Postpollination Stigmatic Constriction, the Basis of Ergot Resistance in Selected Lines of Pearl Millet

Willingale, Julia; Mantle, Peter G.; Thakur, R. P.

doi:10.1094/phyto-76-536

Cited by 29 publications

(15 citation statements)

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“…As Willingale and Mantle (1985) have pointed out, the zone may also act as a self-incompatibility barrier, promoting outcrossing by preventing later selfpollination in highly protogynous pearl millet cultivars. A third significant function of the AZ in the pearl millet stigma, first recognized by Willingale and Mantle (1985) and Willingale et al (1986), is as a device regulating the period during which the ovary is open to invasion by pathogens. The rapid formation of a virtually complete seal at the entry into the ovary following a successful pollination ensures that the pathway for potentially invasive hyphae is rapidly blocked.…”

Section: Discussionmentioning

confidence: 99%

“…The operation of the abscission system could be critically important not only in regulating pollination but also in providing a barrier to infection after the end of the pollenreceptive period. Willingale and Mantle (1985) and Willingale et al (1986) provided the first direct evidence for this in a detailed study of the role of the activatable zone in resistance to ergot, discussed below. We report here on cytological features of the AZ of millet and comment on various aspects of the physiology of the abscission process itself, including the role of the calcium oxalate druses copiously distributed in the cells of the AZ.…”

Section: Introductionmentioning

confidence: 92%

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The pollen tube activated abscission zone in the stigma of pearl millet: structural and physiological aspects

Heslop‐Harrison¹,

Heslop‐Harrison²

1997

Can. J. Bot.

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Abscission of the stigmas of pearl millet (Pennisetunl typhoides (Burman) Stapf et Hubbard) after pollination results from the activation of a specialized zone of tissue near the base. This abscission zone comprises a well-defined stretch of the basal column made up of thin-walled cells lacking a cuticularized epidermis. The penetration of the first few pollen tubes following a compatible pollination results in loss of turgor throughout the tissue, followed by loss of adhesion between the cells and ultimately disruption of the whole zone. Pectolytic enzymes are released concomitantly, but the cellulosic skeletons of the cells persist. Numerous calcium oxalate druses, identified cytochemically and by energy-dispersive X-ray analysis, are present in the cells of the abscission zone; these undergo dissolution after activation of the zone, while simultaneously the druse population in the stigma stump and the upper ovary wall increases. The barrier formed by the degenerating abscission zone tissues excludes pollen tubes arriving after the initial activation and prevents the penetration of pathogens such as ergot and so has a prophylactic role. We suggest that the collapsed abscission zone forms not only a physical barrier but also a chemical one. Dissolution products of the numerous calcium oxalate druses during the breakdown of the tissue are likely to raise the calcium ion concentrations beyond the optimum for pollen-tube growth, thereby preventing further penetration. Inhibited tubes swell at the tips and may show growth disorientation before arrest, responses similar to those seen in pearl millet tubes in culture when exposed to higher than normal calcium ion concentration.Resum6 : L'abscission des stigmates du millet perlt (Penniseturn typhoides (Burman) Stapf et Hubbard), aprks la pollinisation, rtsulte de I'activation d'une zone sptcialiste du tissus situC a sa base. Cette zone d'abscission comporte une portion bien dCfinie de la colonne basale, constitute de cellules i paroi mince dCpourvues d'Cpiderme cuticularist.La penetration du premier grain de pollen, i la suite d'une pollinisation compatible, conduit i une perte de turgescence dans l'ensernble du tissus, suivi par une perte de cohtsion entre les cellules et tventuellement d'une dCsorganisation de I'ensemble de la zone. Des enzymes pectolytiques sont reldchtes i ce moment mais le squelette cellulosique des cellules persiste. De nombreux cristaux d'oxalate de calcium, identifiCs cytochimiquement et par I'tnergie dispersive des rayons X, sont prtsents dans les cellules de la zone d'abscission; ceux-ci subissent une dissolution aprks l'activation de la zone, alors que simultanCment la population de cristaux dans la base du stigmate et dans la partie suptrieure de l'ovaire augmente. La barrikre formte par les tissus de la zone d'abscission en dCgtntrescence exclut les tubes polliniques qui arrivent aprks l'activation initiale et prtvient la ptnttration par des organismes pathogknes tels que I'ergot, comportant ainsi des proprittts prophylactiques. Les auteur...

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 92%

The pollen tube activated abscission zone in the stigma of pearl millet: structural and physiological aspects

Heslop‐Harrison¹,

Heslop‐Harrison²

1997

Can. J. Bot.

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“…Further support for the notion that pollen availability or viabihty is a key factor in sugary disease development comes from work carried out on pearl millet. THAKUR et al (1983) andWILLINGALE et al (1986) showed that pollination prevents infection of pearl millet by C. fusiformis Loveless or restricts hyphae from reaching the ovary. CHALAL et al (1987) observed a relationship between protogyny and ergot susceptibility of millet.…”

Section: Discussionmentioning

confidence: 99%

Relationship between Climatic Variables during Early Flowering of Sorghum and the Incidence of Sugary Disease caused by Sphacelia sorghi

McLaren¹,

Wehner

1990

Journal of Phytopathology

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The relationship between sugary disease incidence and six climatic variables during the early stages of flowering was determined in field trials conducted over three seasons. Daily maximum temperature was highly significantly correlated with sugray disease incidence and accounted for 83 % of the variation observed in disease incidence. The critical period for infection was limited to 5 days after commencement of pollen shed. Deviations from the temperature × sugary disease model occurred in late flowering plots. These were correlated with low temperatures during the 2 weeks prior to pollen shed and, thus, possibly, a reduction in pollen vigour.

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“…Pollination and fertilization are primary factors affecting ergot development in cereals (MCLAREN & WEHNER, 1992). In pearl millet, pollination prevents infection by C. fusiformis (LOVELESS, 1967) or restricts hyphae from reaching the ovary (THAKUR & WILLIAMS, 1980, WILLINGALE et al, 1986. Susceptibility of millet genotypes to ergot is inversely related to the duration of protogeny while pollen availability, as determined by pollen donor:female ratios in breeding plots, affects ergot incidence (THAKUR & RAO, 1983).…”

Section: Introductionmentioning

confidence: 99%

The influence of low temperatures on the incidence of sugary disease on sorghum

et al. 2006

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Postpollination Stigmatic Constriction, the Basis of Ergot Resistance in Selected Lines of Pearl Millet

Cited by 29 publications

References 0 publications

The pollen tube activated abscission zone in the stigma of pearl millet: structural and physiological aspects

The pollen tube activated abscission zone in the stigma of pearl millet: structural and physiological aspects

Relationship between Climatic Variables during Early Flowering of Sorghum and the Incidence of Sugary Disease caused by Sphacelia sorghi

The influence of low temperatures on the incidence of sugary disease on sorghum

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