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Results and
discussion
Yield in each treatment is presented in Table1.
The great effect of Septoria nodorum blotch was shown on the yields
of natural seeds with reduction in 37% in 1989 and 14% reduction in
1990 in the plot of artificial infection. Unfavourable climate
conditions for development of this disease were the reason for that
the yield in 1990 was increased tremendously than that in
1989. The fungicide treatment alleviated the effect of the disease on
yield. These results agree with those reported in the previous
investigations (Koric 1980, 1987a). The results also indicate that
the effect of this disease on yield could not be completely
eliminated with one treatment at early heading stage, maybe because
climatic conditions were favourable for the development of the
disease under natural conditions. This disease also reduced the yield
of processed seed to 52% and 81% without and with the treatment of a
fungicide in relation to the check, respectively, in 1989. Percentage
of discarded seeds was 23% higher than that of the check when wheat
was severely infected with Septoria nodorum blotch. One treatment of
a fungicide resulted 11% lesser discarded seeds than those in the
check. Such reduction in discarded seeds can easily be explained by
the effect of fungicide which protect upper leaves from disease
attack, thus providing normal vegetative condition of the plant and
kernel formation
Table
2 gives the yield
classified by a share of each grade for each treatment in year 1989.
Percentage of grades that passed through opening lesser than 2.2 mm
(discarded seed) was far greater in the plots of artificial
infection than in other two treatments. A similar ratio was
observed with a share of grade 2.2 mm. Share of grades with screen
perforations 2.5 mm was more or less identical in all treatments,
whereas the one with perforations 2.8 mm was the markedly highest in
the cheek. Based on this investigation and all others carried
out up to now in our Institute, we concluded that Septoria nodorum
blotch affects kernel size and hence, directly seed quality.
Comparing the results of Table1
and Table
2, ie, the
results obtained after processing and grading mean sample (1 kg) of
the same seed, virtually the same ration of high and low-quality seed
was obtained for all the treatment examined, when kernels smaller
than 2.5 mm were classified as lowquality, and those above 2.5 mm as
high quality seed. Significantly different rations in seed grades
over 2.5 mm were observed among the treatments, namely 67%, 76.5% and
83% in artificial infection, fungicide application and natural
infection, respectively, which were much higher percentages than
smaller seed grades of 2.5 mm. Also is a well-known fact that kernel
size above 2.5 mm provided the highest seed capacity, ie, the highest
productivity which is a result of kernel size or absolute seed
weight.
Results of testing sanitary condition of the seed for each treatment
showed that endosperm infection with Leptosphaeria nodorum
were from 7 to 71% which depends on year and treatments
(Table1).
That is the same as the investigation before (Koric1987b). Percentage
of Leptosphaeria nodorum grain infection was
significantly higher in artificially infected plants than those
in the check plot. With one fungicide application, infection was
somewhat less severe, but still very high, 49% and 27% in 1989 and
1990, respectively, and far from Croatia's regulations in which only
seeds up to 3% of infection can be marketed as commodity.
References
Eyal Z, Scharen AL Prescott JM, and Ginkel M van (1987) The
Septoria Diseases of Wheat: Concepts and methods of disease
management Mexico, DF: CIMMYT
Koric B (1980) Cemical control of septoria nodorum blotch in wheat.
Glasnik zastite bilja vol 9 (5): 196-202 (in Croatian).
Koric B (1987a) Investigation of effects some fungicides in control
of Leptosphaeria nodorum causal septoria nodorum blotch.
Proceedings of Yugoslav conference for application of pesticides.
201-203 (in Croatian).
Koric B (1987 b) Investigation of seed-boorn infection with
Leptosphaeria nodorum. Rachis, vol. 6 (l): 44-45.
Mathur SB and Lee Silvia, LN (.1987) A quick method for screening
wheat seed samples for Septoria nodorum. Seed Science and Technology
6: 925-926.
Strona IG and Ubozenko, AG (1970) Importance of bigness seed in seed
production. Selekcija i semenovodstvo 1: 48-51 (in Russian).
Zadoks JC, Chang TT and Konzak CF (1974) A decimal code for the
growth astages of cereals. Weed Research 14: 415-421.
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