Integrated protection from prevalent wheat parasites in semiarid region

Abstract

This paper is aimed at presenting contemporary knowledge in the field of integral wheat protection against parasites, i.e. the use of cultural measures and genetic analyses directed at adequate use of breeding results, monitoring and forecasting of prevalent parasite growth and development with the aim of rational fungicide application. In addition, the paper suggests the proper use of biological measures through artificial infection with Pyrenophora tritici repentis (Ptr) in years not favourable for facultative parasite development. Growing of the varieties not lower than 85 cm with optimal stem growth ratio in regions with 550-650 mm precipitation, deep and complete soil cultivation plus nutrition before sowing in late October reduced the risk of facultative parasite appearance on lower and middle leaves by over 15%, which was considered useful because of the antagonism to obligate parasites. Severity of Puccinia triticina on last two leaves when facultative parasites were absent was increased at 60-70% as maximal level according to suggested SAGR. Nevertheless, we suggest growing of varieties with prolonged latency period resistant to Puccinia triticina. The aim is to avoid overaccumulation of resistance genes consequential through the decrease of wheat grain yielding potential. Genes facilitating toxin from Ptr spreading have to be excluded because of necessary antagonistic effect from the middle leaves. This implies gene for the obligate parasite specific resistance diversity of varieties in order to reduce the probability of simultaneous overcoming of resistance and avoid insurmountable changes in seed production. The final result of the proposed system should be the last two leaves with mostly minimal parasite appearance and the possibility of economical and efficient single curative treatment application once in ten years when facultative parasites are absent in spring or after the resistance of variety is overcome in standard conditions. The practical aim was also dependent on leaf rust development and green leaf area dissapearence forecasting models as well as balance between the size of the farm and equipment due to short deadlines.

Savremena saznanja iz oblasti integralne zaštite pšenice u semiaridnim regionima, odnosno primena agrotehničkih mera i genetičkih analiza u smeru adekvatnog korišćenja rezultata oplemenjivanja te praćenja i prognoze rasta i razvoja prevalentnih parazita radi racionalne upotrebe fungicida uz predlog biološke mere, tj. veštačke infekcije s Pyrenophora tritici repentis (Ptr) u godinama nepovoljnim za razvoj fakultativnih parazita su prikazana u radu. Gajenjem sorti ne nižih od 85 cm optimalnog rasta delova stabla, primenom pune agrotehnike, ishrane i kasnijom setvom smanjena je opasnost od infekcija fakultativnih parazita na donjem i srednjem lišću preko 15% koja je smatrana korisnom usled antagonizma s obligatnim parazitima a povećan je maksimalni mogući intenzitet obligatnih parazita na 60-70% zahvaćenosti gornjih listova. Sugerisano je gajenje sorti s produženim latentnim periodom umesto kompletno otpornih prema prouzrokovaču lisne rđe radi izbegavanja štetnih efekata preakumuliranih gena za specifičnu otpornost na prinos zrna. Sorte efikasne prema širenju toksina Ptr je potrebno isključiti usled obezbeđenosti dovoljnog antagonističkog efekta sa srednjeg lišća. Predloženo podrazumeva različitost gena za navedenu specifičnu otpornost sorti kako bi bila smanjena verovatnoća istovremenog prevazilaženja otpornosti te izbegnute nesavladive promene u semenarstvu. Krajnji rezultat predloženog sistema su dva gornja lista bez parazita i mogućnost ekonomične i efikasne jednokratne kurativne zaštite jednom u deset godina kada fakultativni paraziti izostanu ili nakon prevaziđene otpornosti sorte u standardnim uslovima. Praktična primena predloženih rešenja takođe je zavisna od prognoznih modela razvoja lisne rđe i nestanka zelene lisne površine i usklađenosti veličine i opremljenosti poljoprivrednih gazdinstava usled kratkih rokova.