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The Effects of Biotic Stress on Onion Physiology.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	The Effects of Biotic Stress on Onion Physiology./
Author:	Wood, Joseph.
Description:	1 online resource (106 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 84-12, Section: B.
Contained By:	Dissertations Abstracts International84-12B.
Subject:	Plant sciences. -
Online resource:	click for full text (PQDT)
ISBN:	9798379732486

The Effects of Biotic Stress on Onion Physiology.
Wood, Joseph.

The Effects of Biotic Stress on Onion Physiology. - 1 online resource (106 pages)

Source: Dissertations Abstracts International, Volume: 84-12, Section: B.

Thesis (Ph.D.)--New Mexico State University, 2023.

Includes bibliographical references

Bulb onion (Allium cepa L.) is an economically valuable vegetable crop in the United States. Onion production is threatened by onion thrips, the vector of Iris yellow spot virus, causal agent of Iris yellow spot (IYS). New Mexico State University (NMSU) breeding lines, 12-236, 12-238, 12-243, and 12-337, have exhibited fewer IYS disease symptoms in the field; however, little is known about the effects of the disease on photosynthesis rate (Pn). We hypothesized that these NMSU breeding lines would have a higher Pn than IYS-susceptible cultivars Rumba and Stockton Early Yellow. To test this hypothesis, a field study was conducted for three years at NMSU and Pn was measured five times throughout each season at two-week intervals. In years 2 and 3 of the experiment, along with Pn, the effects of the disease on effective quantum yield of photosystem II (⏀PSII), the maximum quantum yield of photosystem II (Fv/Fm), electron transport rate (ETR) and intercellular carbon dioxide concentration (Ci) were also evaluated. We hypothesized that these NMSU breeding lines would have a higher FPSII, Fv/Fm and ETR than IYS-susceptible cultivar Stockton Early Yellow because this would indicate the NMSU breeding lines were under less stress than the susceptible cultivar. During bulb development and maturation, which occurred at 10 and 12 weeks post transplanting, all NMSU breeding lines exhibited a higher Pn when compared to an IYSsusceptible cultivar. Pn was highest at the end of the vegetative growth stage and decreased as bulbs approached maturation for all entries. In addition, a high Pn at 10 and 12 weeks post transplanting coincided with high bulb weight at harvest for NMSU breeding lines. ⏀PSII, Fv/Fm and ETR were highest at the end of the vegetative growth stage and decreased as bulbs approached maturation for all entries. NMSU breeding lines had an elevated Pn compared to IYS-susceptible cultivars at weeks 10 and 12 after transplanting and resulted in larger, more marketable bulbs. These results indicate that maintaining Pn may be a component of reduced IYS symptom expression in onion. Biotic stress causes physiological changes at the cellular level that can be observed and quantified using confocal fluorescence microscopy. Chlorophyll and lignin are commonly imaged using fluorescence microscopy because they are natural fluorophores. To determine the influence of natural leaf senescence and insect damage on relative chlorophyll concentrations in onion leaves, we conducted a study to image leaves as they senesced naturally and were fed on by thrips. We hypothesized that the healthy leaves would have the most chlorophyll and that the damaged leaves would have the least chlorophyll. The images obtained after 90 days post seeding showed a decrease in relative chlorophyll area as the leaves went from healthy to necrotic. Understanding the physiology of photosynthesis in onions bred for reduced symptom expression of IYS will further aid breeders in developing future onion germplasm.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2024

Mode of access: World Wide Web

ISBN: 9798379732486Subjects--Topical Terms:

1179743
Plant sciences.
Subjects--Index Terms:

Allium cepaIndex Terms--Genre/Form:

554714
Electronic books.

The Effects of Biotic Stress on Onion Physiology.
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504 $a Includes bibliographical references
520 $a Bulb onion (Allium cepa L.) is an economically valuable vegetable crop in the United States. Onion production is threatened by onion thrips, the vector of Iris yellow spot virus, causal agent of Iris yellow spot (IYS). New Mexico State University (NMSU) breeding lines, 12-236, 12-238, 12-243, and 12-337, have exhibited fewer IYS disease symptoms in the field; however, little is known about the effects of the disease on photosynthesis rate (Pn). We hypothesized that these NMSU breeding lines would have a higher Pn than IYS-susceptible cultivars Rumba and Stockton Early Yellow. To test this hypothesis, a field study was conducted for three years at NMSU and Pn was measured five times throughout each season at two-week intervals. In years 2 and 3 of the experiment, along with Pn, the effects of the disease on effective quantum yield of photosystem II (⏀PSII), the maximum quantum yield of photosystem II (Fv/Fm), electron transport rate (ETR) and intercellular carbon dioxide concentration (Ci) were also evaluated. We hypothesized that these NMSU breeding lines would have a higher FPSII, Fv/Fm and ETR than IYS-susceptible cultivar Stockton Early Yellow because this would indicate the NMSU breeding lines were under less stress than the susceptible cultivar. During bulb development and maturation, which occurred at 10 and 12 weeks post transplanting, all NMSU breeding lines exhibited a higher Pn when compared to an IYSsusceptible cultivar. Pn was highest at the end of the vegetative growth stage and decreased as bulbs approached maturation for all entries. In addition, a high Pn at 10 and 12 weeks post transplanting coincided with high bulb weight at harvest for NMSU breeding lines. ⏀PSII, Fv/Fm and ETR were highest at the end of the vegetative growth stage and decreased as bulbs approached maturation for all entries. NMSU breeding lines had an elevated Pn compared to IYS-susceptible cultivars at weeks 10 and 12 after transplanting and resulted in larger, more marketable bulbs. These results indicate that maintaining Pn may be a component of reduced IYS symptom expression in onion. Biotic stress causes physiological changes at the cellular level that can be observed and quantified using confocal fluorescence microscopy. Chlorophyll and lignin are commonly imaged using fluorescence microscopy because they are natural fluorophores. To determine the influence of natural leaf senescence and insect damage on relative chlorophyll concentrations in onion leaves, we conducted a study to image leaves as they senesced naturally and were fed on by thrips. We hypothesized that the healthy leaves would have the most chlorophyll and that the damaged leaves would have the least chlorophyll. The images obtained after 90 days post seeding showed a decrease in relative chlorophyll area as the leaves went from healthy to necrotic. Understanding the physiology of photosynthesis in onions bred for reduced symptom expression of IYS will further aid breeders in developing future onion germplasm.
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653 $a Confocal microscopy
653 $a Dormancy
653 $a Fluorescence
653 $a Photosynthesis
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710 2 $a New Mexico State University. $b Plant and Environmental Sciences. $3 1437702
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