QTL analysis of soft scald in two apple populations

The apple (Malus×domestica Borkh.) is one of the world's most widely grown and valuable fruit crops. With demand for apples year round, storability has emerged as an important consideration for apple breeding programs. Soft scald is a cold storage-related disorder that results in sunken, darkened tissue on the fruit surface. Apple breeders are keen to generate new cultivars that do not suffer from soft scald and can thus be marketed year round. Traditional breeding approaches are protracted and labor intensive, and therefore marker-assisted selection (MAS) is a valuable tool for breeders. To advance MAS for storage disorders in apple, we used genotyping-by-sequencing (GBS) to generate high-density genetic maps in two F1 apple populations, which were then used for quantitative trait locus (QTL) mapping of soft scald. In total, 900 million DNA sequence reads were generated, but after several data filtering steps, only 2% of reads were ultimately used to create two genetic maps that included 1918 and 2818 single-nucleotide polymorphisms. Two QTL associated with soft scald were identified in one of the bi-parental populations originating from parent 11W-12-11, an advanced breeding line. This study demonstrates the utility of next-generation DNA sequencing technologies for QTL mapping in F1 populations, and provides a basis for the advancement of MAS to improve storability of apples.

Use of descriptive analysis and preference mapping for early-stage assessment of new and established apples

BACKGROUND

This research compared four new apple selections with 16 established apples using descriptive analysis (DA), instrumental analyses and preference mapping, in order to identify suitable selections for commercialization and further research.

RESULTS

DA revealed that the new apple selections (PARC1, PARC2, PARC3, PARC4) were very similar in texture/mouthfeel (T) but differed in their flavor (F) and appearance (A) characteristics. Preference mapping revealed that consumers' T preferences were driven primarily by crispness, juiciness and lack of skin toughness, while F preferences were driven by sweetness, lack of tartness and presence of fruity flavor. Consumers' A preferences were driven by a high percentage of red color and degree of striping. The majority of consumers had similar T (82-85%) and F (88-92%) preferences for the early- and mid/late-harvest apples. In contrast, consumers' A preferences were differentiated into three subgroups (60%, 24%, 16%) for the early-harvest apples, but not for the mid/late-harvest apples. The new apple selections were among those most liked for T, F and A.

CONCLUSION

This early-stage consumer research confirmed that the new apples were comparable, if not superior, to the established apples. As such, it provided the necessary feedback to industry to proceed with commercialization and optimization of cultural and storage practices.

Does the genome of Corylus avellana L. contain sequences homologous to the self-incompatibility gene of Brassica?

Self-incompatibility is a genetic mechanism enforcing cross-pollination in plants. Hazelnut (Corylus avellana L.) expresses the sporophytic type of self-incompatibility, for which the molecular genetic basis is characterized only in Brassica. The hypothesis that the hazelnut genome contains homologs of Brassica self-incompatibility genes was tested. The S-locus glycoprotein gene (SLG) and the kinase-encoding domain of the S-receptor kinase (SRK) gene of B. oleracea L. were used to probe blots of genomic DNA from six genotypes of hazelnut. Weak hybridization with the SLG probe was detected for all hazelnut genotypes tested; however, no hybridization was detected with PCR-generated probes corresponding to two conserved regions of the SLG gene. One of these PCR probes included the region of SLG encoding the 11 invariant cysteine residues that are an important structural feature of all S-family genes. The present evidence suggests that hazelnut DNA hybridizing to SLG differs significantly from the Brassica gene, and that the S-genes cloned from Brassica will not be useful for exploring self-incompatibility in hazelnut.

Effects of temperature, salt, and osmotic potential on early growth of wheat (Triticum aestivum). I. Germination

Kernels of spring wheat (cv. Katepwa) were germinated in Petri dishes at six osmotic potentials (−0.3 to −1.8 MPa) and eight temperatures (6–34 °C) in single-salt solutions of a variety of chloride and sulfate salts, and the time to onset of germination, germination rate index, and final percent germination were determined. Percent germination was maximal at 18–22 °C in the presence of osmotic stress, but was unaffected by temperature in its absence. At temperatures below 10 °C or above 30 °C and osmotic potentials below −0.3 MPa, germination was delayed, slowed down, and eventually inhibited. Temperature stress intensified the effects of osmotic stress on germination and vice versa. Main effects of temperature, osmotic potential, and salt type and all their interactions were highly significant (P < 0.01) for all variables.

Effects of temperature, salt, and osmotic potential on early growth of wheat (Triticum aestivum). II. Early seedling growth

Kernels of spring wheat (cv. Katepwa) were germinated in Petri dishes at six osmotic potentials (−0.3 to −1.8 MPa) and three temperatures (10, 18, and 30 °C) in single-salt solutions of a variety of chloride and sulfate salts, or in polyethylene glycol. Shoot length and maximum root length were measured at 7 days, and membrane damage of roots was assayed by measuring leakage of UV-absorbing compounds. Low temperature and osmotic potential decreased root and shoot length. High (30 °C) temperature enhanced growth in distilled water controls and in polyethylene glycol, but reduced growth if salt stress below -0.6 MPa was present. All salts greatly enhanced osmotically induced membrane leakage. Changes in membrane leakage with temperature may be partially responsible for observed salt–temperature interactions on growth.