| Abstract | Simbiozni odnos kvržičnih bakterija i mahunarki ima važnu ulogu u poljoprivrednoj proizvodnji. Veliku važnost ima odabir sojeva koji su otporni na stresne uvjete u tlu. Danas se sve više susrećemo s ekstremnim vremenskim uvjetima te je od velike važnosti selekcija visoko učinkovitih sojeva kvržičnih bakterija, kako bi predsjetvena bakterizacija sjemena mahunarki bila uspješna. Glavni cilj rada je utvrditi fenotipske karakteristike sojeva kvržičnih bakterija izoliranih iz kvržica soje u uvjetima koji su izvan optimalnih vrijednosti za njihov rast. Sposobnost rasta sojeva istražen je na različitim pH vrijednostima, temperaturama, koncentracijama soli, izvorima ugljikohidrata i testirana je osjetljivost na određene antibiotike. Provedena su oksidaza, ureaza, i katalaza testovi, ispitana je mobilnost fosfata, sposobnost korištenja citrata te hidroliza škroba. Istražene su morfološke karakteristike izolata, te otpornost na fitopatogene gljive iz roda Phomopsis. Uzorci tla za izolaciju sojeva su prikupljeni s područja Koprivničko – križevačke, Bjelovarsko – bilogorske i Vukovarsko – srijemske županije. Istraživanjem je obuhvaćeno 18 izolata simbioznih fiksatora dušika soje, te pet tipskih i jedan referenti soj. Utvrđeno je da su svi ispitani izolati gram negativne, štapićaste bakterije koje ne sadrže kapsule. Rezultati su pokazali da većina ispitanih izolata tolerira rast u lužnatim i kiselim sredinama te mogu rasti na temperaturi od 37 °C. Svi izolati pokazali su dobar rast na različitim izvorima ugljikohidrata (galaktoza, laktoza, dekstroza, saharoza, maltoza, rafinoza i fruktoza), dok su referentni sojevi većinom pokazali znatno slabiji rast. Izolati sa područja Koprivničko – križevačke županije jedini su pokazali mogućnost rasta na podlogama koje sadrže značajno povećani sadržaj soli (1 %, 2 % i 3 % NaCl-a). Oksidaza testom dokazano je da 40 % izolata posjeduje enzim citokromoksidazu. Sve bakterije koje posjeduju enzim citokromoksidazu koriste kisik kao terminalni akceptor elektrona u disanju. Sposobnost hidrolize škroba pokazalo je 60 % ispitanih izolata.
Jedan od osnovnih problema koji donosi povećanje površina i intenzivna proizvodnje soje svakako je problem bolesti i to prije svega bolesti uzrokovanih fitopatogenim gljivama na koje otpada oko 80 % svih bolesti soje. U istraživanju antagonističke aktivnosti izolata prema pojedinim gljivama 6 od 18 izolata pokazalo otpornost na fitopatogene gljive iz roda Phomopsis. Dobiveni rezultati ukazuju na značaj selekcije autohtonih sojeva. |
| Abstract (english) | The symbiosis of nodule bacteria and legumes plays a very important role in agricultural production. It is essential that the highly effective strains that are resistant to various unfavorable conditions in the soil are chosen. Today we are increasingly faced with extreme weather, so the selection of highly efficient strains of rhizobia is of great importance to the success of legumes seed inoculation.
The aim of this study is to determine the phenotypic characteristics of nodule bacteria isolated from soybean nodules under conditions that are beyond the optimum value for their growth. The growth of the strains was studied at different pH values, temperatures, concentrations of salts, carbohydrate sources and resistance to antibiotics. The oxide, the urease, and catalase of test and of phosphate mobility were made. Furthermore, the ability to use citrate and starch hydrolysis was investigated. The resistance to phytopathogenic fungus isolates from genus Phomopsis and the morphologic characteristics were performed as well. The soil samples were collected from the counties Koprivničko – križevačka, Bjelovarsko – bilogorska and Vukovarsko – srijemska. Eighteen isolates of symbiotic soybean fixators, five types and one referent strain were included in the study.
It was found that all the tested isolates were gram negative, stinging bacteria that did not contain capsules. Most of the tested isolates tolerated alkaline and acidic environment and they can be grown at the temperature of 37 °C. Furthermore, all the isolates showed good growth on different sources of carbohydrates (galactose, lactose, dextrose, sucrose, maltose, raffinose and fructose), and on the other hand, the reference strains showed a much weaker growth. The isolates from the area of Koprivnica - Križevci County were the only ones that showed the possibility of growth on substrates containing significantly increased salt content (1 %, 2 % and 3 % NaCl). Forty percent of the tested isolates possess the cytochrome oxidase enzyme by examining the test oxidase. All bacteria that possess the cytochrome oxide enzyme use oxygen as the terminal electron acceptor in breathing. The ability of starch hydrolysis showed 60 % of the tested isolates.
One of the basic problems which occurs more intensive soybean production is definitely a disease problem. First of all, diseases were caused by phytopathogen funguses, causing about 80 % of all soybean disease. In the study of the antagonistic activity of isolates, according to individual funguses, 6 of all 18 isolates showed the resistance to the phytopathogen funguses Phomopsis. The obtained results indicate the importance of selection of autochthonous strains. |
