The interactions between irrigation and crop level with respect to fruit size distribution and soil and stem water potentials were investigated in a nectarine (Prunus persica (L.) Batsch. `Fairlane') orchard located in a semiarid zone. Irrigation treatments during stage III of fruit growth ranged from 0.62 to 1.29 of potential evapotranspiration (ETp). Fruit were hand thinned to a wide range of fruit levels (200 to 1200 fruit/tree in the 555-tree/ha orchard). Total yield did not increase with increasing irrigation rate above 0.92 ETp in 1996 and maximum yield was found at 1.06 ETp in 1997. Fruit size distribution was shifted towards larger fruit with increasing irrigation level and with decreasing crop level. The two highest irrigation treatments had similar midday stem water potentials. Our findings indicate that highest yields and highest water use efficiency (yield/water consumption) are not always related to minimum water stress. Total yield and large fruit yield were highly and better correlated with midday stem water potential than with soil water potential. This confirms other reports that midday stem water potential is an accurate indicator of tree water stress and may have utility in irrigation scheduling.
A. Naor, I. Klein, H. Hupert, Y. Grinblat, M. Peres and A. Kaufman
A. Naor, H. Hupert, Y. Greenblat, M. Peres, A. Kaufman and I. Klein
The interactions between irrigation and crop level with respect to fruit size distribution and midday stem water potential were investigated for 3 years in a nectarine (Prunus persica L. `Fairlane') orchard located in a semi-arid zone. Wide ranges of crop loads and irrigation rates in stage III were employed, extending from practically nonlimiting to severely limiting levels. Irrigation during stage III of fruit growth ranged from 0.63 to 1.29 of potential evapotranspiration (ETp). Fruit were hand thinned to a wide range of fruit levels (300 to 2000) fruit/tree in the 555-tree/ha orchard. The yields and stem water potentials from 1996, 1997 and 1998 were combined together and the interrelations among yield, crop load and stem water potential were examined. Fruit <55 mm in diameter growing at 400 fruit per tree were the only ones not affected by irrigation level. The yield of fruit of 60 to 75 mm in diameter increased with irrigation level, but only a slight increase was observed when the irrigation rate rose above 1.01 ETp. A significant decrease in the yields of 60 to 65, 65 to 70, and 70 to 75-mm size grades occurred at crop levels greater than 1000, 800, and 400 fruit per tree, respectively. Midday stem water potential decreased with increasing crop level, and it is suggested that midday stem water potential responds to crop load rather than crop level. Relative yields of the various size grades were highly correlated with midday stem water potential. It was suggested that the midday stem water potential integrates the combined effects of water stress and crop load on nectarine fruit size.
Zhiguo Ju, Yousheng Duan and Zhiqiang Ju
`Feicheng' peach is a favorite cultivar in China due to is large size and high eating quality. However, its storage quality is poor and its market life is relatively short. Different combinations of AVG and GA3 applied at various stages of fruit development were evaluated to prolong market life of this fruit. A combination of 80-100 mg/L AVG and 80-100 mg/L GA3 at the end of pit hardening gave the best results. This treatment retarded the change in ground color, loss of firmness, and reduction in acidity by2 to 3 weeks. Since harvest was delayed, soluble solid content increased compared with the control that was harvested earlier. Fruit size increased significantly on treated trees. During 6 weeks of storage at 0 °C, ethylene evolution increased and fruit firmness decreased slowly in control fruit, but in AVG+GA3-treated fruit, they did not change from the low initial levels. At the end of storage, control fruit developed a high percentage (83%) of tissue browning and mealiness after warming at 20 °C for 4 days, but the AVG+GA3-treated fruit ripened normally and developed much less (16%) tissue browning and mealiness. Our results showed that the market life of `Feicheng' peaches can be prolonged by at least 4 weeks by using the AVG+GA3 treatment to delay harvest and improve storage quality.
Gene E. Lester and Kevin M. Crosby
Two important chemicals and an essential mineral (phytonutrients) for human health and well-being are ascorbic acid, 5-methyl-tetrahydrofolic acid (folic acid) and potassium. The influence of cultivar, fruit size, soil type and year on these compounds in [Cucumis melo L. (Inodorous Group)] was determined. Fully mature (abscised) commercial size fruit: 4, 5, 6, 8, and 9 (fruit/0.031 m3 shipping box) from three commercial cultivars: Mega Brew, Morning Ice, and TAM Dew Improved (TDI); and one experimental hybrid `TDI' × `Green Ice' were grown on both clay loam and sandy loam soils. Total ascorbic acid and folic acid content increased with an increase in fruit size up to a maximum (size 6 or 5), then decreased with further fruit size increase. Total ascorbic acid and folic acid content for most fruit sizes were higher when grown on clay loam versus sandy loam soils. The experimental hybrid compared to the commercial cultivars contained generally higher total ascorbic acid levels and significantly higher folic acid levels regardless of fruit size or soil type. Free ascorbic acid and dehydroascorbic acid contents were generally higher from clay loam versus sandy loam soils and in the experimental line versus the commercial cultivars. However, free ascorbic acid content was high in small fruit and remained unchanged with an increase in fruit size until size 6 or 5 then significantly decreased; while dehydroascorbic acid content linearly increased with an increase in fruit size. Potassium content averaged 1.7 mg·g-1 fresh weight for each line and did not significantly differ due to fruit size, but did for soil type and year. Analyses of variance for the phytonutrients assayed demonstrated that cultivar (genetics) always was very highly significant (P = 0.001), whereas, soil and year (environment) were not.
