Phenological and ecophysiological responses of Capsicum annuum var. glabriusculum to native arbuscular mycorrhizal fungi and phosphorus availability

- Results showed a high sunlight regimes and a high thermal time during growing season.
- P availability and the levels of AMF propagules in the soil significantly modified the macro and micro-nutrient acquisition patterns and biomass allometric allocation.
- Mycorrhizal growth responses decreased as the availability of P increases.
- The reproductive yield was promoted by the native AMFCag inoculum.
- A high functional AMF colonization (predominantly Arum-Paris type) was promoted by the AMFCag inoculum except at higher levels of P availability.

Due to climate change, the assessment of environmental variations associated to phenology and ecophysiology of iconic Sonoran Desert plants such as Capsicum annuum var. glabriusculum (Cag), during their interaction with the native arbuscular mycorrhizal fungi (AMF) and soil nutrients availability, is the keystone to understand its biological significance in the extreme conditions of semiarid environments. Seasonal patterns of high solar radiation regimes and extreme daily air temperatures thresholds were reflected in a high accumulation of heat from physiological maturity (2699 °D) until the end of reproduction season (4002 °D). In treatments without chemical fertilization, low and intermediate P availability, the native AMFCag inoculum significantly increased Cag's relative growth rates and changed the biomass allometric allocation patterns causing a lower partition to the roots and a higher partition to the growth of shoots and photosynthetic assimilation surface. Depending on the phenological stage, the levels of P availability and the levels of native AMF propagules in the soil, significantly modified the content of C, H, S, P, N, Ca, Fe, Mn or Ni in the shoots. The native AMFCag inoculum significantly increased the functional colonization (Arum-Paris type) of roots except with higher P availability. However, when AMF propagules in the soil are low, P increase and presence of other mineral nutrients is detrimental to symbiotic establishment. Conversely, when AMF propagules in the soil are high, symbiotic traits indicate that the native AMF taxa tested, have different tolerance capabilities to colonize functionally the roots to obtain the carbon for their development even under a high P and other mineral nutrients availability in the soil. In extreme conditions of sunlight and air temperatures, Cag's phenological and ecophysiological traits were enhanced by the native AMFCag inoculum in different P availability levels, however, the mycorrhizal growth response decreased significantly as the availability of P increases, and the highest level of native AMF propagules in soil was the factor that promoted the increase of reproductive yield of Cag plants, not the increase of nutrients availability. This study provides novel information on AMF-Cag symbiotic interactions during plant development and phenological stages, as well as proposes different insights and hypothesis of research about Cag-AMF ecophysiology.