Vinko Kozumplik

Genetic diversity of Bradyrhizobium japonicum field population revealed by RAPD fingerprinting

RAPD fingerprinting was used for strain identification and the assessment of genetic diversity within a field population of Bradyrhizobium japonicum. Total genomic DNAs from 13 field isolates and two inoculant strains were amplified using six different 10‐mer primers. Different and informative band patterns were obtained for all strains analysed. Cluster analysis unexpectedly revealed that none of the field isolates was identical to inoculant strains which were regularly used for soybean inoculation. Among field isolates two highly divergent groups were determined. The results indicate that RAPD is a very discriminative and efficient method for differentiating and studying genetic diversity of B. japonicum strains.

Originality of M3S maize population and changes in allele frequencies revealed by SSR markers after two cycles of selfed progeny recurrent selection

Maksimir 3 Synthetic (M3S) maize population was developed at the Faculty of Agriculture University of Zagreb by intercrossing inbred lines, whose origins trace back to several open-pollinated varieties and local populations from different regions of the former Yugoslavia. The population was subjected to two cycles of selfed progeny recurrent selection for grain yield. The objectives of this study were: (i) to determine genetic distances among the parental inbred lines of the M3S population (M3S progenitors), the M3S population before and after two cycles of recurrent selection, and elite inbred lines representing the BSSS and Lancaster heterotic group; and (ii) to examine the effect of two cycles of recurrent selection on allele frequency changes in the population. Nine M3S progenitors, three BSSS lines, and three Lancaster lines were genotyped at 24 SSR loci, out of which nine randomly chosen loci were used for genotyping 96 individuals from both C0 (the M3S population before selection) and from C2 (M3S population after two cycles of selection). A total of 101 alleles were detected across 24 loci in the 15 lines, whereas 83 alleles were found in the nine M3S progenitors. Among the latter 83 alleles 31 were unique, i.e. found only in one of the progenitors. Mean genetic distance among nine M3S progenitors was 0.61 indicating a broad genetic base of the M3S population. High mean genetic distance was found between M3S progenitors and BSSS lines (0.69) and M3S progenitors and Lancaster lines (0.71). This indicates that the M3S population represents a germplasm source unrelated to both the BSSS and Lancaster germplasm. Mean genetic distance between the M3S population and BSSS as well as Lancaster lines decreased slightly after two cycles of recurrent selection suggesting the need to introduce testers from both groups in future selection in the M3S population in order to maintain heterotic complementarity of the M3S population to these groups. A test of selective neutrality identified several non-neutral loci in the population whose allele frequency changes from the C0 to the C2 cannot be explained by genetic drift. The majority of non-neutral alleles, whose frequency increased after two cycles of selection, were present in at least one line from the BSSS or Lancaster heterotic group.

Improvement of stalk rot resistance and grain yield in the maize synthetic FAOSYNFR1B by recurrent selection

Two cycles of simultaneous selection for stalk rot resistance and grain yield have been conducted in the FAOSYNFR1B population synthesized from Eastern European maize germplasm. The objectives of this study were: 1) to compare expected genetic gain from S 1 and HSI methods of selection in the second cycle and 2) to evaluate improvement (gain) of stalk rot resistance and grain yield in the population per se associated with two cycles of selection. In the first cycle of selection, S 1 method and HSI method (using an inbred tester) were combined (S 1 -HSI) to produce C1 population. In the second cycle of selection the S 1 and HSI methods were applied separately to produce C2(S 1 ) and C2(HSI) populations, respectively. In 1996, the C0, C1, C2(S 1 ), and C2(HSI) populations per se were evaluated at four locations in natural conditions and at one under artificial stalk infection. Combined S 1 -HSI method was successful in improving both stalk rot resistance and grain yield. In the second cycle, further improve...

Response of flue-cured tobacco to reduced fertilization

One of the biggest challenges for the safe maize production is the yield stability in a wide range of environments with different soil fertility, weather conditions, prevailing pests and diseases as well as cultural practices. In order to achieve it, new hybrids with higher tolerance to biotic and abiotic stress are continuously being created. In order to compare performance of maize hybrids in environments with different levels and types of stress, and relate it to the stalk lodging incidence, we compared performance of 64 maize hybrids obtained by crossing 16 inbred lines with four inbred testers in three different environments. Two environments at same location (Rugvica) differed in crop rotation, and the third environment at location Botinec was considered as dry because of low water capacity of the soil. Mixed models that included all design elements and genetic background of hybrids were used to analyze the effect of lodging on yield in different environments. The results show that stalk lodging had a significant effect on yield, but significant lodging x environment interaction indicates that this effect was rather environment specific.Sweet pepper Istra F1 hybrid was grown in a greenhouse on K rich soil. For evaluation of K antagonism, two K rates (55 and 85 kg ha-1) were applied in a randomized complete block design with four replications. Total number of fruits, total number of BER affected fruits as well as average fruit mass were recorded for each harvest. Fruit and leaf K and Ca content were determined at three plant growth stages (at the stage of the first, third and fifth fruit cluster). Higher K rate gave higher : average fruit mass (169.45 g), total number of fruits per plant (7.95), number of BER affected fruits per plant (3.82), K in leaves (5.44% DM), K in fruits (6.35% DM), but negatively correlated with Ca concentration in fruits (0.57% DM) and leaves (3.24% DM). This resulted in decreased marketable yield of sweet pepper fruits.

