The uniform seed material is a prerequisite of stable yields. Therefore, the aim of the study was to observe variability of physiological seed traits depending on the classification of seeds by size and shape, and to determine advantages of large over small seed fractions. Three maize (Zea mays L.) hybrids (ZP 505, ZP 677, ZP 684), produced in two locations (Orahovo, Plavna), were classified into six fractions; small flat seed (SFS), medium small flat seed (MSFS), large flat seed (LFS), small round seed (SRS), medium small round seed (MSRS) and large round seed (LRS). Two laboratory treatments were applied on seed: TR1 (cold test) and TR2 (20/30 ºC). In both temperature treatments, the first evaluation was done after 72-h germination, and then every 24 h until 7^th day. The highest total germination (G) was recorded for ZP 677 (93.7%), location Orahovo (94.9%), temperature TR2 (95.2%) and MSFS fraction (89.7%). The total proportion of factors in the variance for G was R² = 0.694. Locations and genotypes predominantly affected the germination rate (GR), η = 0.338. Flat fraction seeds had more rapid emergence (> 90%) of seedlings than the round fraction seeds (> 85%). Round seeds were more susceptible and seed size had a greater effect on vigour than LRS, 70%. The partial effect of the fraction on G was not estimated (η = 0.037), but its cumulative effect with other factors was evident (Hybrid × Fraction, η = 0.070).

Blackleg outbreaks were noticed on three fields (about 100 ha total) in 2 consecutive years (2018, 2019) in one of the main potato growing areas in Serbia (Bačka region, Vojvodina). The percentage of infected plants reached 40 to 70%, with 10.5 to 44.7% yield reductions. From the three fields, out of 90 samples Pectobacterium carotovorum subsp. brasiliensis was most frequently identified and diagnosed as causal agent of potato blackleg in Serbia for the first time (29 isolates). Dickeya dianthicola was a less frequently causative bacterium, which was also noticed for the first time (nine isolates). A total of 38 isolates were characterized based on their phenotypic and genetic features, including a pathogenicity test on potato. The repetitive element PCR (rep-PCR) using BOX, REP, and ERIC primer pairs differentiated five genetic profiles among 38 tested isolates. Multilocus sequence analysis (MLSA) of four housekeeping genes, acnA, gapA, icdA, and mdh, revealed the presence of three so far unknown P. c. subsp. brasiliensis multilocus genotypes and confirmed clustering into two main genetic clades as determined in other studies. MLSA also revealed the presence of a new genotype of D. dianthicola in Serbia.

The objective of this study was to investigate the influence of seed coat colour on the seed quality of four red clover cultivars (germination, dormancy (hard seeds), dead seeds and initial seedling growth (vigour)) produced in Serbia over a period of two years. The seeds analyzed were first separated visually into bright, dark and mixed seed groups, followed by subsequent digital colour measurements. The results obtained showed that the seed coat colour of red clover could be considered a good indicator of seed quality and seedling growth ability. The results furthermore showed that bright-coloured seeds of red clover cultivars indicated increased vigour and seed quality compared to other colours. The impact of the production area and year on the seed quality parameters was inconclusive. A high variability in hard (CV = 22.22 %) and dead seeds (CV = 40.18 %) was recorded between different seed lots of red clover. A lower variability was found in the germination parameter of bright- and mixed-coloured seeds (CV = 4.53 % and CV = 8.53 %). The seed coat colour could be an important factor in determining the quality of red clover seeds, potentially increasing germination simply by removing dark-coloured seeds.

Indoleacetic acid (IAA) producing Pseudomonas isolates from the rhizosphere of maize (Q4 and Q20), alfalfa (Q1 and Q16) and wild red clover (B25) were selected for the investigation of their effect on the biological vitality of the potato seed tubers. The production of IAA ranged from 4.09 to 15.9 ? gmL- 1 after 24h of cultivation and 4.08 to 26.4 ? gmL-1 after 48h of cultivation. The molecular comparison by RAPD analysis also was done. RAPD patterns of selected Pseudomonas spp. isolates obtained by BC318, AF14, SPH 1 and AP 10 primers demonstrated the suitability of RAPD method in distinguishing a high variability among the four isolates (44 to 68%). The effect on the biological viability of potato (industrially important variety Pirol) was observed during the seven weeks of sprouting at the temperature of 18-20?C. Potato tubers treated by the selected isolates formed slightly lower number of sprouts, but statistically higher mean length - up to 129.9% higher than the control. The mean sprouting capacity was 64.5% higher than a control. Obtained results suggested positive effects of selected IAA producing Pseudomonas isolates on the length of potato tubers and sprouting capacity as the parameters which define biological viability.