Recent Japanese pear cultivars and breeding lines show unique characteristics, such as a milky-sweet flavor or a pineapple-like aroma. To efficiently breed Japanese pear varieties with excellent flavor using these aroma traits, it is necessary to identify the aroma components responsible for the characteristic flavor and their related genes. We conducted a non-targeted analysis of the aroma components of 14 Japanese pear cultivars and 14 breeding lines. These cultivars and breeding lines exhibited a range of aromas, including milky, pineapple-like, and green notes. We annotated 132 of the volatile compounds in the pear fruit. Esters and aldehydes accounted for half of the total number of components. Alcohols and lactones followed. Among them, nicotinate esters (methyl and ethyl nicotinate) and diol acetates (1,2-propanediol diacetate and 1,2-propanediol 1-acetate) were detected for the first time as aroma components of Pyrus fruit. Ethyl esters such as ethyl 2-methylbutanoate, and acetate esters such as hexyl acetate, acetoin, and eugenol were the characteristic components of the pears with a pineapple-like aroma, being consistent with the progeny of pears from Nepal. It was considered that γ-decalactone was a significant contributor to the sweet aroma reminiscent of sweetened condensed milk. All of the γ-decalactone-rich cultivars used in this study were derived from ‘Chikusui’. The relationships among the milky-sweet aroma, ‘Chikusui’ progeny, and γ-decalactone should be further investigated.

Oriental persimmon (Diospyros kaki Thunb.) is classified into four types: pollination constant and non-astringent (PCNA), pollination variant and non-astringent (PVNA), pollination variant and astringent (PVA), and pollination constant and astringent (PCA). Furthermore, PCNA is subdivided into two types: Japanese (JPCNA) and Chinese (CPCNA). The mechanisms underlying the removal of astringency differ between the two types. Moreover, the JPCNA trait is recessive, and so only recessive homozygotes exhibit the PCNA trait, whereas the CPCNA trait is controlled by the dominant gene at a different locus from JPCNA. In this study, we compared fruit weight, fruit shape, and two types of cracking habits in PCNA and non-PCNA offspring segregated from pseudo-backcrosses ([non-PCNA × JPCNA] × JPCNA) and crosses between CPCNA and non-PCNA. Analysis of variance revealed significantly lower family means of fruit weight in PCNA than non-PCNA individuals in both types of cross. No significant interactions between astringency type and cross were identified, which indicates that PCNA traits similarly influenced the decrease in fruit weight in both types of crosses. The fruit weight of PCNA offspring was 14 and 13% lower than that of non-PCNA offspring in the JPCNA pseudo-backcross and CPCNA cross, respectively. The fruit shape in PCNA was flatter than that in non-PCNA in the CPCNA cross. The family means of cracking at the fruit apex in PCNA offspring were significantly larger than those in non-PCNA offspring in the JPCNA pseudo-backcross. However, cracking at the calyx end did not significantly differ among astringency types in both types of cross.

A sensory analysis of 10 Japanese pear cultivars conducted by trained panelists revealed that the cultivar ‘Hatsumaru’ exhibited and candy made from it. Subsequently, the correlation between this aroma and the juices obtained from the same pears was examined. The strongest correlation was observed between the milky aroma and γ-decalactone. When gas chromatography-olfactometry (GC-O) was performed with stepwise dilutions of the aroma concentrates obtained from the juice mixtures of 3 cultivars exhibiting the milky aroma, γ-decalactone was the only component detected at a 64-fold dilution by all four GC-O panel members, with its odor described as milky and peachy. ‘Shurei’-like aroma was also perceived by a pear breeder, a member of the GC-O panels. These findings indicate that γ-decalactone is the primary contributor to the milky aroma of ‘Shurei’ × ‘Kanta’ progenies. In addition, the pear breeder also perceived the ‘Shurei’ aroma in decanoic acid, suggesting that a combination or interaction between γ-decalactone and decanoic acid may contribute to the milky aroma of ‘Shurei’ progenies. The milky aroma component may have been inherited from ‘Chikusui’, the progenitor of ‘Shurei’.