Stalk rot resistance in Maksimir 3 synthetic maize population after four cycles of recurrent selection

Fusarium stalk rot (FSR) and anthracnose stalk rot (ASR), caused by Fusarium spp. and Colletotrichum graminicola (Ces.) G.W. Wils. respectively, are the two most important stalk diseases in maize which increase the incidence of stalk lodging and reduce grain yield. The aim of the present study was to (1) evaluate the effect of four cycles of recurrent selection in the Maksimir 3 Synthetic (M3S) maize population on ASR and FSR resistance and (2) to investigate the correlation among the different disease rating methods. The experiment included six M3S cycle populations per se and their test-crosses with a single cross hybrid. ASR resistance was estimated on artificially inoculated plant rows using three ratings (the number of infected internodes, the number of internodes rotten more than 75% and evaluation of outer stalk discoloration) whereas FSR resistance was estimated in artificially inoculated rows as well as in naturally inoculated rows by rating severity of disease symptoms on longitudinally cut stalks using the standard resistance scale. The results of the present study showed that four cycles of selection in the M3S maize population, conducted primarily for grain yield improvement, did not significantly affect its resistance to both ASR and FSR. Among the disease ratings a moderate positive correlation was found only between two ASR resistance ratings (the number of infected internodes and the number of internodes rotted more than 75%) in both population per se (r=0.49**) and population test-crosses (r=0.56**).

Comparing estimates of variances and correlations for two recurrent selection methods in the maize synthetic FAOSYNFR1B

The objective of this study was to compare estimates of variances and correlations for S1 and HSI methods in the second cycle of recurrent selection in the FAOSYNFR1B synthetic for stalk rot resistance and grain yield. We compared estimates of variance and correlations for S1 and HSI methods in the second cycle of recurrent selection in the maize synthetic FAOSYNFR1B for stalk rot resistance and grain yield when the components were re-estimated with restricted maximum likelihood (REML) method. There were some differences between variance components estimated by REML analysis and ANOVA due to adjusting of estimates in extended random model and by re-estimating the other variances because of some negative estimates. There was no either phenotypic or genotypic correlation between the two traits for the S1 method, while the both correlations for the HSI method were negative and very weak. The estimates of phenotypic and genotypic correlations were similar for both selection methods indicating that phenotypic correlations could alone accurately reflect expected correlated responses between the traits when sample size is relatively large.

Morphological and agronomic characteristics of Croatian red clover ( Trifolium pratense L.) breeding populations tolerant to abiotic stress

Red clover (Trifolium pretense L.) is a temperate species originated from Southeast Europe and Asia Minor near the Mediterranean Sea (Taylor and Quesenberry, 1996). It is a short-lived perennial diploid species with seven pairs of chromosomes (Taylor and Quesenberry, 1996), insect pollinated and self incompatible. Red clover can be grown across a wide range of soil types, pH levels, and environmental conditions, and gives good yields in areas not suitable for growing alfalfa (Smith et al., 1985). Knowledge of the amount and distribution of genetic variability within species is crucial for breeders when selecting breeding germplasm (Muntean and Savatti, 2003). Genetic variation is frequently estimated using morphophysiological characters, which often show multigenic inheritance with strong environmental modification (Kolliker et al., 2001). Tolerance of field crop to abiotic stress, such as drought and cold tolerance (Peter et al., 2006 ; Pepo et al., 2006 ; Czi vek et al., 2006) is of primary importance for sustainable crop production in stress environment. Tolerance to abiotic stresses in red clover was analysed in few studies (Nowak et al., 1992 ; Nelke et al., 1999). Red clover is the most important fodder crop in north-western region of Croatia where climate is humid, soils shallow and wet, and vegetation period short (Gagro, 1998). Due to small producing input and multiplied gain, red clover gets more on its importance in sustainable agricultural production where the complete producing cycle tends to be included within the land and facilities of one farm. Main objective of this research was to estimate variations in morphological and agronomic characteristics among red clover breeding populations tolerant to abiotic stress developed at the Faculty of Agriculture in Zagreb during the last ten years.