OTIORRHYNCHUS LIGUSTICI L. (COLEOPTERA: CURCULIONIDAE) III. MODELING SCALE FOR RESISTANCE IN ALFALFA VARIETIES

DOI: 10.7904/2068 – 4738 – III(6) – 81

Ivelina NIKOLOVA, Nataliya GEORGIEVA

 Abstract: In 2006–2009 period in the experimental field of IFC–Pleven were carried out studies with 8 alfalfa varieties included in the Official variety catalog of Bulgaria (2005): Europe (France), Prista 2 (Obraztsov Chiflik, Ruse), Prista 3 (Obraztsov Chiflik, Ruse), Prista 4 (Obraztsov Chiflik, Ruse), Obnova 10 (IFC, Pleven), Pleven 6 (IFC, Pleven), Dara (IFC, Pleven) and Multifoliate (Obraztsov Chiflik, Ruse). For evaluation of the resistance in alfalfa varieties to Otiorrhynchus ligusticiwas developed 5–graded scale based on the numbers of furrows on the root system. Withthe most strongly pronounced damage and high percentage of plants with score 3, 4 and 5 was distinguished the fourth year in alfalfa cultivation. Asmiddle resistance varieties tothe attack from O. lygusticiwere Europe, Prista 2 and Multifoliate (the index of attack was 21.7, 22.9 and 23.0% respectively) which is important for the selection and practice.

Key words: alfalfa varieties, scale for resistance, Otiorrhynchus ligustici

 

OTIORRHYNCHUS LIGUSTICI L. (COLEPTERA: CURCULIONIDAE) II. METHOD FOR DETERMINATION OF THE DEGREE OF DAMAGE BY LARVA AND BIOCHIMICAL COMPOSITION OF THE ROOT SYSTEM IN DIFFERENT ALFALFA VARIETIES

DOI: 10.7904/2068 – 4738 – III(6) – 75

Ivelina NIKOLOVA, Nataliya GEORGIEVA, Anna ILIEVA

 Abstract: During the period 2006–2009 in the experimental field of IFC–Pleven were conducted studies with 8 varieties of alfalfa included in the Official variety catalog of Bulgaria (2005): Europe (France), Prista 2 (Obraztsov Chiflik, Ruse), Prista 3 (Obraztsov Chiflik, Ruse), Prista 4 (Obraztsov Chiflik, Ruse), Obnova 10 (IFC, Pleven), Pleven 6 (IFC, Pleven), Dara (IFC, Pleven) and Multifoliate (Obraztsov Chiflik, Ruse). For determination of the damage from the large alfalfa weevil Otiorrhynchus ligustici on the root system of plants was developed methodology depending on the root area and the damage area. The area of the roots was calculated by the formula S = (π * d * L) / 2, where π is 3.14; d–diameter of the root collar, L–length of the root. The area of the furrows оn the root system was product of length and width of the furrows. With the lowest percentage of furrows and tolerant to O. ligustici were Multifoliate, Prista 2 and Europe–respectively 10.38, 11.41 and 11.68%. Highly sensitive, with high percentage of damage were distinguished Dara, Prista 4 and Prista 3 (respectively 14.28, 14.05 and 13.58%). As a result of the caused damage the content of sugars and saponins increased as depending on the sensitivity of varieties the increase was different. In the tolerant varieties to the pest the increase in sugar content was less pronounced, but in the sensitive ones–stronger. In regard to the saponins the trend was reversed–the increase in the sensitive varieties was less and in the tolerant varieties–stronger which could be explained with the defensive reaction of plants to compensate the losses from damages of the pest.

Key words: alfalfa, varieties, method of damage degree, biochemical composition, Otiorrhynchus ligustici

OTIORRHYNCHUS LIGUSTICI L. (COLEOPTERA: CURCULIONIDAE) I. COMPARATIVE STUDY OF THE RESISTANCE OF ALFALFA VARIETIES

 DOI: 10.7904/2068 – 4738 – III(6) – 68

Ivelina NIKOLOVA, Nataliya GEORGIEVA

Abstract: From studies carried out during the period 2006–2009 in the experimental field of the IFC–Pleven with 8 alfalfa varieties included in the Official variety catalog of Bulgaria (2005): Europe (France), Prista 2 (Obraztsov Chiflik, Rouse), Prista 3 (Obraztsov Chiflik, Rouse), Prista 4 (Exemplary Chiflik, Rouse), Obnova 10 (EFC, Pleven), Pleven 6 (EFC, Pleven), Dara (EFC, Pleven) and Multifoliate (Obraztsov Chiflik, Rousse) it was found that in the year of the establishment of the stand there was partial damage from Otiorrhynchus ligustici. It was found that surface of caused damage was a major sign to determination ofthe degree ofinfestation from the insect pest as it increased from second tofourth yearon average from 5.6 to 42.1 cm2.Varieties of Multifoliate, Europe and Prista 2 were the least preferred and with low values of surface of damage, number and length of the gnawed furrows. These varieties can be used as sources of germplasm resistant to Otiorrhynchus ligustici.

Keywords: alfalfa, varieties, damage, Otiorrhynchus ligustici