Agriculture Reference
In-Depth Information
Figure 12. Effect of addition of lysine at a rate of 1mg g-1 together with different BCAs on bacterial
wilt of tomato. Data are means ±SE of triplicates.
Even at a rate of 0.25 mg g
-1
pumice, lysine addition significantly suppressed bacterial wilt if
it was added at the same timing as the inoculation of the pathogen. When the pathogen was
firstly inoculated and lysine was added one to two weeks later, no disease suppression was
observed by lysine. In 2006, tomato was grown using the same 0.05 m
2
pot, the same
conditions as 2005 experiment, to which lysine was added at a rate of 0.25 mg g
-1
at the
seeding and two weeks intervals after that, together with a biocontrol agent K20. A single
inoculation of K20 significantly decreased bacterial wilt incidence and a combination of K20
and lysine and the addition of only lysine further decreased bacterial wilt incidence. The
tendency was supported by tomato growth and yield. Tomato yield was about 2500 g plant
-1
in control(-), K20, K20+lysine and lysine plots and 1400 g plant
-1
in control(+) and the
difference was highly significant. This absolute yield was not so high in terms of commercial
level, but this is considered due to our not-sophisticated cultivation technique. An important
result was considered that the yield of lysine, K20 and K20+lysine plots was not different
from that of control(-), suggesting little inhibitory effect of these treatments on tomato yield.
This was further supported by the quality of tomato evaluated by sugar, lycopene and vitamin
C contents: there was no significant difference in the parameters between control(-) and
lysine, K20 and K20+lysine plots. The cost of lysine was calculated to be 100 yen (0.8 $) per
plant when lysine is added to each plant at a rate of 0.25 mg g
-1
every two weeks during 24
weeks. But this cost is based on the price of 4,300 yen (35.8$) per 500 g of the reagent lysine
(special grade, Wako Pure Chemical Industries, Osaka, Japan). In contrast, alternative lysine
for an additive of pig fodder costs only 500 yen (4.2$) per 1 kg (personal communication),
and its effect on bacterial wilt is now under investigation in comparison with pure lysine.
These results suggested that lysine addition to pumice every two weeks markedly suppress
bacterial wilt and does not inhibit tomato growth and yield. Therefore, it was concluded that
lysine may be an effective and economical means by which bacterial wilt be controlled in
hydroponics.
