Wilson J P
USDA-ARS Crop Genetics and Breeding Research Unit, University of Georgia Coastal Plain Experiment Station, Tifton 31793.
Plant Dis. 2002 Aug;86(8):833-839. doi: 10.1094/PDIS.2002.86.8.833.
Stalk rot is frequently observed in maturing, rust-infected pearl millet (Pennisetum glaucum). Fungi were isolated from internal stalk tissue, and their association with node discoloration and rust infection at different stages of plant maturity was determined to gain a greater understanding of stalk rot etiology. In 1995, stalk rot was observed in a breeding population of pearl millet. Stalks of 10 rust-infected plants were collected on each of three dates during grain fill. Frequency of symptomatic, discolored nodes was higher in the later sampling dates. Stalk sections from 119 discolored nodes were surface sterilized and plated onto agar media. Fungi most frequently isolated from symptomatic nodes were Bipolaris setariae (isolated from 47% of discolored nodes), Fusarium semitectum (28.6%), and F. moniliforme sensu lato (23.5%). Isolation frequency of these fungi differed (P < 0.05) with sampling date. In 1996 and 1997, the hybrid HGM 100 was evaluated at two dates of planting in each year. Ten stalks were sampled at each of four growth stages: panicle emergence, stigma emergence, milk, and hard dough. A total of 140 stalks was assessed for rust severity and for internal stalk discoloration at the nodes. The frequency of discolored nodes increased with plant maturation and was correlated (P < 0.01) with severity of rust infection. All nodes were plated on an agar medium, and a total of 1,512 isolates from 30 fungal genera or species were isolated from the 1,540 nodes of the sampled stalks. F. moniliforme was isolated most frequently (isolated from 23.5% of all nodes). Frequency of isolation of F. moniliforme from nodes within stalks increased with advancing maturity in the earlier dates of planting, but was not correlated with rust infection. B. setariae (isolated from 9.2% of all nodes) was more frequently isolated from plants at the dough stage in three plantings, and was correlated (P < 0.01) with rust severity. Trends in the frequency of isolation of other fungi were inconsistent between planting dates or among growth stages. Frequency of isolation of F. semitectum (isolated from 11.0% of all nodes) and Alternaria spp. (6.9% of all nodes) was correlated (P < 0.05) with rust severity. Frequency of isolation of Curvularia spp. (isolated from 7.0% of all nodes) was negatively correlated (P < 0.05) with rust severity. Isolation of Alternaria spp. and B. setariae was more frequently associated with node discoloration than was isolation of the other fungi. Stalk rot of pearl millet is the result of a complex of several fungi whose incidence was influenced by rust infection, plant maturation, and environmental factors associated with differences among years and dates of planting.
在成熟的、感染锈病的珍珠粟（黍稷）中经常观察到茎腐病。从茎内部组织分离出真菌，并确定它们在植物成熟的不同阶段与节部变色和锈病感染的关系，以更深入了解茎腐病的病因。1995年，在珍珠粟的一个育种群体中观察到茎腐病。在灌浆期的三个日期，分别采集了10株感染锈病植株的茎。在后期采样日期，有症状的、变色节的频率更高。对119个变色节的茎段进行表面消毒，然后接种到琼脂培养基上。从有症状的节中最常分离出的真菌是狗尾草平脐蠕孢（从47%的变色节中分离得到）、半裸镰刀菌（28.6%）和广义串珠镰刀菌（23.5%）。这些真菌的分离频率随采样日期而不同（P < 0.05）。1996年和1997年，每年在两个种植日期对杂交种HGM 100进行评估。在四个生长阶段（穗抽出、柱头抽出、乳熟和硬面团期）的每个阶段，各采样10株茎。共评估了140株茎的锈病严重程度和茎内部节部的变色情况。变色节的频率随植物成熟而增加，并且与锈病感染严重程度相关（P < 0.01）。将所有节接种到琼脂培养基上，从采样茎的1540个节中总共分离出30个真菌属或种的1512个分离物。串珠镰刀菌分离频率最高（从所有节的23.5%中分离得到）。在较早的种植日期，串珠镰刀菌从茎内节的分离频率随成熟度增加，但与锈病感染无关。狗尾草平脐蠕孢（从所有节的9.2%中分离得到）在三次种植中，在面团期的植株中分离频率更高，并且与锈病严重程度相关（P < 0.01）。其他真菌的分离频率趋势在不同种植日期或不同生长阶段之间不一致。半裸镰刀菌（从所有节的11.0%中分离得到）和链格孢属（所有节的6.9%）的分离频率与锈病严重程度相关（P < 0.05）。弯孢属（从所有节的7.0%中分离得到）的分离频率与锈病严重程度呈负相关（P < 0.05）。链格孢属和狗尾草平脐蠕孢的分离比其他真菌的分离更常与节部变色相关。珍珠粟茎腐病是几种真菌复合侵染的结果，其发生受锈病感染、植物成熟以及与年份和种植日期差异相关的环境因素影响。
