Stimulating the growth and development of beans (Phaseolus vulgaris L.) with Trichoderma fungi and their effect on the alliviating of salinity stress

Extended abstract

Background and Objectives
Salinity is one of the most important environmental stresses after water stress in Iran, which has affected about 50% of agricultural lands with different intensities. The growth and development of crop plants in these areas are constantly exposed to salinity and other stresses at the same time, which causes morphological, physiological, and biochemical responses. Alleviating the negative effects of salinity in the crops is mainly done by agronomic and breeding methods. The use of appropriate microorganisms is one of the agronomic methods that can directly and/or indirectly reduce some limitations of salinity stress. In recent years, the necessity of biological study in rhizosphere microorganisms to improve nutrition and plant growth and, to control stress factors has been considered. Some species of Trichoderma fungi are known as plant growth stimulants in normal and stressful conditions. Since the bio-treatment of Trichoderma fungus for alleviation of salt stress in the Pinto bean has not been evaluated, so, the inoculation effects of different species of this fungus were studied on the plant growth and development under salinity conditions.

Methodology
A field split-plot experiment based on a randomized complete block design with three replications were carried out at the Nuclear Agriculture Research Institute in Karaj on Pinto bean plants of Saleh 2. The main factor (salinity) was in two levels of non-saline (ECe=1.1 dS m-1) soil and saline (ECe=6 dS m-1), soil and the secondary factor with 11 levels, including; T. harzianum (MW718882), T. lixii (MW719563), T. ghanens (MW719590), T. virens (MW719876) and (MW719255) and their mutant isolates, namely NAS108 M1, NAS114-M17, ON545796, NAS115 M17, and NAS112M2, respectively, and the control treatment was without inoculation.

Findings
The results showed that the effect of salinity and the biopriming on the characteristics of emergence percentage, plant height, harvest index, number of pods, number of seeds per pod, seed weight, seed yield, biological yield, branching, seed protein and leaf area was significant (p≤0.01). Also, the results showed that the interaction effect of salinity and biopriming on emergence percentage, plant height, seed yield, biological yield, seed protein and leaf area was significant at p≤0.01, however, harvest index, the number of pods per plant, The number of seeds per pod and the seed weight were not influenced by treatment interactions. All studied characteristics were significantly reduced under salt stress compared to the control. The decrease in yield component traits was more than vegetative traits. The biopriming of Trichoderma species except T. lixii improved all traits of growth, development and seed protein of the plant in saline and non-saline conditions. T. harzianum, T. ghanens and T. atroviride along with their mutants produced the highest salinity resistance induction. Among them, the effect of T. atroviride was more obvious on saline condition while its mutant was superior in non-saline condition. The symbiosis efficiency of Trichoderma with this plant shows that under non-saline condition the efficiency varies between 16 to 70%, and the lowest is in T. lixii m and the highest in T. atroviride m. Also, except in T. atroviride treatment, the index was declined by salinity to the range of 3 to 58% for the rest of the fungi .

Conclusion
In general, the results of the experiment showed that the growth and development of pinto beans are affected by salinity, inoculation by the Trichoderma species and their interactions. As a result, the effects of different Trichoderma species are not the same under saline and non-saline conditions. Although under salinity treatment, the potential of the fungi in supporting of the vegetative traits, yield and yield component decreased, however, the values of all the traits in saline conditions were higher than the control without inoculation. This article shows that choosing the right and sustainable fungal treatment can partially alleviate the effects of the moderate salinity in the pinto bean plants. Therefore, it is possible to optimize bean production by inducing salinity resistance by selecting suitable Trichoderma. Overall and according to the results, seed biopriming treatment with Trichoderma species improves the vegetative and reproductive traits of pinto bean in saline and non-saline conditions, and the use of T. harzianum, T. ghanens and T. atroviride along with their mutants is recommended to maximize of the plant yield in the field conditions .