Quality traits of date palm fruits in a center of origin and center of diversity.

Multivariate statistical analyses were employed in data reduction of six fruit qualitative traits, along with economic value and a final score of fruit quality, scored on fruits of 203 date palm varieties grown in 19 ecogeographical regions in six countries of the Arabian Peninsula. Fruit color and shape were highly diverse across ecogeographical regions, whereas fruit softness and consumption stage were the least diverse. Principal component extraction revealed highly intricate trait associations among single principal components with a minimum 52% (United Arab Emirates) and a maximum 72% (Kuwait) variance being explained by three principal components. Anthropogenic factors reflected the number of traits forming a two-, three-, or four-trait log-linear model for each country. However, fruit color, shape, size and ripening and their interactions predominantly reflect differences in consumer preferences in these countries. Long-term intra- and inter-country selection for specific fruit quality traits was quantified as a diversity index (I) and ranged from 0 in one region of Oman for fruit softness to 1.7 for fruit color in one region in the United Arab Emirates. Trait richness, at an ecogeographical or country level, reflects farmers' and consumers' preferences and allows for targeted selection and introduction of date palm varieties. The Central region in Saudi Arabia has the highest trait richness (6.08) for fruit color whereas the Dakhliya region of Oman has the highest trait richness for fruit ripening (3.91), fruit size (3.9) and fruit texture (5.86). Three predictors of fruit economic value (fruit color, softness and consumption stage) explained 65.5% of its total variation and delineated clear sub-regional differences in consumer preferences. A classification matrix based on discriminant analysis of all quality traits showed that Kuwaiti varieties were unique, with percent correct classification of 88%, and may have originated from countries outside the Arabian Peninsula, whereas Qatar has the least (55%) number of varieties correctly classified. Values for the remaining countries were: 63% for Bahrain, 70% for Saudi Arabia, 75% for Oman and 79% for United Arab Emirates. A Mahalanobis distance matrix between countries of origin indicated that geographical distances are indicative of quality differences between varieties. However, the intra- and inter-country shared varieties expressed as a percentage turnover of varieties between regions within one country and among countries implied that germplasm exchange is widely practiced in this part of the date palm center of origin and center of diversity.