2019 ASHS Annual Conference

Pericarp integrity is associated with seed vigour in shrunken-2 (sh-2) maize. Genetic improvement of the pericarp is one of the strategies for improving seed quality in sh-2 maize. Genetic information on pericarp integrity, inferred from leachate conductivity, was elucidated from seeds of 10 S₇ parental inbred lines derived from a tropicalized sh-2 maize population, their testcrosses, and reciprocal crosses. Two- and four-month old seeds were assayed. Experimental design was completely randomized with three and six replications for two and four-month old seeds, respectively. Leachate conductivity of the inbred lines ranged from 32.2 to 113.3 µs/cm/g in two-month old seeds and 47.0 to 152.2 µs/cm/g in four-month old seeds, while for the testcrosses it ranged from 27.6 (UISS7 - female parent) to 148.3 µs/cm/g in two-month old seeds and 36.2 (UISS7 - female parent) to 227.4 µs/cm/g in four-month old seeds; differences among the entries within each group were significant (P < 0.05). Significant differences in leachate conductivity were obtained in nine each of the 15 and 14 pairs of reciprocal crosses in two- and four-month old seeds, respectively. Differences in leachate conductivity between pairs of significantly different reciprocal crosses ranged from 33.9 to 377.3 µs/cm/g with an average of 147.2 µs/cm/g in two-month old seeds and 119.0 µs/cm/g in four-month old seeds. Crosses involving Inbred Line UISS 7 did not show significant reciprocal differences. Crosses in which Inbred Lines UISS 9 and UISS 4 were used as female parents had high leachate conductivity; UISS 7 as male parent, however, reduced the leachate conductivity of crosses involving these lines. The increase in leachate conductivity of four-month old seeds over two-month old seeds averaged 31.6% for the inbred lines, 40.0% for the testcrosses and 20.9% for the reciprocal crosses. Correlation between leachate conductivity of two- and four-month old seeds for the parental inbred lines, testcrosses, and reciprocal crosses ranged from 0.86 and 0.96 (P < 0.01). Correlation coefficient values between leachate conductivity of inbred lines and their testcrosses were not significant. Genetic variation for pericarp integrity was present among the inbred lines. In addition to the presence of reciprocal differences, this study provides evidence of a role for the male parent in pericarp integrity, despite the female parent origin of the pericarp. The development of sh-2 hybrids with excellent pericarp integrity requires a careful choice of parents.