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  • Author or Editor: S. Nemec x
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Three sites (A-C) were prepared for citrus groves in Florida from 1985 to 1986. Nine soil amendments applied at either one or two rates were deep-tilled 3.9 to 4.9 ft (1.2 to 1.5 m) deep and 4.9 ft (1.5 m) wide in the row before planting. Maximum treatment rates were limestone 50,000 at lb/acre (56 000 kg·ha−1), phosphoclay at 80,000 lb/acre (89 600 kg·ha−1), humate at 77,612 lb/acre (86 912 kg·ha−1), shrimp waste at 73,052 lb/acre (81 805 kg·ha−1), peat at 250,000 lb/acre (280 000 kg·ha−1), bentonite clay at 73,051 lb/acre (81 805 kg·ha−1), mined gypsum at 2000 lb/acre (2240 kg·ha−1), calcium humate at 2000 lb/acre (2240 kg·ha−1), and phosphogypsum at 10,000 lb/acre (11 200 kg·ha−1). Deep-tilled controls and a no-till control were established at sites A and B and a deep-tilled control at site C. A fourth grove (site D) was planted in 1970 and included the treatments surface tillage (ST), deep tillage (DT), and DT plus lime (DTL) at 45,407 lb/acre (50,848 kg·ha−1). Mycorrhizal fungus infection was found in roots in 1987 at sites A and B and in 1989 in site C. Fungus infection ranged from 6% (no-till control) to 64% at site A, 64% to 81% at site B, and 15% to 47% at site C. At all sites, amendments did not increase percentage infection and vesicle and hyphae ratings significantly over the deep-tilled control. At site A, percentage infection in the limestone treatment was the highest (64%) and was significantly higher than infection in phosphogypsum, peat, and the no-till control treatments. No treatment had a suppressive effect on infection. Mycorrhizal infection in roots was high (94% to 95%) at site D but did not differ significantly between treatments.

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Abstract

Carbohydrates were analyzed in mycorrhizal and nonmycorrhizal citrus rootstock seedlings in greenhouse studies. Inoculated seedlings grew taller or weighed more and their leaves contained greater amounts of total soluble sugar, sucrose, reducing sugars, starch, and total nonstructural carbohydrate per gram of tissue than noninoculated controls, in a low P soil (9–12 ppm). Only the reducing sugars, fructose and glucose, increased slightly in roots of inoculated seedlings over those levels found in uninoculated control seedlings. Levels of reducing sugars were higher in leaves than in roots. Uninoculated seedlings grown in high P soil (210 ppm) were about the same height and their leaves contained levels of total soluble and reducing sugars similar to those in inoculated rootstocks grown in low P soil. It does not appear that these mycorrhizal fungi mobilize sugars as a sink for photosynthate in roots.

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Abstract

Twenty-three strawberry cultivars, naturally infected with Diplocarpon earliana (Ell. & Ev.) Wolf, ranged from resistant in cultivars such as ‘Earlibelle’, ‘Albritton’ and ‘Empire’ to very susceptible in the cultivars ‘Redglow’, ‘Jerseybelle’ and ‘Vesper’. In general, leaf scorch resistance ratings were similar to those for the same cultivars tested elsewhere.

In 14 progenies from crosses involving 9 cultivars a larger % of seedlings were rated resistant from selfed resistant (R) parents than from selfed susceptible (S) or intermediate (I) parents, or from crosses involving these parents.

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