Screening of Wild Strawberry Genotypes against Iron Deficiency under Greenhouse Conditions

The cultivated strawberry Fragaria × ananassa Duch. is the natural hybrid of F. chiloensis (L.) Mill. and F. virginiana Mill. The progenitor species have high genetic diversity compared with the cultivated genotypes; therefore, the use of wild relative in F. chiloensis breeding could provide a good for broadening the available genetic variations of cultivated species. In present study, 13 genotypes selected from strawberry super core collection were tested under Fe (-) and Fe (+) conditions for their response against Fe deficiency conditions in a growth medium (GM) (soil + sand + perlite), potentially able to simulate the actual GM in nature. SPAD-meter readings indicating chlorophyll levels of the leaf, shoot dry matter yield, Fe-efficiency rate, shoot total and active Fe concentrations were determined to evaluate the resistance levels of strawberry genotypes against Fe deficiency. Results of this study indicated that different response for strawberry subspecies and genotypes of the same subspecies grown in GM against Fe deficiency. Symptom for Fe deficiency of genotypes varied between 1-5, SPAD-meter readings 3, shoot dry matter yields and shoot Fe concentrations varied between 6.5-38, 1.02-6.06 g plant-1 and 41.8-233.1 mg kg-1 respectively. Iron-efficiencies of genotypes were found between 58–98%. Strawberry subspecies, F. virginiana spp. glauca, F. chiloensis ssp. chiloensis and F. chiloensis ssp. pacifica showed Fe-efficiency values of 93.8, 79.5 and 79.1% respectively. We concluded that shoot growth performance, Fe intake from GM, transfer of Fe from roots to shoots, shoot Fe-use efficiency, Fe deficiency symptom levels and SPAD-meter readings indicating chlorophyll levels were significant parameters to evaluate the resistance of strawberry genotypes against Fe deficiency. The most Fe-efficient genotypes belonging to F. virginiana spp. glauca could be used in breeding programs aiming at developing new strawberry genotypes suitable for growing under Fe deficient conditions.

Mystery Spot of `Enterprise' Apples Appears to Be a Low-calcium Disorder

The apple cultivar Enterprise is a product of the Purdue–Rutgers–Illinois (PRI) disease-resistant apple breeding program. It has field immunity to apple scab, has a high level of resistance to cedar apple rust and fire blight, and is moderately resistant to apple powdery mildew. This resistance to these diseases makes the production of this cultivar desirable, especially on the popular fire blight-susceptible M.26 rootstock. Compared to many other scab-resistant cultivars, `Enterprise' has performed well in the mid-Atlantic area. However, this cultivar has been reported to be susceptible to low-Ca disorders when grown in New Jersey and Virginia. The mid-Atlantic area is notorious for the production of fruit with high levels of corking and bitter pit. This may be due to factors such as vigorous tree growth and low transpirational flow, which may be weather-related. Circumstantial evidence based on the production of clean `Enterprise' at Biglerville, Pa., where moderately high rates of CaCl2 have been applied in cover sprays, indicate that this disorder may be a Ca deficiency symptom. A replicated trial of many scab-resistant cultivars was established in 1990, 1991, and 1992. Due to the common incidence of low-Ca disorders, CaCl2 has been added to the cover spray program that is applied for insect control. Low-Ca disorders have never been seen in fruit produced at Biglerville, and the cover spray program applied 67 and 73 kg·ha–1 of CaCl2 (77% to 80% CaCl2, flake) in 1993 and 1994, respectively.