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3 results on '"P. A. Counce"'

1. Genotype‐dependent and heat‐induced grain chalkiness in rice correlates with the expression patterns of starch biosynthesis genes

Author

Peter James Gann, Manuel Esguerra, Paul Allen Counce, and Vibha Srivastava

Subjects
chalkiness, heat stress, high nighttime temperature, rice grain, starch biosynthesis, Environmental sciences, GE1-350, Botany, QK1-989
Abstract

Abstract Starch biosynthesis is a complex process underlying grain chalkiness in rice in a genotype‐dependent manner. Coordinated expression of starch biosynthesis genes is important for producing translucent rice grains, while disruption in this process leads to opaque or chalky grains. To better understand the dynamics of starch biosynthesis genes in grain chalkiness, six rice genotypes showing variable chalk levels were subjected to gene expression analysis during reproductive stages. In the chalky genotypes, peak expression of the large subunit genes of ADP‐glucose pyrophosphorylase (AGPase), encoding the first key step in starch biosynthesis, occurred in the stages before grain filling commenced, creating a gap with the upregulation of starch synthase genes, granule bound starch synthase I (GBSSI) and starch synthase IIA (SSIIA). Whereas, in low‐chalk genotypes, AGPase large subunit genes expressed at later stages, generally following the expression patterns of GBSSI and SSIIA. However, heat treatment altered the expression in a genotype‐dependent manner that was accompanied by transformed grain morphology and increased chalkiness. The suppression of AGPase subunit genes during early grain filling stages was observed in the chalky genotypes or upon heat treatment, which could result in a limited pool of ADP‐Glucose for synthesizing amylose and amylopectin, the major components of the starch. This suboptimal starch biosynthesis process could subsequently lead to inefficient grain filling and air pockets that contribute to chalkiness. In summary, this study suggests a mechanism of grain chalkiness based on the expression patterns of the starch biosynthesis genes in rice.

Published
2021
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2. Tillage Influence on Soluble Salt Movement in Silt Loam Soils Cropped to Paddy Rice

Author

David M. Miller, C. E. Wilson, Terry C. Keisling, D. L. Frizzell, A. D. Pearce, Carl R. Dillon, and P. A. Counce

Subjects
Tillage, Salinity, Agronomy, Soil test, Loam, Soil water, food and beverages, Soil Science, DNS root zone, Environmental science, Paddy field, Soil horizon
Abstract

Rice (Oryza sativa L.) produced in a dry-seeded, delayed-flood system common to the southern USA is extremely sensitive to excessive accumulation of soluble salts during the seedling growth stage. Recent observations have been made by producers, county agents, and researchers that the use of conservation tillage systems, particularly no-till systems, may increase the level of salinity in the rice root zone in dry-seeded, delayed-flood systems during the 4- to 6-wk period prior to permanent flood establishment. With the use of conservation tillage practices for rice production steadily increasing in the southern USA, it is important to determine if these practices increase potential for accumulation of soluble salts, to determine the mechanisms involved, and to develop management strategies to overcome the problem. A 2-yr study was initiated in the fall of 1994 to monitor salt distribution within the soil profile under different tillage regimes. A conventional system, a para-till operation, a chisel plow operation, and a no-till system were implemented in the fall and Br - was applied to monitor salt movement. 'Kaybonnet' rice was seeded during 1995 and 1996 and soil samples were collected from each plot at the two-to three-leaf growth stage. Salt accumulation at the rice seedling growth stage near the soil surface was higher in the no-till treatment than in any of the other tillage treatments based on higher electrical conductivity, Cl - concentration, and NO 3 - concentration in the top 2.5-cm depth. At this depth, the electrical conductivity was 30 to 40% greater, the Cl - concentration was 30 to 160% greater, and the NO 3 - concentration was 10 to 160% greater in the no-till treatment than in the other tillage treatments. Salt distribution within the profile was similar for all treatments beyond the 2.5-cm depth. The data suggest that tillage does tend to reduce the potential for salt accumulation in the root zone.

Published
2000

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