Search Results

RAPD and phenotypic analysis were conducted to assess clonal stability of hazelnuts generated from axillary buds cultured in vitro for long-term. The nuts produced on in vitro-propagated plants were indistinguishable from those of donor plants. With the exception of rare horizontal (plagiotropic) growth, all in vitro-propagated plants exhibited phenotypes similar to those of donor plants. RAPD analysis did not reveal any somaclonal variation between donor plants from which in vitro cultures were initiated and micropropagated plants (6-year cultures), and no somaclonal variation was detected among in vitro-propagated plants. However, polymorphism (15.6%) was detected between the parent plant and its in vitro-propagated progenies (from seedlings). These results show a good discriminatory power of RAPD to detect polymorphism between samples where it is expected, and it can be effectively used for genetic assessment of micropropagated hazelnut. No evidence of genetic or epigenetic changes was observed in long-term cultured hazelnut, and thus long-term in vitro culture of hazelnut does not seem to limit its clonal propagation.

Common bacterial blight, incited by Xanthomonas campestris pv. phaseoli (Xcp) is a serious disease of common bean (Phaseolus vulgaris L.). Randomly amplified polymorphic DNA (RAPD) markers and flower color (V gene) previously were reported to be associated with six quantitative trait loci (QTL) affecting leaf and pod resistance to Xcp. However, the markers for the QTL were not confirmed in different populations and environments to indicate their merit in breeding. The objective was to determine if the associations of RAPD markers and the V gene with QTL for leaf and pod resistance to Xcp in a recombinant inbred (RI) backcross population from the cross BC₂F₆ `PC-50' × XAN-159 and for leaf resistance to Xcp in an F<sub>2</sub> population from a different cross pinto `Chase' × XAN-159 could be confirmed. One or two genes from XAN-159 controlled leaf and pod resistance to Xcp. Among six QTL previously detected, five in the RI backcross population and three in the F₂ population were confirmed to be associated with resistance to Xcp. The V gene and RAPD marker BC437.1050 on linkage group 5 were most consistently associated with leaf and pod resistance to two to five Xcp strains in the RI backcross population and with leaf resistance to two Xcp strains in the F₂ population. One to three QTL affecting leaf and pod resistance to Xcp accounted for 22% to 61% of the phenotypic variation. Gene number (one to two) estimations and number of QTL (one to three) detected for leaf and pod resistance to Xcp in the RI backcross population were generally in agreement. The marker BC437.1050 and V gene, along with other resistance genes from other germplasm, could be utilized to pyramid the different genes into a susceptible or partially resistant bean line or cultivar to enhance the level of resistance to Xcp.

Common bacterial blight, incited by Xanthomonas campestris pv. phaseoli (Xcp), is a serious disease of common bean (Phaseolus vulgaris). RAPD markers and flower color (V gene) previously had been reported to be associated with six QTL affecting leaf and pod resistance to Xcp. However, the markers for the QTL were not confirmed in different populations and environments to indicate their merit in breeding. Our objective was to determine if the associations of RAPD markers and the V gene with QTL for leaf and pod resistance to Xcp in a RI backcross population from the cross BC₂F₆ `PC-50' × XAN-159 and for leaf resistance to Xcp in a F<sub>2</sub> population from a different cross Pinto `Chase' × XAN-159 could be confirmed. Among six QTL previously detected, five in the RI backcross population and three in the F₂ population were confirmed to be associated with resistance to Xcp. The V gene and RAPD marker BC437.1050 on linkage group 5 were most consistently associated with leaf and pod resistance to two to five XCP strains in the RI backcross population and with leaf resistance to two Xcp strains in the F₂ population. The confirmed marker BC437.1050 and V gene on linkage group 5, along with other resistance genes from other germplasm, could be used to pyramid the different genes into a bean cultivar to enhance the resistance to Xcp.

There is a dearth of information about turfgrass drought resistance and adaptation in the Mediterranean region of Turkey. Turfgrass managers in this region need this information to help them make informed decisions regarding turfgrass selection and management. This research was conducted to assess the drought resistance of bermudagrass (Cynodon dactylon), buffalograss (Buchloe dactyloides), bahiagrass (Paspalum notatum), seashore paspalum (Paspalum vaginatum), zoysiagrass (Zoysia japonica), centipedegrass (Eremochloa ophiuroides), and tall fescue (Lolium arundinaceum) under Mediterranean conditions of Turkey. The study was conducted at two locations, Antalya and Mersin, and was repeated in 2006 and 2007 at both locations. One year after establishment, the turfs were subjected to drought stress for 90 days, which was followed by resumption of irrigation for recovery of the turf. Percentage leaf firing, turfgrass quality, and percent green shoot recovery were recorded. There were inter and intraspecies differences detected for percentage leaf firing and shoot recovery. Bermudagrass, bahiagrass, and buffalograss exhibited superior drought resistance as demonstrated by lower leaf firing and better shoot recovery values when compared with other species studied. Centipedegrass and zoysiagrass demonstrated a high leaf firing and very poor shoot recovery, whereas zoysiagrass and tall fescue were unable to recover from the drought stress in the sandy soil. Results showed that ‘SWI-1045’ (Contessa®) and ‘SWI-1044’ bermudagrass and ‘Cody’ buffalograss possessed superior drought resistance with acceptable turfgrass quality up to 30 days under drought stress that can be used for water-efficient turf management under the Mediterranean environment.