RELATION BETWEEN DRYING RATES AND MYCOTOXINS CONTAMINATION IN LATE SOWN MAIZE.

ESPÓSITO MA; FERRAGUTI, F.

BIOCELL

INST HISTOL EMBRIOL-CONICET

Año: 2021 vol. 45 p. 8 - 9

0327-9545

Maize grain innocuity can be affected by the presence of mycotoxigenic fungi of Fusarium Genus producing fumonisins (FBs), zearalenons (ZEA) and deoxinivalenol (DON) and Aspergillus Genus producing aflatoxins (AFL). The tolerable levels in grains recommended by the WHO are 2000ppb for FBs; 1000 ppb for DON, 100 ppb for ZEA and 20 ppb for AFL. Recent studies in the Rolling Pampas Region showed different susceptibility of hybrids to ear pathogens and proposed that extended field drydown could increase mycotoxin content. Drying of late sown maize from physiological maturity (MF) is typically described with a bilinear pattern. In the first phase (F1) the loss of moisture is rapid due to the greater difference between the water content of the grain and the atmospheric demand. Then, after an inflection point (Pi) a second phase (F2) is observed, where the drying rate is a fraction of the F1 rate. The objective of this work was to determine the relationship between drying rates and mycotoxin content. In order to do so, the drydown parameters obtained in seven commercial hybrids sown in two years with contrasting environmental conditions were analyzed: 2019 (Year1) and 2020 (Year2). The design used was randomized complete blocks with three repetitions. During 100 days after MF, grain moisture (% H) was determined on a weekly basis. The samples at two harvest moments (MC), Pi and at the end of F2, were ground and mycotoxins content was determined by NIR spectroscopy (Pegasus®). A correlation analysis was carried out using the Pearson test. The rates in F1 and F2 differed from each other, although they were not affected by Year or by hybrid. The differences observed in the length of drydown period were attributed to variations in %H MF and %H Pi. A correlation was found between the %H at MF and the length of F1 (0.64; p = 0.01); and in the same way the %H Pi was correlated with the %H F2 (0.51; p = 0.06). AFL and DON were always found below tolerable levels, like most of the ZEA samples, except for specific cases. With the exception of two hybrids in Pi, all FB samples greatly exceeded tolerable levels. There were significant differences between years for the content of FBs: in Year 1 there was 50% more FBs than in Year 2 (4356ppb). Year x MC interaction was observed for FBs and ZEA. In Year 1 the content of FBs in F2 doubled Pi, while in Year 2 the increase was 20%. In the case of ZEA, in Year1, MC F2 had 50% more than in Pi while in Year2 it was + 13%. A high correlation was found between the content of ZEA and the F1 rate (0.67; p = 0.01) while the final content of FBs was correlated (0.60; p = 0.02) with the length of F1. No correlation was found between drydown parameters and DON or AFL content. The drying rate may be determined by the combination of environmental conditions and morphophysiological characteristics of the hybrids, while mycotoxin content would depend on the susceptibility of hybrids, the presence of inoculum and environmental conditions. The delay in MC increases the mycotoxin content, affecting the innocuity of the grains.