Pollen Viability, Pollen Shedding, and Combining Ability for Tassel Heat Tolerance in Maize¹

Abstract

High temperatures during maize (Zea mays L.) pollination limit kernel number. Knowledge is limited on the effect of heat stress on both pollen viability and tassel shedding characteristics or of possible heat tolerance sources and testers. The purpose of this research was to determine the tassel response to heat stress, as measured by in vitro pollen viability and shedding characteristics, and the combining ability for these traits using a diallel of four heat‐tolerant and three heat‐intolerant inbreds. Tassels from field‐grown plants were excised at the beginning of anthesis, immediately placed in sufficient water to cover the base, and transferred to growth chambers. The growth chambers were maintained at light period temperatures of 29 and 38°C and dark period temperatures of 24 and 32°C, respectively. In vitro germination, anther emergence, and tassel color were determined after 24 h in the growth chamber. Due to bursting, low levels of germination were obtained, but the percentage of nongerminated pollen increased greatly at the high temperature (65% mean increase). The increase in nongerminated pollen varied among the genotypes, and all except B73 × Mo17 and N28 × Mo17 had statistically significant increases at the high temperature. Mo17 had the most desirable general combining ability (GCA) effect at the high temperature for nongerminated pollen. Specific combining ability effects were significant for nongerminated pollen and accounted for 51% of the genotype and genotype × temperature sum of squares. Anther emergence of the central tassel spike decreased differentially among the hybrids at the high temperature. Mo17 had the most desirable GCA effect for anther emergence. Anther emergence and pollen viability did not always respond the same to high temperature. Results from this study indicate pollen shed and viability must be considered in tassel heat tolerance and hybrids involving Mo17 had the most heat tolerant tassels.

Maize Production in a Changing Climate

“…High temperature during the reproductive phase is associated with a decrease in yield due to a decrease in the number of grains and kernel weight. Under high temperatures, the number of ovules that are fertilized and develop into grain decreases (Schoper et al, 1987a and b). A comparison of the response of male and female reproductive tissues to heat stress demonstrated that female tissues have greater tolerance (Dupis and Durnas, 1990).…”

“…Pollen production and/or viability have been highlighted as major factors responsible for reduced fertilisation under high temperatures. Pollen produced under high temperature has reduced viability and in vitro germination (Herrero and Johnson, 1980;Schoper et al, 1986;Schoper et al, 1987a and b;Dupis and Durnas, 1990). Additionally, high temperatures are responsible for reduced pollen water potential, quantity of the pollen shed and pollen tube germination (Schoper et al, 1987;Dupis and Durnas, 1990).…”

A case study of GM maize gene flow in South Africa

“…The methods used to study gene flow include potential pollen-mediated gene flow (which includes the analysis of pollen viability, pollen dispersal and deposition, pollen capture and computer modelling) [17][18][19][20][21][22][23][24][25][26] and pollen-mediated gene flow (which involves determining the extent of cross-pollination over distance and computer modelling) [27][28][29][30][31][32][33][34][35][36][37][38]. While several studies have determined the extent of cross-pollination at different distances ranging from 34 to 650 m, it is not certain how applicable these data are to the maize growing region of South Africa.…”

Is change in ovary carbon status a cause or a consequence of maize ovary abortion in water deficit during flowering?

“…In maize (Zea mays), ovary development is highly drought sensitive (Boyer and Westgate, 2004) while pollen viability is not (Herrero and Johnson, 1981;Schoper et al, 1986Schoper et al, , 1987. A disruption of carbon metabolism in ovaries has been suggested to be the main cause of abortion, based on a series of experiments showing that Suc feeding can partly reverse the effect of WD on abortion (Boyle et al, 1991;Zinselmeier et al, 1995aZinselmeier et al, , 1999McLaughlin and Boyer, 2004).…”