Marker-assisted selection of male sterile seedlings improves breeding of seedless citrus varieties. We have identified a nuclear DNA region (MS-P1) related to male sterility caused by the Kishu cytoplasm, and classified the region into seven haplotypes (HT1–HT7) using SSR markers. The haplotype combination determines male sterility. This finding can be used in citrus breeding programs to select male sterile seedlings with the SSR markers. However, the high cost of SSR marker analysis prevents its widespread use in breeding programs at public research institutes in each prefecture. The aim of this study was to develop a simple and low-cost DNA marker that enables the selection of male sterile seedlings using PCR and agarose gel electrophoresis. Candidate markers were designed using InDel sequences near the MS-P1 region referred from Mikan Genome DB. The InDel marker (MS-P1 InDel) detected HT1 as the B allele, HT2 as the A allele, HT3, HT4, HT6, and HT7 as the C allele, and HT5 as the no-amplification allele. These alleles were discriminated by their amplified sizes using agarose gel electrophoresis. Correlation analysis with F₁ populations demonstrated that MS-P1 InDel could select male sterile seedlings with marked accuracy. HT4 was specifically detected by the CAPS marker (MS-P1 InDel-CAPS) using HT4-specific SNP in the sequence amplified by MS-P1 InDel. These haplotyping procedures were accelerated by a simple DNA extraction protocol. The results show that MS-P1 InDel and MS-P1 InDel-CAPS enable simple and low-cost selection of male sterile seedlings.

To develop a tree management strategy for the recently bred apple cultivar ‘Kinshu,’ we investigated the frequency distribution of bearing shoot length and its effect on fruit quality. Length distribution showed a bimodal curve, in which the most frequent shoot length was 30 cm, and the mean length was more than 20 cm. Short (≤ 5 cm), middle (5.1–10 cm), and long (≥ 10.1 cm) shoots accounted for approximately 20, 5, and 75%, respectively. Compared with 2022, when the crop loads and fruit quality were normal, more shoots and fruits were set in 2023. This resulted in lower fruit quality without a large reduction in the leaf-fruit ratio, probably due to light interception. Fruit size was negatively correlated with bearing shoot length in 2022 but not 2023. Fruit acidity slightly increased with shoot length across both years, and similar slight increases in firmness and the starch index indicated that maturation may be delayed in fruits on longer shoots. However, these quality changes with shoot length were small when compared with the quality variation observed within fruits on similar length shoots. Moreover, there were no clear relationships between shoot-length and color or soluble solid content. As a result, the effect of bearing shoot length was relatively small. In ‘Kinshu,’ the frequent longer bearing shoots are associated with a stable high leaf-fruit ratio, which allows a stable, high yield, but can reduce light penetration. Thus, it is suggested that exploration of adequate pruning/tree-training may be effective to determine how to obtain a stable, high yield of high-quality fruits.

The whole harvest cultivation method for one-year-old plants of asparagus (new cultivation method) does not require occupying the field for a long time, as it shortens the growing period, compared with conventional methods, enabling asparagus, a perennial crop, to be incorporated into crop rotation. To establish the new cultivation method’s profitability in crop rotation, it is necessary to assess its effects on soil chemistry, growth, and yield. In this study, following asparagus cultivation and harvest using the new method, sweetcorn was cultivated in the same field. Subsequently, the growth and yield of asparagus and sweetcorn, and soil chemistry after the second cycle of crop rotation were investigated. Results indicated that the effects of asparagus and sweetcorn rotations on the growth and yield of each crop were small up to the first cycle of crop rotation, facilitating problem-free asparagus and sweetcorn cultivation. However, potassium accumulated in the soil due to the crops’ rotation. Therefore, future studies should address compost application and fertilizer quantities for crop rotation of asparagus and sweetcorn after the third cycle of rotation.

There are concerns that the rise in average temperatures due to global warming will lead to an increase in sunburn of grapes. However, the conditions under which sunburn occurs in ‘Kyoho’ grapes are unclear, so we conducted a test to clarify the causative conditions and verify effective countermeasures. After heating in a constant temperature machine, the symptoms of sunburn when the surface temperature of the fruit bunch reached 39.1 to 40.0°C and browning of the small peduncles appeared when the temperature reached 42.5°C, and these symptoms were considered to be caused by high-temperature damage. In addition, the incidence of high-temperature damage decreased after the beginning of coloring, and it was confirmed that the resistance to high temperatures was improved. In field measures, it is considered that high-temperature damage occurs due to an increase in the surface temperature of the fruit bunch, and such damage increases especially under extremely high-temperature conditions of 47.5°C or above. It has been shown that suppressing the rise in surface temperature of the fruit bunch by shade installation and increasing LAI is effective in preventing occurrence.