Endosperm cell number in barley
Grain weight is one of the major components of grain yield and it has been suggested that in wheat, final grain weight may be a function of endosperm cell number1. If grain weight is to be increased by increasing the rate and/or duration of endosperm cell division, it is important to establish the stage of development at which maximum endosperm cell number is attained. Evers2 reported that no cell division occurred in the endosperm of wheat later than 16 days after anthesis and other workers3,4 have come to a similar conclusion using cell counts. However, biochemical analyses5 have shown that the maximum DNA content of wheat endosperm is not reached until 25 days after anthesis and both Donovan6 and Radley7 have suggested that endosperm cell division may continue until about 30 days after anthesis. We have estimated the number of endosperm nuclei in developing caryopses of barley and have examined transverse sections of endosperms of different ages. We report here that cell division in barley endosperm continues until 28–30 days after anthesis.
A method for the determination of cell number in plant tissues.
Summary A new method of estimating cell numbers in young plant tissue is described. Tissue was stained in bulk with Feulgen's reagent and macerated by fungal cellulase. The stained nuclei were precipitated from an aliquot of the resulting suspension and counted under the microscope.
Effect of Soybean Cyst Nematode (Heterodera glycines) on Yield of Resistant and Susceptible Soybean Cultivars Grown in Ohio.
Soybean (Glycine max) producers in Ohio rarely use soybean cyst nematode (Heterodera glycines, SCN)-resistant cultivars because of concerns over limited yield potential and lack of resistance to Phytophthora sojae. A two-year study was initiated to determine grain yield and nematode population increase on soybean cyst nematode-resistant cultivars in maturity groups II and III in production fields. Sites differed in soil texture, nematode densities, and P. sojae infestation at a number of locations in Ohio. Soil was assayed for nematode densities before planting and at harvest. Yields of resistant cultivars averaged 0% to 18% higher than those of susceptible cultivars in fine-textured soils with average preplant populations ranging from 463 to 14,330 SCN eggs/100 cm(3) soil. In coarse-textured soils, yields of susceptible cultivars were 21% to 56% less than the resistant cultivars with average preplant densities ranging from 1,661 to 15,558 SCN eggs/100 cm(3) soil. The reproductive index ranged from 0.1 to 5.5 for resistant cultivars and 0.4 to 112 for susceptible cultivars. In 1993, yield of P. sojae-susceptible, nematode-resistant 'Asgrow A 3431' was as high as yield of the P. sojae-resistant, nematode-susceptible cultivar 'Resnik' in a Phytophthora-infested field. The nematode-resistant cultivars Madison Experimental 131527 and Asgrow A3431 had higher yields than AgVenture AV1341 and susceptible cultivars Resnik and Kenwood when compared over five nematode-infested sites. Nematode-resistant cultivars were found to be excellent alternatives to currently grown susceptible cultivars for managing SCN where group III cultivars are used. However, better cultivar alternatives may be needed for sites with combined Phytophthora root rot and cyst nematode problems.