernels promoted (i) a more pronounced LS in AX 610 than in AX 820 (P<0.01), and (ii) the active growth of other sinks (secondary ears) in AX 820 but not in AX 610. These responses were independent of the early (treatment 5) or delayed (treatments 2 and 4) arrest of grain growth in the apical ear. Our results highlight the importance of active growing sinks on maize leaf senescence, independently of the characteristics (grain or non grain) and size (KNP) of these sinks.