Research on the climatic conditions . In the Spanish trial , trees subjected to the mild deficit irrigation treatment had LWP of -1.0 to -1.5 MPa at midday . The moderate deficit irrigation treatment resulted in LWP of -1.5 to -2.0 MPa at midday . So , these deficits would be expected to possibly limit fruit growth .
The moderate deficit treatment increased SSC by 1 – 2 %. However , as expected , it also significantly reduced the number of harvestable fruit per tree and average fruit size . Total yield was reduced almost 30 %, probably making this treatment uneconomic .
In contrast , the mild deficit treatment did not affect fruit size or yield . Soluble solids concentration was also unaffected , or even slightly reduced compared to the fully irrigated controls . Despite this , consumers consistently graded these fruit as sweeter and more flavoursome . Over two harvest times , consumer acceptance was increased by 15 to 20 % for the mild deficit irrigation fruit ( Figure 1 ).
HARVEST 1 HARVEST 2 normal irrigation
mild deficit irrigation
normal irrigation
mild deficit irrigation
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Figure 1 . Consumer responses to nectarines grown with normal irrigation or with a mild deficit in irrigation .
The authors show that , over two seasons at least , consumer liking of nectarines had a strong relationship with midday LWP at harvest . That is , as LWP decreased
20 %
( due to water stress ), consumer liking increased ( Figure 2 ).
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Like Indifferent Dislike
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Figure 2 . The relationship between Leaf Water Potential at harvest and the percentage of consumers who liked the nectarines .
It is not quite clear why this effect occurs . Whether people liked or disliked the nectarines was not easily linked to sugars , acid or firmness . It is most likely consumers were responding to fruit flavour .
Flavour compounds in many fruit and vegetables increase in response to stress . For example , aroma volatiles in apples have shown this effect . This may be one of the reasons some people think organic products taste better . The same could be true for stonefruit .
Alternatively , mild water stress may be advancing fruit maturity . Earlier research showed that the percentage of consumers who liked nectarines increased from 0 to 85 % over five weekly harvests . Effectively , this study showed that delaying picking by 12 to 16 days from minimum harvest maturity increased acceptability to consumers by 26 %.
-1.6 -1.4
-1.2 -1.0
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-0.6 Leaf Water Potential ( MPa )
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Irrigation patterns before harvest can have a large effect on both yield and fruit quality . However , it is important that quality improvements are not at the expense of profitability .
Well-watered trees can produce large , but potentially somewhat flavourless , fruit . Too little water reduces fruit size , numbers and yield . However , just the right amount of pre-harvest water stress can leave yield unaffected , improve fruit quality and have customers coming back for more .
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Consumer liking (%)
1
Lopez G et al . 2011 . Instrumental and sensory evaluation of fruit quality for ‘ Ryans ’ s Sun ’ peach grown under deficit irrigation . HortTechnology 21:712-719 .
2
Lopez G et al . 2016 . Water stress for a short period before harvest in nectarine : Yield , fruit composition , sensory quality and consumer acceptance of fruit . Scientia Hort . 211:1-7 .
3
Naor A et al . 2001 . The response of nectarine fruit size and midday stem water potential to irrigation level in stage III and crop load . J . Amer . Soc . Hort . Sci . 126:140-143 .
4
Iglesias I , Echeverria G . 2009 . Differential effect of cultivar and harvest date on nectarine colour : quality and consumer acceptance . Sci . Hortic . 120:41-50 .
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