The Occurrence of Pecan Kernel Necrosis

Abstract

<jats:p>Pecan [<jats:italic>Carya illinoinensis</jats:italic> (Wangenh.) C. Koch] kernels (cotyledon) of ‘Pawnee’ displayed a consistent malady not described previously that was designated as “kernel necrosis.” The most severe form of the problem was blackened, necrotic tissue engulfing the basal one-half to one-third of the kernel. The mildest form was darkened tissue in the dorsal grove at the basal end of the kernel. The problem was first observable during the gel stage of kernel development. No symptoms of kernel necrosis were visible on the shuck (involucre). Kernel necrosis was more prominent on ‘Pawnee’, ‘Choctaw’, and ‘Oklahoma’ than other cultivars observed. At maturity, nuts with kernel necrosis had a larger volume than nuts with normal kernels. There were few differences in elemental concentrations of normal kernels from a severely affected orchard and an orchard with little kernel necrosis, and none of the differences appeared to be associated with this disorder. ‘Pawnee’ kernels with necrosis had more phosphorus, zinc, and manganese than normal kernels. Basal segments of necrotic kernels had more boron and acetic acid-extractable and water-soluble calcium than distal segments or normal kernels. Higher elemental concentrations in basal segments of necrotic kernels did not appear sufficient to cause tissue damage.</jats:p> <jats:p>Soil from the orchard with severe kernel necrosis had unusually high concentrations of nitrate, expressed as nitrogen (NO<jats:sub>3</jats:sub>-N), in the soil profile. Groundwater used for irrigation was contaminated with 34 mg·L<jats:sup>−1</jats:sup> NO<jats:sub>3</jats:sub>-N. An experiment on ‘Pawnee’ evaluated three nitrogen (N) rates, 0, 0.8 g·cm<jats:sup>2</jats:sup> cross-sectional trunk area applied in March, and 1.6 g + 1.6 g + 1.2 g·cm<jats:sup>2</jats:sup> cross-sectional trunk area N applied during the second week in March, first week in June, and first week in September, respectively, on the incidence of kernel necrosis, leaf N concentration, soil NO<jats:sub>3</jats:sub> concentration, yield, nut quality, and growth over 5 years. Leaf N was affected by treatment only once during the study. Nitrates accumulated in the soil, increasing 24% in 3 years when no supplemental N was applied, except in the contaminated irrigation water. Kernel necrosis was either unaffected by N treatment or during 1 year, kernel necrosis was highest without supplemental N application. Tree yield, kernel quality, and growth were unaffected by N treatment. Yield fluctuations among years were apparent demonstrating that an abundant N supply did not prevent alternate bearing. Kernel necrosis was a severe problem in one orchard and was identified in several orchards at low frequencies. The cause of kernel necrosis remains unknown.</jats:p>

Impact of Room-Temperature Storage on the Pecan Kernel Color, Carotenoids, Polyphenols, and Physicochemical Properties

“…Although no literature has documented the reasons for the darker color at ventral side, naturally, dorsal and ventral sides have different groove depths and widths, which might cause different color intensities. In addition, pecan kernel necrosis could cause darkened tissues, although we did not perceive that this was the case for the kernel samples in this study. In addition, this color change was observed in all five tested pecan varieties, although some differences were noted between the varieties.…”

“…The mean score and standard deviation for each point could be found in Table S1. 19 although we did not perceive that this was the case for the kernel samples in this study. In addition, this color change was observed in all five tested pecan varieties, although some differences were noted between the varieties.…”

Ambered Kernels in Stenospermocarpic Fruit of Eastern Black Walnut

“…Unlike black walnut, Persian walnut fruiting shoots with oilless nuts produce sparse leaves with interveinal chlorosis and these fruiting spurs often die the next winter (Grant et al, 1985). Necrosis has also been reported on the basal area of pecan kernels and it affects certain cultivars such as 'Pawnee', 'Choctaw', and 'Oklahoma' more so than 'Cheyenne' (Smith et al, 2007). Although the cause of pecan kernel necrosis is unknown, it does not appear to be the result of stink bug damage, pecan weevil feeding, or a nutritional disorder.…”