Jorge A. Zegbe and Jaime Mena-Covarrubias
return. Therefore, fruit suitable for export is now the goal for Mexican growers. As for other fruit crops exemplified by apple [ Malus × domestica ( Kilili et al., 1996 )], fruit size of cactus pear depends on orchard management practices during the
Hisayo Yamane, Megumi Ichiki, Ryutaro Tao, Tomoya Esumi, Keizo Yonemori, Takeshi Niikawa and Hino Motosugi
Fruit size is one of the most important traits that affect the economic value of fruit. Although fruit size is controlled by both environmental and genetic factors, the latter have the greatest impact, because small genetic changes can
Gerry Neilsen, Frank Kappel and Denise Neilsen
., 2005 ). A major management issue concerning cherry production on dwarfing rootstocks has been the possibility of reduced fruit size ( Franken-Bembeck, 1998 ). Hence, a number of bloom ( Whiting et al., 2006 ) and postbloom ( Lenahan and Whiting, 2006
D. Scott NeSmith and Gerard Krewer
Plants of the rabbiteye blueberry (Vaccinium ashei Reade) cultivars Brightwell, Climax, and Tifblue were subjected to pollination with bees or to applications of 250 mg·L-1 of gibberellic acid (GA3) to examine the influence on fruit size and maturation period. Plants were thinned to a similar fruit density (FD) 4 weeks after anthesis. `Tifblue' and `Climax' fruit were smaller on GA3-treated than on bee-pollinated plants, but no difference was observed for `Brightwell'. The fruit maturation period for `Climax' was not affected by treatments, but `Brightwell' and `Tifblue' fruit on pollinated plants ripened 2 weeks earlier than fruit on GA3-treated plants. These data suggest that excess fruit load is not the primary factor responsible for the smaller fruit size and lengthened fruit development period resulting from GA3 applications to rabbiteye blueberries.
Thomas E. Clark, Terence L. Robinson, Alan N. Lakso and Warren C. Stiles
In 1996, benzyladenine, or GA4+7, or different ratios of BA: GA4+7 (100:1, 10:1 and 1:1) were applied to 10-year-old `Empire' apple trees on M.9 at 10-mm fruit size and 19-year-old `Redchief Delicious' apple trees on M.9 or M.9/MM.111 at 7.6-mm fruit size. Each chemical or combination of BA and GA was applied at three rates (50, 100, or 150 ppm) and at 75 ppm with 1.25 ml of carbaryl/L. At harvest, fruits were sampled from each treatment to determine fruit shape, firmness, color, total cell number, average cell size, and percentage of intercellular space. The positive rate response on fruit size and negative rate response on crop load of `Empire' became less significant for each formulation as the amount of GA4+7 in the formulation increased. The same was true for `Delicious', but less pronounced. At low rates of BA, formulations containing GA resulted in more thinning than BA alone. However, at higher rates of BA, formulations containing GA caused significantly less thinning than BA alone. For treatments combined with carbaryl, crop load increased linearly in `Empire' with increasing amounts of GA4+7 in the formulation. The treatment that provided the largest fruit size for `Empire' was BA@150 ppm, while for `Delicious' it was BA@75 ppm + carbaryl. Both varieties showed the greatest reduction in crop load with the 100:1@75 ppm+ carbaryl treatment when compared to the controls. These data suggest that GA4+7 in formulation with BA may inhibit the thinning action of BA at moderate and high rates.
E.W. Stover, P.J. Stoffella, S.A. Garrison, D.I. Leskovar, D.C. Sanders and C.S. Vavrina
A commercial mixture of 1-naphthaleneacetamide and 1-naphthaleneacetic acid (Amcotone) was applied to tomato (Lycopersicon esculentum Mill.) and pepper (Capsicum annuum L.) at various timings from early bloom through early fruit development to evaluate effects on fruit size and both early and total marketable yield. Amcotone was applied at rates from 10 to 40 mg·L-1, at three sites for each of the species studied. Measured yield response variables in tomato did not differ between the control and Amcotone treatments, regardless of location. Amcotone treatments did not affect yields or fruit size for pepper at the New Jersey or Texas sites. However, at Ft. Pierce, Fla., early marketable yield of pepper was increased in plots receiving three Amcotone applications at 10 mg·L-1, but total marketable yield was significantly reduced in all plots receiving more than two Amcotone sprays, and mean fruit weight was reduced by all Amcotone treatments. Early and total marketable yield of pepper at Ft. Pierce were markedly reduced in plots receiving four applications of 40 mg·L-1, which was a high rate used to assess potential phytotoxicity. While minimal benefit from auxin application was observed in this study, earlier studies suggest that these results may have been influenced by favorable environmental conditions for fruit development or negative effects on unopened flowers during all Amcotone spray applications.