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Aramaki S.,Fruit Tree Research Division
American Society of Agricultural and Biological Engineers Annual International Meeting 2011, ASABE 2011

It is effective to control the water stress of satsuma mandarin trees artificially in order to yield fruits with high sugar content. In the remote sensing, it is known that the water stress will cause the blue shift of the red edge wavelength in spectral reflectance of leaves. In this research, the authors prepared the test fields with various water stressed trees in 2010, and they investigated the movement of the red edge wavelength in spectral reflectance of leaves and the water potential of leaves. In the present paper, measurement experimentation for the evaluation of the water stress was executed at the test field using the spectral reflectance measurement device originally developed. As a result, there was little instability of spectrum characteristic feature by scan condition, for instance position of the device and sun elevation angle. The differential of the red edge wavelength obtained from the green leaf spectrum characteristic is little. And the estimation of the water potential from spectrum analysis of leaves derived the presumption accuracy, standard error of calibration (SEC) was 0.17[MPa], standard error of prediction (SEP) was 0.20[MPa], and coefficient of determination (R2) was 0.7. This presumption accuracy suggests a practical possibility for producing high quality fruits, because it is said that the presumption accuracy of 0.2[MPa] is necessary for it. Source

Hiehata N.,Fruit Tree Research Division | Fukuda S.,Fruit Tree Research Division | Sato Y.,Fruit Tree Research Division | Tominaga Y.,Fruit Tree Research Division | And 2 more authors.

Loquat canker, caused by Pseudomonas syringae pv. eriobotryae, is a serious disease of loquat [Eriobotrya japonica (Thunb.) Lindl.] in some countries such as Japan. Therefore, improved canker resistance is an important objective for loquat breeding. The resistance to loquat canker Group C in descendants of ‘Shiromogi’ was expressed only in homozygotes with a recessive gene at a single locus, which was designated pse-c/pse-c. ‘Champagne’, which is distantly related to ‘Shiromogi’, is another cultivar with resistance to Group C. The inheritance of this resistance in progenies of crosses between ‘Champagne’ and susceptible cultivars was examined. The offspring seedlings from 14 crosses between ‘Champagne’ (pse-c/pse-c) and 12 susceptible cultivars (Pse-c/Pse-c or Pse-c/pse-c) were classified into two types of resistant and susceptible. All of the hybrid progenies between ‘Champagne’ (pse-c/pse-c) and Pse-c/Pse-c parents showed two types of resistant and susceptible. The proportion of resistant offspring showed great differences significantly, depending on the hybrid combinations. It ranged from 0.203 to 0.596 with an average of 0.407. It indicated that the resistance was controlled by one or more additional genes or loci other than the Pse-c (pse-c) locus. In addition, the proportion of resistant offspring from crosses between ‘Champagne’ (pse-c/pse-c) and Pse-c/pse-c parents ranged from 0.463 to 0.701 (and averaged 0.601), which seriously deviated from the segregation of 1:1, indicating that the segregation was both Mendelian and polygenic in a threshold character. The proportion of resistant seedlings cannot be predicted by the phenotype and the genotype in the Pse-c (pse-c) locus. Therefore, the general combining ability of ‘Champagne’ resulting from the additional gene effect was estimated, which was 0.407 and 0.101 for ‘Champagne’ × Pse-c/Pse-c and ‘Champagne’ × Pse-c/pse-c cultivars, respectively. The gene effect of susceptible cultivars ranged from -0.204 (‘Yougyoku’) to +0.189 (‘Togoshi’) for ‘Champagne’ × Pse-c/Pse-c cultivars and from -0.138 (‘Taisho’) to +0.089 (‘Nagasakiwase’) for ‘Champagne’ × Pse-c/pse-c cultivars. © 2014, American Society for Horticultural Science, Inc. All rights reserved. Source

Hiehata N.,Fruit Tree Research Division | Sato Y.,Fruit Tree Research Division | Sato Y.,National Institute of Fruit science | Fukuda S.,Fruit Tree Research Division | And 4 more authors.
Journal of the American Society for Horticultural Science

Loquat canker (Pseudomonas syringae pv. eriobotryae) is a serious disease of loquat (Eriobotrya japonica), and no commercial cultivar in Japan is resistant to all strains of the disease. Loquat cultivar Shiromogi, which was selected from progeny seedlings of 'Mogi', is resistant to loquat canker Group C and has good fruit characteristics. This study was conducted to determine the inheritance of resistance to loquat canker Group C in 'Shiromogi'. Seedlings produced from crosses between two resistant and 13 susceptible genotypes were classified as either resistant (R) or susceptible (S) based on the appearance of black-brown cankers ≈2 months after inoculation with a bacterial suspension of loquat canker Group C. Cross combinations between resistant parents 'Champagne' and 'Shiromogi' and selfing of 'Shiromogi' produced all resistant seedlings. Most crosses between 'Shiromogi' and susceptible parents either produced only susceptible seedlings or segregated for resistance in a ratio of 1 R:1 S. Seedlings produced by selfing two of the susceptible parents segregated in a ratio of 1 R:3 S. These results indicate that the resistance to loquat canker Group C of 'Shiromogi' is conferred by a single recessive gene, designated pse-c. Based on the crossing tests, we conclude that resistant parents 'Shiromogi' and 'Champagne' are homozygous for pse-c; the susceptible parents 'Fukuharawase', 'Fusahikari', 'Gold Nugget', 'Kusunoki', Nagasaki No. 2, 'Tanaka', 'Tsukumo', and 'Yougyoku' are homozygous for Pse-c; and the other susceptible parentsinthis experiment ('Mogi', 'Nagasakiwase', Nagasaki No. 3, 'Taisho', and 75-142) are heterozygous. Based on the pedigree of 'Shiromogi' and the results reported here, pse-c is probably derived from 'Mogi', a major cultivar in Japan. Source

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