Effects of Plant

Effects of Plant-growth-promoting-rhizobacteria on Biomass, Flowering, and Yield of Field Tomatoes

Bonnie H. Ownley, Danesha Seth, Choo Hamilton, and Mary Dee

Interpretative Summary

There were significant increases in growth of ‘Mountain Spring’ tomato plants seeded in potting mix amended with plant-growth-promoting rhizobacteria treatments LS213, LS254, LS255, LS256, and LS257. Due to enhanced growth, these treatments were ready for transplant 7 to 14 days earlier than the untreated control. Treatments LS213 and LS254 promoted earlier flowering, however, there were no significant increases in total or early yield with the treatments.

Introduction

Plant-growth-promoting-rhizobacteria (PGPR) are beneficial bacteria that enhance plant growth and reduce disease in many different agronomic crops. Some formulations of PGPR are now available and others are in commercial development. Bacillus subtilis GB03 is a PGPR organism with activity against soilborne fungal root pathogens. Treatment of seed with GB03 has been reported to promote growth and increase yields in several crop species. The objective of this study was to determine the effect of applying GB03 in combination with other beneficial bacteria to potting mix at seeding on early growth and flowering, and yield of tomato.

Materials and Methods

‘Mountain Spring’ tomato seeds were planted in Speedling potting mix amended with six bacterial treatments and a control (Table 1) on May 18, 2001. Seedlings were produced in 128-cell Styrofoam float trays in the greenhouse. Control plants were planted in potting mix with no bacterial treatment. Five of the bacterial treatments were mixed into potting mix at the rate of 2.5% weight/weight, while LS290 was applied at 1.0 % w/w. Treatments LS290 and LS213 had the same bacterial components but the rate of incorporation was different.

Table 1. Treatments applied to planting mix for production of tomato transplants

Treatment	Composition
Control	Untreated control
LS290	B. subtillis GB03 + Bacillus amyloliquefaciens IN937a at 1% w/w
LS213	B. subtillis GB03 + Bacillus amyloliquefaciens IN937 a at 2.5 w/w
LS254	Bacillus subtillis GB03 + Bacillus pumillis SE-37 at 2.5% w/w
LS255	B. subtillis GB03 + Bacillus subtillis IN937a at 2.5% w/w
LS256	B. subtillis GB03 + Bacillus pumillis INR-7 at 2.5% w/w
LS257	B. subtillis GB03 + Bacillus pumillus T4 at 2.5% w/w

Tomato seedlings were transferred to an outdoor shade (12%) house when the mean shoot height of a specific treatment was approximately 20 cm (8 in). On June 25, all seedlings were transplanted to the field. The seedlings were planted in eight blocks (replicates) with 5 plants per plot. Treatment plot rows were spaced 6 ft apart and were arranged in a randomized complete block design. Each treatment plot consisted of one 10-ft mounded row with black plastic mulch and trickle irrigation. Plots were not fumigated. Fertilizer (10-10-10) was applied prior to planting at 600 lbs / acre. Diseases and insects were controlled with scheduled fungicide and insecticide applications.

Shoot height, weight, and number of leaves were recorded on June 20 (33 days after seeding). The percentage of plants in each treatment that were blooming was determined at several dates between 68 and 80 days after seeding. Yield was recorded over a 3-week period (Sep 10 - 26). The number and weight of graded fruit was determined.

Results and Discussion

Growth measurements. At 33 days after seeding, there were significant differences between treatments for number of leaves, shoot height, and fresh shoot weight (Table 2). Growth was greatest in all measured parameters with LS213. Treatments LS254, LS255, LS256, and LS257 resulted in greater growth than the untreated control and in some cases they were not significantly different from the growth of LS213. The growth of plants treated with LS290 was not different from the untreated control.

Early flowering and fruit set. There were significant differences between treatments in percentage of plants blooming at 68 days after seeding (Table 3). Treatments LS213 and LS257 had significantly higher percentages of flowering plants than the control on the first evaluation date. There were no differences on subsequent evaluation dates. Although 20% of plants treated with LS213 and LS257 had fruit at 68 DAP, this percentage was not significantly different from the untreated control with 12.5%.

Table 2. Effect of treatment on growth of tomato plants 33 days after seeding

Treatment	Number of leaves	Shoot height (cm)	Fresh shoot weight (g)
Untreated	3.0 c^a	25.5 d	2.08 c
LS290	3.4 bc	27.2 cd	2.79 b
LS213	4.2 a	35.3 a	4.00 a
LS254	4.0 a	33.9 a	3.13 b
LS255	3.8 ab	27.3 c	2.91 b
LS256	3.8 ab	34.0 a	3.23 b
LS257	3.8 ab	30.7 b	3.36 ab

^{aWithin each column, means followed by the same
letter are not different according to an F-protected Least Significant
Difference test at P=0.05.

Table 3. Effect of treatment on percentage of tomato plants flowering at 68,
74, and 80 days after seeding, and on percentage of plants with fruit at 68 DAP.}

Treatment	Percentage of plants flowering			Percentage of plants with fruit
	68 DAP^a	74 DAP	80 DAP	68 DAP
Untreated	73.3 bc^b	92.5	100.0	12.5
LS290	67.5 c	97.5	100.0	5.0
LS213	87.5 ab	95.	100.0	20.0
LS254	80.0 abc	97.5	100.0	12.5
LS255	75.0 bc	95.	100.0	12.5
LS256	72.5 c	95.	100.0	12.5
LS257	92.5 a	100.0	100.0	20.0

^{ADAP = days after planting.

Bwithin each column, means followed by the same letter are not different
according to an F-protected Least Significant Difference test at P=0.10.

Yield. There were no significant differences in number and weight of
marketable fruit on any of the three harvest dates, or for total yield (Table
4).
Table 4. Effect of treatment on yield of tomato. Means are yield of 5 plants
per replicate plot.}

	Total Yield (3 harvests) (Sep 10 to 26)		Yield for Week 1 (Sep 10)
Treatment	Number of marketable fruit^a	Weight of marketable fruit (kg)	Number of marketable fruit	Weight of marketable fruit (kg)
Untreated	70.9^b	9.7	26.9	3.98
LS290	67.5	9.3	23.4	3.50
LS213	86.0	10.7	30.0	3.97
LS254	77.6	10.1	26.9	3.60
LS255	80.7	10.5	31.8	4.23
LS256	67.8	8.6	30.9	4.01
LS257	86.8	10.8	30.0	4.02

^{aTotal marketable fruit includes all fruit in
Grades 1, 2, 3, 4, and 5.

^{bWithin each column, means followed by the same letter or no letter are
not different according to a F-protected Least Significant Difference test at P=0.05.}
The PGPR formulations tested promote early plant growth and flowering. Based
on size, plants treated with LS213, LS254, and LS256 were ready to transplant to
the field 10 to 14 days earlier than the untreated control. Treatments LS255 and
LS257 were ready for transplant about 7 days earlier then the control. This
could be economically important for transplant producers who could shorten the
time needed to produce plants in the greenhouse. Although early flowering was
detected with LS213 and LS254, we were unable to demonstrate significant
increases in total yields or in the first harvest}

Email all comments and suggestions to ghonea@utk.edu
Copyright © 1999 by The University of Tennessee. All rights reserved.

This research represents one season's data and does not constitute recommendations. After sufficient data is collected over the appropriate number of seasons, final recommendations will be made through research and extension publications.