Content uploaded by Eugenio Cozzolino
Author content
All content in this area was uploaded by Eugenio Cozzolino on Oct 15, 2016
Content may be subject to copyright.
Atti del XLV Convegno della Società Italiana di Agronomia Sassari, 20-22 Settembre 2016
134
Effects of Trichoderma on Growth and Nitrogen Uptake
of Lettuce (Lactuca sativa L.)
Nunzio Fiorentino1, Armando De Rosa1, Laura Gioia1, Mauro Senatore1, Donato Visconti1,
Lucia Ottaiano1, Vincenzo Cenvinzo1, Eugenio Cozzolino2, Youssef Rouphael1, Sheridan
Woo1, Mauro Mori1, Massimo Fagnano1
1Dip. di Agraria, Univ. di Napoli Federico II , IT, nunzio.fiorentino@unina.it
2 Consiglio per la ricerca in agricoltura e analisi dell’ economia agraria, Laboratorio di Caserta, IT.
Introduction
N fertilizer excess can cause the accumulation of high levels of nitrate in leafy vegetables, mainly when
grown under reduced light levels, exposing consumers to important health risks (EFSA, 2008).
Appropriate agronomic practices can limit nitrate accumulation in vegetables, while producing optimal
yields with low N inputs. Plant-microbial interactions play an important role in nutrient cycling, allowing
plants to grow in nutrients depleted zones (Marschener, 1994) and reducing its accumulation under high
nutrients conditions (Azcòn, 2003). In this study Trichoderma spp. were tested as bio-stimulators of plant
(Lactuca sativa L.) growth in different N availability conditions. The effect of inoculation on total-N and
nitrate accumulation in the vegetable was also investigated.
Methods
The experiment was carried out from February 2nd to March 31st 2016 in a 240 m2 polyethylene
greenhouse in Portici (Campania region, Southern-Italy). Lactuca sativa var. iceberg cv. Silvinas was
transplanted in double rows with a density of 11 pt m2. An optimal fertilization of 90 kg N ha-1 (100N)
was compared to a non-fertilized control (0N) and an excess N-dose of 180 kg N ha-1 (200N). Two
Trichoderma strains (T. harzianum T22 and T. virens GV41, labelled as T1 and T2 respectively) were
compared to a non-inoculated control (T0). A split-plot design with three replicates (randomized blocks)
was adopted with fertilization (3 levels) as main factor and Trichoderma inoculation (3 levels) as sub-
factor. A spore suspension (concentration 1 x 107spml-1) of Trichoderma was used for lettuce inoculation
at transplant (root dip) and during the crop cycle (24 days after transplant, by watering 50 ml plant-1).
Total yield, number of leaves, SPAD index (SPAD-502; Minolta Corp. Ltd, Osaka, Japan), leaf area (LI-
3100 C Area Meter; LI-COR Lincoln, NE, USA), nitrate and total N in leaves were measured at the end
of the cropping cycle. The leaf thickness index was calculated as the ratio between leaf dry weight and
leaf area. All data were subjected to ANOVA and means separated according to LSD test (p<0.05).
Results
The optimal N dose (100N) increased the yield by 71% compared to non-fertilized control (0N), while
the excess-dose (200N) did not increase yield compared to 100N (Fig.1a). Trichoderma significantly
enhanced plant growth both with 0 N and 100 N fertilization, regardless of the strains. The corresponding
effect of Trichoderma on fresh weight, decreased with increased doses of N (Fig.1a) coherently with
findings from Bal et al. (2008) and Harman (2000), indicating a higher effect of Trichoderma under
suboptimal N conditions. Moreover, Trichoderma spp. augmented the yield by 25% in 0N and 14% in
100N, regardless of strain type, whereas in 200 N no increase was recorded. Furthermore, the quality of
lettuce was positively affected by Trichoderma, whereby both in 0N and 100N fertilization, strain T2
enhanced the leaf thickness, one of the most important quality standards evaluated for lettuce iceberg
(Fig.1b).As expected, SPAD index values (Fig.1c) were found higher for high N input with no difference
between 100N and 200N. Nitrate content in leaves ranged between 185 - 422 mg NO3- kg-1 (fresh weight
basis), significantly lower than the maximum threshold of nitrates (2500 mg NO3- kg-1) recommended
by Commission Regulation (EC) No 1881/2006 for food contaminants. As shown in Fig.1c, at 200N
fertilization, the T1 inoculation reduced NO3-content in leaves. We can exclude a dilution effect due to
Atti del XLV Convegno della Società Italiana di Agronomia Sassari, 20-22 Settembre 2016
135
an increase of plant biomass, since yield of inoculated plants was not different from control. Probably,
higher mineral N surplus of 200N fertilization increased bioassimilation/biodegradation of soil N by
Trichoderma and soil microbes reducing N availability to lettuce (Azcòn et al, 2003).
Conclusion
An excessive N fertilization does not provide any yield benefit, but it could increase the risk of N
accumulation in leaves, N volatilization and contamination of groundwater.
Trichoderma could be a useful tool to increase crop performance of lettuce in soils with a low N fertility
or under low and conventional N input management. In addition, plants treated with T. virens strain
GV41 developed a greater leaf thickness that corresponds to increased crispness, and improved quality
of lettuce cv. Iceberg for salads.
The T. harzianum strain T22 was effective in reducing NO3-content in lettuce under excess-N
fertilization, suggesting that this strain could be useful for preserving lettuce quality in cropping systems
with high N fertile soils. On the other hand, Trichoderma could allow the use of reduced fertilizer
applications and optimize N use efficiency, minimizing at the same time the risk of dietary nitrate
exposure and their potential negative effects in the environment (Lopez et al., 2015).
References
Azcón R. et al. 2003. Nutrient acquisition in mycorrhizal lettuce plants under different phosphorus and nitrogen
concentration. Plant Science, 165.5: 1137-1145.
Bal U. and Altintas S. 2008. Effects of Trichoderma harzianum on lettuce in protected cultivation. Journal Central
European Agriculture Vol.9 1: 63-70
EFSA, European Food Safety Authority. 2008. Nitrate in vegetables. Scientific Opinion of the Panel on Contaminants in
the Food chain. The EFSA Journal 689: 1-79.
Lopez-Bucio J. et al. 2015. Trichoderma as biostimulant: exploiting the multilevel properties of a plant beneficial
fungus. Scientia Horticulturae 196: 109-123.
Marschner H. and Dell B. 1994. Nutrient uptake in mycorrhizal symbiosis. Plant Soil, 159: 89-102.
Figure 3 a) Effect of Trichoderma x fertilization on lettuce fresh weight (g pt-1; b) Effect of Trichoderma x fertilization on
leaves thickness; c) Effect of fertilization on SPAD Index; d) Effect of Trichoderma on nitrate content (mg kg-1) of leaves in
200N Columns with different letters are significantly different (p<0.05). 0N: not fertilized; 100N: 90 kg N ha-1; 200N: 180 kg
N ha-1; T1: T22 strain; T2: GV41 strain
d
c
a
b
