The amounts of limonoate A-ring lactone (LARL) and limonin 17-d-o-glucopyranoside (LG) in navel oranges were measured during fruit growth and maturation. The LARL content (grams/fruit) increased sharply from June to August, reached a maximal level at the end of August, and then decreased gradually thereafter.LG began to appear in the flesh portion in September and in the peel 1 month later. Its content increased sharply from September to November and then slowly thereafter. The decrease in LARL and the increase in LG content occurred simultaneously at late stages of fruit growth and maturation, suggesting that LG is a metabolite of LARL. The amounts of total limonin (LARL + LG) continued to increase until the end of November and then remained fairly constant thereafter. This showed that the biosynthesis of LARL and its further conversion to LG appeared to continue in the fruit until the end of November.Bitterness due to limonin in a variety of citrus juices is major problem of the citrus industry, worldwide, and has significant negative economic impact. In general, bitterness occurs in juices extracted from early-season to midseason fruits of winter citrus, such as navel orange, Shamouti orange, grapefruit, and Natsudaidai. Bitterness is greatly reduced in juice extracted from fruits harvested later in the season. The concentration of limonoate A-ring lactone (LARL), a precursor of limonin, decreases as fruit maturation progresses (Maier et al., 1980). However, how

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Fruit production and tree size were measured and yield efficiency was computed for 11-year-old trees of ‘Washington’ navel and ‘Olinda Valencia’ oranges [Citrus sinensis (L.) Osbeck], ‘Minneola’ tangelo (C. paradisi Macf. × C. reticulata Blanco), and ‘Lisbon’ lemon (C. limon Burm. f.) on 21 rootstocks in the San Joaquin Valley of California. Performance of most rootstocks was similar over all scions, and several rootstocks produced trees with higher yields than ‘Troyer’ and ‘Carrizo’ citranges [C. sinensis × Poncirus trifoliata (L.) Raf.], the current standard rootstocks. ‘Yuma Ponderosa’ lemon (× C. limon) had the highest yields, but several trees on this rootstock died or were declining. Trees on ‘C-32’ citrange (C. sinensis × P. trifoliata) were largest, and yielded nearly as much as those on ‘Yuma Ponderosa’ lemon. ‘C-35’ citrange (C. sinensis × P. trifoliata) produced smaller trees with excellent yield efficiencies, and should be suitable for higher-density plantings with most scions, except perhaps navel orange, because this combination yielded poorly at other locations. ‘Rangpur’ lime (C. limonia Osbeck) was promising only with lemon scion, and ‘Swingle’ citrumelo (C. paradisi × P. trifoliata) only with ‘Minneola’.

The effect of various integrated crop management practices on productivity (fruit yield, grade, and sire) and returns of `Washington Navel' oranges [Citrus sinensis (L.) Osbeck] was determined in the San Joaquin Valley of California. Seventy-two combinations of treatments comprised of three irrigation levels [80%, 100%, and 120% evapotranspiration demand (ETc)], three N fertilizer levels (low, medium, and high based on 2.3%, 2.5%, and 2.7% leaf N, respectively), gibberellic acid (±), miticide (±), and fungicide-nematicide (±) were included in the analysis. Using a partial budgeting procedure, returns after costs were calculated for each treatment combiition. Costs of treatments, harvesting, packing, and processing were subtracted from the value of the crop. The value of the crop was calculated as the sum of returns of crop in each size and grade category. The overall result indicated that returns after costs were higher for the +fungicide-nematicide treatment and also were generally more with increased irrigation. The combination of 120% ETc, +fungicide-nematicide, medium or high N, -miticide, and -gibberellin showed the highest return of all treatment combinations. Second highest returns were obtained with high N or with miticide and gibberellin used together.