Effects of the field environment before and after seed physiological maturity on hollow heart occurrence in garden pea (Pisum sativum)

Abstract

Hollow heart, a pea seed disorder, reduces pea seed vigour. It is associated with high temperature after seed set, but the susceptible seed development stage is not entirely clear. A field trial in New Zealand involving three sowing times (September, October, and November 2003) and three garden pea (Pisum sativum) cultivars ('Rainier', 'Early Onward', and 'Alderman') was conducted to determine if the predisposing stage to the disorder couldbe identified. Hourly thermal time (HTT) at a base temperature (T b ) of 25°C when seed moisture content (SMC) was 70-80% was correlated positively with hollow heart incidence at harvest maturity (HM), but this response differed among cultivars. HTT (T b = 25°C) when SMC was 15-25% was not correlated with hollow heart incidence at HM, if data for all cultivars were included in the correlation analysis. However, an increase in hollow heart incidence after seed had dried to between 15% and 25% SMC occurred with increasing HTT (T b = 25°C) in 'Alderman'. These results demonstrate that there are genetic differences in susceptibility to hollow heart. The hypothesis that hollow heart is associated with a starch deficiency in the adaxial region of the cotyledons, and that cultivar differences are related to differing efficiencies of assimilate transport into seeds at high temperatures is discussed.

Location of deterioration within garden pea(Pisum sativum)cotyledons is associated with the timing of exposure to high temperature

“…This result agreed with those of our previous field experiment (Shinohara et al 2006), in which we hypothesised that cultivar difference was associated with different abilities for assimilate transport into seeds under high temperature because of different growth habits, rather than differences in flowering duration, plant population or seed size between the cultivars.…”

“…In a previous field experiment (Shinohara et al 2006), 'Alderman' showed greater susceptibility to hollow heart than 'Early Onward'.…”

“…This disrupts starch accumulation and results in whitecore grains (WCRG); groups of starch cells around the central part of the endosperm which are whitish and fragile because of the presence of cracks or specialised pleat-like tissue (Taira 1995). Shinohara et al (2006) found higher hollow heart incidence in seeds harvested before pm if seeds were exposed to high temperature when SmC was 70-80%, but the incidence gradually decreased with sequential harvests until pm. During the pre-pm phase, seeds are still attached to, and therefore able to accept nutrients supplied from the mother plant (Le Deunff & rachidian 1988).…”

“…hollow heart incidence can also be increased with increasing duration of exposure to high temperature after pm (Castillo et al 1992). however, in recent research (Shinohara et al 2006) hollow heart was observed to increase after pm with increasing hourly thermal time (hTT) at a base temperature of 25°C only in one out of three cultivars used. Since the stage of predisposition to the disorder is not clearly identified, the mechanism of hollow heart development has not yet been elucidated.…”

“…Don et al (1984) using the tetrazolium technique, reported that seeds with this seed disorder had deteriorated cells at the adaxial region of the cotyledons. high air temperatures (>25°C) when seed moisture content (SmC) is 70-80% predispose seeds to the disorder (halligan 1986;Shinohara et al 2006). hollow heart incidence can also be increased with increasing duration of exposure to high temperature after pm (Castillo et al 1992).…”